JPH0738152A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enable a semiconductor light emitting element to emit green light of wavelengths 494nm to 550nm high in efficiency and luminance by a method wherein a P-N Junction formed of II-VI compound semiconductor layers whose band gaps are correspondent to a wavelength range of 494nm to 550nm is formed on an InP substrate. CONSTITUTION:An LED element has such a structure that a P-type InP buffer layer 12, a P-type CdS layer 13, and an N-type CdS layer 14 are successively laminated on a P-type InP substrate 11. An N-type InP contact layer 15 is formed in a limited area on the N-type CdS layer 14, an electrode layer 16 is formed on the upside of the N-type InP contact layer 15, and an electrode layer 17 is formed on the underside of the P-type InP substrate 11. By this setup, as electrons and holes are recombined in a direct transition manner, the LED of this constitution can be enhanced in luminance. Furthermore, the LED emits light ray 520nm in wavelength, whereby green light adequate to a wavelength range of 494nm to 550nm can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is particularly concerned with full color LEDs.
[Light Emitting Diode], traffic light,
Alternatively, the present invention relates to a semiconductor light emitting device that emits green light and is suitable for use as a safety sign or the like.

[0002]

2. Description of the Related Art Since LEDs have high luminous efficiency and long life, they have lower power consumption and higher reliability than conventional display devices such as light bulbs, and are expected to be used in a wide range of fields. The emission wavelength that is the emission color of this LED is the band gap [b] which is the width of the forbidden band of the semiconductor crystal.
and gap]. Initially used as LEDs, III-V group compound semiconductors such as GaAs have a relatively narrow bandgap and are biased toward the long wavelength side, so that they are in the infrared region (wavelength of about 780 nm or more) or red (wavelength of about 650 nm). Only the emission color was obtained.

However, recently, as a wide band gap material, SiC (a wavelength of 470 nm) using SiC, which is an indirect transition type semiconductor but is a group IV compound semiconductor, or a direct transition type semiconductor is III. Blue-purple (wavelength 460 nm) in which ZnSSe which is a II-VI group compound semiconductor is formed on a GaAs substrate which is a -V group compound semiconductor
The following luminescent colors have been developed. In addition, as a green emission color (wavelength around 550 nm) having a wavelength between these, an LED using InGaAlP on a GaP or GaAs substrate of a III-V group compound semiconductor has been developed.

[0004]

By the way, it is known that most colors can be produced by combining a plurality of basic three or more colors. In the field of color displays, etc., from red, green and blue. 3 primary colors (RGB
3 primary colors) are often used. When such three primary colors are used, the CIE [International Commiss] shown in FIG. 12 is used.
ion on Illumination] (International Commission on Illumination) It is possible to represent the color inside a triangle whose vertices are the points corresponding to the three primary colors on the chromaticity diagram. For example, a combination of three primary colors consisting of a red color with a wavelength of 650 nm, a green color with a wavelength of 540 nm and a blue color with a wavelength of 470 nm forms the triangle A in FIG. 12, and in order to perform full-color display, at least within the range of the triangle A. You will be able to express colors. In addition,
Regarding the above green color, when it is used for a safety sign light such as a traffic light, it conforms to the JIS standard (JIS Z 9109, JIS E).
3303), the wavelength range of 494 nm to 550 nm (range B in FIG. 12) is designated.

Further, in the above-mentioned direct transition type semiconductor, in the energy band structure, the band gap becomes the narrowest at the point where the wave number vector becomes zero, so that the wave number vector (momentum) is generated when the electrons and holes are recombined. Since it does not change, light can be efficiently emitted. On the other hand, in the case of an indirect transition semiconductor, the wave vector at the minimum point of the conduction band where the band gap becomes the smallest is not zero, so that the wave vector changes when electrons and holes recombine, Luminous efficiency deteriorates. Therefore, in the indirect transition type semiconductor, the LED
High brightness is limited.

However, the GaP, which has been conventionally used as an LED emitting green light, has an emission wavelength of 555.
Since it is nm, when it is used as a green color of the three primary colors of RGB, it is not possible to express a color in a sufficiently wide range.
There is a problem that it cannot be adapted to the green wavelength range of the IS standard safety sign lamp. Moreover, since this GaP is an indirect transition type semiconductor, there is a problem that it is not possible to sufficiently increase the brightness of the LED.

In the case of InGaAlP, it is possible to obtain an emission color having a wavelength shorter than that of GaP by adjusting the mixed crystal ratio, but the recombination of electrons and holes is a direct transition type. The emission wavelength is 56
The limit is up to about 0 nm, and if an emission color with a shorter wavelength is to be obtained, the band gap at the minimum point where the wave vector in the conduction band is other than zero becomes narrower, so the indirect transition type is dominant. Therefore, there is a problem that the luminous efficiency is sharply reduced. Moreover, even if the light is emitted as a direct transition type light at a wavelength of 560 nm, when it is used as a green color of the RGB three primary colors, the color can be expressed only within the range of the triangle C in FIG. Not only can colors not be fully expressed, but also JIS
There was also a problem that it could not conform to the green wavelength range of the standard safety indicator light.

All II-VI group compound semiconductors are direct transition type semiconductors, and generally have band gaps of III-V.
Since it is closer to the shorter wavelength side than the group compound semiconductor, it can be an optimal semiconductor material for a green-emitting LED. For example, CdS has a bandgap corresponding to an emission wavelength of 516 nm and can express a sufficiently wide range of colors even when used as the above-mentioned RGB three primary colors of green, and also conforms to the green wavelength range of JIS safety indicator lights. To do. However, II-VI
Some group compound semiconductors, such as CdS, usually have a Wurtzite-type hexagonal system. With such a crystal structure, a substrate having high conductivity and good crystallinity should be prepared. Was difficult. Further, since the II-VI group compound semiconductor has a strong self-compensation effect, it is often difficult to arbitrarily control the p-type and the n-type by an ordinary impurity addition method. Therefore, conventionally, it has been impossible to practically manufacture an LED by using the II-VI group compound semiconductor as it is.

In view of the above circumstances, it is an object of the present invention to provide a semiconductor light emitting device which is a direct transition type and which can efficiently emit green light in the wavelength range of 494 nm to 550 nm.

[0010]

In the semiconductor light emitting device of the present invention, a pn junction of a II-VI group compound semiconductor layer corresponding to a wavelength range of a band gap of 494 nm or more and 550 nm or less is formed on an InP substrate. Therefore, the above object is achieved thereby.

In this semiconductor light emitting device, the group II element constituting the semiconductor layer is at least one of zinc and cadmium, and the group VI element constituting the semiconductor layer is one of selenium, sulfur and tellurium. It can be more than one.

Further, the InP substrate is of a first conductivity type, and the semiconductor layer is formed by laminating a CdS layer of a first conductivity type and a CdS layer of a conductivity type opposite to the first conductivity type. Can be configured. Further, the InP substrate is of the first conductivity type, and the semiconductor layer is of the first conductivity type Z.
n _x Cd _1-x S cladding layer, Zn _y Cd _1-y S (0 ≦ x ≦
1; 0 ≤ y <1; y <x) An active layer and a Zn _x Cd _1-x S clad layer having a conductivity type opposite to the first conductivity type may be sequentially stacked. In addition, the InP substrate is of the first conductivity type, and the semiconductor layer is of the first conductivity type.
Conductive CdS _v Te _1-v clad layer, CdS _w Te
_1-w (0 ≦ v ≦ 1; 0 ≦ w <1; w <v) active layer and a CdS _v Te _1-v clad layer having a conductivity type opposite to the first conductivity type, which are sequentially laminated It can be configured. Further, the semiconductor layer has a lattice constant that matches that of the InP substrate within 0.5%, and constitutes the semiconductor layer.
The group II element is one or more of zinc, cadmium and magnesium, and the group VI element forming the semiconductor layer is
The composition may be one or more of selenium, sulfur and tellurium.

The semiconductor light emitting device of the present invention comprises a GaP substrate,
III-V compound semiconductor layer of the same conductivity type as the corresponding substrate and III-V of the opposite conductivity type on the GaAs substrate or Si substrate
Since the superlattice layer in which the group compound semiconductor is alternately laminated is formed so that the band gap corresponds to the wavelength range of 494 nm or more and 550 nm or less, the above object is achieved thereby.

In this semiconductor light emitting device, the GaA
On the s substrate, InGa whose lattice constant is almost the same as that of the s substrate.
The superlattice layer including a P layer and an InAlP layer may be formed. The superlattice layer composed of a GaP layer and an AlP layer may be formed on the GaP substrate or the Si substrate.

The semiconductor light-emitting device of the present invention is one in which two kinds of II-VI group compound semiconductors are laminated on a substrate of a II-VI group compound semiconductor, and one of the semiconductors has a band gap of 550 nm or more of an emission wavelength. And the other semiconductor has a strained superlattice layer having a bandgap corresponding to an emission wavelength of 494 nm or less. Therefore, the above object is achieved.

In this semiconductor light emitting device, the substrate is made of ZnS, and the strained superlattice layer is a ZnTe layer and a ZnS layer.
The structure may be composed of layers.

[0017]

In the present invention, the pn junction of the II-VI group compound semiconductor layer is formed on the InP substrate of the III-V group compound semiconductor. II-VI group compound semiconductors
All are direct transition type semiconductors, and their band gap is generally
Since it is closer to the shorter wavelength side than the III-V group compound semiconductor, as shown in FIG. 11, the band gap of many of them including CdS is 494 nm to 550 n of the emission wavelength.
It corresponds to the range of m (between the one-dot chain line a and the one-dot chain line a in the figure). In addition, since the InP substrate of the III-V compound semiconductor is a zinc blende [Zinc blende] type cubic system, the II-VI group compound semiconductor layer laminated on this layer has the same zinc blende type crystal structure. Becomes Moreover, as shown in FIG. 11, since the lattice constants of many II-VI group compound semiconductors corresponding to the emission wavelength range of 494 nm to 550 nm are close to the lattice constant of InP (one-dot chain line c), InP A II-VI group compound semiconductor crystal corresponding to this wavelength range can be formed on the substrate without defects. Therefore, such In
The combination of the P substrate and the pn junction of the II-VI group compound semiconductor makes it possible to obtain a green light emitting semiconductor light emitting device with high luminous efficiency and high brightness.

The pn junction of the II-VI group compound semiconductor layer is
In addition to the homojunction type [homojunction], it may be a double heterojunction type. As the homojunction type, for example, CdS corresponding to an emission wavelength of 516 nm substantially matches the lattice constant of InP.
A CdS layer of the opposite conductivity type is laminated on this CdS layer of the same conductivity type as the nP substrate, or ZnCdSSe is 494n.
Since the lattice constant is substantially the same as that of InP when the ratio corresponding to the wavelength range of m to 550 nm is used, it is preferable to use the ZnCdSSe layer of the opposite conductivity type laminated on the ZnCdSSe layer of the same conductivity type as the InP substrate. it can. As the double heterojunction type, for example, ZnCdS, which has a larger proportion of Cd than Zn, is 494 nm to 550 nm.
Since it corresponds to the wavelength range of nm and the lattice constant is substantially the same as that of InP, this Zn _{x of the} same conductivity type as the InP substrate is used.
A Zn _y Cd _1-y S active layer having a narrow band gap between the Cd _1-x S clad layer and the opposite conductivity type Zn _x Cd _1-x S clad layer (0 <x ≦ 1, 0 ≦ y <1, y <x) is laminated, or CdSTe, which has a larger proportion of S than Te, is 49
Since it corresponds to the wavelength range of 4 nm to 550 nm and the lattice constant is almost the same as that of InP, this CdS _x Te _1-x clad layer of the same conductivity type as the InP substrate and Cd of the opposite conductivity type to the InP substrate.
Cd with a narrow bandgap between the S _x Te _1-x clad layers
S _y Te _1-y active layer (0 <x ≦ 1, 0 ≦ y <1, y <x)
It is possible to use a laminate of the above. In addition, in the case of this double heterojunction type, since it is necessary to form active layers having different band gaps between the cladding layers, there may be a difference in the lattice constant here, but the ratio of ZnCd is higher than that of Mg. 494 nm to 550 n when there are many matches
If ZnCdMgSe corresponding to the wavelength range of m is used,
If the ratio of Zn and Cd is selected so that the lattice constant is substantially matched to InP, the lattice constant has the property of hardly changing even if the band gap is changed by changing the amount of Mg. The p-n junction can be made a very good quality and thick crystal without dislocations.

Among III-V group compound semiconductors, those having a wide band gap and corresponding to short wavelengths are indirect transition type such as GaP and InGaAlP having an emission wavelength of 560 nm or less. However, even such a III-V group compound semiconductor is of a direct transition type by forming a superlattice layer in which a large number of extremely thin layers having different compositions are alternately stacked as in the structure of claim 7. can do. Therefore, by using such a III-V compound semiconductor superlattice layer having a bandgap corresponding to a wavelength range of 494 nm to 550 nm, it is possible to obtain a semiconductor light emitting device that efficiently emits green light as a direct transition type. become.

Examples of the superlattice layer having an emission wavelength in the range of 494 nm to 550 nm include InGaP and InAl.
A combination of P and a combination of GaP and AlP are possible. The superlattice layer having such a wavelength range is shown in FIG.
As shown in FIG. 1, GaA of the same III-V compound semiconductor
Since it has a lattice constant smaller than s, it can be formed on this GaAs substrate, a GaP substrate having a smaller lattice constant than this, or a Si substrate of a group IV semiconductor.

In the present invention, the strained superlattice layer of the same II-VI group compound semiconductor is formed on the substrate of the II-VI group compound semiconductor. When only the II-VI group compound semiconductor is used, there are problems that it is difficult to obtain a good substrate and it is difficult to arbitrarily control p-type and n-type. Is 494n
It was not possible to form a semiconductor light emitting device in the range of m to 550 nm. However, the strained superlattice layer is a stack of two kinds of II-VI compound semiconductors having different lattice constants, and the emission wavelength is a value between two wavelengths corresponding to the band gaps of these two kinds of semiconductors. Therefore, by selecting a combination of these two kinds of II-VI group compound semiconductors, it is possible to obtain a semiconductor light emitting device capable of emitting green light in the range of 494 nm to 550 nm.

For example, ZnS which is a II-VI group compound semiconductor is
A wurtzite type crystal structure may be adopted, but a zincblende type substrate with good crystallinity can also be formed. However, normally only n-type conductivity is obtained, and the emission wavelength corresponds to the ultraviolet region (wavelength of 380 nm or less). Also, for example, ZnTe
Usually obtains only p-type conductivity, but its emission wavelength exceeds 550 nm. On the n-type ZnS substrate or the ZnS layer formed on the n-type ZnS substrate, an extremely thin layer of p-type ZnTe and undoped ZnS is alternately stacked to form a p-type strained superlattice layer as a whole. Stack and p-
When an n-junction is formed, the emission wavelength of this strained superlattice layer is adjusted to 494 nm by adjusting the ratio of ZnTe and ZnS.
It becomes possible to set it in the range of up to 550 nm. Therefore,
With such a combination, it is possible to obtain a semiconductor light emitting device that emits green light in the range of 494 nm to 550 nm using only the direct transition type II-VI group compound semiconductor.

The various substrates used in the present invention include not only the wafer substrate itself, but also those obtained by growing a semiconductor having the same composition as that of the substrate as a buffer layer on the surface layer thereof.

[0024]

Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a vertical sectional view showing the structure of an LED element, and FIG. 2 is a perspective view of an LED lamp. 3 is a perspective view of a full-color LED lamp.

In the LED element of this embodiment, a case where a homojunction pn junction of CdS is formed on an InP substrate will be described.

As shown in FIG. 1, this LED element comprises a p-type InP substrate 11 having a thickness of 300 μm, a p-type InP buffer layer 12 having a thickness of 1 μm, a p-type CdS layer 13 having a thickness of 5 μm, and a thickness of 5 μm. A 1 μm n-type CdS layer 14 is sequentially stacked. A thickness of 0.5 μm is formed on the n-type CdS layer 14.
The n-type InP contact layer 15 of m is formed in a limited range, the electrode layer 16 is formed on the upper surface of the n-type InP contact layer 15, and the electrode layer 17 is formed on the lower surface of the p-type InP substrate 11. There is.

The LED device having the above-mentioned structure is manufactured by a conventional molecular beam epitaxy (MBE) method or a metal organic chemical vapor deposition (MOCVD) method.
por Deposition]) method or the like, but here, the case of manufacturing by molecular beam epitaxy will be described.

The molecular beam epitaxy method is used for the p-type InP substrate 1
1, p-type InP buffer layer 12, p-type CdS layer 13,
It is used for forming the n-type CdS layer 14 and the n-type InP contact layer 15. Impurities are often attached to the substrate surface of the semiconductor wafer, and it may not be sufficiently removed by chemical and physical treatments. p-type In
The P buffer layer 12 is formed on the p-type InP substrate 11 for this purpose. Then, the p-type CdS layer 13 and the n-type CdS layer
The layer 14 is also preferably grown continuously on the p-type InP buffer layer 12. Therefore, as the molecular beam epitaxy apparatus, one having two growth chambers which can be moved in a vacuum and which can move the wafer is used. First, in the first growth chamber, p-type In is used.
After the p-type InP buffer layer 12 is grown on the P substrate 11, the p-type CdS layer 13 and the n-type CdS layer 14 are sequentially grown on the second growth chamber. After this, the n-type InP contact layer 1 is returned to the first growth chamber again.
Grow 5

In the second growth chamber, the p-type InP substrate 11 in vacuum is heated to about 300 ° C. and irradiated with a molecular beam to grow the p-type CdS layer 13 and the n-type CdS layer 14. For the molecular beam used as the growth material for the p-type CdS layer 13 and the n-type CdS layer 14, high-purity cadmium (Cd) and sulfur (S) with a purity of 99.99% or more are used, and p-type conductivity type is used. Nitrogen (N) is used as the impurity material (dopant) for controlling the conductivity, and chlorine (Cl) is used as the impurity for controlling the n-type conductivity. Since the p-type InP substrate 11 and the p-type InP buffer layer 12 of the III-V group compound semiconductor are of the zinc blende type cubic system, the p-type CdS layer 13 of the II-VI group compound semiconductor laminated thereon is formed. The n-type CdS layer 14 also has the same zinc blende type crystal structure. Further, since the lattice constant of CdS substantially matches the lattice constant of InP, it is possible to grow a good quality crystal without dislocation or the like.

When the processing by the molecular beam epitaxy is completed, the wafer is taken out from the growth chamber, and the electrode layer 17 made of gold (Au), germanium (Ge) and nickel (Ni) is vapor-deposited on the lower surface of the p-type InP substrate 11. In addition, the upper surface of the n-type InP contact layer 15 has gold and zinc (Z
The electrode layer 16 composed of n) is vapor-deposited and heated in vacuum to form an ohmic connection with the semiconductor layer.
Further, after applying a photoresist on the upper layer of the electrode layer 16, the photoresist is etched into a circular pattern having a diameter of about 100 μm by using a normal photolithography method, and the photoresist pattern is used as a mask, for example, argon (Ar). The electrode layer 16 and the n-type InP contact layer 15 are etched by an ion beam etching method using an ion beam or the like. Then, if this wafer is divided by dicing, as shown in the drawing, the LE in which the n-type InP contact layer 15 and the electrode layer 16 are formed by limiting the range only to the central portion of the upper surface of the n-type CdS layer 14.
D element is completed.

In the above LED element, when a voltage is applied to the electrode layers 16 and 17 with the p-type InP substrate 11 side being a positive potential,
Electrons are injected from the electrode layer 16 and holes are injected from the electrode layer 17. Then, the electrons pass through the n-type and p
Although it diffuses to the mold side, holes do not diffuse much to the n-type side.
Therefore, if the p-type CdS layer 13 is formed thick, the electrons efficiently recombine with the holes remaining therein and emit light. In addition, since the recombination of electrons and holes at this time is performed by a direct transition type, it is possible to manufacture a high-luminance one. Furthermore, the emission wavelength is 520 nm of CdS as shown in FIG. 11, and green emission suitable for the wavelength range of 494 nm to 550 nm can be obtained.

FIG. 2 shows an LED emitting such a green color.
It is a perspective view which shows the LED lamp which used the element 1. In this LED lamp, the substrate-side electrode of the LED element 1 is mounted on the heat sink 2 and then fused to the first lead frame 3, and the space between the electrode on the other side and the second lead frame 4 is reduced. Wire boding at line 5,
These are sealed (molded) with an epoxy resin 6.

By forming the epoxy resin 6 into a lens shape as shown in the drawing, it is possible to give an appropriate directivity. This LED lamp has an emission wavelength of 520 nm
Therefore, it conforms to the green wavelength range of JIS safety light. Therefore, if the number of LED elements 1, the material of the epoxy resin 6, the lens shape, etc. are appropriately designed so as to satisfy other requirements such as brightness and directivity, they can be used as a JIS standard safety sign. . If you need to see this safety sign from a distance,
Since the short wavelength component is scattered by the fine particles in the air and the color tends to be reddish, it is necessary to use the LED element 1 having an emission wavelength sufficiently close to the short wavelength in advance.

FIG. 3 shows a full-color LED lamp using the above-mentioned LED element 1 which emits green light. This L
The ED lamp includes the LED element 1 and GaAlAs / G.
The LED element 7 for emitting red light such as aAs system and the LED element 8 for emitting blue light such as SiC are mounted on the heat sink 2 and then fused to the lead frame 3, and the other side of these LED elements 1, 7, 8 The electrode and the other three lead frames 4, 4 and 4 are wire-bonded with a gold wire 5 and then sealed with an epoxy resin 6.

In this full-color LED lamp, the emission wavelength of the green LED element 1 is 520 nm.
It is possible to represent a wider range of colors than the triangle A on the CIE chromaticity diagram shown in FIG. By arranging a large number of full-color LED lamps in a two-dimensional manner, a full-color LED panel can be configured and can be used for a computer display or the like that requires complicated and diverse color expression. .

When used as the LED panel, a large number of LED elements 1, 7 and 8 may be arranged in a two-dimensional array. Then, in this case, it is not always necessary to form the sealing material in a lens shape. Also,
Similar to the conventional LED panel, when the sealing material is not transparent and scatters light, an LED panel having wide directivity can be obtained.

In addition, the red light emitting LED element 7 and the blue light emitting LED element 8 in the above full color LED lamp.
Even when only one of them is combined with the green-emitting LED element 1 of this embodiment, a multi-color LED lamp can be obtained. The reason is that the LED element 1
This is because one of the LED element 7 and the LED element 8 can express each color on the line connecting these two emission wavelengths on the CIE chromaticity diagram shown in FIG.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

The LED device of the present embodiment comprises a Zn _x Cd _1-x S clad layer and a Zn _y Cd _1-y S active layer (0
A case where a double heterojunction pn junction is formed by <x ≦ 1, 0 ≦ y <1, y <x) will be described. However, here, the ratio is x = 0.15 and y = 0.

This LED element has an n-type InP buffer layer 22 having a thickness of 1 μm, an n-type Zn0.15Cd0.85S cladding layer 23 having a thickness of 1 μm, and a thickness of 1 μm on an n-type InP substrate 21 having a thickness of 300 μm. p-type CdS light emitting layer 24 and thickness 1
A p-type Zn0.15Cd0.85S cladding layer 25 having a thickness of μm is laminated in this order. On the uppermost p-type Zn0.15Cd0.85S cladding layer 25, a p-type InP contact layer 26 having a thickness of 0.5 μm is formed in a limited range.
An electrode layer 27 is formed on the contact layer 26, and an electrode layer 28 is formed below the n-type InP substrate 21.

The LED element having this structure can be manufactured in the same manner as in the first embodiment. For example, in the case of the molecular beam epitaxy method, the n-type InP substrate 21 set in the evacuated first growth chamber is heated to about 300 ° C. and irradiated with a molecular beam, so that n-type Zn0.15Cd0. 85S cladding layer 23, p-type CdS light-emitting layer 24 and p-type Zn0.15Cd
The 0.85S clad layer 25 is grown. In this growth, the molecular beam used as a growth material for these ZnCdS layers is
Zinc (Z
n), cadmium (Cd) and sulfur (S),
Nitrogen (N) is used as the impurity material for controlling the conductivity type to be the p-type, and chlorine (Cl) is used as the impurity material for the n-type.

Next, the p-type InP contact layer 26 is grown in the second growth chamber. After the processing by the above molecular beam epitaxy is completed, the electrode layers 27 and 28 are vapor-deposited and etching is performed. As a result, the illustrated LED element is completed.

In the LED element thus manufactured, the ZnCdS layer of II-VI group compound semiconductor has the same zinc blende type crystal structure as the n-type InP substrate 21 as in the case of the first embodiment. . The lattice constant of ZnCdS is
As shown in FIG. 11, if the proportion of Zn is smaller than that of Cd (in the example, x = 0.15, y = 0,
Is sufficiently small) and the lattice constant of InP is almost the same, so that it is possible to grow a good quality crystal without dislocation or the like.

In the above LED element, when a voltage is applied to the electrode layers 27 and 28 with the n-type InP substrate 21 side as a negative potential,
Holes are injected from the electrode layer 27 and electrons are injected from the electrode layer 28. Here, as shown in FIG. 11, ZnCdS has a narrower band gap as the proportion of Zn decreases, so the band gap of the p-type CdS light emitting layer 24 where the proportion of Zn is zero (y = 0) is. The band gap is narrower than that of the n-type Zn0.15Cd0.85S cladding layer 23 and the p-type Zn0.15Cd0.85S cladding layer 25 containing a small amount of Zn (x = 0.15). Therefore, the electrons are p-type Cd
S light emitting layer 24 and p-type Zn0.15Cd0.85S clad layer 25
Holes are blocked at the interface between the p-type CdS light-emitting layer 24 and the n-type Zn0.15Cd0.85S cladding layer 23, so that they are both retained in the p-type CdS light-emitting layer 24 and efficiently recombine. Will be emitted. Since this light emission is performed by the p-type CdS light emitting layer 24,
It is the same direct transition type as in the example, and the emission wavelength is 520 nm. Further, in the double heterojunction structure in which the active layer having a narrow band gap is formed between the p-type and n-type cladding layers in this way, electrons and holes can be efficiently confined and recombination can be performed. In addition to improving the luminous efficiency, the p-type CdS light emitting layer 24 can be thinned to improve the productivity.

In the case of the present embodiment, if the proportion of Zn in ZnCdS is increased (the values of x and y are increased), FIG.
As shown in (1), the band gap is widened and the emission wavelength can be further shortened. For example, if about 10% of Zn is added to the p-type CdS light emitting layer 24, an emission wavelength of 494 nm can be obtained. However, if the emission wavelength is too short, the lattice constant also decreases, and the n-type InP substrate 2
Since the difference from the lattice constant of 1 becomes large, there is a possibility that the crystal defects increase and the reliability decreases.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

In the LED device of this embodiment, the CdS _x Te _1-x clad layer and the CdS _y Te _1-y active layer (0
A case where a double heterojunction pn junction is formed by <x ≦ 1, 0 ≦ y <1, y <x) will be described. However, here, the ratio of x = 1 and y = 0.85 is set.

This LED device comprises an n-type InP substrate 31 having a thickness of 300 μm, an n-type InP buffer layer 32 having a thickness of 1 μm, an n-type CdS cladding layer 33 having a thickness of 1 μm, and a p-type CdS0. 85Te 0.15 light emitting layer 34 and thickness 1
A μm p-type CdS cladding layer 35 is sequentially stacked. A p-type InP contact layer 36 having a thickness of 0.5 μm is formed in a limited range on the uppermost p-type CdS cladding layer 35.
An electrode layer 37 is formed on the lower surface of the type InP substrate 31, and an electrode layer 38 is formed on the lower surface of the type InP substrate 31.

The LED element having the above structure can be manufactured in the same manner as in the first and second embodiments. For example, in the case of the molecular beam epitaxy method, the n-type CdS cladding layer 33 is heated by heating the n-type InP substrate 31 set in the first growth chamber in a vacuum to about 300 ° C. and irradiating with the molecular beam. , A p-type CdS0.85Te0.15 light emitting layer 34 and a p-type CdS cladding layer 35 are grown. In this growth, the molecular beam used as the growth material for these CdSTe layers is
Cadmium (Cd), sulfur (S) and tellurium (Te), both of which are highly pure with a purity of 99.99% or higher, are used.
Nitrogen (N) is used as the impurity material for controlling the conductivity type to be the p-type, and chlorine (Cl) is used as the impurity material for the n-type.

Next, the p-type InP contact layer 36 is grown in the second growth chamber. After the above-mentioned processing by the molecular beam epitaxy method is completed, the electrode layers 37 and 38 are vapor-deposited and etched. As a result, the illustrated LED element is completed.

In the LED element thus manufactured, the CdSTe layer of the II-VI group compound semiconductor has a zinc blende type crystal structure like the ZnCdS of the second embodiment.
Further, the lattice constant of CdSTe is as shown in FIG.
If the proportion of S is larger than that of Te (x =
1, y = 0.85, and the ratio of S is large enough),
Since it substantially matches the lattice constant of InP, it is possible to grow a good quality crystal without dislocation or the like.

As shown in FIG. 11, CdSTe is Te
The more the ratio of, the narrower the band gap, so
In the LED element, as in the case of the second embodiment, electrons and holes stay in the p-type CdS0.85Te0.15 light emitting layer 34 having a narrow band gap and efficiently recombine to emit light. Since this light emission is performed by the p-type CdS0.85Te0.15 light emitting layer 34, it is a direct transition type, and the emission wavelength is 550 nm, which is a little longer than CdS. Further, by adopting the double heterojunction structure in this way, it becomes possible to further improve the light emission efficiency and the productivity as in the second embodiment.

In the case of this embodiment, p-type CdS0.85Te0.15
By reducing the proportion of Te in the light emitting layer 34 (increasing the value of y), the emission wavelength is set to 520 n of CdS.
It can be shortened to about m. In addition, n-type Cd
The S clad layer 33 and the p-type CdS clad layer 35 may be made of ZnCdS as in the second embodiment.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

The LED element of the present embodiment is composed of (Zn0.52Cd0.48) _x Mg _1-x Se clad layer and (Zn0.52Cd0.48) _x InZ substrate on the InP substrate.
0.52Cd0.48) _y Mg _1-y Se active layer (0 ≦ x <1, 0 <
A case where a double heterojunction pn junction is formed by y ≦ 1, y> x) will be described. However, here, the ratio is x = 0.5 and y = 0.75.

This LED device comprises a p-type InP substrate 41 having a thickness of 300 μm, a p-type InP buffer layer 42 having a thickness of 1 μm, and a p-type (Zn0.52Cd0.48) 0.5M having a thickness of 1 μm.
g0.5 Se clad layer 43, 1 μm thick p-type (Zn0.5
2Cd0.48) 0.75Mg0.25Se light emitting layer 44 and thickness 1μ
An n-type (Zn0.52Cd0.48) 0.5Mg0.5Se cladding layer 45 of m is laminated in order. Top n-type (Zn0.52
On the Cd0.48) 0.5Mg0.5Se cladding layer 45, an n-type InP contact layer 46 having a thickness of 0.5 μm is formed. Note that the description of the electrode layers is omitted in the following examples.

The LED device having the above structure is the same as that of the second embodiment except that sulfur (S) of the VIb group element is changed to selenium (Se) and magnesium (Mg) of the IIa group element is added. , Can be manufactured similarly. However,
When growing using the molecular beam epitaxy method, Se is used.
Is likely to be a solidified form of 5 or more atoms and does not decompose into single atoms well on the substrate, so it is better to use a cracking cell that raises the temperature of the molecular beam to prevent Se from solidifying. Further, since Mg easily oxidizes, special care must be taken to completely remove oxygen in the growth chamber.

As in the case of the second embodiment, the LED element of the present embodiment is a p-type (Zn0.52Cd) having a narrow band gap.
0.48) In the 0.75Mg0.25Se light emitting layer 44, electrons and holes can be directly recombined as a transition type, and the double heterojunction structure further improves the light emission efficiency and the productivity. You can also plan.

Further, ZnCdMgSe can have a lattice constant almost equal to that of InP by setting the ratio of Zn and Cd to 0.52 and 0.48. Moreover, as shown in FIG. 11, even if the proportion of ZnCd and Mg is changed, this lattice constant hardly changes, and only the band gap can be changed. Therefore, II
The ZnCdMgSe layer of the -VI compound semiconductor is a p-layer of the lower layer.
Between the p-type InP substrate 41 and the p-type InP buffer layer 42,
And wide bandgap p-type (Zn0.52Cd0.48) 0.
5Mg0.5Se clad layer 43 and n-type (Zn0.52Cd0.4
8) Since the lattice constants between the 0.5Mg0.5Se cladding layer 45 and the p-type (Zn0.52Cd0.48) 0.75Mg0.25Se light-emitting layer 44 having a narrow bandgap are substantially the same, an extremely high-quality thick zinc blende It can be grown as a crystal of the mold. And p-type (Zn0.52Cd0.48) 0.75Mg0.25
The light emitted from the Se light emitting layer 44 can be taken out to the outside without waste through the high quality crystal having no defect.

The LED element of this embodiment has an emission wavelength of 49
It becomes 4 nm, but as shown in FIG. 11, if the proportion of Mg to ZnCd is reduced, emission of longer wavelength is possible, and the value of 1-y is in the range of 0.25 to 0.07. By changing it, an arbitrary emission wavelength in the range of 494 nm to 550 nm can be obtained.

(Fifth Embodiment) FIG. 7 shows a fifth embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

In the LED element of this embodiment, a case where a homojunction pn junction of (Zn0.3Cd0.7) (S0.3Se0.7) is formed on an InP substrate will be described.

This LED device comprises a p-type InP substrate 51 having a thickness of 300 μm, a p-type InP buffer layer 52 having a thickness of 1 μm, and a p-type (Zn0.3Cd0.7) (S0.3 having a thickness of 5 μm).
Se0.7) layer 53 and n-type (Zn0.3Cd0.
7) The (S0.3Se0.7) layer 54 is sequentially laminated. Top n-type (Zn0.3Cd0.7) (S0.3Se0.7) layer 54
An n-type InP contact layer 55 having a thickness of 1 μm is formed thereon.

In the above LED element, except that sulfur (S) is added to selenium (Se) as a VIb group element and magnesium (Mg) of the IIa group element is not used, a II-VI group of a pn junction is used. The compound semiconductor has the same composition as in the fourth embodiment and can be manufactured in the same manner. However, since the easily oxidizable Mg is not used, the degree of vacuum in the growth chamber is not required to be as strict as in the fourth embodiment. This ZnCdSSe is
As shown in FIG. 11, (Zn0.3Cd0.7) (S0.3Se
The ratio of 0.7) makes the emission wavelength 545
nm, and the lattice constant can be made to substantially match InP. Therefore, it is possible to form a thick crystal of good quality without dislocation or the like.

The LED element of this embodiment has the same homo-connection type pn junction as that of the first embodiment, and is injected when a voltage is applied with the p-type InP substrate 51 side as a positive potential. The electron is n-type (Zn0.3Cd0.7) (S0.3Se0.
7) Propagates quickly to the p-type side through the layer 54, but holes are not so diffused from the p-type (Zn0.3Cd0.7) (S0.3Se0.7) layer 53 to the n-type side. Therefore, this p-type (Zn
By forming the 0.3Cd0.7) (S0.3Se0.7) layer 53 sufficiently thick, electrons can be efficiently recombined with holes that remain therein to emit light. The emission wavelength is 545 nm as described above.

(Sixth Embodiment) FIG. 8 shows a sixth embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

The LED element of the present embodiment is a p-type device formed of a InGaP / InAlP short period superlattice layer on a GaAs substrate.
A case where an n-junction is formed will be described.

This LED element comprises a p-type GaAs substrate 61 having a thickness of 300 μm, a p-type GaAs buffer layer 62 having a thickness of 1 μm, a p-type In0.5Al0.5P cladding layer 63 having a thickness of 1 μm, and an n-type superlattice. The layers 64 are sequentially stacked.
The n-type superlattice layer 64 is a Si-doped n-type In0.5Ga0.5P film 6 having a thickness of 3 monolayers (about 8.5 angstroms).
4a and a superlattice composed of a Si-doped n-type In0.5Al0.5P film 64b having a thickness of 17 monolayers (about 48.0 angstroms), which is a short-period superlattice layer. The n-type superlattice layer 64 has an n-layer of a thickness of 1 μm as an upper layer.
A type GaAs contact layer 65 is formed.

The LED element having the above structure can be manufactured by using a usual metal organic chemical vapor deposition method or the like. The metal-organic vapor phase epitaxy method uses p-type GaAs on a p-type GaAs substrate 61.
Buffer layer 62, p-type In0.5Al0.5P cladding layer 6
3, n-type superlattice layer 64 and n-type GaAs contact layer 6
It is used for forming 5.

That is, p-type Ga placed in a vacuum growth chamber
The As substrate 61 is heated to 560 ° C., and G is added to this growth chamber.
Trimethylgallium (TM), which is the source gas for a and As
G) and tertiary butyl arsine (TBA),
A p-type GaAs buffer layer 62 is grown by flowing a hydrogen selenide (H2Se) gas as a doping material.

Next, only tert-butylphosphine (TBP) was flowed into the growth chamber for several seconds to expel tert-butylarsine as an As raw material, and then triethylindium (TEI) which was a raw material gas for In, Al and P. In addition to trimethylaluminum (TMA) and tert-butylphosphine previously used, hydrogen selenide gas as a doping material is flowed to grow a p-type In0.5Al0.5P cladding layer 63.

When the formation of the p-type In0.5Al0.5P clad layer 63 is completed, trimethylaluminum and hydrogen selenide gas are stopped, trimethylgallium and silane (SiH4) gas as a doping material are caused to flow, and an n-type superlattice is produced. Layer 6
No. 4, the first Si-doped n-type In0.5Ga0.5P film 64a is grown. After this, by switching only trimethylgallium and trimethylaluminum, this S
i-doped n-type In0.5Ga0.5P film 64a and Si-doped n
The n-type superlattice layer 64 is formed by alternately stacking and growing the In0.5Al0.5P films 64b.

Finally, in addition to the source gases of Ga and As, trimethylgallium and tertiary butylarsine,
A n-type GaAs contact layer 65 is grown by flowing a silane gas as a doping material.

The p-type In0.5Al0.5P clad layer 63
And In0.5Ga0.5P and In0.5A of the n-type superlattice layer 64
As shown in FIG. 11, the lattice constant of 10.5P is substantially the same as that of GaAs, so that a p-type GaAs substrate 61 is used as the substrate.

The LED element of the present example emits light by the same action as a single heterojunction type LED in which a clad layer having a wide band gap is provided only on the p-type side. That is, p
When a voltage is applied with the positive GaAs substrate 61 side being a positive potential, the electrons diffuse beyond the hetero interface between the n-type GaAs contact layer 65 and the n-type superlattice layer 64, so that they diffuse too deeply to the p-type side. I can't. Further, since holes also do not diffuse much to the n-type side, they are mostly retained in the n-type superlattice layer 64. Therefore, electrons and holes are efficiently recombined in the n-type superlattice layer 64 to emit light. Therefore, even if the n-type superlattice layer 64 is formed thicker than that in the embodiment, it has little meaning.

Here, In0.5Al0.5P itself usually becomes an indirect transition type semiconductor and hardly emits light. However, in the case where the film is an extremely thin film as in the present embodiment, preferably a film in which each layer has 20 monolayers or less, the InGaP / InAlP superlattice is a direct transition type due to the synergistic effect of the zone folding effect and the band mixing effect. Is known to be. The emission wavelength of the n-type superlattice layer 64 is determined by the superlattice structure, and the n-type superlattice layer 6 of the entire Si-doped n-type In0.5Al0.5P film 64b is formed.
If the ratio of the thickness to 4 is 75% or more, this emission wavelength can be set to 550 nm or less. Therefore, with the configuration using the n-type superlattice layer 64 of the III-V group compound semiconductor as described above, efficient green light emission of direct transition type can be performed. In the case of the present embodiment, the emission wavelength is 535 nm. I was able to

(Seventh Embodiment) FIG. 9 shows a seventh embodiment of the present invention and is a vertical sectional view showing a structure of an LED element.

In the LED element of this example, a case where a pn junction is formed by a GaP / AlP short-period superlattice layer on a GaP substrate will be described.

This LED device comprises an n-type GaP substrate 71 having a thickness of 300 μm, an n-type GaP buffer layer 72 having a thickness of 1 μm, an n-type AlP clad layer 73 having a thickness of 1 μm, and a p-layer.
The type superlattice layers 74 are sequentially stacked. The uppermost p-type superlattice layer 74 is a Se-doped p-type GaP film 74a having a thickness of 3 monolayers (about 8.2 angstroms) and a thickness of 17
This is a short-period superlattice layer in which, for example, 20 layers of a monolayer (about 46.4 Å) non-doped AlP film 74b and a superlattice. A p-type GaP contact layer 75 having a thickness of 1 μm is formed on the p-type superlattice layer 74.

The LED element having such a structure can also be manufactured by using a usual metal organic chemical vapor deposition method or the like, as in the sixth embodiment. The metal organic chemical vapor deposition method is used to form the n-type GaP buffer layer 72, the n-type AlP cladding layer 73, the p-type superlattice layer 74, and the p-type GaP contact layer 75 on the n-type GaP substrate 71.

That is, n-type Ga placed in a vacuum growth chamber
The P substrate 71 is heated to 350 ° C., and Ga is placed in this growth chamber.
In addition to trimethylgallium and tert-butylphosphine, which are source gases for P and P, a silane gas, which is a doping material, is flowed to grow the n-type GaP buffer layer 72.

Next, in the growth chamber, silane gas, which is a doping material, is flowed in addition to trimethylaluminum, which is a source gas of Al and P, and tert-butylphosphine, and an n-type AlP cladding layer 73 is grown.

When the formation of the n-type AlP clad layer 73 is completed, G instead of trimethylaluminum and silane gas is used.
The first Se-doped p-type GaP film 74a of the p-type superlattice layer 74 is grown by flowing trimethylgallium as the source gas of a and hydrogen selenide gas as the doping material. After that, by switching trimethylgallium and trimethylaluminum, and stopping the hydrogen selenide gas when flowing trimethylaluminum, the S
e-doped p-type GaP film 74a and non-doped AlP film 74
b and p are alternately stacked and grown to form a p-type superlattice layer 74. The reason why the hydrogen selenide gas is stopped when the non-doped AlP film 74b is formed is that when doping AlP, a deep level is likely to be formed and crystallinity is deteriorated. When this AlP is made non-doped, a low concentration of n
The p-type superlattice layer 74 as a whole can be made p-type by increasing the doping amount to the Se-doped p-type GaP film 74a sufficiently.

Finally, in addition to trimethylgallium and tert-butylphosphine, which are source gases of Ga and P, a hydrogen selenide gas, which is a doping material, is caused to flow to p-type Ga.
The P contact layer 75 is grown.

As shown in FIG. 11, the n-type AlP clad layer 73 and the GaP and AlP of the p-type superlattice layer 74 have substantially the same lattice constant, and therefore the same GaP n-type GaP substrate 71 is used as the substrate. Is used. It should be noted that this FIG.
As shown in Fig. 1, the lattice constant of Si of the group IV semiconductor is also Ga.
Since it is almost the same as P, it is possible to form the p-type superlattice layer 74 and the like of this embodiment on the Si substrate. In this case, since the growth temperature of the p-type superlattice layer 74 and the like is low as described above, the LED element of this embodiment may be formed on a Si substrate on which an electronic circuit such as a transistor is formed by a normal diffusion method or the like. Therefore, the LED element and its control circuit can be made monolithic.

Also in the LED element of this embodiment, the injected electrons and holes are efficiently recombined in the p-type superlattice layer 74 to emit light, as in the sixth embodiment. Also, Al
P itself usually becomes an indirect transition type semiconductor and hardly emits light. However, when an extremely thin film, preferably a film having 20 monolayers or less in each layer, is used as in this example, the GaP / AlP superlattice is a direct transition type due to the synergistic effect of the zone folding effect and the band mixing effect. Is known to be. The emission wavelength of the p-type superlattice layer 74 is determined by the superlattice structure, and the p-type superlattice layer 74 of the entire non-doped AlP film 74b is formed.
If the ratio of the thickness to is 75% or more, the emission wavelength can be set to 550 nm or less. Therefore,
The III-V compound semiconductor p-type superlattice layer 74
With the configuration using, it is possible to perform direct transition type efficient green light emission, and in the case of the present embodiment, the emission wavelength is set to 5
It could be 20 nm.

(Eighth Embodiment) FIG. 10 shows an eighth embodiment of the present invention and is a vertical sectional view showing the structure of an LED element.

In the LED element of this example, a case will be described in which a pn junction is formed by a ZnTe / ZnS strained superlattice layer on a ZnS substrate.

In this LED element, an n-type ZnS buffer layer / cladding layer 82 having a thickness of 1 μm and a p-type strained superlattice layer 83 having a thickness of 1 μm are sequentially laminated on an n-type ZnS substrate 81 having a thickness of 300 μm. The p-type strained superlattice layer 83 is made of Sb-doped p-type Zn having a thickness of 5 monolayers (about 15.3 angstroms).
For example, a strained superlattice layer is formed by stacking, for example, 20 layers of a Te film 83a and a strained superlattice made of a non-doped ZnS film 83b having a thickness of 30 monolayer (about 81.2 angstrom). An Sb-doped p-type ZnTe contact layer 84 having a thickness of 150 angstrom is formed on the p-type strained superlattice layer 83.

The LED element having such a structure can be manufactured in substantially the same manner as in the first embodiment. For example, in the case of the molecular beam epitaxy method, the n-type ZnS substrate 81 in vacuum is set to 2
By heating to about 50 ° C and irradiating with molecular beam,
An n-type ZnS buffer layer / cladding layer 82, a p-type strained superlattice layer 83 and an Sb-doped p-type ZnTe contact layer 84 are grown. The molecular beam used as a growth material has a purity of 9
Zinc (Zn), zinc chloride (ZnCl2), tellurium (Te), sulfur (S), and antimony (Sb) having a high purity of 9.99% or more are used.

The manufacturing process will be described in detail below. First,
By irradiating with the molecular beam of Zn, S and ZnCl2,
An n-type ZnS buffer layer / cladding layer 82 is grown on the n-type ZnS substrate 81. ZnCl2 is used as a dopant material for controlling the conductivity type because Cl is excellent as an n-type material and has good controllability.

Next, by irradiating with a molecular beam of Zn, Te and Sb, the first Sb in the p-type strained superlattice layer 83 is irradiated.
The doped p-type ZnTe film 83a is grown. The film thickness is monitored by a usual reflection type high energy electron diffraction (RHEED) apparatus. In addition, this Sb-doped p-type ZnTe film 8
By irradiating the upper layer of 3a with a molecular beam of Zn and S,
The non-doped ZnS film 83b is grown. Then, these Sb-doped p-type ZnTe film 83a and non-doped ZnS
The p-type strained superlattice layer 83 is formed by repeating the procedure of alternately growing the films 83b by a predetermined thickness. The non-doped ZnS film 83b is normally n-type, but the Sb-doped p-type ZnTe film 83a can be heavily doped with Sb to be highly concentrated p-type, so that the p-type strained superlattice layer 83 as a whole is p-type. It can be a mold.

After the formation of the p-type strained superlattice layer 83 is completed, the molecular beam of Zn, Te and Sb is finally irradiated to grow the Sb-doped p-type ZnTe contact layer 84 to complete the LED element.

The LED element of the present embodiment emits light by the pn junction composed of the n-type ZnS buffer layer / cladding layer 82 and the p-type strained superlattice layer 83. When a voltage is applied with the n-type ZnS substrate 81 side as a negative potential, holes injected into the p-type strained superlattice layer 83 have a wider bandgap in the n-type ZnS buffer layer / cladding layer 82. It is blocked at the interface with the n-type ZnS buffer layer / cladding layer 82 and remains in the p-type strained superlattice layer 83. And n-type Z
The electrons injected from the nS substrate 81 are the p-type strained superlattice layer 8
Light is emitted by diffusing into 3 and efficiently recombining with the holes.

The emission wavelength at this time is the p-type strained superlattice layer 8
It is determined by the band gap of 3 and is 50 in this embodiment.
It becomes 5 nm. This emission wavelength is Sb-doped p-type ZnT
The total thickness of the e-film 83a can be adjusted by the ratio of the p-type strained superlattice layer 83. However, this Z
As shown in FIG. 11, nTe has an extremely large difference in lattice constant from ZnS, which is 13%, and therefore Sb-doped p-type ZnT
The e film 83a cannot have a film thickness of 5 monolayers or more. Therefore, here, the emission wavelength must be adjusted by adjusting the film thickness of the non-doped ZnS film 83b. In the case of the present embodiment, the entire film thickness of the non-doped ZnS film 83b is the p-type strained superlattice layer 83. 88% of the share
By the following, an emission wavelength of 494 nm or more could be obtained.

The Sb-doped p-type Z used in this embodiment is also used.
Since the nTe film 83a can be heavily doped with Sb to be a high-concentration p-type as described above, it is possible to reduce the element resistance and provide a highly reliable LED element.

It is of course possible to use the LED elements of the second and subsequent embodiments as the LED lamps shown in FIGS. 2 and 3 similarly to the LED element of the first embodiment.

[0099]

As is clear from the above description, according to the semiconductor light emitting device of the present invention, it is possible to emit green light in the wavelength range of 494 nm to 550 nm with high efficiency and high brightness. It can be used to express a wide range of colors and can be used as a safety sign lamp that conforms to the standard.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 2 shows a first embodiment of the present invention, which is LE
It is a perspective view of a D lamp.

FIG. 3 shows a first embodiment of the present invention and is a perspective view of a full-color LED lamp.

FIG. 4 shows a second embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 5 shows a third embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 6 shows a fourth embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 7 shows a fifth embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 8 shows a sixth embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 9 shows a seventh embodiment of the present invention, which is LE
It is a longitudinal cross-sectional view showing a configuration of a D element.

FIG. 10 shows an eighth embodiment of the present invention, in which L
It is a longitudinal cross-sectional view showing a configuration of an ED element.

FIG. 11 is a diagram showing a relationship between a semiconductor lattice constant and a band gap.

FIG. 12 is a CIE chromaticity diagram.

[Explanation of symbols]

11 p-type InP substrate 13 p-type CdS layer 14 n-type CdS layer 21 n-type InP substrate 23 n-type Zn0.15Cd0.85S clad layer 24 p-type CdS light emitting layer 25 p-type Zn0.15Cd0.85S clad layer 31 n-type InP Substrate 33 n-type CdS clad layer 34 p-type CdS0.85Te0.15 light-emitting layer 35 p-type CdS clad layer 41 p-type InP substrate 43 p-type (Zn0.52Cd0.48) 0.5 Mg0.5Se clad layer 44 p-type (Zn0. 52 Cd0.48) 0.75 Mg0.25 Se light emitting layer 45 n-type (Zn0.52 Cd0.48) 0.5 Mg0.5 Se clad layer 51 p-type InP substrate 53 p-type (Zn0.3 Cd0.7) (S0.3 Se0.7) layer 54 n-type (Zn0.3Cd0.7) (S0.3Se0.7) layer 61 p-type GaAs substrate 63 p-type In0.5Al0.5P clad layer 64 n-type superlattice layer 71 n-type GaP substrate 73 n-type AlP clad layer 74 p-type superlattice layer 8 n-type ZnS substrate 82 n-type ZnS buffer layer and the cladding layer 83 p-type strained superlattice layer

Claims (11)

[Claims] 1. A band gap of 49 is formed on an InP substrate.
II-VI corresponding to the wavelength range from 4 nm to 550 nm
A semiconductor light emitting device having a pn junction formed of a group compound semiconductor layer. 2. The Group II element constituting the semiconductor layer is at least one of zinc and cadmium,
The semiconductor light emitting device according to claim 1, wherein the group VI element forming the semiconductor layer is one or more of selenium, sulfur and tellurium. 3. The InP substrate is of a first conductivity type, and the semiconductor layer is formed by stacking a CdS layer of a first conductivity type and a CdS layer of a conductivity type opposite to the first conductivity type. The semiconductor light emitting device according to claim 2, wherein 4. The InP substrate is of a first conductivity type, and the semiconductor layer is a Zn _x Cd _1-x S cladding layer of the first conductivity type, Zn _y Cd _1-y S (0 ≦ x ≦ 1; 0 ≦ y <1; y <
x) Active layer and Zn of a conductivity type opposite to the first conductivity type
The semiconductor light emitting device according to claim 2, wherein the semiconductor light emitting device is formed by sequentially laminating _x Cd _1-x S cladding layers. 5. The InP substrate is of a first conductivity type, and the semiconductor layer is a CdS _v Te _1-v clad layer of the first conductivity type, CdS _w Te _1-w (0 ≦ v ≦ 1; 0 ≦ w <1; w <
v) the active layer and Cd of a conductivity type opposite to the first conductivity type
S _v Te _1-v semiconductor light-emitting device according to claim 2 consisting of those were sequentially laminated clad layer. 6. The semiconductor layer is matched with the InP substrate in a lattice constant within 0.5%, and the Group II element constituting the semiconductor layer is one or more of zinc, cadmium and magnesium. The semiconductor light emitting device according to claim 2, wherein the Group VI element forming the semiconductor layer is one or more of selenium, sulfur, and tellurium. 7. A superlattice in which a III-V group compound semiconductor layer of the same conductivity type and a III-V group compound semiconductor of the opposite conductivity type are alternately stacked on a GaP substrate, a GaAs substrate or a Si substrate. A semiconductor light-emitting device in which the layer is formed with a band gap corresponding to a wavelength range of 494 nm or more and 550 nm or less. 8. The semiconductor light emitting device according to claim 7, wherein the superlattice layer including an InGaP layer and an InAlP layer having substantially the same lattice constant as that of the substrate is formed on the GaAs substrate. 9. On the GaP substrate or Si substrate, Ga
The semiconductor light emitting device according to claim 7, wherein the superlattice layer including a P layer and an AlP layer is formed. 10. A II-VI group compound semiconductor on a substrate, 2
It is a stack of two or more II-VI group compound semiconductors, one of which has a bandgap corresponding to an emission wavelength of 550 nm or more, and the other of which has a bandgap corresponding to an emission wavelength of 494 nm or less. A semiconductor light emitting device in which a lattice layer is formed. 11. The semiconductor light emitting device according to claim 10, wherein the substrate is made of ZnS, and the strained superlattice layer is made of a ZnTe layer and a ZnS layer.