JPH08264832A - Gallium nitride compound semiconductor light emitting element - Google Patents

Abstract

PURPOSE: To provide a gallium nitride compound semiconductor light emitting element, which improves its luminous intensity. CONSTITUTION: A multiple quantum well structure (MQW) has a structure, wherein a well layer 52 is encircled with large-band gap layers, which are used as barrier layers 51, on both sides thereof, most of carriers generated in the layers 51 flow in the layer 52 and contribute to a light emission. Therefore, the luminous intensity of the light emitting element is improved and an output of the element is increased. Here, when an acceptor and a donor are simultaneously added to the layer 52, there is a longer wavelength light emission between the acceptor level and the donor level in the layer 52 and as there is a large amount of carriers in the layer 52, the luminous intensity is maintained high.

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, and more particularly to a blue light emitting semiconductor light emitting device (light emitting diode) whose base material is a gallium nitride compound.

[0002]

2. Description of the Related Art Conventionally, as a light emitting diode, a gallium nitride-based (for example, AlGaInN) compound semiconductor is known. Since the compound semiconductor is a direct transition type, it has been noted that it has high emission efficiency, and that blue, which is one of the three primary colors of light, is used as the emission color.

Also in a gallium nitride-based semiconductor, an MIS in which a conventional n-layer and a semi-insulating layer (i-layer) are joined can be doped with Mg and irradiated with an electron beam or can be turned into p-type by heat treatment.
Instead of the mold, a light emitting diode having a double hetero pn junction using an AlGaN p layer, a Zn-doped InGaN light emitting layer, and an AlGaN n layer has been proposed.

Further, the inventors have proposed an unpublished structure (Japanese Patent Application No. 6-113484) in order to further improve the emission brightness. In this gallium nitride compound light emitting diode, the structure is almost the same as that of FIG. 1, and the light emitting layer to be formed is a single layer, and the base material is simultaneously doped with zinc (Zn) which is an acceptor and silicon (Si) which is a donor. The junctions on both sides of the structure are double heterostructures, and a peak wavelength of 420 to 450 nm and an emission output of 1000 mcd are realized. There is a demand for a blue color for a multi-color display as such a blue light emitting element.

In addition, the blue of the traffic signal lamp requires a high-luminance lamp having an emission peak wavelength of about 500 nm, which is problematic in that the blue light emitting element described above has a too short wavelength. In order to set the emission peak wavelength of this blue light emitting element to the long wavelength side, it is required to shorten the width of the energy band of the light emitting layer, and by increasing the In composition ratio of the light emitting layer, the longer wavelength side The emission peak of can be obtained.

Some gallium nitride-based compound semiconductor light-emitting devices have a multi-quantum well structure for the light-emitting layers 44 and 44 'as shown in Japanese Patent Laid-Open No. 6-268257 to improve the light emission output ( (See FIG. 4).

[0007]

However, although the output from the above well layers 44 and 44 'is improved,
The emission wavelength is around 410 nm, which is the same as in the conventional case, because the band-to-band emission is obtained without adding an emission center to the well layer. This has the problem that it cannot be used as the wavelength of 500 nm required for traffic signals. Therefore, there is a demand for a light emitting diode having a longer wavelength and higher emission brightness. Therefore, an object of the present invention is to provide a gallium nitride-based compound semiconductor light emitting device with further improved emission brightness.

[0008]

In order to solve the above problems, the structure of the present invention is a gallium nitride-based compound semiconductor light-emitting device having a double heterostructure in both junctions of the cladding layers sandwiching the light-emitting layer. That is, at least one layer of multiple quantum well structure (MQW) is obtained by simultaneously doping the acceptor and the donor. The structure of the related invention is characterized in that the well layer of the multiple quantum well structure is simultaneously doped with an acceptor and a donor, or,
The light emitting layer is composed of indium aluminum gallium nitride (InAlGaN) and acceptor impurities such as zinc (Z
n), a donor impurity, for example, an active layer to which silicon (Si) is added. A further characteristic structure is that the barrier layer of the multiple quantum well structure is made of an indium aluminum gallium nitride (InAlGaN) -based material with a composition ratio changed from that of the well layer, and preferably the lattice constant of the barrier layer. And the lattice constant of the well layer are equal. Alternatively, in the multi-quantum well structure, acceptors are added to the barrier layers on both sides of each well layer.

[0009]

In the multi-quantum well structure (MQW), the well layer is surrounded on both sides by a layer having a large bad gap as a barrier layer, so that almost all carriers generated in the barrier layer flow into the well layer and contribute to light emission. Therefore, it has a structure in which the emission brightness is improved and the output is increased. If an acceptor and a donor are added at the same time to the well layer to make the emission wavelength shorter, emission occurs at a longer wavelength between the acceptor level and the donor level in the well layer, and light is emitted because there are many carriers. The brightness is kept high.

[0010]

The light emission between the acceptor and the donor in the quantum well layer has a wavelength of about 500 nm, and the emission brightness is several times (4 to 5 cd) as compared with the conventional one, and it is possible to obtain the one which is sufficiently practical. In addition, it can be applied by a normal thin film forming technology (about 100 Å) without using a conventional technique such as an ultra-thin film (5 to 50 Å), and the formation is easy.

[0011]

EXAMPLES The present invention will be described below based on specific examples. (First Embodiment) FIG. 1 is a schematic sectional view of a light emitting diode 10 having a multilayer light emitting layer 5 composed of a well layer according to the present invention. FIG. 2 is a more detailed schematic diagram of the multilayer light emitting layer 5 portion. First, as the first embodiment, as the multilayer light emitting layer 5, Al _x3 In
_y3 Ga _1-x3-y3 N: Zn, Si / Al _x2 In _y2 Ga _1-x2-y2 N: Mg Quantum well structure (MQW) is there. Each layer is alternately composed of an Al _x2 In _y2 Ga _1-x2-y2 N: Mg layer 51 which is a barrier layer and an Al _x3 In _y3 Ga _1-x3-y3 N: Zn, Si layer 52 which is a well layer, Here, 100Å are formed respectively.

A manufacturing method for forming the light emitting layer 5 having this structure will be described. The structure as a light emitting diode is the same as the conventional one,
The clad layer 4 before the formation of the light emitting layer 5 is formed.
Here, the clad layer 4 is made of silicon (Si) -doped Al _x4 In.
_{It is the y4} Ga _1-x4-y4 N layer.

After forming the cladding layer 4, the sapphire substrate 1
Temperature of 850 ℃, N ₂ or H ₂ 20 liter / min, NH
₃ for 10 liter / min, TMG for 1 × 10 ^-5 mol / min, TMI for 1
The light emitting layer 5 is formed by introducing x10 ^-4 mol / min, silane (SiH ₄ ) and diethyl zinc (DEZ). At this time, first, about 100 Å impurities were added to cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as `` CP ₂ Mg
]) And magnesium (Mg) -doped layer 5
1 (barrier layer) is formed, and then the base material is the same material, the same thickness is about 100 Å, and zinc (Z
n), a silicon (Si) -doped layer 52 (well layer) is formed. Continuously with the same thickness, magnesium (Mg) doped layer 5
1 (barrier layer), successively zinc (Zn) and silicon (Si) -doped layers 52 (well layers) are formed, and the well layers 52 and barrier layers 51 are alternately formed. The light emitting layer 5 is formed so as to have a film thickness of about 0.5 μm to form a multilayer structure as shown in FIG. In this state, the multilayer light emitting layer 5 still has high resistance. The concentration of magnesium (Mg) in the P layer of the light emitting layer 5 is 1 × 10 ²⁰ / cm ³ , and in the well layer,
The concentration of zinc (Zn) is 5 × 10 ¹⁸ / cm ³ , and the concentration of silicon (Si) is also 5 × 10 ¹⁸ / cm ³ .

Then, in the conventional technique, the upper cladding layer 6 is formed.
(61, 62, 63) are formed, and finally, the first contact layer 63 and the second contact layer 6 are formed by using a reflection electron beam diffractometer.
2, the p layer 61 and the MQW light emitting layer 5 were uniformly irradiated with an electron beam. Electron beam irradiation conditions are acceleration voltage of about 10KV and sample current of 1
μA, beam moving speed 0.2mm / sec, beam diameter 60μm
φ, vacuum degree is 5.0 × 10 ⁻⁵ Torr. By the irradiation of this electron beam, the first contact layer 63, the second contact layer 62,
The p-layer 61 and the MQW light-emitting layer 51 each have a hole concentration
7 × 10 ¹⁷ / cm ³ , 5 × 10 ¹⁷ / cm ³ , 1 × 10 ¹⁷ / cm ³ , resistivity
It became a p-conduction type semiconductor of 0.5 Ωcm, 0.8 Ωcm, and 4 Ωcm. In this way, a wafer having a multilayer structure as shown in FIG. 2 was obtained. After that, each individual light emitting element (chip) is formed on the wafer as it is, but since this step is already known, the description thereof is omitted here.

In this MQW layer, the transition energy becomes smaller than that of the base material due to the acceptor level of zinc (Zn) and the donor level of silicon, the peak wavelength of light emission shifts to the long wavelength side, and the demand is about 500 nm. Near wavelengths are obtained. In addition, since a large amount of carriers flow from the barrier layer around the p-conductivity type doped with magnesium (Mg), MQ
A large amount of light emission occurs between the acceptor level of zinc (Zn) formed in the W layer and the donor level of silicon, which improves the emission brightness.

The light emitting diode 1 thus obtained
0 was a driving current of 20 mA, a driving voltage of 4 V, an emission peak wavelength of 490 nm, and an emission intensity of 5000 mcd. It has a light emission brightness more than three times that of the conventional one, and the light emission peak wavelength was close to 500 nm required by traffic signals.

The concentration of zinc (Zn) or silicon (Si) in the MQW layer 52 is 1 × 10.
^{The range of 17} to 1 × 10 ²⁰ / cm ³ is desirable in terms of improving the emission intensity.

In the above embodiment, the barrier layers 51,
A heterojunction is formed between the well layer 52, the cladding layers 4 and 6, and the high carrier concentration n ⁺ layer 3, and the barrier layer 51 of each layer is formed.
The Al, In, and Ga component ratios are selected so as to match the lattice constant of the high carrier concentration n ⁺ layer 3 of GaN.

(Second Embodiment) As a multilayer light emitting layer 5 composed of a quantum well layer, Al _x3 In _y3 Ga _1-x3-y3 N: Zn, Si / Al _x2 In
_The case of using the MQW layer composed of _y2 Ga _1-x2-y2 N is shown in the schematic sectional view of the structure in FIG. That is, the effect is the same even if the barrier layer is not made to be p-conductivity type.

Also in this case, as in the first embodiment, the light emitting layer 5 is formed after the cladding layer 4 is formed. At this time, first, an undoped layer 53 (barrier layer) is formed by adding about 100 Å without adding impurities, and subsequently, the base material is the same material, the same thickness is about 100 Å, and silane and DEZ are added. By using zinc (Zn), silicon (Si) doped layer 52 (well layer)
To form. Then, with the same thickness, the undoped layer 51,
Subsequently, a layer 52 doped with zinc (Zn) and silicon (Si) is formed, and so on.
3 and 3 are alternately formed, and the light emitting layer 5 is formed until the entire film has a thickness of about 0.5 μm to form a multilayer structure as shown in FIG. The concentration of zinc (Zn) in the multilayer light emitting layer 5 is 5
× 10 ¹⁸ / cm ³ and the concentration of silicon (Si) is also 5 × 10 ¹⁸ / cm ³
Is.

The light emitting diode 1 thus obtained
0 had a driving current of 20 mA, a driving voltage of 4 V, an emission peak wavelength of 490 nm, and an emission intensity of 4000 mcd. This also has a light emission brightness more than double that of the conventional one, and the light emission peak wavelength is close to 500 nm required by traffic signals.

As the acceptor and donor to be added to the light emitting layer 5, since the base material is a III-V compound semiconductor, zinc (Zn) is added when a combination of a Group 2 element and a Group 4 element is added. And Group 2 elements such as cadmium (Cd), beryllium (Be), magnesium (Mg), and mercury (Hg) are acceptors, silicon (Si), germanium (Ge), carbon (C), tin (S).
Group 4 elements such as n) and lead (Pb) serve as donors. In addition, in the combination of the group 4 element and the group 6 element, the group 4 element becomes the acceptor, and the group 6 element such as sulfur (S), selenium (Se) and tellurium (Te) serves as the donor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a light emitting diode according to a first embodiment of the present invention.

FIG. 2 is a schematic explanatory view of a structure of a multi-layer light emitting layer.

FIG. 3 is a schematic configuration diagram showing a configuration of a light emitting layer according to a second example.

FIG. 4 is a schematic configuration diagram showing a configuration of a conventional light emitting diode.

[Explanation of symbols]

10 Light Emitting Diode 1 Sapphire Substrate 2 Buffer Layer 3 High Carrier Concentration n ⁺ Layer 4 High Carrier Concentration n ⁺ Layer (Clad Layer) 5 Multilayer Light Emitting Layers 51, 53 Barrier Layer 52 Quantum Well Layer (MQW Layer) 6 Contact Layer (Clad Layer) ) 61 p layer 62 second contact layer 63 first contact layer 7, 8 electrode 9 groove

Claims (8)

[Claims] 1. A gallium nitride-based compound semiconductor light-emitting device having a double heterostructure in both junctions of cladding layers sandwiching a light-emitting layer, wherein at least one or more multiple quantum wells in which the light-emitting layer is simultaneously doped with an acceptor and a donor. A gallium nitride-based compound semiconductor light-emitting device having a structure (MQW). 2. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the well layer having the multiple quantum well structure is co-doped with an acceptor and a donor. 3. The light emitting layer is an active layer in which zinc (Zn) and silicon (Si) are added to an indium aluminum gallium nitride (InAlGaN) base material. The gallium nitride-based compound semiconductor light-emitting device according to the above. 4. The indium aluminum gallium nitride (InAlGaN) -based material, the composition ratio of which is different from that of the well layer, in the barrier layer having the multiple quantum well structure. Gallium nitride compound semiconductor light emitting device. 5. The gallium nitride-based compound semiconductor light emission according to claim 4, wherein the composition ratio of the barrier layer is determined so that the lattice constant of the barrier layer matches the lattice constant of the well layer. element. 6. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein in the multiple quantum well structure, acceptor is added to barrier layers on both sides of each well layer. 7. Each well layer of the multiple quantum well structure comprises 50
7. The gallium nitride-based compound semiconductor light emitting device according to claim 1, which has a thickness of Å to 200Å. 8. The gallium nitride-based compound semiconductor light emitting device according to claim 4, wherein the barrier layer has a thickness of between 50Å and 200Å.