JP3433730B2 - Nitride semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device such as a light emitting diode (LED) and a laser diode (LD), and more particularly, a semiconductor layer structure laminated on a substrate is made of a nitride semiconductor. The present invention relates to a nitride semiconductor light emitting device and a light emitting device.

[0002]

2. Description of the Related Art In is used as a material for semiconductor light emitting devices such as LEDs and LDs that emit light in the wavelength range from ultraviolet to red.
Nitride semiconductors such as GaN, AlGaN, and GaN are promising. At present, blue LEDs and blue-green LEDs made of these nitride semiconductor materials have been put to practical use and used for displays, signals and the like.

These blue and blue-green light emitting nitride semiconductors L
The ED element has a double hetero structure and basically includes an n-type contact layer made of n-type GaN and an n-type contact layer on a substrate.
-Type AlGaN n-type cladding layer and n-type InGa
It has a structure in which an active layer made of N, a p-type clad layer made of p-type AlGaN, and a p-type contact layer made of p-type GaN are sequentially stacked. Si, G in the active layer
Donor impurities such as e and / or acceptor impurities such as Zn and Mg are doped. The emission wavelength of this LED element can be changed from the ultraviolet region to the red region by changing the In ratio of InGaN forming the active layer or changing the type of impurities doped in the active layer.

On the other hand, various structures have been conventionally proposed for the LD element. For example, Japanese Patent Laid-Open No. 6-21511
The publication discloses a separate confinement type LD element. In this LD element, an active layer made of InGaN and having a film thickness of 100 angstroms or less is provided with an n-type GaN layer and a p-type Ga layer.
N-type GaN layer and p-type G
p-type AlGaN layer and n-type A on each of the aN layers
The structure has an lGaN layer. In this element,
The AlGaN layer acts as a light confinement layer.

[0005]

With respect to the nitride semiconductor LED element, the light emission output has been improved to a practical level by realizing the double hetero structure as described above. However, not only an LED element that exhibits a higher light emission output is desirable, but in the conventional LED element, the active layer (light emitting layer) is doped with impurities, so that the half-width of the emission spectrum is reduced. There is a tendency to become wider. When the full width at half maximum of the emission spectrum is wide, the emission color looks whitish, so when a full-color display is manufactured using such LED elements, the color reproduction area of the color display becomes narrow. Becomes

On the other hand, the nitride semiconductor LD element theoretically has a double hetero structure having an active layer formed of non-doped InGaN, as described in the above-mentioned Japanese Patent Laid-Open No. 6-21511. Although it is feasible, the LD element has not actually oscillated. In particular, as described in this publication, if the active layer has a quantum well structure, the light emission output should be greatly improved, but as described above, laser oscillation is not actually achieved.

Therefore, when the present invention is applied to an LED element, an LED element having a high emission output and a narrow half width of emission spectrum can be realized, and when applied to an LD element, actual laser oscillation is achieved. An object of the present invention is to provide a nitride semiconductor light emitting device having a novel structure capable of realizing an LD device capable of performing the above.

[0008]

The inventors of the present invention have earnestly studied a nitride semiconductor light emitting device having a structure in which an active layer is sandwiched between a p-type semiconductor layer and an n-type semiconductor layer.
By using GaN and having a quantum well structure (including both a single quantum well structure and a multiple quantum well structure), light emission from the active layer can be based on InGaN interband light emission. Therefore, a nitride capable of obtaining a light emission having a narrow half width and providing a specific p-type layer or an n-type layer in contact with the active layer, thereby exhibiting a high light emission output and / or capable of actual laser oscillation. It has been found that a semiconductor light emitting device can be obtained. Based on these findings, further research was conducted and the present invention was completed.

More specifically, according to the present invention, an active layer comprising a nitride semiconductor containing indium and gallium, having first and second main surfaces, and the first main surface of the active layer. An n-type nitride semiconductor layer provided on the active layer, and a p-type nitride semiconductor layer provided on the second main surface of the active layer, the p-type nitride semiconductor layer being the first layer of the active layer. A first p-type clad layer formed in contact with the second main surface and made of a p-type nitride semiconductor containing aluminum and gallium;
It is provided at a position farther from the active layer than the mold cladding layer,
A second p-type clad layer having a bandgap larger than that of the first p-type clad layer and made of a p-type nitride semiconductor containing aluminum and gallium; the first p-type clad layer; (where, 0 <m <1) p-type disposed between the second p-type cladding layer _in m _{Ga 1-m} N or p-type and the p-type layer made of GaN, p-type Ga as the outermost layer
There is provided a nitride semiconductor light emitting device including a p-type contact layer made of N.

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

In the present invention, the active layer constitutes a single quantum well structure composed of well layers having a thickness of 100 angstroms or less, or composed of a well layer composed of a nitride semiconductor containing indium and gallium and a nitride semiconductor. A multiple quantum well structure formed by stacking a barrier layer can be formed.

In the present invention, the active layer is preferably non-doped.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Note that, throughout the drawings, similar portions are often denoted by the same reference numerals.

FIG. 1 is a schematic sectional view showing the structure of one embodiment of the nitride semiconductor light emitting device according to the present invention.

The nitride semiconductor light emitting device 10 shown in FIG.
The active layer 15 and the first sandwiching the active layer 15 on both sides
The semiconductor laminated structure is composed of the n-type clad layer 14 and the p-type clad layer 16. This semiconductor laminated structure is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13.

The active layer 15 contains a nitride semiconductor containing indium and gallium. A nitride semiconductor containing indium and gallium can be represented by In _m Al _n Ga _1-mn N (where 0 <m <1, 0 ≦ n <1, and m + n = 1). Most preferably, the active layer 15 is of the formula In _m G
It includes a nitride semiconductor represented by a _1-m N (where 0 <m <1). By changing the ratio of indium, that is, the value of m in each formula, the band gap can be changed so as to obtain emitted light in the region from ultraviolet to red. In the following description, the formula In _m Ga _1-m N
(Here, 0 <m <1) or a nitride semiconductor represented by an equivalent formula may be simply referred to as InGaN.

The active layer 15 has a quantum well structure. When the active layer 15 has a quantum well structure, LE
Whether it is a D element or an LD element, a high output light emitting element can be realized by the strain quantum well effect, the exciton light emitting effect, and the like.

In the present invention, the quantum well structure refers to a structure that causes interquantum level light emission of a nitride semiconductor (InGaN) forming an active layer, and includes both a single quantum well structure and a multiple quantum well structure. It is a concept that includes.

The single quantum well structure means a structure in which the well layer is composed of a single layer of nitride semiconductor having a single composition. That is,
An active layer having a single quantum well structure is composed of only a single well layer.
The two clad layers sandwiching (made of GaN) on both sides form the barrier layer.

The multiple quantum well structure refers to a multilayer film structure in which well layers and barrier layers are sequentially laminated. The minimum stacking structure of the multiple quantum well structure is a three-layer structure including one barrier layer and (two) well layers provided on both sides of the barrier layer, or one well layer and two well layers provided on both sides thereof (2 It may be a three-layer structure consisting of one barrier layer. In the multiple quantum well structure, the two outermost layers on both sides are each constituted by a well layer or a barrier layer. In the case of a multi-quantum well structure in which the two outermost layers of the active layer are each formed by a well layer, two clad layers sandwiching the active layer on both sides form a barrier layer. In the active layer having the multiple quantum well structure, the well layer and the barrier layer can be formed of a nitride semiconductor (preferably InGaN) containing indium and gallium (however, the composition of the two is different).
The well layer may be formed of a nitride semiconductor containing indium and gallium (preferably InGaN), and the barrier layer may be formed of another nitride semiconductor such as InN or GaN. That is, the active layer having the multiple quantum well structure also includes the nitride semiconductor containing indium and gallium.

The active layer 15 has a well layer having a thickness of 100 Å or less in the case of a single quantum well structure, and has a thickness of 100 Å or less and each barrier layer in the case of a multiple quantum well structure. The layers are preferably formed to a thickness of 150 Å or less. In any case, the well layer more preferably has a thickness of 70 angstroms or less, and most preferably 50 angstroms or less. More preferably, the barrier layer in the active layer is formed to a thickness of 100 angstroms or less. The active layer of the multiple quantum well structure particularly preferably has a thickness of 200 Å or more, and can usually have a thickness of up to 0.5 μm.

In the active layer 15 of either the single quantum well structure or the multiple quantum well structure, the active layer may be either n-type or p-type. It is particularly preferable because interluminescence, exciton emission, or quantum well level emission can be obtained.

When the active layer 15 is doped with a donor impurity and / or an acceptor impurity, if the crystallinity of the active layer doped with the impurity is substantially the same as that of the non-doped active layer, the donor impurity is doped. The inter-band emission intensity of the active layer can be higher than that of the non-doped active layer, while the active layer doped with the acceptor impurity is on the low energy side about 0.5 eV lower than the original peak wavelength of inter-band emission. The shifted emission peak wavelength is shown, but the full width at half maximum tends to widen. In addition, if both the acceptor impurity and the donor impurity are doped,
The emission intensity of the active layer doped with only the acceptor impurities can be further increased. In particular, when an active layer doped with acceptor impurities is to be obtained, it is preferable that the conductivity type of the active layer is n-type by doping with donor impurities such as Si.

However, in the present invention, since it is ideal that the active layer emits light strongly by band-to-band emission, it is most preferable that the active layer 15 is not doped with impurities. In addition, a light emitting element having a non-doped active layer can have a lower Vf (forward voltage) than a light emitting element having an active layer doped with impurities.

The first n-type cladding layer 14 provided in contact with the first main surface of the active layer 15 is made of an n-type nitride semiconductor containing indium and gallium. Since the nitride semiconductor containing In and Ga has a relatively soft crystal, it acts as a buffer layer, so to speak, as will be described below, the active layer 15 and other nitrides that may be formed on the active layer 15 or itself. The semiconductor layer is prevented from cracking and its crystallinity is not deteriorated, thereby improving the light emission output of the light emitting element. First n-type cladding layer 14
Is preferably formed of n-type In _j Ga _{1 -j} N (0 <j <1). In this In _j Ga _1-j N, the value of j is preferably within the range of 0 <j ≦ 0.5. Generally, the crystallinity of InGaN tends to gradually deteriorate as the In ratio increases, and in order to cause the light emitting element to emit light having a high light emission output practically as an n-type cladding layer, the j value is 0. It is preferably 0.5 or less. The j value is more preferably in the range of 0 <j ≦ 0.3, most preferably 0 <j ≦ 0.2.

The carrier concentration of the first n-type cladding layer 14 is preferably in the range of 1 × 10 ¹⁸ / cm ³ to 1 × 10 ²⁰ / cm ³ . If the carrier concentration in the n-type cladding layer 14 is less than 1 × 10 ¹⁸ / cm ^{3, the} efficiency of electron injection into the active layer 15 tends to decrease, and the emission output tends to decrease. This is because when the carrier concentration is higher than 1 × 10 ²⁰ / cm ³ , the crystallinity of the first n-type cladding layer is deteriorated and the emission output tends to be reduced.

The thickness of the first n-type cladding layer 14 is not particularly limited, but the active layer 15 and the first n-type cladding layer 14 have a total thickness of 300 angstroms or more. Is desirable. The total thickness of the nitride semiconductor layer (active layer + first n-type cladding layer) containing In and Ga is 30.
If the thickness is less than 0 angstrom, the lattice constant mismatch and the coefficient of thermal expansion may occur in the active layer 15 and the first n-type cladding layer 14, and also in another nitride semiconductor layer provided in contact with the first n-type cladding layer. This is because cracks are likely to occur due to strain stress that may be present at those interfaces due to the difference in the above. As described above, the nitride semiconductor containing In and Ga is useful for relieving this stress because its crystal is relatively soft, but its total thickness is 300 angstroms or more. By doing so, the stress can be further alleviated. This total thickness is preferably 1 μm or less.

The p-type cladding layer 16 formed in contact with the second main surface of the active layer 15 is made of a p-type nitride semiconductor. Such a nitride semiconductor has the formula In _s Al _t G
a _{1- st} N (where 0 ≦ s, 0 ≦ t, and s + t ≦ 1).

The substrate 11 is made of sapphire (C plane, R plane, A plane).
Surface), SiC (including 6H-SiC, 4H-SiC), Si, ZnO, GaAs, spinel (MgAl).
It can be formed of 2 O 4, particularly (111) plane thereof, GaN, or an oxide single crystal having a lattice constant close to that of a nitride semiconductor, but sapphire, spinel, GaN or SiC is generally used. .

Buffer layer 1 formed on substrate 11
2 is normally formed in order to relax the lattice mismatch between the substrate 11 and the nitride semiconductor layer formed thereon, and is formed of, for example, GaN, AlN, GaAlN or the like in a thickness of several hundred angstroms. To be done. The substrate 11 is made of Si having a lattice constant close to that of the nitride semiconductor formed on the substrate 11.
The buffer layer 12 may not be formed when it is formed of a material such as C or ZnO, and when the substrate 11 is lattice-matched with the nitride semiconductor formed thereon.

An n-type contact layer 13 is formed on the buffer layer 12 in contact with the first n-type cladding layer 14. The n-type contact layer 13 is made of GaN or AlGa.
It is preferably formed of N or the like.

After forming the predetermined semiconductor layers on the substrate 11, the negative electrode 18 is formed on the surface of the n-type contact layer exposed by etching.

When the n-type contact layer 13 is formed of GaN, a more preferable ohmic contact with the negative electrode 18 is achieved, and the forward voltage (Vf) of the light emitting device is further reduced. In addition, since GaN is superior in crystallinity to other ternary mixed crystal and quaternary mixed crystal nitride semiconductors, a nitride semiconductor layer such as the first n-type clad layer 14 grown thereon is formed. Since the crystallinity can be improved, the light emission output of the light emitting element is improved.

Further, the carrier concentration of the n-type contact layer 13 is 5 × 10 ¹⁷ / cm ³ from the viewpoint of achieving preferable ohmic contact with the negative electrode 18 and, as a result, lowering Vf and preventing lowering of emission output. ~ 5 x 10 ¹⁹ / c
It is desirable to be within the range of m ³ .

The negative electrode 18 is made of a metal material containing titanium (Ti) and gold (Au), for example, a laminated structure or alloy thereof, or Ti, from the viewpoint of achieving preferable ohmic contact with the n-type contact layer 13. Most preferably, it is formed of a metal material containing aluminum (Al), for example, a laminated structure or alloy thereof. In this case, the negative electrode 18 is particularly preferably formed as a two-layer structure including a titanium layer provided in direct contact with the n-type GaN contact layer 13 and an aluminum layer formed thereon.

A p-type contact layer 17 is formed on the p-type clad layer 16, and a positive electrode 19 is formed thereon. The p-type contact layer 17 is made of GaN or AlGa.
It is preferably formed of N or the like. In particular, when the p-type contact layer 17 is formed of GaN, a more preferable ohmic contact with the positive electrode 19 is achieved, and V of the light emitting device is achieved.
f can be reduced.

The carrier concentration of the p-type contact layer 17 is 1 × 10 ¹⁷ / cm ³ to 1 from the viewpoint of achieving preferable ohmic contact with the positive electrode 19 and resulting reduction of Vf and reduction of emission output. It is preferably in the range of × 10 ¹⁹ / cm ³ .

The positive electrode 19 is formed of a metal material containing nickel (Ni) and gold (Au), for example, a laminated structure or an alloy thereof, from the viewpoint of achieving preferable ohmic contact with the p-type contact layer 17. Is most preferred. In this case, it is particularly preferable that the positive electrode 19 be formed as a two-layer structure including a nickel layer provided in direct contact with the p-type GaN contact layer 17 and a gold layer formed thereon.

FIG. 2 shows another embodiment of the nitride semiconductor light emitting device according to the present invention.

The light emitting device 20 shown in FIG. 2 has the nitride shown in FIG. 1 except that the second n-type cladding layer 21 is provided between the first n-type cladding layer 14 and the n-type contact layer 13. It has the same structure as the physical semiconductor element.

In the light emitting device 20, the second n-type cladding layer 21 provided in addition to the light emitting device structure shown in FIG. 1 is formed of an n-type nitride semiconductor containing aluminum and gallium. By providing such a second n-type cladding layer 21, it is possible to increase the band gap difference between the second n-type cladding layer 21 and the first n-type cladding layer 14 and improve the luminous efficiency of the light emitting element.

The second n-type cladding layer 21 is preferably formed of n-type Al _a Ga _{1 -a} N (where 0 <a <1). In this case, the value of a is 0 <a ≦
It is preferably in the range of 0.6. If the crystal of AlGaN is relatively hard and is larger than 0.6, cracks tend to occur relatively easily in the first n-type clad layer 14 despite the presence of the first n-type clad layer 14, and the emission output tends to decrease. Because there is. Most preferably, the a value is in the range of 0 <a ≦ 0.4. In the present specification,
A nitride semiconductor represented by Al _a Ga _1-a N or an equivalent formula may be simply referred to as AlGaN.

In addition, the carrier of the second n-type cladding layer 21 is
Oh, the concentration is 5 × 10¹⁷/ Cm³~ 1 x 10¹⁹/ Cm³of
It is desirable to be within the range. The carrier concentration is 5 ×
10 ¹⁷/ Cm³Lower than that, the resistivity of AlGaN is high.
Therefore, the Vf of the light emitting element becomes high, and the luminous efficiency is low.
On the other hand, the carrier concentration is 1 × 10
¹⁹/ Cm³If it is higher than this, the crystallinity of AlGaN deteriorates.
This is because the luminous efficiency is reduced. Second n-type cladding layer
21 is typically 50 Å to 0.5 μm thick
It can be formed with

The substrate 11, the buffer layer 12, the n-type contact layer 13, the n-type cladding layer 14, the active layer 15, the p-type cladding layer 16, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are related to FIG. It is exactly as explained.

FIG. 3 is a schematic sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention.

The nitride semiconductor light emitting device 30 shown in FIG.
The semiconductor laminated structure has an active layer 15, and an n-type cladding layer 34 and a first p-type cladding layer 36 that sandwich the active layer 15 on both sides. This semiconductor laminated structure is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13 as in the structure shown in FIG.

The first p-type cladding layer 36 provided in contact with the second main surface of the active layer 15 is formed of a p-type nitride semiconductor containing indium and gallium. Since the nitride semiconductor containing In and Ga has a relatively soft crystal, it acts as a buffer layer, so to speak, and as described below, the active layer 15 and other nitride semiconductors that can be formed on the active layer 15 itself. The layer is prevented from cracking and the crystallinity thereof is not deteriorated, thereby improving the light emission output of the light emitting device. The first p-type cladding layer 36 is
It is preferably formed of p-type _{In k Ga 1-k N (} 0 <k <1). In this In _k Ga _1-k N, the value of k is
It is preferable to be in the range of 0 <k ≦ 0.5. Generally, the crystallinity of InGaN tends to gradually deteriorate as the In ratio increases, and in order to cause the light emitting element to emit light with a high light emission output as a p-type cladding layer, the k value is 0. It is preferably 0.5 or less. The k value is more preferably in the range of 0 <k ≦ 0.3, most preferably 0 <k ≦ 0.2.

The carrier concentration of the first p-type cladding layer 36 is preferably in the range of 1 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ³ . First p-type cladding layer 3
If the carrier concentration in 6 is less than 1 × 10 ¹⁷ / cm ^{3, the} efficiency of electron injection into the active layer 15 tends to decrease and the emission output tends to decrease, while the carrier concentration in the p-type cladding layer 36 tends to be 1 If it is larger than × 10 ¹⁹ / cm ^3, the crystallinity of the first p-type cladding layer will be deteriorated, and the emission output will tend to be reduced. The first p-type cladding layer 36 is preferably obtained by the method described for the p-type cladding layer 16 in the structure shown in FIG.

The thickness of the first p-type cladding layer 36 is not particularly limited, but the active layer 15 and the first p-type cladding layer 36 have a total thickness of 300 angstroms or more. Is desirable. The total thickness of the nitride semiconductor layer (active layer + first p-type cladding layer) containing In and Ga is 30.
If the thickness is less than 0 angstrom, the lattice constant mismatch and the coefficient of thermal expansion may occur in the active layer 15 and the first p-type cladding layer 36, and also in another nitride semiconductor layer provided in contact with the first p-type cladding layer. This is because cracks are likely to occur due to strain stress that may be present at those interfaces due to the difference in the above. As described above, the nitride semiconductor containing In and Ga is useful for relieving this stress because its crystal is relatively soft, but its total thickness is 300 angstroms or more. By doing so, the stress can be further alleviated. This total thickness is preferably 1 μm or less.

The n-type cladding layer 34 formed in contact with the first main surface of the active layer 15 is made of an n-type nitride semiconductor. Such a nitride semiconductor has the formula In _u Al _v G
a _{1- uv} N (where 0 ≦ u, 0 ≦ v, u + v ≦ 1).

The substrate 11, the buffer layer 12, the n-type contact layer 13, the active layer 15, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are as described with reference to FIG.

FIG. 4 shows another embodiment of the nitride semiconductor light emitting device according to the present invention.

The light emitting device 40 shown in FIG. 4 is nitrided as shown in FIG. 3 except that the second p-type cladding layer 41 is provided between the first p-type cladding layer 36 and the p-type contact layer 17. It has the same structure as the physical semiconductor element.

In this light emitting device 40, the second p-type cladding layer 41 provided in addition to the light emitting device structure shown in FIG. 3 is formed of a p-type nitride semiconductor containing aluminum and gallium. By providing such a second p-type cladding layer 41, it is possible to increase the band gap difference between the second p-type cladding layer 41 and the first p-type cladding layer 36, and improve the luminous efficiency of the light emitting element.

The second p-type cladding layer 41 is preferably formed of p-type Al _b Ga _{1 -b} N (where 0 <b <1). In this case, the value of b is 0 <b ≦
It is preferably in the range of 0.6. If the crystal of AlGaN is relatively hard and is larger than 0.6, despite the existence of the first p-type cladding layer 36, cracks are relatively likely to occur in that layer, and the emission output tends to be reduced. Because there is. Most preferably, the b value is within the range of 0 <b ≦ 0.4.

In addition, the carrier of the second p-type cladding layer 41 is
Oh, the concentration is 1 × 10¹⁷/ Cm³~ 1 x 10¹⁹/ Cm³of
It is desirable to be within the range. The carrier concentration is 1 ×
10 ¹⁷/ Cm³Lower than that, injection of holes into the active layer 15
The input efficiency tends to decrease, and the luminous efficiency tends to decrease.
However, the carrier concentration is 1 x 10¹⁹/ Cm³Higher than
And the crystallinity of AlGaN deteriorates and the luminous efficiency decreases?
It is. The second p-type cladding layer 41 is usually 50
It should be formed with a thickness of ngstrom to 0.5 μm.
You can

The substrate 11, the buffer layer 12, the n-type contact layer 13, the active layer 15, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are as described with reference to FIG. 34 and the first p-type cladding layer 36 are as described with respect to FIG.

FIG. 5 is a schematic sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention.

The nitride semiconductor light emitting device 50 shown in FIG.
A semiconductor laminated structure including an active layer 15, an n-type semiconductor layer 501 including a first n-type cladding layer 54 sandwiching the active layer 15 on both sides thereof, and a p-type semiconductor layer 502 including a second p-type cladding layer 41 is formed. Have. This semiconductor laminated structure is
Similar to the structure shown in FIG. 1, it is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13.
In FIG. 5, the n-type semiconductor layer 501 is composed of the first n-type cladding layer 54.

It can be said that the light emitting device 50 has a semiconductor laminated structure in which the n-type clad layer structure in the light emitting device 10 shown in FIG. 1 and the p-type clad layer structure shown in FIG. 4 are combined, but in this special case. The first n-type clad layer 54 corresponds to the first n-type clad layer 14 shown in FIG.
It was found that not only the nitride semiconductor containing indium and gallium constituting the above but also GaN can be formed and the same effect can be obtained. Further, in this case, it was also found that the first p-type clad layer 56 may be formed of any p-type nitride semiconductor, like the p-type clad layer 16 in the light emitting device 10 shown in FIG. . Even with such a semiconductor laminated structure, the light emitting device exhibits the same excellent characteristics.

More specifically, the first n-type cladding layer 54 is formed of an n-type nitride semiconductor containing no aluminum. The first n-type cladding layer 54 is
It is preferable to form the n-type In _w Ga _1-w N (where 0 ≦ w <1). That is, the first n-type clad layer 54 can be formed of the n-type nitride semiconductor described in regard to the first n-type clad layer 14 of the light emitting device 10 shown in FIG. 1, or can be formed of n-type GaN. can do. For the same reason as that described for the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. 1, w
The value of is preferably in the range of 0 ≦ w ≦ 0.5, more preferably in the range of 0 <w ≦ 0.3, and most preferably in the range of 0 <w ≦ 0.2. For the same reason, the carrier concentration of the first n-type cladding layer 54 is also 1 × 10 ¹⁸ /
It is desirable to be in the range of cm ³ to 1 × 10 ²⁰ / cm ³ . The thickness of the first n-type cladding layer 54 is also not particularly limited, but for the same reason, the total thickness of the active layer 15 and the first n-type cladding layer 54 is 300 angstroms or more. It is desirable to have and can have a thickness of 1 μm or less.

In the light emitting device 50 shown in FIG. 5, the first p-type cladding layer 56 formed in contact with the second main surface of the active layer may be formed of any p-type nitride semiconductor. However, it is preferable to form the p-type nitride semiconductor containing no aluminum. More specifically, the first p-type cladding layer 56 is made of p-type In _x Ga _1-x N (where 0 ≦ x
It is desirable to form in <1). Light emitting device 30 of FIG.
For the same reason as the reason described for the first p-type cladding layer 36 in the above, the x value is preferably within the range of 0 ≦ x ≦ 0.5, and more preferably 0 ≦ x ≦ 0.
It is within the range of 3, and most preferably within the range of 0 ≦ x ≦ 0.2. If the first p-type cladding layer 56 is also made of GaN, it acts as a buffer layer. The carrier concentration of the first p-type cladding layer 56 is also 1 × 10 ¹⁷ / cm ³ to 1 × 10 5 for the same reason.
It is desirable to be within the range of ¹⁹ / cm ³ . Further, the thickness of the first cladding layer 56 is not particularly limited, but for the same reason, it is desirable that the total thickness of the first cladding layer 56 and the active layer 15 is 300 Å or more, and the thickness of 1 μm or less is preferable. . The first p-type cladding layer 56
Although it may be omitted, it is clear that if it is formed, cracks are less likely to occur because the first p-type cladding layer acts as a buffer layer, and the light emitting device exhibits even more excellent characteristics. Ah

The second p-type cladding layer 41 is as described for the second cladding layer 41 in the light emitting device 40 shown in FIG.

The substrate 11, the buffer layer 12, the n-type contact layer 13, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are the same as those described for the light emitting device 10 shown in FIG.

FIG. 6 is a schematic sectional view showing the structure of another embodiment of the semiconductor light emitting device according to the present invention. This light emitting device 60 is the same as the light emitting device 50 shown in FIG. 5 except that the second n-type cladding layer 21 is additionally formed between the n-type contact layer 13 and the first n-type cladding layer 54. It has a similar structure. The second n-type cladding layer 21 is as described for the second n-type cladding layer 21 in the light emitting device 20 shown in FIG. It should be noted that it is similar to the case of the light emitting device 50 shown in FIG. 5 that the first p-type cladding layer 56 is preferably provided rather than omitted.

Although the nitride semiconductor light emitting devices according to some aspects of the present invention have been described above, it goes without saying that the structures of these light emitting devices can be applied to both LED devices and LD devices. The structure of the LD is, for example, the structure shown as a perspective view in FIG. 7. In FIG. 7, the semiconductor layer 71 on the substrate 11 is a semiconductor layer including the buffer layer 12, the n-type contact layer 13, the first n-type cladding layer, and the second n-type layer when formed. The semiconductor layer 72 formed on the active layer 15 is a semiconductor layer including the first clad layer, the second clad layer, and the p-type contact 17 layer in the above-described case. The applied current concentrates and flows in the region 15a corresponding to the positive electrode 19 in the active layer 15.

In the case of an LD element, the first n-type cladding layer of any one of the light emitting elements 10 to 60 and n
When a second n-type cladding layer is formed between the second n-type cladding layer 13 and the contact layer 13,
A second p-type clad layer is formed between the p-type contact layer 13 and / or the first p-type clad layer and the p-type contact layer 17 of any of the light emitting devices 10 to 60. In that case, between the second p-type cladding layer and the n-type contact layer 13, a multilayer film formed by laminating at least two types of nitride semiconductor layers having different compositions from each other is formed as a light reflecting film. You can also

FIG. 8 shows an example in which the above-mentioned multilayer light reflection film is applied to the light emitting device structure shown in FIG. A nitride semiconductor light emitting device 80 shown in FIG. 8 has a first multilayer light reflection film (n-type) 81 between the n-type contact layer 13 and the second n-type cladding layer 21.
And a second multilayer light reflection film (p-type) 82 between the second p-type cladding layer 41 and the p-type contact layer 17.

First multilayer film 81 and second multilayer film 82
Are each made of a nitride semiconductor having a different composition, that is, a nitride semiconductor having a different refractive index from each other, for example, λ / 4n (where λ is the wavelength of light emitted from the active layer 15 and n is the refractive index). It is formed by alternately stacking two or more layers with the thickness calculated in (), and is designed so that the emitted light from the active layer 15 can be reflected by these films. When the positive electrode 19 is formed as a stripe electrode having a shape as shown in FIG. 7 to have a width of 10 μm or less and laser oscillation is performed, the emitted light of the active layer 15 can be confined in the active layer 15 by the multilayer reflective layer. Since it can be further facilitated, laser oscillation can be easily performed. In addition, even in the LED mode, leakage of emitted light is suppressed by the multilayer reflective layer,
The external quantum efficiency is improved.

The multilayer light reflection films 81 and 82 are doped with a donor impurity and an acceptor impurity, respectively, and have a predetermined conductivity type.

In the structure shown in FIG. 8, the first multi-light reflection layer film 81 includes the n-type contact layer 13 and the second n-type contact layer 13.
Although it is formed between the n-type contact layer 13 and the type clad layer 21, it may be formed in the n-type contact layer 13 instead. Similarly, the second multilayer light reflection film 82 may be formed in the p-type contact layer 17. Even if the multilayer light reflection film is formed in the contact layer, the emitted light from the active layer 16 can be similarly confined. Further, either the first multilayer light reflection film 81 or the second multilayer light reflection film 82 may be omitted.

Further, as shown in FIG. 8, when a laser device is manufactured by using an insulating material such as sapphire as the substrate 11, the structure of the laser device is a flip chip system.
That is, both the positive and negative electrodes 19, 1 are provided on the same surface side of the substrate 11, more specifically, on the nitride semiconductor layer formation side of the substrate 11.
8 is formed. In this case, as shown in FIG. 8, the first multilayer light reflection film 81 formed on the n-type layer side is located on the p-layer side, that is, above the horizontal plane of the n-type contact layer 13 on which the negative electrode 18 is formed. It is preferably formed in a position. When the first multilayer light reflection film 81 is formed on the substrate 11 side with respect to the horizontal plane of the n-type contact layer 13, the second n
Since the difference in refractive index between the type cladding layer 21 and the n-type contact layer 13 is small, the emitted light from the active layer 15 spreads into the n-type contact layer 13 located below the active layer 15. , Because it may not be possible to confine enough light. This is a phenomenon peculiar to a nitride semiconductor laser using an insulating substrate such as sapphire.

Now, at least one of the two kinds of nitride semiconductors constituting the multilayer light reflection films 81 and 82 contains a nitride semiconductor (for example, In _q Ga).
It is preferably _1-q N (where 0 <q <1) or GaN. This is because when a single layer is laminated to form a multilayer light reflecting film, one of the single layers is made of InGaN or Ga.
InGaN or GaN by being formed of N
This is because the layer can act as a buffer layer and prevent cracking of the other single layer. This is because the InGaN layer and GaN layer crystals are AlGa.
This is because it is softer than N. On the other hand, a multi-layered light-reflecting film is formed, for example, with Al having different Al compositions.
If the GaN layer is formed in multiple layers to have a total film thickness of, for example, 0.5 μm or more, cracks occur in the multilayer film, making it difficult to manufacture the device.

Two kinds of nitrides constituting each multilayer light reflection film
The best combination of semiconductor layers is one with I as described above.
n_cGa_1-cN or GaN, the other is Al
Nitride semiconductor containing minium and / or gallium
(For example, Al_cGa_1-cN (where 0 ≦ c <1))
There is something to form. In_qGa_1-qN and Al_cGa
_1-cSince there is a large difference in the refractive index from N, many of these materials
By constructing a layer light reflection film, it is possible to
It is possible to design a multilayer light reflecting film having a high emissivity. Also,
In_qGa_1-qSince N can act as a buffer layer,
Al_cGa_1-c10 layers or more without cracks in N layer
Can be overlaid. InN, GaN, and
And AlN have refractive indices of 2.9, 2.5, and
And 2.15. The refractive index of these mixed crystals is
Assuming that the law is followed, calculate as proportional to composition
be able to.

FIG. 9 is a schematic sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention, showing the structure as an LD device.

The nitride semiconductor light emitting device 90 shown in FIG.
The semiconductor layered structure has an active layer 95 and an n-type nitride semiconductor layer 94 and a p-type nitride semiconductor layer 96 that sandwich the active layer 95 on both sides. This semiconductor laminated structure is
Via the buffer layer 92 and the n-type contact layer 93,
It is provided on the substrate 91.

Similar to the active layer 15 in the semiconductor light emitting device 10 shown in FIG. 1, the active layer 95 includes a quantum well structure (single quantum well structure or multiple quantum well structure) including a nitride semiconductor containing indium and gallium. The above description of the active layer 15 also applies to the active layer 95 as it is.

The p-type nitride semiconductor layer 96 is formed on the first p-type cladding layer 96a formed directly in contact with the second main surface of the active layer 95 and on the first p-type cladding layer 96a. A second p-type cladding layer 96b.

The first p-type cladding layer 96a is formed of a p-type nitride semiconductor containing aluminum and gallium. When the first p-type cladding layer 96a is formed of a nitride semiconductor containing aluminum and gallium, the optical confinement in the active layer 95, which may be insufficient due to the quantum well structure, becomes more complete, and thus the first p-type cladding layer 96a is formed. p-type clad layer 95
Has been found to act as a good light guide layer for confining light in the active layer 95.

The first p-type cladding layer 96a is made of p-type Al.
Most preferably, it is formed of _d Ga _{1 -d} N (where 0 <d <1). This is because it is easy to obtain a p-type AlGaN having a high carrier concentration, and the band gap difference and the refractive index difference of the active layer 95 containing InGaN can be made larger than those of other nitride semiconductors. In addition, p-type AlGaN has a property of being less likely to be decomposed during growth as compared with other nitride semiconductors. For example, when the p-type AlGaN is grown by a metal organic vapor phase epitaxial growth method (MOVPE method), InGaN of the active layer 95 of
Is suppressed, and as a result, the active layer 95 having excellent crystallinity is provided, and thus the output of the light emitting device is improved.

The first p-type cladding layer 96a preferably has a thickness of 10 angstroms or more and 1.0 μm or less. If the thickness is less than 10 angstrom, the effect of providing the first p-type cladding layer cannot be obtained,
On the other hand, if the thickness is more than 1.0 μm, the first p-type cladding layer itself is likely to be cracked, which tends to make it difficult to manufacture the device. First p-type cladding layer 96
It is more preferable that a has a thickness of 10 angstroms or more and 0.5 μm or less.

The first p-type cladding layer 96a preferably has a thickness within the above range in general, including in the case of an LED element, but particularly in the case of an LD element, it is 100 angstroms or more (similarly. For that reason, it is more preferable to have a thickness of 1.0 μm or less). When the thickness is less than 100 angstrom, the first p-type cladding layer becomes difficult to act as an optical guide layer. In this case, the first p-type cladding layer 96a has a thickness of 10
Most preferably, it has a thickness of 0 angstrom or more and 0.5 μm or less.

The second p-type clad layer 96b provided on the first p-type clad layer 96a has a band gap larger than that of the first p-type clad layer 96a and has a p-type nitride semiconductor containing aluminum and gallium. Is formed by. The second p-type cladding layer 9 is made of such a p-type nitride semiconductor.
It was found that by forming 6b, the second cladding layer effectively acts as a light confining layer, and an effective LD element or the like can be provided.

The second p-type cladding layer 96b is also made of the first p-type cladding layer 96b.
As in the case of the type clad layer 96a, a p-type layer having a high carrier concentration is easily obtained, so that the ternary mixed crystal p-type A
Most preferably, it is formed of l _e Ga _1-e N (where 0 <e <1). In addition, the second p-type cladding layer 96b
When this is formed of p-type AlGaN, it is possible to increase the difference in band gap and the difference in refractive index with the first p-type cladding layer, so that it acts more effectively as an optical confinement layer. Become. The second p-type clad layer 96b has a larger bandgap than the first p-type clad layer 96a.
The value of f in _e Ga _{1 -e} N is the same as that of Al _d that constitutes the latter.
It takes a value larger than the value of e in Ga _1-d N. Even in this case, if possible, the d value and the e value in these formulas are preferably more than 0 and up to 0.6, and more preferably more than 0 and up to 0.4.

The thickness of the second p-type cladding layer 96b is not particularly limited, but is 500 angstroms or 1
It preferably has a thickness of about μm. By forming the second p-type clad layer with such a thickness, the number of cracks in the p-type AlGa layer itself is reduced, and therefore the crystallinity is better, and the p-type AlGa having a high carrier concentration is used.
Thus, the N layer is obtained.

The first p-type cladding layer 96a and the second p-type cladding layer 96b are both 1 × 10 ¹⁷
It can be provided as having a high carrier concentration of ˜1 × 10 ¹⁹ / cm ³ .

In addition, the first p-type cladding layer 96a and the second p-type cladding layer 96a
Layer of p-type InGaN or p-type GaN between the p-type clad 96b layer of
It may be formed to a thickness of up to μm. This layer acts as a light guide layer and a buffer layer.

The n-type cladding layer 94 provided in contact with the first main surface of the active layer 95 can be formed of any n-type nitride semiconductor. However, since the n-type clad layer 94 can be formed as a layer having more excellent crystallinity, it is preferable to form the n-type mixed crystal or ternary mixed crystal nitride semiconductor of GaN, AlGaN, InGaN, or the like. . In particular, by forming the n-type clad layer 94 of InGaN or GaN, a better active layer 95 can be provided thereon, and the output of the light emitting element is significantly improved.

In the case of an LD element, the n-type cladding layer 94 is preferably formed with a film thickness of 100 angstroms or more and 1 μm or less.

The substrate 91 is the same as the substrate 11 in the light emitting element 10 shown in FIG. 1, and the above description of the substrate 11 can be applied to this substrate 91 as it is.

Buffer layer 9 formed on substrate 92
2 is also the buffer layer 12 in the light emitting device 10 shown in FIG.
The above description of the buffer layer 12 can be applied to this buffer layer 12 as it is. Similarly, in a special case, the buffer layer 92 may be omitted.

The n-type contact layer 93 provided on the buffer layer 92 is also the n-type contact layer 93 in the light emitting element 10 shown in FIG.
The n-type contact layer 13 is similar to the n-type contact layer 13.
The same can be applied to 3 as it is.

The p-type contact layer 97 provided on the second p-type clad layer 96b is also the same as the p-type contact layer 17 in the light emitting device shown in FIG. The above description can be applied to the p-type contact layer 97 as it is.

The negative electrode 98 formed on the exposed surface of the n-type contact layer 93 is also the same as the negative electrode 18 in the light emitting element shown in FIG. 1, and the description of the negative electrode 18 is given above. Can be applied as is.

The positive electrode 99 provided so as to be connected to the p-type contact layer 97 is also the same as the positive electrode 19 in the light emitting element shown in FIG. 1. The positive electrode 19 is described above. Can be applied as is.
However, in the LD structure shown in FIG. 9, the current confinement layer 100 having a through hole 100a and made of an insulating material such as silicon dioxide is provided on the p-type contact layer 97, and the positive electrode 99 is The through hole 100 of the current constriction layer 100
It is in contact with the p-type contact layer 97 through a.

Although the present invention has been described with reference to FIG. 9 mainly with respect to the LD element, it is not necessary to provide the current confinement layer 100 in the case of the LED element. Also, LE
In the case of the D element, the second p-type clad layer 96b can be omitted. Furthermore, in the case of an LED element, n
The preferable thickness of the type cladding layer 94 is 10 angstroms or more and 1.0 μm or less, more preferably 30 angstroms or 1.0 μm, or the n-type cladding layer 94 itself can be omitted. When the n-type clad layer 94 is omitted, the n-type contact layer 93 can act as a clad layer. In the case of an LED element, in the structure shown in FIG. 9, the n-type clad layer 94 is omitted, the second p-type clad layer 96b is omitted, the current constriction layer 100 is also omitted, and the n-type contact layer is n. Type GaN and the p-type contact layer 97 formed of p-type GaN, that is, an active layer having a quantum well structure including a nitride semiconductor containing indium and gallium, and on a first main surface thereof. An n-type GaN layer was formed on the second main surface of the active layer, a p-type nitride semiconductor layer containing aluminum and gallium was formed on the second main surface, and a p-type GaN layer was formed on the p-type nitride semiconductor. The most preferable LED element structure is one having a structure. This corresponds to the nitride semiconductor light emitting device according to the present invention.

FIG. 10 is a schematic cross-sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention, and shows the structure as an LD device as in FIG.

The nitride semiconductor light emitting device 200 shown in FIG.
Is the active layer 95, and the n-type nitride semiconductor layer 294 and the p-type nitride semiconductor layer 2 sandwiching the active layer 95 on both sides.
It has a semiconductor laminated structure of 96. This semiconductor laminated structure is provided on the substrate 91 via the buffer layer 92 and the n-type contact layer 93.

The n-type nitride semiconductor layer 294 is the active layer 95.
Of the first n-type cladding layer 294a formed in direct contact with the first main surface of the
It includes a second n-type cladding layer 294b formed thereover.

The first n-type cladding layer 294a is made of n-type G
It is formed of an n-type nitride semiconductor containing aN or indium and gallium. Forming the first n-type cladding layer 294a from GaN or a nitride semiconductor containing indium and gallium results in more complete optical confinement in the active layer 95, which may be insufficient due to the quantum well structure. The first n-type clad layer 294a not only acts as a good light guide layer for confining light in the active layer 95 (in the case of an LD element), but also the first n-type clad layer as a buffer layer. It has been found that it is possible to reduce the occurrence of cracks in the active layer 95 formed thereon by acting to increase the light emission output of the light emitting device.

The first n-type cladding layer 294a is made of In _r
Most preferably, it is formed of Ga _1-r N (where 0 <r <1). In this case, the value of r is preferably 0.5, more preferably 0.3, and further preferably 0.2 for the same reason as above. Also, the carrier concentration is preferably 1 × 10 ¹⁸ / cm ³ to 1 × 10 ²⁰ / cm ³ for the same reason as above.

The first n-type cladding layer 294a preferably has a thickness of 10 Å or more. The first n-type clad layer 294a is formed to have a thickness of 10 angstroms or more, so that the first n-type clad layer 294a acts more effectively as a buffer layer between the active layer 95 and the second n-type clad layer 294b described later. . That is, the first n
InGa or Ga forming the clad layer 294a
Since the crystal of N is relatively soft, it is possible to more effectively absorb the strain caused by the lattice constant mismatch between the second n-type cladding layer 294b and the active layer 23 and the difference in thermal expansion coefficient. As a result, the buffer layer functions more effectively. As a result, even if the active layer 95 is sufficiently thin, the presence of the first n-type cladding layer 294a prevents the active layer 95 and the second n-type cladding layer 294 from being formed.
b, by extension, cracks are less likely to occur in the p-type cladding layer 296 and their crystallinity is improved, so that the light emission output of the light emitting element is further increased.

The first n-type cladding layer 294a is an LED
In the case of an element, it is preferable to have a thickness within the above range, but particularly in the case of an LD element, it is particularly preferable to have a thickness of 100 angstroms or more. When the thickness is less than 100 Å, it becomes difficult to act as the light guide layer.

Further, the first n-type cladding layer 294a is
In any case, it is preferable to have a thickness of 1.0 μm or less. When the thickness is thicker than 1.0 μm, the color of the crystal becomes blackish and a large number of pits tend to be formed in the crystal, so that a high power LED,
It can be difficult to obtain an LD element.

The second n-type cladding layer 294b provided in contact with the first n-type cladding layer 294a is made of any nitride semiconductor as long as the band gap is larger than that of the first n-type cladding layer 294a. May be, for example,
It can be formed of a binary semiconductor such as GaN or AlGaN, or a ternary mixed crystal nitride semiconductor. By forming the second n-type cladding layer 294b of such an n-type nitride semiconductor, the second n-type cladding layer 294b effectively acts as a light confining layer, and an effective LD element or the like is provided. I knew I could do it.

The second n-type cladding layer 294b is an n-type A
l_fGa_1-fN (where 0 <f <1)
Is most preferred. n-type AlGaN includes InGaN
Band gap and refractive index
The difference can be made larger than other nitride semiconductors.
is there. In this case, the value of f is the same as the above reason.
For the reason, it is preferable to take a value up to 0.6, and a value of 0.
It is more preferable to take a value up to 4. That career
The concentration is 5 × 10 for the same reason as above. ¹⁷/ Cm
³~ 1 x 10¹⁹/ Cm³Is preferred. Again
2 n-type clad layer 294b and n-type contact layer 93
By providing a layer made of n-type InGaN between
The second n-type clad layer made of AlGaN
Grows with crystallinity to reduce the occurrence of cracks
be able to.

The thickness of the second n-type cladding layer 294b is not particularly limited, but 500 angstroms or more,
It preferably has a thickness of 1.0 μm or less. By forming the second n-type cladding layer 294b to a thickness within this range, the second n-type clad layer 294b having no crack and excellent crystallinity is formed.
Thus, the mold clad layer 294b is obtained.

The p-type semiconductor layer (cladding layer) 296 provided in contact with the second main surface of the active layer 95 can be formed of any p-type nitride semiconductor. However, since the p-type clad layer 296 can be formed as a layer having more excellent crystallinity, it is preferable to form the p-type AlGaN. Compared to other nitride semiconductors, p-type AlGaN has a property of being less likely to be decomposed during growth. For example, when the p-type AlGaN is grown by a metal organic vapor phase epitaxy method (MOVPE method), a lower active layer is formed. The decomposition of InGaN in 95 is suppressed, and as a result, the active layer 95 having excellent crystallinity is provided, and thus the output of the light emitting device is improved. In this case, it is similarly preferable that the ratio of aluminum and the carrier concentration are set to values that are preferable for the first p-type cladding layer 96a and the second p-type cladding layer 96b in the light emitting device 90 shown in FIG. .

In the case of an LD element, the p-type clad layer 296 is preferably formed with a film thickness of 100 angstroms or more and 1 μm or less.

The active layer 95, the substrate 91, the buffer layer 92 formed on the substrate 91, the n-type contact layer 93 provided on the buffer layer 92, the p-type contact layer 97, the negative electrode 98, and the positive electrode. Electrode 99 and current constriction layer 1
00 is as described for the light emitting device shown in FIG.

Although the present invention has been described mainly with reference to FIG. 10 for the LD element, the current confinement layer 100 need not be provided in the case of an LED element. Also, L
In the case of an ED element, the second n-type cladding layer 294b can be omitted. In that case, the n-type contact layer 9
3 acts as a second n-type cladding layer.

FIG. 11 is a schematic cross-sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention, and shows the structure as an LD device as in FIGS. 9 and 10.

The nitride semiconductor light emitting device 300 shown in FIG.
Is the active layer 95, and the n-type nitride semiconductor layer 294 and the p-type nitride semiconductor layer 9 that sandwich the active layer 95 on both sides.
6 has a semiconductor laminated structure. This semiconductor laminated structure is provided on the substrate 91 via the buffer layer 92 and the n-type contact layer 93.

In the light emitting device 300 shown in FIG. 11, the n-type nitride semiconductor layer has the n-type nitride semiconductor layer 294 (the first n-type cladding layer 294a and the second n-type clad layer 294a) in the light-emitting device 200 shown in FIG. Clad layer 294b) and the p-type nitride semiconductor layer includes a p-type nitride semiconductor layer 96 (first p-type clad layer 96a and second p-type clad layer 96b) in the light emitting device 90 shown in FIG. Is applied and is one of the most preferable embodiments of the present invention. Regarding each semiconductor layer and other configurations, with reference to FIGS. 9 and 10, including the above description of the nitride semiconductor layer that can be omitted particularly in the case of an LED element and the thickness of the nitride semiconductor layer particularly in the case of an LED element. What is explained can be applied as it is, and no other words are necessary. Therefore, in the light emitting device shown in FIG. 11, the n-type contact layer 93 is made of n-type GaN, and the second n-type cladding layer 2 is formed.
94b is n-type AlGaN, and the first n-type cladding layer 29
4a is n-type InGaN or n-type GaN, the first p-type cladding layer 96a is p-type AlGaN, the second p-type cladding layer 96b is p-type AlGaN, and the p-type contact layer 9 is formed.
Most preferably, the active layers 95 are formed of p-type GaN and the active layer 95 is non-doped. Note that L shown in FIG.
In the case of the D element structure, it goes without saying that the first n-type cladding layer 294a is the optical guide layer and the second cladding layer 29.
It is also apparent that 4b acts as an optical confinement layer, the first p-type cladding layer 96a acts as an optical guide layer, and the second p-type cladding layer 96b acts as an optical confinement layer. A layer made of p-type InGaN or p-type GaN may be formed as a buffer layer between the first p-type clad layer 96a and the second p-type clad layer 96b, or the n-type contact layer 93 may be formed.
Between the n-type InG and the second n-type cladding layer 294b.
You may form the layer which consists of aN as a buffer layer.

Further, according to the present invention, an active layer having a quantum well structure including a nitride semiconductor containing indium and gallium is provided between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer, The p-type nitride semiconductor layer includes a first p-type cladding layer formed in contact with the active layer and made of a p-type nitride semiconductor containing aluminum and gallium, and the first p-type cladding layer has a thickness of 10 angstroms or more. Provided is a nitride semiconductor light emitting device having a thickness of 1.0 μm or less.

This light emitting device basically corresponds to a special case in which the second p-type cladding layer 96b is omitted from the structure of the light emitting device 90 shown in FIG. In this special case,
Further, one of the n-type contact layer 93 and the n-type cladding layer 94 may be omitted from the structure of the light emitting device shown in FIG. 9 (when the n-type cladding layer 94 is omitted,
The n-type contact layer 93 acts as an n-type clad layer), and the p-type contact layer 97 may be omitted.

Furthermore, in this special case, the second p-type cladding layer 96b in the light emitting device 90 shown in FIG. 9 is used.
The second p-type cladding layer corresponding to can be formed of p-type GaN or a p-type nitride semiconductor (preferably InGaN) containing indium and gallium, for which the light emitting device 10 shown in FIG. The description of the n-type clad layer 14 can be applied. Furthermore, in contact with the n-type cladding layer (first n-type semiconductor layer) corresponding to the n-type cladding layer 94 in the light emitting device 90 shown in FIG. 9, that is, the first n-type cladding layer 94 and the n-type contact layer. 9
3 and n-type GaN or a second n-type nitride semiconductor containing aluminum and gallium (preferably AlG).
It is also preferable to provide aN). For this case,
The description of the second n-type cladding layer 21 in the light-emitting element 20 shown in FIG. 2 including the n-type GaN layer can be applied.

FIG. 12 is a schematic sectional view showing the structure of one form of the nitride semiconductor light emitting device according to the present invention, and shows one of the structures particularly preferable as the LD device. 12
It can be said that the nitride semiconductor light emitting device of 1) substantially corresponds to the preferable form described with reference to FIG. 6 except for the first p-type cladding layer described below.

A nitride semiconductor light emitting device 400 shown in FIG.
Comprises an active layer 405, on the first major surface of which a first
N-type clad layer 414 and second n-type clad layer 424
And an n-type semiconductor layer including the n-type contact layer 403. In addition, the first main surface of the active layer 405 has a first p-type cladding layer 416, a second p-type cladding layer 426, a third p-type cladding layer 436, and a p-type contact as the outermost layer. It has a p-type nitride semiconductor layer including the layer 407. In the structure shown in FIG. 12, such a laminated structure is provided on the substrate 401 via the buffer layer 402.

The active layer 405 contains a nitride semiconductor containing indium and gallium, and has a structure which causes interquantum level emission of the nitride semiconductor containing indium and gallium, in other words, a quantum well structure. Make up. For such a structure, the light emitting device 1 shown in FIG.
All the explanations regarding the active layer 0 of 0 apply as is. In the case of the LD element, it is most preferable that the active layer 405 has a multiple quantum well structure.

The first n-type cladding layer 414 provided in contact with the first main surface of the active layer 405 functions as an optical guide layer, and n containing indium and gallium.
Type nitride semiconductor or n-type GaN. More specifically, the first n-type cladding layer 54 is formed of n-type In _y Ga _1-y N (where 0 ≦ y <1). That is, the first n-type cladding layer 414 is the same as the first n-type cladding layer 1 in the light emitting device 10 shown in FIG.
It may be formed of n-type InGaN described in No. 4 or n-type GaN. For the same reason as that described for the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. 1, the value of y is 0 ≦ y.
It is preferably in the range of ≦ 0.5, more preferably 0 <y ≦ 0.3, and most preferably 0 <y ≦ 0.2. For the same reason, the carrier concentration of the first n-type cladding layer 414 is also 1 × 10 ¹⁸ / cm ³ to 1 × 1.
It is desirable to be in the range of 0 ²⁰ / cm ³ . First n
The type clad layer 414 is also not particularly limited in its thickness,
For the same reason, the active layer 15 and the first n-type cladding layer 4 are
It is desirable that 14 has a total thickness of 300 angstroms or more, and can have a thickness of 1 μm or less.

The second n-type clad layer 424 provided on the first n-type clad layer acts as an optical confinement layer and has a larger bandgap than the first n-type clad layer 414. And an n-type nitride semiconductor containing aluminum and gallium or n-type GaN. By providing such a second n-type cladding layer 424, it is possible to increase the band gap difference between the second n-type cladding layer 424 and the first n-type cladding layer 414 and improve the light emission efficiency of the light emitting element.

When the second n-type cladding layer 424 is formed of n-type Al _g Ga _{1 -g} N (where 0 <g <1), the value of g is 0 <g ≦ 0. It is preferably in the range of 0.6. The crystal of AlGaN is relatively hard, and
When it is larger than 6, cracks are relatively likely to occur in the first n-type cladding layer 414 despite the existence of the first n-type cladding layer 414, and the emission output tends to be reduced. g
Most preferably, the value is in the range 0 <g ≦ 0.4.

The carrier concentration of the second n-type cladding layer 424 is 5 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ^3.
It is desirable to be within the range. The carrier concentration is 5
If it is lower than × 10 ¹⁷ / cm ³ , the resistivity of AlGaN is particularly high, so that the Vf of the light emitting element tends to be high and the light emission efficiency tends to be low, while the carrier concentration thereof is 1 or less.
This is because if it is higher than × 10 ¹⁹ / cm ³ , the crystallinity of AlGaN is deteriorated and the luminous efficiency is lowered.

The second n-type cladding layer 424 is usually 5
It can be formed with a thickness of 0 angstrom to 0.5 μm.

It is formed as the outermost layer of the n-type semiconductor layer (layer located farthest from the active layer) (in FIG. 12,
(Formed in contact with the second n-type cladding layer 424)
The n-type contact layer 403 is made of n-type GaN. The n-type contact layer 13 in the light emitting device 10 of FIG.
For the same reason that it is preferable to form the n-type GaN, the n-type contact layer 403 is made of n-type GaN.
Is formed by. It is similarly preferable that the other carrier concentrations are the concentrations described as being preferable for the n-type contact layer 13 in the light emitting device 10 shown in FIG.

The first p-type clad layer 416 provided in contact with the second main surface of the active layer 405 functions as a cap layer, and the first p-type clad layer 416 in the other embodiments described so far. Similar to the p-type cladding layer, the active layer is prevented from being decomposed to improve the light emission output of the light emitting device. The first p-type cladding layer 416 is formed of a p-type nitride semiconductor containing aluminum and gallium.
It has been found that by providing such a first p-type cladding layer 416, a more excellent LD element can be provided.

The first p-type cladding layer 416 is preferably p-type Al _h Ga _{1 -h} N (where 0 <h <1).
Is formed by. In this case, the value of h is 0 <h ≦
It is preferably in the range of 0.6. This is because the crystal of AlGaN is relatively hard, cracks are likely to occur in the layer, and the emission output tends to be reduced. Most preferably, the h value is within the range of 0 <h ≦ 0.4.

The carrier concentration of the first p-type cladding layer 416 is 1 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ^3.
It is desirable to be within the range. The carrier concentration is 1
If it is lower than × 10 ¹⁷ / cm ^{3, the} efficiency of injecting holes into the active layer 405 tends to decrease, and the luminous efficiency tends to decrease.
On the other hand, if the carrier concentration is higher than 1 × 10 ¹⁹ / cm ³ , the crystallinity of AlGaN is deteriorated and the luminous efficiency is reduced.

The first p-type clad layer 416 is usually 5
It can be formed with a thickness of 0 angstrom to 0.5 μm.

Provided on the first p-type cladding layer 416
The second p-type clad layer 426 serving as an optical guide layer
Acting as a p-type nitride half containing indium and gallium
It is formed of a conductor or p-type GaN. More specifically
Is the first p-type cladding layer 416 is p-type In_zGa
_1-zN (where 0 ≦ z <1) is desirable.
Yes. First p-type cladding layer in the light emitting device 30 of FIG.
For the same reason as described for 36, the z value is
It is preferable that 0 ≦ z ≦ 0.5, and
It is preferably within the range of 0 ≦ z ≦ 0.3, and most preferably 0.
It is within the range of ≦ z ≦ 0.2. This first p-type cladding
Similarly, the layer 416 may also be formed of GaN so that it is a buffer.
Similarly acts as a layer. In addition, this first p-type class
For the same reason, the carrier concentration of the dead layer 416 is 1 ×.
10¹⁷/ Cm³~ 1 x 10¹⁹/ Cm ³Within the range of
And is desirable. Further, the thickness of the first cladding layer 416
Is not particularly limited, but for the same reason as the active layer 405,
Has a total thickness of 300 angstroms or more
Desirably, it may have a thickness of 1 μm or less.

The third p-type clad layer 436 provided on the second p-type clad layer 426 acts as an optical confinement layer, has a larger band gap than the second p-type clad layer 426, and It is formed of a p-type nitride semiconductor containing aluminum and gallium. Such a third
By providing the p-type clad layer 436, the band gap difference with the second p-type clad layer 426 can be increased, and the light emission efficiency of the light emitting element can be improved.

The third p-type cladding layer 436 is preferably p-type Al _i Ga _{1 -i} N (where 0 <i <1).
Is formed by. In this case, the value of i is 0 <i ≦
It is preferably in the range of 0.6. If the crystal of AlGaN is relatively hard and is larger than 0.6, cracks are relatively likely to occur in the second p-type cladding layer 426 despite the existence of the second p-type cladding layer 426, and the emission output tends to be reduced. Because there is. Most preferably, the b value is within the range of 0 <b ≦ 0.4.

The carrier concentration of the third p-type cladding layer 436 is 1 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ^3.
It is desirable to be within the range. The carrier concentration is 1
If it is lower than × 10 ¹⁷ / cm ^{3, the} efficiency of injecting holes into the active layer 405 tends to decrease, and the luminous efficiency tends to decrease.
On the other hand, if the carrier concentration is higher than 1 × 10 ¹⁹ / cm ³ , the crystallinity of AlGaN is deteriorated and the luminous efficiency is reduced. The third p-type cladding layer 436 is typically 5
It can be formed with a thickness of 0 angstrom to 0.5 μm.

It is formed as the outermost layer of the p-type semiconductor layer (layer located farthest from the active layer 405) (FIG. 12).
Then, the p-type contact layer 407 (provided in contact with the third p-type cladding layer 436) is formed of p-type GaN. The p-type contact layer 407 is formed of p-type GaN for the same reason as that the p-type contact layer 17 in the light emitting device 10 of FIG. 1 is preferably formed of p-type GaN. For example, the carrier concentration is
The p-type contact layer 17 in the light emitting device 10 shown in FIG.
It is likewise preferred to have the concentrations stated as being preferred in the case of.

Substrate 401, buffer layer 402, negative electrode 4
08 and the positive electrode 409 are the substrate 11, the buffer layer 12, and the negative electrode 1 in the light emitting device 10 shown in FIG. 1, respectively.
8 and the positive electrode 19 are as described above. Further, regarding the current confinement layer 440 having the through hole 440a, the current confinement layer 1 in the light emitting device 90 shown in FIG.
00 is as described above.

Furthermore, according to the present invention, the first and second
An active layer having a quantum well structure having a main surface of a nitride semiconductor containing indium and gallium, an n-type nitride semiconductor layer provided on the first main surface of the active layer, and the active layer. A semiconductor laminated structure having a p-type nitride semiconductor layer provided on the second main surface of
A first p-type layer formed in contact with the second main surface of the active layer and made of a p-type nitride semiconductor containing aluminum and gallium, and a p provided in contact with the first p-type layer. Provided is a nitride semiconductor light emitting device including a second p-type layer made of type GaN. The light emitting device according to this embodiment is a special light emitting device in which the second p-type cladding layer 96b and the n-type cladding layer 94 are omitted from the structure of the light-emitting device 90 shown in FIG. That is the case. In this case, the n-type contact layer 93 can most preferably be formed of n-type GaN.

FIG. 13 shows various nitride semiconductor light emitting devices of the present invention prepared by changing the thickness of the well layer of the active layer of the quantum well structure, and showing the emission output (relative value) and the thickness of the well layer. The result of examining the relationship is shown in a graph. As can be seen from FIG. 13, when the well layer thickness of the active layer of the quantum well structure in the nitride semiconductor light emitting device of the present invention is 70 angstroms or less, the light emission output of the light emitting device is remarkably improved. It can also be seen that when the thickness of the well layer is 50 Å or less, the light emission output of the light emitting element is further improved. Such a tendency is not only confirmed in the active layer having a single quantum well structure and the active layer having a multiple quantum well structure in all the nitride semiconductor light emitting devices of the present invention, but it is widely used. It was also confirmed that one of the two sandwiched clad layers was formed of a p-type nitride semiconductor and the other was formed of an n-type nitride semiconductor.

Therefore, according to the present invention, a quantum well having at least one well layer containing a nitride semiconductor containing indium and gallium between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer. The active layer of the structure is provided, and the well layer is
Provided is a nitride semiconductor light emitting device having a thickness of 70 Å or less.

FIG. 14 shows various nitride semiconductor light emitting devices of the present invention manufactured by changing the thickness of the barrier layer while keeping the thickness of the well layer of the active layer of the multiple quantum well structure constant, and the emission output ( The results of examining the relationship between the relative value) and the thickness of the barrier layer are shown as a graph. As can be seen from FIG.
It can be seen that when the barrier layer of the active layer of the quantum well structure in the nitride semiconductor light emitting device of the present invention has a thickness of 150 Å or less, the light emission output of the light emitting device is significantly improved. It can also be seen that when the thickness of the barrier layer is 100 angstroms or less, the light emission output of the light emitting device is further improved. This tendency has not only been confirmed for all the nitride semiconductor light emitting devices of the present invention, but it is widely known that one of the two clad layers sandwiching the active layer is made of a p-type nitride semiconductor and the other is an n-type. It was also confirmed when it was formed of a nitride semiconductor.

FIG. 15 shows a light emitting device having a structure similar to that shown in FIG. 9 when the thickness of the first p-type cladding layer 96a is changed and the light emission output (relative value).
It is a graph which shows the relationship with. More specifically, FIG. 15 shows an n-type GaN contact layer 93 having a thickness of 4 μm on the sapphire substrate 91 via a GaN buffer layer 92 in the structure shown in FIG.
To a thickness of 500 angstroms, an InGaN active layer 95 having a single quantum well structure is formed to a thickness of 20 angstroms, and a first p-type AlGaN cladding layer 9 is formed thereon.
6a with different thicknesses, a second p-type AlGaN cladding layer 96b with a thickness of 0.1 μm, and a p-type GaN contact layer 97 with a thickness of 1 μm. This is an LED element in which the electrode 98 is formed and the positive electrode 99 is formed without providing the current constriction layer 100.

As shown in FIG. 15, when the thickness of the first p-type cladding layer 96a becomes thicker than 1 μm, the light emission output tends to sharply decrease. This is because such a thickness causes cracks in the first p-type cladding layer 96a and deteriorates the crystallinity of the device. From FIG. 15, L
In the case of an ED element, the film thickness of the first p-type cladding layer 96a is 10 angstroms (0.001 μm) or more, 1
It can be seen that a thickness of μm or less is preferable. Such a tendency has been confirmed for all the nitride semiconductor light emitting devices according to other embodiments of the present invention in which the first p-type cladding layer is formed of AlGaN. In the case of the LD element, the preferable thickness of the first p-type cladding layer is 100 angstroms or more for another reason as described above.

FIG. 16 shows a first n-type cladding layer 294a for a light emitting device having a structure similar to that shown in FIG.
5 is a graph showing the relationship between the thickness and the light emission output (relative value) when the thickness is changed. More specifically, FIG. 16 shows the sapphire substrate 9 in the structure shown in FIG.
N-type GaN contact layer 93 with a thickness of 4 μm and second n-type AlGaN clad layer 294b with a thickness of 0.1 μm on GaN buffer layer 92 to form a first n-type InGaN clad. The layer 294a is formed with a different thickness, and an InGaN active layer 95 having a single quantum well structure is formed on the layer 294a to a thickness of 20 angstroms and p-type AlG is formed.
This is an LED element in which the aN clad layer 296 is formed to a thickness of 0.1 μm, the negative electrode 98 is formed, and the positive electrode 99 is formed without providing the current constriction layer 100.

As can be seen from FIG. 16, when the thickness of the first n-type cladding layer 294a becomes thicker than 1 μm, the light emission output tends to decrease sharply. This is because the crystallinity of the first n-type cladding layer 294a itself is deteriorated, for example, the crystal becomes black or pits are generated. Also the first
Even if the thickness of the n-type clad layer 294a is smaller than 30 angstrom, the light emission output tends to decrease. This is the first n-type cladding layer 2 made of InGaN.
It is shown that the preferable film thickness of 94a which effectively acts as a buffer layer is 30 angstroms or more. Such a tendency is that the first n-type cladding layer is made of InG.
All of the other nitride semiconductor light emitting devices of the present invention formed of aN or GaN have been confirmed. Note that, as described above, the first n-type cladding layer 294a has a thickness of 1
When the thickness is less than 0 angstrom, it does not act as a buffer layer and many cracks are generated in the active layer 95 and the clad layers 294b and 296 formed on the buffer layer, which makes it difficult to manufacture the device and significantly reduces the light emission output. To do.

In the present invention, the nitride semiconductor is
Both of them show n-type even when grown without being doped with a donor impurity, but most preferably, they are doped with a donor impurity such as Si, Ge, Te, and S during crystal growth of a nitride semiconductor. The carrier concentration of the n-type nitride semiconductor layer can be adjusted by adjusting the donor impurity concentration.

In the present invention, the p-type nitride semiconductor layer is made of Mg, Z during the crystal growth of the nitride semiconductor.
It is obtained by doping acceptor impurities such as n, Cd, Ca, Be and C during the crystal growth of the nitride semiconductor. A more preferable p-type nitride semiconductor layer is obtained by annealing the nitride semiconductor layer grown by doping with the acceptor impurity as described above at a temperature of 400 ° C. or higher. By adjusting the concentration of the acceptor impurities, the carrier concentration of the p-type nitride semiconductor layer can be adjusted.

The nitride semiconductor light emitting device of the present invention uses a vapor phase growth method such as MOVPE (metal organic chemical vapor deposition), MBE (molecular beam vapor phase epitaxy), HDVPE (hydride vapor phase epitaxy). Then, it can be preferably manufactured by forming each nitride semiconductor layer on the substrate. For example, a nitride semiconductor source such as an organic indium compound, an organic gallium compound, an organic aluminum compound, or ammonia is used, and if necessary, an impurity source is also used.
Each nitride semiconductor layer is formed on the substrate by the E method, and the positive electrode and the negative electrode are formed to manufacture the nitride semiconductor light emitting device of the present invention.

Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to these. For example, the current confinement layer 100 in FIG. 9 can be applied to the semiconductor light emitting device of the present invention when it is used as an LD device. The description regarding the ratio of indium and the carrier concentration for one n-type or p-type InGaN layer also applies to other n-type or p-type InGaN layers as well.
It will be apparent that the discussion of aluminum ratios and carrier concentrations for layers applies to other n-type or p-type AlGaN layers as well. In addition,
As is clear from the above description, the main surface means the surface of the nitride semiconductor layer (specifically, the active layer) on which other layers are formed.

[0154]

EXAMPLES The present invention will be described below based on examples. In the following examples, all nitride semiconductor layers are grown by the MOVPE method.

Example 1 First, using TMG (trimethylgallium) and NH ₃ as source gases, a GaN buffer layer of 500 was formed at 500 ° C. on the C surface of a sapphire substrate set in a reaction vessel.
It was grown to a thickness of Angstrom.

Next, the temperature was raised to 1050 ° C. and TMG was added.
NH₃Silane gas is added to the above raw material gas consisting of
An n-type contact layer made of doped n-type GaN having a thickness of 4 μm
Grow to thickness. Electronic carrier of this n-type contact layer
A concentration is 2 × 10¹⁹/ Cm ³Met.

Subsequently, TMA (trimethylaluminum) was further added to the above-mentioned source gas, and S at the same temperature of 1050 ° C.
A second n-type cladding layer composed of an i-doped n-type Al _0.3 Ga _0.7 N layer was grown to a thickness of 0.1 μm. This second
N-type cladding layer has an electron carrier concentration of 1 × 10 ¹⁹ / c
It was m ³ .

Next, the temperature is lowered to 800 ° C., and TMG, TMI (trimethylindium), and NH _{3 are used} as source gases.
And silane gas, Si-doped n-type In _0.01 Ga
_A first n-type cladding layer of _0.99 N was grown to a thickness of 500 Å. The electron carrier concentration of this first n-type cladding layer was 5 × 10 ¹⁸ / cm ³ .

Then, using TMG, TMI and NH ₃ as source gases, undoped In _0.05 Ga at 800 ° C.
_0.95 N was grown to a thickness of 30 Å to form an active layer having a single quantum well structure.

Next, the temperature was raised to 1050 ° C., and TMG, TMA, NH ₃ and Cp ₂ Mg (cyclopentadienyl magnesium) were used as source gases, and Mg-doped p
A second p-type clad layer of type Al _0.3 Ga _0.7 N was grown to a thickness of 0.1 μm. The hole carrier concentration of this second p-type cladding layer was 1 × 10 ¹⁸ / cm ³ .

Then, using TMG, NH ₃ and Cp ₂ Mg as source gases, Mg-doped p-type G at 1050 ° C.
A p-type contact layer made of aN was grown to a thickness of 0.5 μm. The hole carrier concentration of this p-type contact layer was 5 × 10 ¹⁹ / cm ³ .

Thereafter, the temperature was lowered to room temperature, the wafer was taken out of the reaction vessel, and the wafer was annealed at 700 ° C. to further reduce the resistance of each p-type layer. Next, a mask having a predetermined shape was formed on the surface of the uppermost p-type contact layer, and etching was performed until the surface of the n-type contact layer was exposed. A negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer, and a positive electrode made of Ni and Au was formed on the surface of the p-type contact layer.

After the electrodes were formed, the wafer was separated into chips of 350 μm square, and an LED element having a directional characteristic of a half-value angle of 15 ° was prepared by a conventional method. This LED device has Vf (forward voltage) of 3.5 at If (forward current) of 20 mA.
V, blue emission having an emission peak wavelength of 415 nm was exhibited, and the emission output was 6 mW. In addition, the full width at half maximum of the emission spectrum was 20 nm, and the emission showed very good color purity.

Example 2 After growing up to a second n-type clad layer made of a Si-doped n-type Al _0.3 Ga _0.7 N layer on a sapphire substrate in the same manner as in Example 1, the second clad layer was formed. Example 1
Under the same conditions as above, non-doped In _0.05 Ga _0.95 N was _added to 40
An active layer having a single quantum well structure was formed by growing the film to a thickness of angstrom.

Next, TM is used as a source gas on the active layer.
800 ° C. using G, TMI, NH ₃ and Cp ₂ Mg
Then, a first p-type clad layer made of Mg-doped p-type In _0.01 Ga _0.99 N was grown to a thickness of 500 Å. The hole carrier concentration after annealing of the first p-type layer was 2 × 10 ¹⁷ / cm ³ .

A desired LED element was obtained in the same manner as in Example 1 except for the subsequent growth of the second p-type cladding layer and p-type contact layer. This LED element is If20mA
, Vf3.5V, emission peak wavelength 410 nm,
The full width at half maximum of the emission spectrum is 20 nm, and the emission output is 5
It was mW.

Example 3 In the same manner as in Example 1, the Si substrate was placed on the sapphire substrate.
N-type In_0.01Ga _0.99First n-type crack consisting of N
On the first n-type cladding layer after the growth of the first n-type cladding layer.
Undoped In_0.05Ga_0.95N 40 angstroms
To form a single quantum well structure active layer.
I made it.

Then, TMG, TMI, and
A first p-type cladding layer of Mg-doped p-type In _0.01 Ga _0.99 N was grown to a thickness of 500 Å at 800 ° C. using NH ₃ and Cp ₂ Mg. The hole carrier concentration after annealing of the first p-type cladding layer was 2 × 10 ¹⁷ / cm ³ .

Then, in the same manner as in Example 1, the first p-type
Mg-doped p-type Al on the clad layer _0.3Ga_0.7From N
Growing a second p-type cladding layer on which
Growth of p-type contact layer made of Mg-doped p-type GaN
Let Then, in the same manner as in Example 1, the desired LED
The device was obtained. This LED element is Vf at If 20mA
3.5V, emission peak wavelength 410nm, emission spectrum
The full width at half maximum was 20 nm and the emission output was 6 mW.

Example 4 In the same manner as in Example 1, the Si substrate was placed on the sapphire substrate.
N-type Al_0.3Ga _0.7Second n-type class consisting of N layers
Of the second n-type cladding layer
On top, a first n-type cladding made of Si-doped n-type GaN
Layer was grown to a thickness of 500 Angstroms. This
The electron carrier concentration of the first n-type cladding layer is 2 × 10
¹⁹/ Cm³Met.

[0171] Next, on the first n-type cladding layer 55 in the same manner as in Example 3, a non-doped In _{0. 05} Ga _0.95 N 40
An active layer having a single quantum well structure was formed by growing the film to a thickness of angstrom.

[0172] Next, on the active layer, in the same manner as in Example 1, second p-type cladding layer and a p-type consisting of Mg-doped p-type GaN composed of Mg-doped p-type Al _0.3 Ga _{0. 7} N Contact layers were grown sequentially. After this, an LED element was obtained in the same manner as in Example 1. This LED element is If2
Vf3.5V at 0 mA, emission peak wavelength 415 nm, half-value width of emission spectrum 20 nm, emission output 5 m
It was W.

Example 5 Example 1 was repeated except that the active layer was formed of In _0.2 Ga _0.8 N.
An LED element was produced in the same manner as in. This LED element exhibited blue light emission of Vf3.5V, emission peak wavelength of 455 nm, and full width at half maximum of 20 nm at If20 mA, and the emission output was 5 mW.

Example 6 This example was performed in the same manner as in Example 1 except that the active layer was formed. That is, in this example, in order to form the active layer, TMG, TMI and NH ₃ were used as source gases, and a non-doped In _0.1 Ga _0.9 N thin film (well layer) was grown to a thickness of 20 Å at 800 ° C. Let Then, an In _0.02 Ga _0.98 N thin film (barrier layer) was applied to
It was grown to Angstrom thickness. This operation is alternately repeated three times, and finally, In _0.1 Ga _0.9 N
A thin film (barrier layer) was grown to a thickness of 20 Å to form an active layer having a multiple quantum well structure with a total thickness of 140 Å. The LED element thus obtained is
At If20 mA, blue light emission with Vf3.5 V and an emission peak wavelength of 420 nm was exhibited, and the light emission output was 7 mW.

Example 7 InZ having a single quantum well structure in which DEZ (diethyl zinc) was used as an acceptor impurity source, silane gas was used as a donor impurity, and Si and Zn were doped as an active layer.
An LED element was produced in the same manner as in Example 1 except that the _0.05 Ga _0.95 N layer was formed to a thickness of 50 Å. This LED element has Vf3.
5 V, emission peak wavelength 450 nm, full width at half maximum 70 nm, blue emission was shown, and emission output was 3 mW.

Example 8 According to the method of Example 1, a Si
N-type In_0.01Ga _0.99First n-type crack consisting of N
Layer, undoped In_0.05Ga_0.95An active layer made of N,
Mg-doped p-type Al_0.3Ga_0.7Second p-type consisting of N
P-type composed of clad layer and Mg-doped p-type GaN
The contact layer was grown. That is, the second n-type class
L was formed in the same manner as in Example 1 except that the dead layer was not formed.
An ED element was obtained. This LED element is rated at If 20mA.
And Vf3.5V, emission peak wavelength 410nm, emission
The output was 5 mW.

Example 9 After growing each semiconductor layer up to the n-type contact layer on a sapphire substrate in the same manner as in Example 1, the temperature was raised to 8.
The temperature was lowered to 00 ° C, and TMG, TMI, NH _{3 were used} as source gases
And silane gas, Si-doped n-type In _0.01 Ga
_A thin film of _0.99 N was grown to a thickness of 380 Å. Next, the temperature was raised to 1050 ° C., and TMG, TMA, NH ₃ and silane gas were used as source gases, and a thin film made of Si-doped n-type Al _0.2 Ga _0.8 N was grown to a thickness of 390 Å. These operations were repeated 20 times to obtain Si-doped n-type In _0.01 Ga
_0.99 N layers and Si-doped Al _0.2 Ga _0.8 N layers alternately 1
An n-type multilayer film (first multilayer reflective film) was formed by stacking 0 layers each.

Next, on the n-type multilayer film, in the same manner as in Example 3, the second n-type cladding layer, the first n-type cladding layer, and
An active layer, a first p-type clad layer, and a second p-type clad layer were sequentially grown.

Next, the temperature is set to 800 ° C. and the raw material gas is
TMG, TMI, NH₃And Cp₂For Mg
Mg-doped p-type In on the second p-type cladding layer_0.01
Ga _0.99N layer grown to a thickness of 380 Å
Then, the temperature was raised to 1050 ° C and TM was used as a raw material gas.
G, TMA, NH₃And Cp₂Using Mg gas, Mg
Doped p-type Al_0.2Ga_0.8N layer is 390 angstrom
It was grown to the thickness of the dome. Repeat these operations, M
g-doped p-type In_0.01Ga_0.99N layer and Mg-doped p-type A
l_0.2Ga_0.8P-type with 10 layers alternately stacked with N layers
A multilayer film (second multilayer reflective film) was formed.

Then, a p-type contact layer was grown on the p-type multilayer film in the same manner as in Example 1.

With respect to the wafer thus obtained, after etching the nitride semiconductor layer in the same manner as in Example 1,
A mask having a predetermined shape is formed on the surface of the uppermost p-type contact layer, and a negative electrode having a width of 50 μm is formed on the n-type contact layer and a positive electrode having a width of 10 μm is formed on the p-type contact layer. did. When the n-type multilayer film is formed on the n-type contact layer in this manner, the horizontal plane forming the negative electrode is n
Lower than the mold multilayer film, that is, the substrate side.

Next, the surface of the sapphire substrate on which the nitride semiconductor layer is not formed is polished to have a substrate thickness of 90 μm, and the M surface of the sapphire substrate surface (corresponding to the side surface of the hexagonal column in the hexagonal system). Scribe). After scribing, the wafer was divided into chips of 700 μm square to produce stripe type LD elements. This LD element has a nitride semiconductor layer surface orthogonal to the stripe-shaped positive electrode as an optical resonance surface. The surface of this LD element is covered with an insulating film (not shown) made of SiO ₂ except the surface of each electrode. Next, when this chip was placed on a heat sink and each electrode was wire-bonded, laser oscillation was attempted at room temperature, and the threshold current density was 1.5 kA / cm ²
It was confirmed that laser oscillation with an oscillation wavelength of 390 nm was carried out.

Example 10 First, TMG and NH ₃ were used as source gases, and the C plane of the sapphire substrate set in the reaction vessel was heated at 500 ° C.
A buffer layer made of GaN was grown to a thickness of 200 Å.

Next, the temperature is raised to 1050 ° C. and TMG is added.
Silane gas was added to the source gases of NH ₃ and NH ₃ to grow an n-type contact layer of Si-doped n-type GaN to a thickness of 4 μm.

Then, the temperature is lowered to 800 ° C., TMI is further added to the above source gas, and Si-doped n-type In _0.05 G
A first n-type cladding layer consisting of an a _0.95 N layer was grown to a thickness of 500 Å.

Subsequently, at 800 ° C., non-doped In _0.2 Ga _0.8 N was grown to a thickness of 20 Å on the first n-type cladding layer to form an active layer having a single quantum well structure.

Next, the temperature was raised to 1050 ° C., and TMG, TMA, NH ₃ and Cp ₂ Mg were used as source gases, and the first p-type clad layer made of Mg-doped p-type Al _0.1 Ga _0.9 N was made to have a thickness of 0. It was grown to a thickness of 1 μm.

Subsequently, at 1050 ° C., Mg-doped p-type A
The second p-type clad layer made of _0.3 Ga _0.7 N was added to _0.2 .
It was grown to a thickness of 5 μm.

Subsequently, at 1050 ° C., Mg-doped GaN
Was grown to a thickness of 1.0 μm.

After the reaction was completed, the temperature was lowered to room temperature, the wafer was taken out of the reaction vessel, and the wafer was annealed at 700 ° C. to further reduce the resistance of the p-type layer. Next, etching was performed from the uppermost p-type contact layer until the surface of the n-type contact layer was exposed. After etching, p
A layer of SiO ₂ is deposited on the surface of the type contact layer, and a through hole is formed in this to form a current confinement layer. Further, Ni and A which are connected to the p type contact layer through the through hole on the current confinement layer.
A positive electrode made of u was formed. A negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer.

Next, the surface of the sapphire substrate on which the nitride semiconductor layer is not formed is polished to a substrate thickness of 90 μm, and the M surface of the sapphire substrate is scribed to forcibly cleave the laser chip. Obtained. After providing a dielectric multilayer film on the cleaved surface, the chip was placed on a heat sink and laser oscillation was attempted at room temperature. The threshold current density was 2.0 kA.
Laser emission with an oscillation wavelength of 450 nm was confirmed at / cm ² .

Example 11 In the same manner as in Example 10, a GaN buffer layer was formed on a sapphire substrate to a thickness of 200 Å, and n-type Ga was formed.
An n-type contact layer made of N was sequentially formed to a thickness of 4 μm.

Next, Si-doped n-type Al _0.3 Ga _0.7 N
After forming the second n-type clad layer of 0.5 μm in thickness, the first n-type clad layer 71 of Si-doped n-type In _0.05 Ga _0.95 N was formed to a thickness of 500 Å.

Next, 20% of undoped In _0.2 Ga _0.8 N is added.
An active layer having a single quantum well structure is formed by growing to a thickness of angstrom, and Mg-doped p-type Al _0.3 G is formed on the active layer.
a second p-type cladding layer made of a _{0. 7} N to a thickness of 0.5 [mu] m, then forming a p-type contact layer made of Mg-doped p-type GaN to a thickness of 1 [mu] m.

After that, when the laser oscillation of the obtained LD element was tried in the same manner as in Example 10, it was confirmed that the laser oscillation with the threshold current density of 2.0 kA / cm ² and the oscillation wavelength of 450 nm was performed.

Example 12 In the same manner as in Example 10, a GaN buffer layer was formed on a sapphire substrate to a thickness of 200 Å, and n-type Ga was formed.
An n-type contact layer made of N was sequentially formed to a thickness of 4 μm.

Next, Si-doped n-type Al _0.3 Ga _0.7 N
After forming the second n-type cladding layer made of 0.5 μm in thickness, the first n-type cladding layer made of Si-doped n-type In _0.05 Ga _0.95 N was formed in thickness of 0.1 μm.

Then, non-doped In _0.2 Ga _0.8 N is grown to a thickness of 20 Å to form an active layer having a single quantum well structure, and Mg-doped p-type Al is formed thereon.
_0.1 Ga _0.9 N for the first p-type cladding layer 0.1
to a thickness of μm, and Mg-doped p-type Al _0.3
The second p-type cladding layer made of Ga _0.7 N has a thickness of 0.5 μm.
And finally a p-type contact layer made of Mg-doped p-type GaN was grown to a thickness of 0.5 μm.

After that, when the laser oscillation of the obtained LD element was tried in the same manner as in Example 10, Example 10
And an oscillation wavelength of 450 n at a threshold current density of 1.0 kA / cm ² lower than the threshold current densities of the LD elements 11 and 11.
Laser oscillation of m was confirmed.

Example 13 In this example, the shape of the first n-type cladding layer and the active layer is
The same procedure as in Example 12 was performed except for the growth. That is, the first
As an n-type cladding layer of Si-doped n-type In _0.05Ga
_0.95Instead of N, a Si-doped n-type GaN layer of 0.1μ
It was grown to a thickness of m. Also, to form the active layer
Undoped In_0.4Ga_0.630 ng N well layer
Grown to a thickness of strom, and then undoped In
_0.08Ga_{0. 92}N barrier layer to a thickness of 50 Å
Repeat the operation of growing the well layer / barrier layer / well
A total thickness of 190 o with a five-layer structure consisting of a door layer / barrier layer / well layer
Grow an active layer with a ngstrom multiple quantum well structure
It was

When laser oscillation was attempted on the obtained LD element in the same manner as in Example 10, laser oscillation of 500 nm was exhibited at a threshold current density of 0.9 kA / cm ² .

Example 14 A sapphire substrate was prepared in the same manner as in Example 10 except that the p-type contact layer was formed without forming the second p-type cladding layer after forming the first p-type cladding layer. Then, each semiconductor layer up to the p-type contact layer was grown. The obtained wafer was subjected to annealing to reduce the resistance of the p-type nitride semiconductor layer and etching from the p-type contact layer to the n-type contact layer, and then, on the p-type contact layer, as in Example 10. A positive electrode made of Ni and Au was directly formed without forming a current constriction layer, and a negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, the desired LED element was obtained. This L
The ED element exhibits blue light emission with Vf3.5V and an emission wavelength of 450 nm at If20 mA, and an emission output of 6 mW.
Met. In addition, the full width at half maximum of the emission spectrum was 20 nm, showing sharp emission between bands.

Example 15 In the same manner as in Example 10, each semiconductor layer up to the p-type contact layer was grown on the sapphire substrate. The obtained wafer was subjected to annealing to reduce the resistance of the p-type nitride semiconductor layer and etching from the p-type contact layer to the n-type contact layer, and then, on the p-type contact layer, as in Example 10. A positive electrode made of Ni and Au was directly formed without forming a current constriction layer, and a negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, the desired LED element was obtained. This LE
The D element showed blue emission at Vf3.5V and emission wavelength of 450 nm at If20 mA, and had a high emission output of 6 mW. The full width at half maximum of the emission spectrum was 20 nm, showing sharp emission between bands.

Example 16 In the same manner as in Example 10, GaN was formed on a sapphire substrate.
The buffer layer has a thickness of 200 angstroms and n-type G
An n-type contact layer made of aN was sequentially formed to a thickness of 4 μm. This n-type contact layer also functions as the first n-type cladding layer in the LED element of this embodiment.

Next, on the n-type contact layer, undoped In _0.2 Ga _0.8 N was grown to a thickness of 30 Å to form an active layer having a single quantum well structure.

Then, Mg-doped p-type Al _0.1 Ga _0.9
A first p-type clad layer made of N is grown to a thickness of 0.05 μm, and p made of Mg-doped p-type GaN is formed on the first p-type clad layer.
The mold contact layer was grown directly to a thickness of 0.5 μm.

Thereafter, in the same manner as in Example 14, after reducing the resistance of the p-type nitride semiconductor layer by annealing and etching from the p-type contact layer to the n-type contact layer, on the p-type contact layer. A positive electrode made of Ni and Au was directly formed on the negative electrode, and a negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, the desired LED element was obtained. This LED element is If20mA
In the above, blue emission of Vf3.5V and an emission wavelength of 450 nm was exhibited, and the emission output was a high output of 7 mW. The full width at half maximum of the emission spectrum was 20 nm, indicating a sharp emission between bands.

Example 17 An LED element was obtained by the same operation as in Example 16 except that In _0.4 Ga _0.6 N was grown to have a thickness of 50 Å as an active layer. This LED element is this LED
The device showed green emission of Vf3.5V and emission wavelength of 520 nm at If20 mA, emission output of 4 mW, and half-width of emission spectrum of 40 nm.

Example 18 An LD element was obtained by performing the same operation as in Example 3 except that the active layer and the first p-type cladding layer were formed. That is, in this example, in order to form an active layer, undoped In _0.15 Ga _0.85 N was grown to a thickness of 25 Å as a well layer on the first n-type cladding layer, and a non-doped barrier layer was formed thereon. The operation of growing In _0.05 Ga _0.95 N to a thickness of 50 angstroms was repeated 13 times, and finally undoped In _0.15 Ga _0.85 N was formed as a well layer.
To a thickness of 25 angstroms and a total thickness of 100
An active layer having a multi-quantum well structure of 0 angstrom was formed. In addition, as the first p-type cladding layer, Al _0.05 G
a _0.95 N was grown to a thickness of 500 Å. The wafer thus obtained was processed in the same manner as in Example 9 to obtain a desired LD element. This LD element has a threshold current density of 1.0 kA / cm ² and a wavelength of 415 nm.
Laser oscillation was shown.

Example 19 An LD element was obtained by performing the same operation as in Example 3 except that the active layer was formed. That is, in this example, in order to form an active layer, undoped In _0.15 Ga _0.85 N was grown to a thickness of 25 Å as a well layer on the first n-type cladding layer, and a non-doped barrier layer was formed thereon. In _0.05
The operation of growing Ga _0.95 N to a thickness of 50 angstroms was repeated 26 times, and finally, undoped In _0.15 Ga _0.85 N was grown to a thickness of 25 angstroms as a well layer to form a multiple quantum well structure with a total thickness of 1975 angstroms. An active layer was formed. The wafer thus obtained was treated in the same manner as in Example 9 to obtain the desired LD.
The device was obtained. This LD element showed laser oscillation of 415 nm at room temperature and a threshold current density of 1.0 kA / cm ² .

Example 20 The blue LED element obtained in Example 16, the green LED element obtained in Example 17, and the conventional GaAs material or AlI
Light emission output of nGaP-based material 3 mW, 660 nm
1 dot for each red LED and 2
When a 56 × 256 pixel full-color LED display was manufactured, the white surface luminance was 10,000 cd, and the color reproduction area was wider than that of the TV.

[0212]

As described in detail above, according to the present invention,
Provided is a nitride semiconductor light emitting device having a high emission output and a narrow half-width of emission spectrum.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of another form of the nitride semiconductor light emitting device according to the present invention.

FIG. 3 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of another form of the nitride semiconductor light emitting device according to the present invention.

FIG. 5 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 6 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 7 is a perspective view showing an example of the structure of a nitride semiconductor laser device of the present invention.

FIG. 8 is a schematic cross-sectional view showing another structure of the nitride semiconductor laser device of the present invention.

FIG. 9 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 10 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 11 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 12 is a schematic cross-sectional view showing the structure of one form of a nitride semiconductor light emitting device according to the present invention.

FIG. 13 is a graph showing the relationship between the thickness of the well layer of the active layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.

FIG. 14 is a graph showing the relationship between the thickness of the barrier layer of the active layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.

FIG. 15 is a graph showing the relationship between the thickness of the p-type AlGaN cladding layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.

FIG. 16 is a graph showing the relationship between the thickness of the n-type InGaN cladding layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.

[Explanation of symbols]

11, 91, 401 ... Substrate 13, 93, 403 ... N-type contact layers 14, 21, 34, 54, 501, 94, 294, 29
4a, 294b, 414, 412 ... N-type cladding layers 15, 95, 405 ... Active layers 16, 36, 41, 56, 502, 96, 96a, 96
b, 296, 416, 426, 436 ... P-type clad layer 17, 97, 407 ... P-type contact layer 18, 98, 408 ... Negative electrode 19, 99, 409 ... Positive electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 7-118046 (32) Priority date May 17, 1995 (May 17, 1995) (33) Priority claim country Japan (JP) Preliminary examination (72) Hiroyuki Kiyohisa, Inventor Hiroyuki Kiyohisa, 491-1, Kaminaka-cho, Anan city, Tokushima prefecture Nichia Chemical Industry Co., Ltd. (56) Reference JP-A-9-36424 (JP, A) JP-A-6-21511 ( JP, 7-15041 (JP, A) JP, 7-249795 (JP, A) JP, 6-164055 (JP, A) JP, 6-268257 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50

Claims (7)

(57) [Claims] 1. An active layer made of a nitride semiconductor having first and second main surfaces and containing indium and gallium, and an n-type nitride semiconductor provided on the first main surface of the active layer. A layer and a p-type nitride semiconductor layer provided on the second main surface of the active layer, the p-type nitride semiconductor layer being formed in contact with the second main surface of the active layer, A first p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium, and a first p-type clad layer provided at a position farther from the active layer than the first p-type clad layer. A second p-type clad layer having a larger bandgap and made of a p-type nitride semiconductor containing aluminum and gallium, the first p-type clad layer and the second p-type clad layer. p-type is provided between _in m _{Ga 1-m} N (where, 0 <m <1) Others a p-type layer made of p-type GaN,
A nitride semiconductor light emitting device comprising a p-type contact layer made of p-type GaN as an outermost layer. 2. The nitride semiconductor light emitting device according to claim 1, wherein the first p-type cladding layer has a thickness of 10 angstroms or more and 1 μm or less. 3. The nitride semiconductor light emitting device according to claim 1, wherein the second p-type clad layer has a thickness of 500 angstroms or more and 1 μm or less. 4. The p-type layer provided between the first p-type cladding layer and the second p-type cladding layer has a thickness of 10 angstroms or more and 1 μm or less. 4. The nitride semiconductor light emitting device according to any one of items 1 to 3. 5. The nitride semiconductor light emitting device according to claim 1, wherein the active layer constitutes a single quantum well structure including a well layer having a thickness of 100 angstroms or less. . 6. The multi-quantum well structure in which the active layer is formed by stacking a well layer made of a nitride semiconductor containing indium and gallium and a barrier layer made of a nitride semiconductor. 5. The nitride semiconductor light emitting device according to any one of items 1 to 4. 7. The nitride semiconductor light emitting device according to claim 1, wherein the active layer is non-doped.