JPH05190902A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To reduce necessity to implement growth on the order of an atomic layer with good controllability by involving another barrier layer in which multiquantum barrier structure is not matching a semiconductor substrate in a lattice. CONSTITUTION:First of all, a comparatively thick layer 31 of InGaAlP is grown on an active layer 13. After that, a well layer 40 of InGaP and barrier layers 35 to 33 of InGaAlP are alternately grown thereon. Each of those layers is matching a substrate of GaAs in a lattice. After the barrier layer 33 of InGaAlP is formed, a barrier layer 42 of InAlP is grown. The barrier layer 42 of InAlP is not matching the substrate of GaAs in a lattice. Thus, a multi-quantum barrier structure 100 has the barrier layer 42 of InAlP made of a semiconductor material which does not match the substrate of GaAs in a lattice. The barrier layer 42 has larger energy-band gap than the barrier layers 35 to 33 of InGaAlP, so that it acts as a barrier well enough against electrons having high energy even when it is not formed in a thin film.

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 element such as a light emitting diode and a semiconductor laser capable of emitting high-luminance short wavelength light in the green band.

[0002]

2. Description of the Related Art In recent years, a light emitting diode (hereinafter referred to as "LED"), which is one of semiconductor light emitting elements, has been attracting attention as a display device used indoors and outdoors. LED
It is considered that the market of LEDs as an outdoor display will expand in the next several years as the brightness of the light emitted by the LED increases. As described above, the LED is expected as a display device to replace the neon sign in the future.

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

As an example of a conventional double hetero type LED, an InGaAlP yellow band LED is shown in FIG. Figure 8
[FIG. 3] is a diagram for explaining an operating principle of an InGaAlP-based yellow LED.

This conventional InGaAlP yellow LED
Is an n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P clad layer (thickness: 1.5 μm) 12 sequentially grown on the n-GaAs substrate 11 by the MOCVD method, and undoped In
_{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 clad 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. In addition, this InGaAlP yellow band LED is n-
An electrode 21 formed on the bottom surface of the GaAs substrate 11, a p-
The electrode 22 is formed on the upper surface of the Ga _0.2 Al _0.8 As current diffusion layer 15. InGaAlP yellow belt LE
The side surface 30 of D is processed by etching in order to improve the light extraction efficiency. The entire chip of the InGaAlP yellow LED shown in FIG. 7 is molded with resin (not shown).

InGaAlP yellow LED 21
When a driving current is passed 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 layer are formed as shown in FIG. A hetero barrier for holes and electrons (about for electrons) between 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, respectively. A barrier of 0.2 eV) is formed. 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 P Since it is effectively confined in the active layer 13, the luminous efficiency is increased.

Among the LEDs that emit light in the green band, an LED based on an indirect transition type N-doped GaP material provides yellow-green light emission having a brightness of 1000 mcd. An LED based on a pure green GaP material that is not N-doped produces a light emission with a brightness of several 100 mcd. However, the luminance of light emission in these green bands is lower than the luminance of light emission in the red to yellow bands.

[0008]

At present, for a visible light LED which emits light in a green band having a relatively low brightness, particularly light having a wavelength of about 555 nm (light emission in a pure green band), the high brightness thereof is great. It is an issue. However, it is very difficult to increase the brightness. The reason is that the GaP-based semiconductor suitable for light emission in the pure green band is originally an indirect transition type semiconductor, and therefore its light emission efficiency is low. Therefore, it has been proposed to form a double heterostructure by using a direct transition type InGaAlP-based material having an energy band gap corresponding to light emission in the green band. The LED having such a double hetero structure has In _0.5 (Ga _{1 -X) in} the cladding layers 12 and 14 of the LED shown in FIG.
Al _x ) _0.5 P (x = 0.7 to 1.0) is replaced with a clad 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 the active layer. However, there is a problem in that the difference in energy gap between the active layer and the cladding layer, particularly ΔE _gc (FIG. 8) corresponding to the electron barrier, cannot be made sufficiently large. When the cladding layer is In _0.5 Al _0.5 P, ΔE _gc = 0.12 eV or so. For this reason, the number of electrons leaking in the hetero barrier increases, so that the light emission efficiency decreases and the high brightness cannot be achieved.

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

FIG. 9 shows a conventional LED having the above-mentioned multiple quantum barrier structure. LED of FIG. 9 and LE of FIG.
The main structural difference from D is that the LED of FIG. 9 has a multi-quantum barrier structure 100 between the active layer 13 and the cladding layer 14.
Is in the point of having. There is no substantial difference between the other components. FIG. 10 shows the structure of the multiple quantum barrier structure 100 included in the LED of FIG. 9 in more detail. As an example, referring to FIG. 10, InGaAl
The structure of the P multiple quantum barrier structure 100 will be described in accordance with its manufacturing method.

First, In _0.5 (Ga) having a relatively large thickness (200 angstrom as an example) is formed on the active layer 13.
_{A 1-X} Al _X ) _0.5 P layer (x = 0.7 to 1.0) 31 is grown. Then, the In _0.5 (Ga _1-X Al _X ) _0.5 P layer 31 is formed.
In _0.5 Ga _0.5 P well layer 40 and In _0.5 (Ga
_1-X Al _X ) _0.5 P layer (x = 0.7 to 1.0) Barrier layer 35
Alternately grow ~ 32. The layer 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. Note that in this specification, an In _0.5 Ga _0.5 P layer and an In _0.5 (Ga _{1 -X} A
The _{l X) 0.5 P (x =} 0.7~1.0) layer, respectively, simplified to, may be expressed as InGaP layer and InGaAlP layers.

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
The P barrier layers 34, 33 and 32 have a layer structure represented by 30 Å × 2, 20 Å × 4 and 10 Å × 6, respectively. All of these layers are lattice-matched to the GaAs substrate 11. After forming the barrier layer 32, the thick InG is continuously formed.
The aAlP clad layer 14 is grown.

The function of the thus-formed multiple quantum barrier structure 100 is as follows. The relatively thick InGaAlP layer 31 adjacent to the active layer 13 and the active layer 13 form a barrier against low energy electrons. This barrier is to prevent electron tunneling. Two pairs of barriers (40 angstroms thick) 35 formed on the InGaAlP layer 31 (rightward in FIG. 10) reflect electrons having a slightly higher energy.
The barriers 34 to 32 successively reflect electrons having high energy and effectively form a barrier Ue higher than the classical barrier (barrier determined by the material) U ₀ .

In this conventional LED that emits light in the green band, the barrier Ue is more than 0. 0% than the barrier U ₀ (0.12 eV).
It is about 1 eV higher. Therefore, a barrier of 0.2 eV or more sufficient to confine the electrons can be obtained.

According to such a structure, a barrier layer having a thin layer thickness (in the present case, the thinnest layer is 10 Å),
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 controlling atomic layer order growth with good controllability is used.

However, with this gas source MBE method, although it is possible to form an ultrathin film structure such as the multiple quantum barrier structure 100, the subsequent growth of a thick clad layer,
There is a problem that it takes a long time to grow a thicker current diffusion layer. Therefore, the LED produced by the gas source MBE method has a drawback that it is not suitable for mass production.

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

Another object of the present invention is to provide a high-brightness 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 includes a semiconductor substrate and a multiple quantum barrier structure including a plurality of barrier layers and well layers lattice-matched to the semiconductor substrate. And the multiple quantum barrier structure is
It further includes a barrier layer that is not lattice matched to the semiconductor substrate, thereby achieving the above objectives.

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
A layer having a larger energy band gap than the P layer is preferable.

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

[0022]

EXAMPLES 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 structure of this example and the structure shown in FIG. 10 lies in the difference in the multiple quantum barrier structure 100.

The structure of the multiple quantum barrier structure 100 of this embodiment will be described below with reference to FIG. 1 and its manufacturing method.

First, on the active layer 13, In _0.5 (Ga) having a relatively large thickness (200 angstrom as an example) is formed.
_{A 1-X} Al _X ) _0.5 P layer (x = 0.7 to 1.0) 31 is grown. Then, the In _0.5 (Ga _1-X Al _X ) _0.5 P layer 31 is formed.
In _0.5 Ga _0.5 P well layer 40 and In _0.5 (Ga
_1-X Al _X ) _0.5 P layer (x = 0.7 to 1.0) Barrier layer 35
Alternately grow ~ 33. In _0.5 Ga _0.5 P well layer 4
Layer thicknesses of 0 are all layer thickness L ₁ = 60 Å. On the other hand, 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 GaA
s Substrate 11 is lattice-matched.

After forming the InGaAlP barrier layer 33,
An In _0.2 Al _0.8 P barrier layer 42 is grown. In _0.2 A
The 1 _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 42 is not lattice-matched to the GaAs substrate 11. All layers constituting the multi-quantum barrier structure 100 are grown by MOCVD. Further, except for the multiple quantum barrier structure 100, it is manufactured by the same method as the conventional method.

Thus, the main feature of the semiconductor light emitting device of this embodiment is that the multiple quantum barrier structure 1 adopted in this embodiment is used.
00 has an In _0.2 Al _0.8 P barrier layer 42 made of a semiconductor material that is not lattice-matched to the GaAs substrate 11. The In _0.2 Al _0.8 P barrier layer 42 is formed of In _0.5 (Ga _{1 -X}
Al _x ) _0.5 P (x = 0.7 to 1.0) barrier layer 35 to 32
Since it has a larger energy band gap of 0.02 eV or more than that of In _0.5 (Ga _1-x Al _x ) _0.5 P barrier layer (10 angstrom) 32, it does not have to be a thin film and has a sufficient barrier against high-energy electrons. Become. The thickness of the In _0.2 Al _0.8 P barrier layer 42 in 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 this embodiment, the thinnest layer has a layer thickness of about 20 Å. Therefore, each of the barrier layers 35 to 33 and 42 and the well layer 40 that form the multi-quantum barrier structure 100 could be grown with good controllability even by the ordinary MOCVD method.

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

FIG. 3 shows the external structure of the second embodiment of the present invention. Details of the construction of the multi-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 nG
n-Ga is provided between the aAs substrate 11 and the n-clad 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 the In _0.5 (Ga _0.3 Al) of the first embodiment is different as shown in FIG.
_0.7 ) _0.5 P layer (thickness 20 Å × 4) 33 is In _0.3 Al _0.7 P barrier layer (thickness 30 Å × 4)
2) It is replaced by 43. This I
The n _0.3 Al _0.7 P barrier layer 43 is also a semiconductor layer having a lattice mismatch.

When the LED of this embodiment is molded in a package having a size of 5 mmΦ and driven by a current of 20 mA, the wavelength is 556 nm and the color is pure green, 4.7c.
Light emission having a brightness of d was obtained.

FIG. 5 shows the external structure of the third embodiment of the present invention. The configuration of the multi-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 has 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 expanded, and the p-Ga _0.2 Al _0.8 As current diffusion layer 15 can be formed thin (for example, formed to about 1 μm). The second difference between the first embodiment and the third embodiment is that, as shown in FIG.
The In _0.2 Al _0.8 P barrier layer 42 of the above example is replaced by a ZnSe layer (thickness 60 Å × 1) 51. The ZnSe layer 51 is also a layer made of a lattice mismatching material. The third difference between the first embodiment and the third embodiment is that the well layer of the multi-quantum barrier structure 100 is not In _0.5 Ga _0.5 P well layer 40 but In
_0.5 (Ga _0.8 Al _0.2 ) _0.5 P Well layer 50.

According to this example, light emission of pure green having a wavelength of 552 nm and a brightness of 6 cd was obtained.

In any of the above embodiments, the barrier layer 42 of a lattice mismatching material having a large energy band gap,
Although 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, they exert a sufficient barrier function. In addition, the barrier layer is MOC
Since it can be grown by the VD method, it is suitable for mass production. Further, the reason why not all the barrier layers are formed of the lattice mismatching material is that the active layer 13 is adversely affected by doing so.

As described above, as the embodiment of the present invention, the conventional LE is used.
I of the lattice-matching system constituting the multi-quantum barrier structure 100 of D
The nGaAlP barrier layers 32 and 33 are made of 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 with a lattice-mismatched InAlP layer or ZnSe layer. However, it is not preferable to configure all the barrier layers with a lattice mismatching material in consideration of the influence on the active layer 13 described above.

In addition, as a material of lattice mismatching system, In
Even materials other than AlP and ZnSe having a larger energy band gap than the lattice matching materials (for example, InGaAlP, ZnS, ZnSSe, and CdZ)
nS or the like).

Further, the present invention is not limited to the semiconductor light emitting device that emits light in the green band. Since the hetero barrier difference is small, the present invention is applied to all semiconductor light emitting devices for emitting light in the wavelength band in which it is difficult to increase the brightness. Furthermore, the present invention is not limited to light emitting diodes, but can be embodied in semiconductor lasers.

[0038]

As described above, according to the present invention, it is possible to form an effective barrier against electrons having high energy even with a barrier layer having a relatively large layer thickness, so that layer growth on the atomic layer order is achieved. The need for good controllability is reduced compared to the prior art. Therefore, since the multiple quantum barrier structure can be easily formed by the MOCVD method instead of the gas source MBE method, 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 can be continuously performed. It doesn't 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 drawings]

FIG. 1 is an energy band diagram showing a multiple quantum barrier in the 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 the wavelength dependence of the brightness 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.

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

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

[Explanation 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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akihiro Matsumoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Tadashi Takeoka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Incorporated (72) Inventor Masaki Kondo, 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) In-house, Osamu Yamamoto 22-22, Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture

Claims (1)

[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 a semiconductor substrate.