JP3068303B2 - 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,
In particular, the present invention relates to a semiconductor light emitting device such as a light emitting diode and a semiconductor laser capable of emitting a high-luminance short wavelength light in a green band.

[0002]

2. Description of the Related Art In recent years, light emitting diodes (hereinafter, referred to as “LEDs”), which are one of semiconductor light emitting elements, have attracted attention as display devices used indoors and outdoors. LED
It is considered that the market for LEDs as outdoor displays will expand in the next few years as the brightness of light emitted from the LED increases. Thus, LEDs are expected as display devices that will replace neon signs in the future.

[0003] Higher luminance of LEDs (higher luminance of light emitted by LEDs) has been realized for several years in red LEDs having a GaAlAs-based double heterostructure. Recently, LEDs that emit high brightness light in the orange-yellow band
Has an InGaAlP double heterostructure
Prototype D. FIG. 6 shows the dependence of the luminance of light emitted from various LEDs on the wavelength.

As an example of a conventional double hetero-type LED, FIG. 7 shows an InGaAlP-based yellow band LED. FIG.
FIG. 4 is a diagram for explaining the operation principle of the InGaAlP-based yellow band LED.

[0005] This conventional InGaAlP-based yellow band LED
Is an n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer (thickness: 1.5 μm) 12 grown sequentially by an MOCVD method on an n-GaAs substrate 11;
_{0.5 (Ga 0.62 Al 0.38) 0} · 5 P active layer (thickness: 0.7 .mu.m
m) 13, p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer (thickness: 1.5 μm) 14, and p-Ga _0.2 Al
_{It has a 0.8} As current diffusion layer (thickness: 5 μm) 15. Also, this InGaAlP-based yellow band LED has n-
An electrode 21 formed on the bottom surface of the GaAs substrate 11;
An electrode 22 formed on the upper surface of the Ga _0.2 Al _0.8 As current diffusion layer 15. InGaAlP yellow band LE
The side surface 30 of D is processed by etching in order to increase the light extraction efficiency. Further, the whole chip of the InGaAlP-based yellow band LED shown in FIG. 7 is molded with resin (not shown).

[0006] Electrode 21 of InGaAlP yellow LED
When a drive current flows between the electrodes 21 and 22 by applying a bias to the electrodes 22 and 22, the non-doped In _0.5 (Ga _0.62 Al _0.38 ) P active layer 13 and the n-In _{Between each of the 0.5} (Ga _0.3 Al _0.7 ) _0.5 P cladding layer 12 and the p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer 14, a hetero barrier for holes and electrons (about an electron). (A barrier of 0.2 eV). In FIG. 8, holes are schematically shown by black circles, and electrons are schematically shown by white circles. Due to this hetero barrier, electrons and holes are non-doped In _0.5 (Ga _0.62 Al
_0.38 ) _{0.5 The} luminous efficiency increases because it is effectively confined in the P active layer 13.

[0007] Among the LEDs that emit light in the green band, an LED based on an indirect transition type N-doped GaP material emits yellow-green light having a luminance of 1000 mcd. According to the LED based on pure green GaP material without N doping, light emission having a luminance of several hundred mcd is obtained. However, the luminance of these green bands is lower than the luminance of the red to yellow bands.

[0008]

At present, a high-brightness LED is used for a visible light LED which emits light in a green band having a relatively low luminance, especially light having a wavelength of about 555 nm (emission in a pure green band). It is an issue. However, it is very difficult to increase the luminance. The reason is that a GaP-based semiconductor suitable for light emission in a pure green band is originally an indirect transition type semiconductor, and therefore has a low light emission efficiency. Therefore, it has been proposed to form a double heterostructure using a direct transition type InGaAlP-based material having an energy band gap corresponding to light emission in the green band. LED having such a double hetero structure, the LED of the cladding layers 12 and 14 shown in FIG. 7 In _0.5 (Ga _1-X
Al _X ) _0.5 P (x = 0.7 to 1.0) is replaced by a cladding layer, and the active layer 13 is replaced with In _0.5 (Ga _0.45 Al _0.55 ) _0.5 P
It can be obtained by replacing with an active layer. However, there is a problem that a difference in energy gap between the active layer and the cladding layer, particularly ΔE _gc (FIG. 8) corresponding to an electron barrier cannot be sufficiently increased. When the cladding layer is made of In _0.5 Al _0.5 P, ΔE _gc is about 0.12 eV. For this reason, electron leakage at the hetero barrier increases, so that the luminous efficiency decreases and high luminance cannot be achieved.

As means for increasing the energy band gap difference between the active layer 13 and the cladding layers 12 and 14, that is, for effectively increasing the barrier height for electrons in the cladding layers 12 and 14, a multiple quantum barrier structure is used. (MQB) is effective.

FIG. 9 shows a conventional LED having the above-described multiple quantum barrier structure. LED of FIG. 9 and LE of FIG.
9 is that the LED of FIG. 9 is a multi-quantum barrier structure 100 between the active layer 13 and the cladding layer 14.
In that it has There is no substantial difference between the other components. FIG. 10 shows the configuration of the multiple quantum barrier structure 100 included in the LED of FIG. 9 in more detail. Referring to FIG. 10, as an example, InGaAl
The structure of the P multiple quantum barrier structure 100 will be described in accordance with its manufacturing method.

First, on the active layer 13, a relatively thick layer (for example, 200 angstroms) of In _0.5 (Ga
_1-X Al _x ) _0.5 P layer (x = 0.7 to 1.0) 31 is grown. Then, an In _0.5 (Ga _1-x Al _x ) _0.5 P layer 31
Above the In _0.5 Ga _0.5 P well layer 40 and the In _0.5 (Ga
_1-X Al _x ) _0.5 P layer (x = 0.7 to 1.0) Barrier layer 35
~ 32 are grown alternately. The thickness of each of these layers is In
_{For each of the 0.5} Ga _0.5 P well layers 40, the layer thickness is L ₁ = 60 Å. In this specification, the In _0.5 Ga _0.5 P layer and the In _0.5 (Ga _1-X A
l _x ) _0.5 P (x = 0.7 to 1.0) layers may be simply referred to as an InGaP layer and an InGaAlP layer, respectively.

Regarding the InGaAlP barrier layers 35 to 32, the InGaAlP barrier layer 35 is composed of two layers having a layer thickness L ₂ = 40 Å (hereinafter, simply referred to as “40 Å × 2”). InGaAl
Each of the P barrier layers 34, 33, and 32 has a layer configuration represented by 30 Å × 2, 20 Å × 4, and 10 Å × 6. All of these layers are lattice-matched to the GaAs substrate 11. After forming the barrier layer 32, the thick InG
aAlP cladding layer 14 is grown.

The function of the multiple quantum barrier structure 100 thus formed is as follows. The relatively thick InGaAlP layer 31 adjacent to the active layer 13 and the active layer 13 form a barrier to low energy electrons. This barrier is for preventing electron tunneling. The two sets of barriers (40 Å thick) 35 formed on the InGaAlP layer 31 (to the right in FIG. 10) reflect slightly higher energy electrons.
Barriers 34-32 would reflect high energy electrons one after another, to form a effectively classical barrier (barrier determined by the material) is higher than U ₀ barrier Ue.

In this conventional LED that emits light in the green band, the barrier Ue is more than the barrier U ₀ (0.12 eV) by 0.1 mm.
About 1 eV higher. For this reason, a barrier of 0.2 eV or more sufficient to confine electrons is obtained.

According to such a structure, a barrier layer having a small thickness (in this case, 10 angstrom in the thinnest layer) is required.
Form an effective barrier to energetic electrons. Therefore, it is very important to form these barrier layers with good controllability. As a means for growing these barrier layers, a gas source MBE method capable of performing growth on the order of an atomic layer with good controllability is used.

However, in this gas source MBE method, it is possible to form an ultra-thin film structure such as the multi-quantum barrier structure 100.
There is a problem that it takes a long time to grow a thicker current diffusion layer. For this reason, the LED produced by the gas source MBE method has a disadvantage that it is not suitable for mass production.

An object of the present invention is to provide a high-brightness semiconductor light emitting device having a multiple quantum structure in which the necessity of performing growth on the order of an atomic layer with good controllability is reduced as compared with the prior art.

Another object of the present invention is to provide a high-luminance semiconductor light-emitting device having a multiple quantum barrier structure which can be easily formed by MOCVD instead of gas source MBE, and suitable for mass production. is there.

[0019]

A semiconductor light emitting device according to the present invention comprises a semiconductor substrate and a multiple quantum barrier structure including a plurality of barrier layers and well layers lattice-matched to the semiconductor substrate. Wherein the multiple quantum barrier structure is
The semiconductor device further includes a barrier layer that is not lattice-matched to the semiconductor substrate, thereby achieving the above object.

The semiconductor substrate is a GaAs substrate, the plurality of barrier layers and well layers lattice-matched to the semiconductor substrate are InGaAlP layers, and the barrier layer not lattice-matched to the semiconductor substrate is The InGaAl
It is preferable that the layer has a larger energy band gap than the P layer.

The barrier layer which is not lattice-matched to the semiconductor substrate is made of InAlP, InGaAlP, ZnS
Preferably, the layer is made of a material selected from the group consisting of e, ZnSSe, and CdZnS.

[0022]

The present invention will be described below with reference to examples.

The semiconductor light emitting device of this embodiment is an LED. The external configuration is almost the same as the configuration shown in FIG. The main difference between the configuration of this embodiment and the configuration shown in FIG. 10 lies in the difference of the multiple quantum barrier structure 100.

The structure of the multiple quantum barrier structure 100 of the present embodiment will be described below with reference to FIG.

First, on the active layer 13, a relatively thick layer (for example, 200 Å) of In _0.5 (Ga
_1-X Al _x ) _0.5 P layer (x = 0.7 to 1.0) 31 is grown. Then, an In _0.5 (Ga _1-x Al _x ) _0.5 P layer 31
Above the In _0.5 Ga _0.5 P well layer 40 and the In _0.5 (Ga
_1-X Al _x ) _0.5 P layer (x = 0.7 to 1.0) Barrier layer 35
~ 33 are grown alternately. In _0.5 Ga _0.5 P well layer 4
All layer thicknesses of 0 are layer thicknesses L ₁ = 60 Å. On the other hand, the InGaAlP barrier layers 35, 34 and 3
3 has a layer structure represented by 40 Å × 2, 30 Å × 2, and 20 Å × 4, respectively. Each of these layers is made of GaAs
Lattice-matched to s-substrate 11.

After forming the InGaAlP barrier layer 33,
The In _0.2 Al _0.8 P barrier layer 42 is grown. In _0.2 A
The l _0.8 P barrier layer 42 has a layer structure represented by 25 Å × 2. This In _0.2 Al _0.8 P
The barrier layer does not lattice match with the GaAs substrate 11. All the layers constituting the multiple quantum barrier structure 100 are grown by MOCVD. Except for the multiple quantum barrier structure 100, it is manufactured by the same method as the conventional one.

As described above, the main feature of the semiconductor light emitting device of the present embodiment is that the multiple quantum barrier structure 1 employed in the present embodiment.
No. 00 has an In _0.2 Al _0.8 P barrier layer made of a semiconductor material that does not lattice match with the GaAs substrate 11. The In _0.2 Al _0.8 P barrier layer 42 is made of In _0.5 (Ga _1-X
Al _x ) _0.5 P (x = 0.7 to 1.0) barrier layers 35 to 32
Since having a large energy band gap than 0.02eV than, without thinned as _{In 0.5 (Ga 1-X Al} X) 0.5 P barrier layers (10 Å) 32, a sufficient barrier against high energy electrons Become. The thickness of the In _0.2 Al _0.8 P barrier layer 42 of this embodiment is about 25 Å. In this embodiment, Ue = 0.
22 eV was obtained.

Of the barrier layers 35 to 33 and 42 constituting the multiple quantum barrier structure 100 of the present embodiment, the thinnest layer has a thickness of about 20 angstroms. Therefore, the barrier layers 35 to 33 and 42 and the well layer 40 constituting the multiple quantum barrier structure 100 can be grown with good controllability even by the ordinary MOCVD method.

When the LED of this example was molded into a package having a size of 5 mmФ and the LED was driven with a current of 20 mA, light emission having a pure green color having a wavelength of 554 nm and a luminance of 5 cd was obtained. This luminance is about 30 times the luminance of the light emitted from the LED based on the GaP-based material.

FIG. 3 shows the external configuration of a second embodiment of the present invention. Details of the configuration of the multiple quantum barrier structure 100 of this embodiment are shown in FIG. The first difference between the first embodiment and the second embodiment is that the second embodiment is different from the n-G
n-Ga between the aAs substrate 11 and the n-cladding layer 12
_{It has a 0.9} Al _0.1 As buffer layer 19.
The second difference between the first embodiment and the second embodiment is that, as shown in FIG. 2, the In _0.5 (Ga _0.3 Al
_0.7 ) _0.5 P layer (thickness 20 Å × 4) 33 is formed of In _0.3 Al _0.7 P barrier layer (thickness 30 Å ×).
2) It is replaced by 43. This I
The n _0.3 Al _0.7 P barrier layer 43 is also a semiconductor layer that causes lattice mismatch.

When the LED of the present embodiment is molded into a package having a size of 5 mm and driven by a current of 20 mA, the wavelength is 556 nm pure green and 4.7 c
Light emission having a luminance of d was obtained.

FIG. 5 shows the external structure of a third embodiment of the present invention. The configuration of the multiple quantum barrier structure 100 of this embodiment is shown in FIG. The first difference between the first embodiment and the third embodiment is that the third embodiment differs from the first embodiment in that p-Ga _0.2
It has a plurality of electrodes 22 formed on the upper surface of the Al _0.8 As current diffusion layer 15. Since the electrodes 22 are dispersed, the light emitting region is enlarged, and the p-Ga _0.2 Al _0.8 As current diffusion layer 15 can be formed thin (for example, to about 1 μm). A second difference between the first embodiment and the third embodiment is that, as shown in FIG.
In this embodiment, the In _0.2 Al _0.8 P barrier layer 42 is replaced by a ZnSe layer (thickness: 60 Å × 1) 51. The ZnSe layer 51 is also a layer made of a lattice mismatched material. A third difference between the first embodiment and the third embodiment is that the well layer of the multiple quantum barrier structure 100 is not the In _0.5 Ga _0.5 P well layer 40 but the In layer.
_0.5 (Ga _0.8 Al _0.2 ) _0.5 is constituted by a P well layer 50.

According to this embodiment, light emission having a luminance of 6 cd was obtained in a pure green color having a wavelength of 552 nm.

In any of the above embodiments, the barrier layer 42 made of a lattice-mismatched material having a large energy band gap is used.
The layers 43 and 51 are thicker than the barrier layers 32 and 33 of the conventional lattice-matching material having a relatively small energy band gap, but exhibit a sufficient barrier function. Also, the barrier layer is MOC
Since it can be grown by the VD method, it is suitable for mass production. Further, all the barrier layers were not formed of the lattice mismatch material because doing so adversely affects the active layer 13.

As described above, as an embodiment of the present invention, the conventional LE
D of the lattice-matched system constituting the multiple quantum barrier structure 100 of FIG.
The nGaAlP barrier layers 32 and 33 are made of lattice mismatched In.
The LED replaced with the AlP layer or the ZnSe layer has been described. However, other InGaAlP barrier layers 34, 35
May be replaced by a lattice-mismatched InAlP layer or a ZnSe layer. However, it is not preferable that all the barrier layers are made of the lattice mismatch material in consideration of the influence on the active layer 13 described above.

The material of the lattice mismatching system is In.
Even materials other than AlP and ZnSe have a larger energy band gap than the lattice matching material (for example, InGaAlP, ZnS, ZnSSe, and CdZ).
nS).

The present invention is not limited to a semiconductor light emitting device that emits green band light. The present invention is applied to all semiconductor light emitting devices for emitting light in a wavelength band in which it is difficult to increase the luminance because the hetero barrier difference is small. Further, the present invention is embodied not only in a light emitting diode but also in a semiconductor laser.

[0038]

As described above, according to the present invention, it is possible to form an effective barrier for electrons having high energy even with a relatively thick barrier layer. The need for better controllability is reduced compared to the prior art. Therefore, the multiple quantum barrier structure can be easily formed by the MOCVD method instead of the gas source MBE method. Therefore, the growth of the thick cladding layer after the formation of the multiple quantum barrier structure and the growth of the thicker current diffusion layer are continuously performed. Does not take a long time to do. Therefore, the gas source M
Compared with the conventional semiconductor light emitting device created by the BE method,
A semiconductor light emitting device suitable for mass production is provided.

[Brief description of the drawings]

FIG. 1 is an energy band diagram showing a multiple quantum barrier according to a first embodiment of the present invention.

FIG. 2 is an energy band diagram showing a multiple quantum barrier according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is an energy band diagram showing a multiple quantum barrier according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a graph showing wavelength dependence of luminance of various LEDs.

FIG. 7 is a diagram showing a conventional semiconductor light emitting device.

FIG. 8 is a diagram for explaining the operation of the semiconductor light emitting device of FIG. 7;

FIG. 9 is a view showing another conventional semiconductor light emitting device.

10 is an energy band diagram showing a multiple quantum barrier in the semiconductor light emitting device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 GaAs substrate 12 InGaAlP clad layer 13 InGaAlP clad layer 14 InGaAlP clad layer 15 Current diffusion layer 19 Buffer layer 21, 22 Electrode 31-35 InGaAlP barrier layer (lattice matching) 42 InAlP barrier layer (lattice mismatch) 43 InAlP barrier layer ( Lattice mismatch) 51 ZnSe barrier layer 100 Multiple quantum barrier layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiro Matsumoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Tadashi Takeoka 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Masaki Kondo 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Osamu Yamamoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-63-46788 (JP, A) JP-A-5-7051 (JP, A) JP-A-5-3367 (JP, A) JP-A-5-243676 (JP, A) JP-A-4-218994 (JP, A) JP-A-1-264287 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A semiconductor light emitting device comprising: a semiconductor substrate; and a multiple quantum barrier structure including a plurality of barrier layers and well layers lattice-matched to the semiconductor substrate, wherein the multiple quantum barrier structure comprises: A semiconductor light emitting device further comprising a barrier layer that is not lattice-matched to the semiconductor substrate.