U.S. patent application number 09/819858 was filed with the patent office on 2001-10-11 for semiconductor light emitting device capable of increasing light emitting efficiency.
Invention is credited to Hosoba, Hiroyuki, Kurahashi, Takahisa, Murakami, Tatsurou, Nakatsu, Hiroshi.
Application Number | 20010028061 09/819858 |
Document ID | / |
Family ID | 18618381 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028061 |
Kind Code |
A1 |
Hosoba, Hiroyuki ; et
al. |
October 11, 2001 |
Semiconductor light emitting device capable of increasing light
emitting efficiency
Abstract
On an n-GaP substrate transparent against a radiation light of
an InAlGaP based semiconductor element, a lattice distortion
relaxation layer, a clad layer 13, an active layer, and a clad
layer are created with InAlGaP. On top of the layers, there is
formed an In.sub.xGa.sub.1-xP current diffusion layer with In
composition ratio x equal to (0<X<1). Through these steps,
uneven depth on the crystal surface is decreased and crystal defect
concentration is lowered. In addition, the energy gap of the
current diffusion layer is made larger than the energy gap of the
active layer, so that the GaP substrate and the uppermost InGaP
current diffusion layer become transparent against a radiation
light from the active layer, resulting in increased light emitting
efficiency. Further, simple formation of layers from the lattice
distortion relaxation layer to the current diffusion layer in
sequence enables reduction of the production costs.
Inventors: |
Hosoba, Hiroyuki;
(Souraku-gun, JP) ; Nakatsu, Hiroshi; (Tenri-shi,
JP) ; Kurahashi, Takahisa; (Kashiba-shi, JP) ;
Murakami, Tatsurou; (Tenri-shi, JP) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Family ID: |
18618381 |
Appl. No.: |
09/819858 |
Filed: |
March 29, 2001 |
Current U.S.
Class: |
257/76 ;
257/87 |
Current CPC
Class: |
H01L 33/30 20130101 |
Class at
Publication: |
257/76 ;
257/87 |
International
Class: |
H01L 031/0256; H01L
027/15; H01L 031/12; H01L 033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2000 |
JP |
2000-104919 |
Claims
What is claimed is:
1. A semiconductor light emitting device comprising: a light
emitting portion made up of at least an active layer and clad
layers; and a current diffusion layer formed above a GaP substrate,
wherein the current diffusion layer is defined as
In.sub.xGa.sub.1-xP (0<X<1) where a composition ratio of In
equals to X.
2. A semiconductor light emitting device comprising: a light
emitting portion made up of at least an active layer and clad
layers; and a current diffusion layer formed above a GaP substrate,
wherein the current diffusion layer is defined as
In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0<y<1) where a
composition ratio of In equals to x and a composition ratio of A1
equals to y.
3. The semiconductor light emitting device according to claim 1,
wherein a normal of the GaP substrate surface inclines with respect
to a normal of a (100) plane toward a [011] direction.
4. The semiconductor light emitting device according to claim 3,
wherein the normal of the GaP substrate surface inclines with
respect to the normal of the (100) plane toward the [011] direction
by a range from 2 to 20 degrees.
5. The semiconductor light emitting device according to claim 1,
wherein the current diffusion layer is larger in an energy gap than
the active layer.
6. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of In equals to x,
and a composition ratio of A1 equals to y.
7. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
Al.sub.xGa.sub.1-xAs (0.ltoreq.x.ltoreq.1) where a composition
ratio of A1 equals to x.
8. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
In.sub.xAl.sub.yGa.sub.1-x-yAs (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of In equals to x,
and a composition ratio of A1 equals to y.
9. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
In.sub.xGa.sub.1-xAs.sub.yP.su- b.1-y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of In equals to x,
and a composition ratio of As equals to y.
10. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
Al.sub.xGa.sub.1-xAs.sub.ySb.s- ub.1-y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of A1 equals to x,
and a composition ratio of As equals to y.
11. The semiconductor light emitting device according to claim 1,
wherein the light emitting portions are defined as
In.sub.xAl.sub.yGa.sub.1-x-yN (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of In equals to x,
and a composition ratio of A1 equals to y.
12. The semiconductor light emitting device according to claim 1,
wherein a current interruption layer is provided in between the
light emitting portions and a current diffusion layer.
13. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is larger in an energy gap
than the active layer.
14. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is disposed in a center of
an interface between the light emitting portions and the current
diffusion layer.
15. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is disposed in a periphery
of an interface between a light emitting portion and a current
diffusion layer.
16. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is made up of a GaP.
17. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is defined as
In.sub.xGa.sub.1-xP (0<X<1) where a composition ratio of In
equals to x.
18. The semiconductor light emitting device according to claim 12,
wherein the current interruption layer is defined as
In.sub.xAl.sub.yGa.sub.1-x-y- P (0<x<1, 0.ltoreq.y.ltoreq.1)
where a composition ratio of In equals to x and a composition ratio
of A1 equals to y.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an AlGaInP-based compound
semiconductor light emitting device formed on a GaP substrate.
[0002] Semiconductor elements using AlGaInP based semiconductor
materials have been used as light emitting devices in a visible
area since they allows lattice-matching with a GaAs substrate and
have a largest direct transition band gap among III-V group
compound semiconductors. In particular, as light-emitting devices,
the semiconductor elements using AlGaInP based semiconductor
materials perform direct transition-type light emission in the
range from 550 nm to 690 nm, which brings about high light emitting
efficiency. However, when the GaAs substrate is used, they serve
not as a transparent layer but as a photoabsorption layer against a
radiation light. Consequently, in the case where plane
emission-type AlGaInP based semiconductor elements are used, high
luminance can not be achieved.
[0003] To solve this problem, there has been proposed an
architecture in which an AlGaInP based semiconductor light emitting
device is placed not on the GaAs substrate but on a GaP substrate
transparent against a radiation light of the AlGaInP based
semiconductor element (as shown in Japanese Patent Laid-Open
Publication No. 2714885).
[0004] The following description discusses the AlGaInP based
semiconductor light emitting device formed on the GaP substrate
with reference to FIG. 10. The AlGaInP based semiconductor light
emitting device formed on the GaP substrate is formed through the
following steps.
[0005] First, as shown in FIG. 10A, an AlGaInP clad layer 2, an
AlGaInP active layer 3, and an AlGaInP clad layer 4 are formed in
sequence on a GaAs substrate 1 by a MOCVD (metal-organic chemical
vapor deposition) method. Next, as shown in FIG. 10B, a GaP layer 5
is formed by a LPE (liquid-phase epitaxy) process utilizing yo-yo
solute supply method or temperature difference method. Then, as
shown in FIG. 10C, the GaAs substrate 1, which serves as a
photoabsorption layer, is removed. After the GaAs substrate 1 is
removed, a GaP current diffusion layer 6 is formed on the AlGaInP
clad layer 2 by the LPE process utilizing yo-yo solute supply
method or temperature difference method. Through the steps stated
above, an AlGaInP based semiconductor light emitting device is
formed on the GaP layer 5 as a substrate.
[0006] In the AlGaInP based semiconductor light emitting device
formed on the GaP substrate shown in FIGS. 10A to 10D, current is
diffused by the GaP current diffusion layer 6 and light is emitted
in the wide range of the active layer 3, which results in increased
light emitting efficiency. In addition, the GaP layer 5 and the GaP
current diffusion layer 6 are larger in the band gap than the
AlGaInP active layer 3, so that the emitted light is transmitted
without being absorbed, which implements high light emitting
efficiency.
[0007] However, the prior art AlGaInP based semiconductor light
emitting device formed on the GaP substrate has a problem stated
below. That is, as large as four steps are required to produce an
AlGaInP based semiconductor light emitting device. More
particularly, AlGaInP based light emitting portions 2 to 4 are
formed on a GaAs substrate 1 in the first production step, a GaP
layer 5 is formed thereon by the LPE process utilizing yo-yo solute
supply method or temperature difference method in the second step,
the GaAs substrate 1 is removed by etching in the third step, and
thereafter a GaP current diffusion layer 6 is formed by the LPE
process utilizing yo-yo solute supply method or temperature
difference method in the fourth step. This causes substantial
increase of the production costs.
[0008] Further, the GaAs substrate 1 is used and removed in the
production process, which causes further increase of the production
costs.
[0009] Accordingly, in order to avoid the step of removing the GaAs
substrate 1, an inventor made a trial of creating the AlGaInP based
light emitting portions and the GaP current diffusion layer
directly on the GaP substrate by the MOCVD method. In this case,
the AlGaInP based semiconductor light emitting device can be
produced by one growth step so that the GaAs substrate is not
necessary, which enables substantial decrease of the production
costs. However, the result of the trail disclosed that the AlGaInP
based light emitting portions having lattice mismatch are created
on the GaP substrate, and further thereon the GaP current diffusion
layer having lattice mismatch is created, so that crystallinity of
the GaP current diffusion layer is degraded, which creates uneven
surface and generates a number of crystal defects.
SUMMARY OF THE INVENTION
[0010] Accordingly, it is an object of the present invention to
provide a semiconductor light emitting device, enabling substantial
decrease of the production costs, having a good crystalline current
diffusion layer, and implementing considerable increase of light
emitting efficiency.
[0011] In order to achieve the above object, there is provided a
semiconductor light emitting device comprising: a light emitting
portion made up of at least an active layer and clad layers; and a
current diffusion layer formed above a GaP substrate,
[0012] wherein the current diffusion layer is defined as
In.sub.xGa.sub.1-xP(0<X<1) where a composition ratio of In
equals to X.
[0013] According to the above structure, the In.sub.xGa.sub.1-xP
current diffusion layer formed on top of the layers has the In
composition ratio X equal to (0<X<1) Consequently, the uneven
depth of the crystal surface is considerably diminished, and the
crystal defect concentration is substantially decreased. As a
result, a current diffusion layer with good crystallinity can be
obtained. In addition, In.sub.xGa.sub.1-xP is used as the current
diffusion layer, so that in the case where the active layer is
composed of an AlGaInP based semiconductor, the light emitted in
the active layer is absorbed neither by the GaP substrate nor by
the current diffusion layer, which implements substantial
improvement of light emitting efficiency. Further, the light
emitting device can be produced simply by forming each layer in
sequence on the GaP substrate, which contributes to reduction of
the production costs.
[0014] Also, there is provided a semiconductor light emitting
device comprising: a light emitting portion made up of at least an
active layer and clad layers; and a current diffusion layer formed
above a GaP substrate, wherein the current diffusion layer is
defined as In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0<y<1)
where a composition ratio of In equals to x and a composition ratio
of A1 equals to y.
[0015] According to the above structure, the
In.sub.xAl.sub.yGa.sub.1-x-yP current diffusion layer formed on top
of the layers has the In composition ratio x equal to
(0<X<1). Consequently, the uneven depth of the crystal
surface is considerably diminished, and the crystal defect
concentration is substantially decreased. As a result, a current
diffusion layer with good crystallinity can be obtained. In the
case where the band gap is decreased by increasing the value of the
In composition ratio x for improving the crystallinity, the band
gap of the current diffusion layer can be increased without
degrading the crystallinity by the step of increasing the value of
the A1 composition ratio y. Accordingly, when the active layer is
made up of an AlGaInP based semiconductor, the light emitted in the
active layer is not absorbed in the current diffusion layer, which
implements substantial improvement of light emitting efficiency.
Further, the light emitting device can be produced simply by
forming each layer in sequence on the GaP substrate, which
contributes to reduction of the production costs.
[0016] In one embodiment of the present invention, a normal of the
GaP substrate surface inclines with respect to a normal of a (100)
plane toward a [011] direction.
[0017] According to the above structure, the normal of the GaP
substrate surface inclines with respect to the normal of the (100)
plane toward the [011] direction, so that during film creation,
there appears on the crystal surface a (111) plane in which V group
atoms are migrating. Therefore, it becomes difficult for VI group
oxygen to mix with crystalls in the current diffusion layer, which
decreases the resistivity and lowers the drive voltage. Further,
there appears on the crystal surface a (111) plane which is easily
crystallized, so that the evenness of the current diffusion layer
is increased and the crystal defects are decreased.
[0018] In one embodiment of the present invention, the normal of
the GaP substrate surface inclines with respect to the normal of
the (100) plane toward the [011] direction by a range from 2 to 20
degrees.
[0019] The above structure brings about the most significant
decrease of the resistivity and improvement of the evenness of the
current diffusion layer.
[0020] In one embodiment of the present invention, the current
diffusion layer is larger in an energy gap than the active
layer.
[0021] According to the above structure, the current diffusion
layer is larger in an energy gap than the active layer, so that in
the case where the active layer is made up of an AlGaInP based
semiconductor, the light emitted in the active layer is absorbed
neither in the GaP substrate nor in the current diffusion layer,
which implements considerable increase of light emitting
efficiency.
[0022] In one embodiment of the present invention, the light
emitting portions are defined as In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) where a composition
ratio of In equals to x, and a composition ratio of A1 equals to
y.
[0023] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
550 nm to 680 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0024] In one embodiment of the present invention, the light
emitting portions are defined as Al.sub.xGa.sub.1-xAs
(0.ltoreq.x.ltoreq.1) where a composition ratio of A1 equals to
x.
[0025] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
700 nm to 880 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0026] In one embodiment of the present invention, the light
emitting portions are defined as In.sub.xA.sub.yGa.sub.1-x-yAs
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) where a composition
ratio of In equals to x, and a composition ratio of A1 equals to
y.
[0027] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
700 nm to 1500 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0028] In one embodiment of the present invention, the light
emitting portions are defined as
In.sub.xGa.sub.1-xAs.sub.yP.sub.1-y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of In equals to x,
and a composition ratio of As equals to y.
[0029] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
900 nm to 1700 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0030] In one embodiment of the present invention, the light
emitting portions are defined as
Al.sub.xGa.sub.1-xAs.sub.ySb.sub.1-y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) where a composition ratio of A1 equals to x,
and a composition ratio of As equals to y.
[0031] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
850 nm to 1700 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0032] In one embodiment of the present invention, the light
emitting portions are defined as In.sub.xAl.sub.yGa.sub.1-x-yN
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) where a composition
ratio of In equals to x, and a composition ratio of A1 equals to
y.
[0033] According to the above structure, the light emitted from the
light emitting portions having the emission wavelength ranging from
500 nm to 600 nm is absorbed neither in the GaP substrate nor in
the current diffusion layer, which implements considerable increase
of light emitting efficiency.
[0034] In one embodiment of the present invention, a current
interruption layer is provided in between the light emitting
portions and a current diffusion layer.
[0035] According to the above structure, the current interruption
layer provided in between the light emitting portions and the
current diffusion layer controls a current route inside the current
diffusion layer.
[0036] In one embodiment of the present invention, the current
interruption layer is larger in an energy gap than the active
layer.
[0037] According to the above structure, the current interruption
layer is larger in an energy gap than the active layer, so that in
the case where the active layer is made up of an AlGaInP based
semiconductor, the light emitted in the active layer is absorbed
neither in the GaP substrate nor in the current interruption layer,
which implements considerable increase of light emitting
efficiency.
[0038] In one embodiment of the present invention, the current
interruption layer is disposed in a center of an interface between
the light emitting portions and the current diffusion layer.
[0039] According to the above structure, the current interruption
layer is disposed in the center of the interface between the light
emitting portions and the current diffusion layer. Therefore,
inside the current diffusion layer, the current route is outspread
to the periphery, as a consequence of which light emission is
performed in the wide range of the active layer, resulting in
considerable increase of light emitting efficiency.
[0040] In one embodiment of the present invention, the current
interruption layer is disposed in a periphery of an interface
between a light emitting portion and a current diffusion layer.
[0041] According to the above structure, the current interruption
layer is provided in the periphery of an interface between the
light emitting portion and the current diffusion layer. Therefore,
inside the current diffusion layer, the current route is
concentrated in the central section, which contributes to
considerable improvement of light emitting directivity.
[0042] In one embodiment of the present invention, the current
interruption layer is made up of a GaP.
[0043] According to the above structure, GaP is used as the current
interruption layer, so that in the case where the active layer is
made up of an AlGaInP based semiconductor, the light emitted in the
active layer is absorbed neither in the GaP substrate nor in the
current interruption layer, which implements considerable increase
of light emitting efficiency.
[0044] In one embodiment of the present invention, the current
interruption layer is defined as In.sub.xGa.sub.1-xP (0<X<1)
where a composition ratio of In equals to x.
[0045] According to the above structure, InGaP is used as the
current interruption layer, so that in the case where the active
layer is made up of an AlGaInP based semiconductor, the light
emitted in the active layer is absorbed neither in the GaP
substrate nor in the current interruption layer, which implements
considerable increase of light emitting efficiency.
[0046] In one embodiment of the present invention, the current
interruption layer is defined as In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) where a composition
ratio of In equals to x and a composition ratio of A1 equals to
y.
[0047] According to the above structure, InAlGaP is used as the
current interruption layer, so that in the case where the active
layer is made up of an AlGaInP based semiconductor, the light
emitted in the active layer is absorbed neither in the GaP
substrate nor in the current interruption layer, which implements
considerable increase of light emitting efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0049] FIG. 1 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as the semiconductor
light emitting device of the present invention;
[0050] FIG. 2 is a view showing the relation between In composition
ratio x in an In.sub.xGa.sub.1-xP layer and an
In.sub.xAl.sub.yGa.sub.1-x-yP layer and the uneven depth of the
crystal surface;
[0051] FIG. 3 is a view showing the relation between In composition
ratio x in an In.sub.xGa.sub.1-xP layer and an
In.sub.xAl.sub.yGa.sub.1-x-yP layer and the crystal defect
concentration;
[0052] FIG. 4 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device different from that of
FIG. 1;
[0053] FIG. 5 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device different from that of
FIGS. 1 and 4;
[0054] FIG. 6 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device different from that of
FIGS. 1, 4, and 5;
[0055] FIGS. 7A and 7B are model views expressing the crystal
surface of a III-V group;
[0056] FIG. 8 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device different from that of
FIGS. 1, and 4 through 6;
[0057] FIG. 9 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device different from that of
FIGS. 1, 4 through 6, and 8;
[0058] FIG. 10 is a schematic view showing production steps of a
prior art AlGaInP based semiconductor light emitting device formed
on a GaP substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Hereinafter, the embodiments of the present invention will
be described in detail with reference to accompanied drawings.
[0060] (First Embodiment)
[0061] FIG. 1 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device in this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 1.
[0062] First, on an n-GaP substrate 11, there are created in
sequence in a laminated state: an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0<y<1) lattice distortion relaxation layer 12
(e.g. x=0.3, y=0.4, Si density of 5.times.10.sup.17 cm.sup.-3) with
the film thickness of 1 .mu.m; an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0<y<1) clad layer 13 (e.g. x=0.5, y=0.5, Si
density of 5.times.10.sup.17 cm.sup.-3) with the film thickness of
1 .mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 14 (e.g. x=0.5, y=0.15) with the
film thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.- 1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 15 (e.g.
x=0.5, y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; and a p-In.sub.xGa.sub.1-xP
(0<X<1) current diffusion layer 16 (e.g. x=0.01, Zn density
of 5.times.10.sup.18 cm.sup.-3) with the thickness of 5 .mu.m.
Next, an electrode 17 is formed below the n-GaP substrate 11, and
an electrode 18 is formed above the current diffusion layer 16.
Through the steps stated above, an AlGaInP-based compound
light-emitting device is completed.
[0063] In this embodiment, a p-In.sub.xGa.sub.1-xP layer (x=0.01)
is used as the current diffusion layer 16. FIG. 2 refers to the
relation of In composition ratio x in an In.sub.xGa.sub.1-xP layer
(0<x<0.5) and an In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<0.5, y=0.5) layer to the uneven depth of the crystal
surface. As shown in FIG. 2, in the GaP layer and the
Al.sub.0.5Ga.sub.0.5P layer with In composition ratio x=0, the
uneven depth on the crystal surface is as high as 1000 .ANG..
Contrary to this, if In composition ratio x is not equal to 0 and
an In content is present though how small, the uneven depth on the
crystal surface is considerably decreased. In the level of In
composition ratio x=0.01, the uneven depth is decreased to 200
.ANG. or lower. Therefore, the uneven depth of the crystal surface
can be decreased to 200 .ANG. or lower by creating the current
diffusion layer 16 which constitutes the uppermost layer of the
AlGaInP-based compound light-emitting device, with the
p-In.sub.xGa.sub.1-xP layer where In composition ratio x equals to
0.01.
[0064] FIG. 3 refers to the relation of In composition ratio X in
an In.sub.xGa.sub.1-xP layer (0<x<0.5) and an
In.sub.xAl.sub.yGa.sub.1- -x-yP (0<x<0.5, y=0.5) layer to the
crystal defect concentration. As shown in FIG. 3, in the GaP layer
and the Al.sub.0.5Ga.sub.0.5P layer with In composition ratio x=0,
the crystal defect concentration is extremely high. Contrary to
this, if In composition ratio x is not equal to 0 and an In content
is present though how small, the crystal defect concentration is
remarkably decreased. In the level of In composition ratio x=0.01,
the concentration is decreased to 500 defects/cm.sup.2 or lower.
Therefore, the crystal defect concentration can be decreased to 500
defects/cm.sup.2 or lower by creating the current diffusion layer
16 which constitues the uppermost layer of the AlGaInP-based
compound light-emitting device, with the p-In.sub.xGa.sub.1-xP
layer where In composition ratio x equals to 0.01.
[0065] The above-stated effect is obtained by the following two
reasons. The GaP layer has large energy to bond Ga atoms and P
atoms in its crystal, so that it is difficult to achieve migration
of Ga atoms across the growing crystal surface, which brings about
not a good layer growth but an insular growth of the crystal.
Therefore, it can be said that the GaP layer has a factor to
facilitate generation of crystal defects. On the other hand, In
atoms have small energy to bond with P atoms, so that it is easy to
achieve migration of In atoms across the growing crystal surface,
which brings about a good layer growth of the crystal. As a result,
the uneven depth on the crystal surface is remarkably decreased and
the evenness is improved, while at the same time, the crystal
defect concentration is considerably decreased.
[0066] Further in this embodiment, with the
In.sub.xAl.sub.yGa.sub.1-x-yP (x=0.5, y=0.15) active layer 14
(Eg=1.9 eV), p-In.sub.xGa.sub.1-xP (x=0.01) (Eg=2.26 eV) is used as
the current diffusion layer 16. Consequently, the
p-In.sub.xGa.sub.1-x-yP current diffusion layer 16 is larger in the
band gap than the active layer 14, so that the light emitted in the
In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 14 having the emission wavelength
ranging from 550 nm to 680 nm is extracted without being absorbed
by the n-GaP substrate 11 nor by the current diffusion layer 16
transparent against a radiation light of an InAlGaP based
semiconductor element.
[0067] In this embodiment as stated above, on the n-GaP substrate
11 transparent against a radiation light of an InAlGaP based
semiconductor element, there are formed a lattice distortion
relaxation layer 12 and a clad layer 13 composed of
In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0<y<1), and
thereafter formed an In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) active layer 14. Then,
there are further formed an In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 15, and an
In.sub.xGa.sub.1-xP (0<X<1) current diffusion layer 16.
Consequently, the uppermost layer is composed of the
In.sub.xGa.sub.1-xP current diffusion layer 16 where In composition
ratio x equals to (0<X<1). As a result, the uneven depth on
the crystal surface is decreased and the crystal defect
concentration is lowered.
[0068] Further, it is possible to make the energy gap of the
In.sub.xGa.sub.1-xP (0<X<1) current diffusion layer 16
(Eg=2.26 eV) larger than that of the active layer 14 (Eg=1.9 eV) by
setting the In composition ratio x of the current diffusion layer
16 equal to "0.01". Consequently, the lowermost layer n-GaP
substrate 11 and the uppermost p-InGaP current diffusion layer 16
are made transparent against the radiation light from the InAlGaP
active layer 14, by which light emitting efficiency is
increased.
[0069] In addition, an AlGaInP-based compound light-emitting device
in this embodiment can be obtained simply by forming a lattice
distortion relaxation layer 12 to a current diffusion layer 16 in
sequence on the n-GaP substrate 11 by the MOCVD method or the like.
Therefore, compared to the prior art AlGaInP based semiconductor
light emitting device created by the steps shown in FIG. 10, the
AlGaInP-based compound light-emitting device in this embodiment can
implement reduction of the production costs.
[0070] Hereinafter, description will be given of the present
invention in comparison to an AlGaInP-based compound semiconductor
light emitting device having a structure of FIG. 1, formed not on
the n-GaP substrate but on a GaAs substrate as stated below.
[0071] First, on an n-GaAs substrate there are created in sequence
in a laminated state an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0<y<1) buffer layer (e.g. x=0.3, y=0.4, Si
density of 5.times.10.sup.17 cm.sup.-3) with the film thickness of
1.0 .mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1,
0<y<1) clad layer (e.g. x=0.5, y=0.5, Si density of
5.times.10.sup.17 cm.sup.-3) with the film thickness of 1 .mu.m; an
In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer (e.g. x=0.5, y=0.2) with the film
thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.1- -x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer (e.g. x=0.5,
y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the film
thickness of 1.0 .mu.m; and a p-In.sub.xGa.sub.1-xP (0<X<1)
current diffusion layer (e.g. x=0.01, Zn density of
5.times.10.sup.18 cm.sup.-3) with the film thickness of 5 .mu.m.
Next, an electrode is formed below the n-GaAs substrate, and
another electrode is formed above the current diffusion layer.
[0072] In the case where the AlGaInP-based compound semiconductor
light emitting device is formed on the n-GaAs substrate as stated
above, the active layer and the clad layer have lattice-matching
with the n-GaAs substrate. Consequently, the p-In.sub.xGa.sub.1-xP
(0<X<1) current diffusion layer created thereon shows
relatively good crystallinity. However, the light emitted in the
active layer is absorbed by the n-GaAs substrate which acts as a
photoabsorption layer against a radiation light of an AlGaInP based
semiconductor element. As a result, light emitting intensity is
considerably decreased.
[0073] In an AlGaInP-based compound semiconductor light emitting
device of the present invention, other materials were used as the
active layer as an Al.sub.xGa.sub.1-xAs layer (0.ltoreq.x.ltoreq.1)
(light emitting wavelength of 700 nm to 880 nm); an
In.sub.xAl.sub.yGa.sub.1-x-yAs layer (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) (light emitting wavelength of 700 nm to 1500
nm); an In.sub.xGa.sub.1-xAs.sub.yP.sub.1-y layer
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) (light emitting
wavelength of 900 nm to 1700 nm); an
Al.sub.xGa.sub.1-xAs.sub.ySb.sub.1-y layer (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) (light emitting wavelength of 850 nm to 1700
nm); and an In.sub.xAl.sub.yGa.sub.1-x-yN layer
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) (light emitting
wavelength of 500 nm to 600 nm). In either case, the light emitted
in the active layer was not absorbed by the GaP substrate nor by
the In.sub.xGa.sub.1-xP current diffusion layer, so that sufficient
effects were verified.
[0074] It is noted that in this embodiment even if the composition
ratios x and y are properly changed in all the layers, sufficient
effects can be obtained which include considerable reduction of the
uneven depth on the crystal surface, substantial decrease of the
crystal defect concentration, and high light emitting efficiency
with transparency against a radiation light from the active layer.
It goes without saying that these effects are obtainable regardless
of structural differences such as the form of electrodes 17 and 18,
the presence and the form of a current interruption layer described
after, and the formation of a quantum well for the active layer
14.
[0075] (Second Embodiment)
[0076] FIG. 4 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device of this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 4. This
embodiment is identical to the first embodiment except the point
that the current diffusion layer uses an
In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0<y<).
[0077] First, on an n-GaP substrate 21, there are created in
sequence in a laminated state an n-AlGaInP lattice distortion
relaxation layer 22 (e.g. Si density of 5.times.10.sup.17
cm.sup.-3) with the film thickness of 0.5 .mu.m; an
n-In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) clad layer 23 (e.g. x=1.0, y=0.5, Si density
of 5.times.10.sup.17 cm.sup.-3) with the film thickness of 1 .mu.m;
an In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 24 (e.g. x=0.5, y=0.4) with the
film thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) active layer 25 (e.g.
x=0.5, y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; and a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0<y<1) current diffusion layer 26 (e.g. x=0.2,
y=0.2) with the thickness of 5 .mu.m. Next, an electrode 27 is
formed below the n-GaP substrate 21, and an electrode 28 is formed
above the current diffusion layer 26. Through the steps stated
above, an AlGaInP-based compound light-emitting device is
completed.
[0078] In this embodiment, a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(x=0.2, y=0.2) is used as the current diffusion layer 26. As shown
in FIGS. 2 and 3, as In composition x of the
p-In.sub.xAl.sub.yGa.sub.1-x-yP current diffusion layer 26 is
increased, the uneven depth on the crystal surface and the crystal
defect concentration are decreased. On the other hand, the band gap
is also decreased. However, as is clear from FIGS. 2 and 3, the
relation of In composition ratio x in the
p-In.sub.xAl.sub.yGa.sub.1-- x-yP layer to the uneven depth on the
crystal surface and the crystal defect concentration is independent
from Al composition ratio y.
[0079] Accordingly, in this embodiment, the A1 composition ratio y
of the p-In.sub.xAl.sub.yGa.sub.1-x-yP current diffusion layer 26
is increased, by which the band gap of the current diffusion layer
26 (Eg=2.3 eV) is made larger than the band gap of the
In.sub.xAl.sub.yGa.sub.1-x-yP (x=0.5, y=0.2) active layer 24
(Eg=2.0 eV) without changing the uneven depth on the crystal
surface and the crystal defect concentration. As a result, the
light emitted in the active layer 24 can be extracted without being
absorbed by the GaP substrate 21 or by the current diffusion layer
26 either.
[0080] (Third Embodiment)
[0081] FIG. 5 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device of this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 5. This
embodiment is identical to the first embodiment except the point
that the In.sub.xAl.sub.yGa.sub.1-x-yP current diffusion layer is
different in values of the composition ratio x and y.
[0082] First, on an n-GaP substrate 31, there are created in
sequence in a laminated state an n-AlGaInP lattice distortion
relaxation layer 32 (e.g. Si density of 5.times.10.sup.17
cm.sup.-3) with the film thickness of 0.5 .mu.m; an
n-In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) clad layer 33 (e.g. x=0.5, y=0.5, Si density
of 5.times.10.sup.17 cm.sup.-3) with the film thickness of 1.0
.mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 34 (e.g. x=0.5, y=0.15) with the
film thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 35 (e.g.
x=0.5, y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; and a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0<y<1) current diffusion layer 36 (e.g. x=0.2,
y=0.5) with the film thickness of 5 .mu.m. Next, an electrode 37 is
formed below the n-GaP substrate 31, and an electrode 38 is formed
above the current diffusion layer 36. Through the steps stated
above, an AlGaInP-based compound light-emitting device is
completed.
[0083] In this embodiment, a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(x=0.2, y=0.5) is used as the current diffusion layer 36. As shown
in FIGS. 2 and 3, as In composition x of the
p-In.sub.xAl.sub.yGa.sub.1-x-yP current diffusion layer 36 is
increased, the uneven depth on the crystal surface and the crystal
defect concentration are decreased because the relation of In
composition ratio x in the p-In.sub.xAl.sub.yGa.sub.1-x-yP layer to
the uneven depth on the crystal surface and the crystal defect
concentration is independent from A1 composition ratio y. On the
other hand, however, the band gap is decreased. Accordingly, the
band gap of the current diffusion layer 36 is smaller than the band
gap of the In.sub.xAl.sub.yGa.sub.1-x-yP (x=0.5, y=0.15) active
layer 34 (Eg=1.9 eV), which causes absorption of light in the
current diffusion layer 36.
[0084] Therefore, in this embodiment, the A1 composition ratio y is
increased to 0.5, by which the band gap of the current diffusion
layer 36 (Eg=2.0 eV) is made larger than the band gap of the active
layer 34. As a result, the light emitted in the active layer 34 can
be extracted without being absorbed by the GaP substrate 31 nor the
current diffusion layer 36 either.
[0085] (Fourth Embodiment)
[0086] FIG. 6 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device of this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 6. This
embodiment is identical to the third embodiment except the point
that the normal of the n-GaP substrate surface inclines with
respect to the normal of the (100) plane toward the [011]
direction.
[0087] First, on an n-GaP substrate 41 whose surface has a normal
inclining with respect to the normal of the (100) plane toward the
[011] direction by 15 degrees, there are created in sequence in a
laminated state an n-AlGaInP lattice distortion relaxation layer 42
(e.g. Si density of 5.times.10.sup.17 cm.sup.-3) with the film
thickness of 0.5 .mu.m; an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 43 (e.g.
x=0.5, y=0.5, Si density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) active layer 44 (e.g.
x=0.5, y=0.2) with the film thickness of 0.5 .mu.m; a
p-In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) clad layer 45 (e.g. x=0.5, y=0.5, Zn density
of 5.times.10.sup.17 cm.sup.-3) with the film thickness of 1.0
.mu.m; and a p-In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1,
0<y<1) current diffusion layer 46 (e.g. x=0.5, y=0.5, Zn
density of 5.times.10.sup.18 cm.sup.-3) with the thickness of 5
.mu.m. Next, an electrode 47 is formed below the n-GaP substrate
41, and an electrode 48 is formed above the current diffusion layer
46. Through the steps stated above, an AlGaInP-based compound
light-emitting device is completed.
[0088] In this embodiment, a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(x=0.5, y=0.5) is used as the current diffusion layer 46 the third
embodiment. Here, the normal of the n-GaP substrate 41 surface
inclines with respect to the normal of the (100) plane toward the
(011) direction, so that the resistance of the current diffusion
layer 46 is reduced, which enables decrease of drive voltage.
[0089] The reason for the above-stated effect will be described
hereinbelow with reference to FIGS. 7A and 7B. FIGS. 7A and 7B are
model views showing the crystal surface of a III-V group. As shown
in FIG. 7A, double-bonded V group atoms are present on the surface
of the (100) plane. As shown in FIG. 7B, however, with inclination
toward the [011] direction, there appears in the form of steps a
(111) plane, that is a crystal surface having single-bonded III
group atoms. The (111) plane is covered with single-bonded III
group atoms, so that in the process of film creation, V group atoms
(P atoms in the case of this embodiment) are supplied and bonded
with III group atoms in the (111) plane. However, since these
bonding are single bonding, the bonding strength thereof is weak
and therefore the bonds are easily relieved, resulting in migration
of V group atoms on the surface.
[0090] On the other hand, one of the reasons for high resistivity
of the p-In.sub.xAl.sub.yGa.sub.1-x-yP layer resides in mixture of
O (oxygen). O (oxygen) is a VI group element and therefore it is
easily fitted into a lattice position of a V group site. However,
in this embodiment, V group atoms are migrating on the crystal
surface because of the above-stated reason, so that a number of V
group atoms are present on the crystal surface, which hinders O
(oxygen) from going into a lattice position of a V group site. As a
result, the resistivity of the current diffusion layer 46 is
decreased.
[0091] Further, the normal of the n-GaP substrate 41 surface
inclines with respect to the normal of the (100) plane toward the
[011] direction, so that a (111) plane appears on the crystal
surface like steps. This means that a good crystal surface which
can easily achive layer growth is formed per step, which implements
remarkable reduction of the uneven depth of the crystal surface and
improvement of the evenness.
[0092] It is noted that in this embodiment, an angle of the normal
of the n-GaP substrate 41 surface inclines with respect to the
normal of the (100) plane toward the [011] direction is set to be
"15 degrees". However, it will be understood that the inclination
angle in the present invention is not limited to the angle stated
above, so that the same effect is achievable if the angle is within
the range from 2 degrees to 20 degrees.
[0093] Further, in this embodiment, inclination of the normal of
the n-GaP substrate surface is applied to the third embodiment in
which In.sub.xAl.sub.yGa.sub.1-x-yP is used as a current diffusion
layer. However, it will be understood that the inclination is also
applicable to the first embodiment in which In.sub.xGa.sub.1-xP is
used as a current diffusion layer.
[0094] (Fifth Embodiment)
[0095] FIG. 8 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device of this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 8. This
embodiment is identical to the third embodiment except the point
that a current interruption layer is provided in the central
portion in between the clad layer and the current diffusion
layer.
[0096] First, on an n-GaP substrate 51, there are created in
sequence in a laminated state an n-AlGaInP lattice distortion
relaxation layer 52 (e.g. Si density of 5.times.10.sup.17
cm.sup.-3) with the film thickness of 0.5 .mu.m; an
n-In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) clad layer 53 (e.g. x=0.5, y=0.5, Si density
of 5.times.10.sup.17 cm.sup.-3) with the film thickness of 1.0
.mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 54 (e.g. x=0.38, y=0.2) with the
film thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 55 (e.g.
x=0.5, y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0.ltoreq.y.ltoreq.1) current interruption layer 56
(e.g. x=0.20, y=0.20, Si density of 5.times.10.sup.17 cm.sup.-3)
with the film thickness of 0.5 .mu.m; and a
p-In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0.ltoreq.y.ltoreq.1)
current diffusion layer 57 (e.g. x=0.2, y=0.2, Zn density of
5.times.10.sup.18 cm.sup.-3) with the film thickness of 5 .mu.m.
Next, an electrode 58 is formed below the n-GaP substrate 51, and
an electrode 59 is formed above the current diffusion layer 57.
Through the steps stated above, an AlGaInP-based compound
light-emitting device is completed.
[0097] The In.sub.xAl.sub.yGa.sub.1-x-yP current interruption layer
56 is disposed in the central portion of the interface between the
clad layer 55 and the current diffusion layer 57. The electrode 59
on the current diffusion layer 57 is disposed in the central
portion of the upper surface of the current diffusion layer 57 so
as to be overlapped with the current interruption layer 56.
[0098] As shown in the above description, in this embodiment, the
current interruption layer 56 is provided in the central portion in
between the clad layer 55 and the current diffusion layer 57.
Accordingly, with the effect of the current interruption layer 56,
current supplied from the electrode 59 is further diffused widely
inside the current diffusion layer 57. As a result, light emission
is performed in the wide range of the active layer 54, by which
light extraction efficiency is further increased.
[0099] Although In.sub.xAl.sub.yGa.sub.1-x-yP is used as the
current interruption layer 56 in the above-stated embodiment, it
will be understood that the same effect can be implemented by using
GaP or In.sub.xGa.sub.1-xP.
[0100] (Sixth Embodiment)
[0101] FIG. 9 is a cross sectional view showing an AlGaInP-based
compound semiconductor light emitting device as a semiconductor
light emitting device of this embodiment. Hereinbelow, description
will be made of the AlGaInP-based compound semiconductor light
emitting device in this embodiment with reference to FIG. 9. This
embodiment is identical to the fifth embodiment except the point
that the current interruption layer between the clad layer and the
current diffusion layer as well as an electrode on the current
diffusion layer are provided on the periphery.
[0102] First, on an n-GaP substrate 61, there are created in
sequence in a laminated state an n-AlGaInP lattice distortion
relaxation layer 62 (e.g. Si density of 5.times.10.sup.17
cm.sup.-3) with the film thickness of 0.5 .mu.m; an
n-In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) clad layer 63 (e.g. x=0.5, y=0.5, Si density
of 5.times.10.sup.17 cm.sup.-3) with the film thickness of 1.0
.mu.m; an In.sub.xAl.sub.yGa.sub.1-x-yP (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1) active layer 64 (e.g. x=0.5, y=0.2) with the
film thickness of 0.5 .mu.m; a p-In.sub.xAl.sub.yGa.sub.1-x-yP
(0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) clad layer 65 (e.g.
x=0.5, y=0.5, Zn density of 5.times.10.sup.17 cm.sup.-3) with the
film thickness of 1.0 .mu.m; an n-In.sub.xAl.sub.yGa.sub.1-x-yP
(0<x<1, 0.ltoreq.y.ltoreq.1) current interruption layer 66
(e.g. x=0.01, y=0.01, Si density of 5.times.10.sup.17 cm.sup.-3)
with the film thickness of 0.5 .mu.m; and a
p-In.sub.xAl.sub.yGa.sub.1-x-yP (0<x<1, 0.ltoreq.y.ltoreq.1)
current diffusion layer 67 (e.g. x=0.2, y=0.2, Zn density of
5.times.10.sup.18 cm.sup.-3) with the film thickness of 5 .mu.m.
Next, an electrode 68 is formed below the n-GaP substrate 61, and
an electrode 69 is formed above the current diffusion layer 67.
Through the steps stated above, an AlGaInP-based compound
light-emitting device is completed.
[0103] In this embodiment, a current interruption layer 66 is
disposed in the peripheral portion between the clad layer 65 and
the current diffusion layer 67. Accordingly, with the effect of the
current interruption layer 66, current supplied from the electrode
69 is concentrated in the central portion inside the current
diffusion layer 67, by which light emission directivity is
improved.
[0104] Although In.sub.xAl.sub.yGa.sub.1-x-yP is used as the
current interruption layer 66 in the above-stated embodiment, it
will be understood that the same effect can be implemented by using
GaP or In.sub.xGa.sub.1-xP.
[0105] It goes without saying that in the fifth and sixth
embodiments, the same effect as in the case of the fourth
embodiment can be implemented by inclining the normal of the n-GaP
substrate 61 surface with respect to the normal of the (100) plane
toward the [011] direction.
[0106] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
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