JPH11307880A - Semiconductor light emitting device - Google Patents

Abstract

(57) [Problem] AlGa capable of improving luminous efficiency
Provided is an InNP-based semiconductor light emitting device. SOLUTION: On an n-type GaAs substrate 101, an n-type Ga
As buffer layer 102, n-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P cladding layer 103, non-doped (Al _0.5 Ga _0.5 )
_0.5 In _0.5 P lower optical waveguide layer 104, non-doped Ga _0.5
In _0.5 P intermediate layer 105a, non-doped Ga _0.6 In _0.4
N _0.01 P _0.99 light emitting layer 106, non-doped Ga _0.5 In _0.5
P intermediate layer 105b, non-doped (Al _0.5 Ga _0.5 ) _0.5 I
n _0.5 P upper optical waveguide layer 107, p-type (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P cladding layer 108, p-type Ga _0.5 In _0.5 P spike prevention layer 109, p-type GaAs contact layer 110
Are sequentially stacked.

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 which can be used for a writing device for an optical disk or the like.

[0002]

2. Description of the Related Art Conventionally, the emission wavelength is 680 nm to 630 nm.
It has been known that in a semiconductor laser device using an AlGaInP-based material, it is difficult to perform high-temperature high-output operation because the band discontinuity on the conduction band side is small. In order to realize a high-temperature and high-output operation, a structure as shown in FIG. 7 has been proposed (Japanese Patent Application Laid-Open No. 08-307005). The structure of FIG.
On an n-type GaAs substrate 1 having a (001) plane, an n-type Ga
As buffer layer 2, n-type AlGaInP optical waveguide layer 3, three undoped GaInNP compression-strained quantum well layers with a thickness of 7 nm and 1.5% strain, and undoped AlGaI with a thickness of 4 nm
A film thickness of 1 is formed on both sides of the nP strain-free quantum barrier layer and the quantum well layer.
Multiple quantum well active layer 4, composed of undoped strain-free AlGaInP light separating confinement layer with 0 nm, p-type Al
GaInP optical waveguide layer 5, p-type AlGaInP etch stop layer 6, p-type AlGaInP optical waveguide layer 7, p-type GaI
The nP layer 8 is formed by sequentially epitaxially growing the nP layer 8 by a metal organic chemical vapor deposition method. Thereafter, a SiO ₂ mask is formed by photolithography, and the layers 8 and 7 are etched and removed until the layer 6 by chemical etching to form a ridge stripe. Next, an n-type GaAs current confinement layer / light absorption layer 9 is selectively grown while leaving the SiO ₂ mask. Further, after the p-type GaAs contact layer 10 is buried and grown, a p-electrode 11 and an n-electrode 12 are deposited. Further, the substrate is cut into pieces in the form of an element by cleavage scribing to obtain an element having a sectional structure shown in FIG.

In the semiconductor laser device shown in FIG. 7, the conduction band discontinuity ratio is reduced from 0.5 to 0.6 to 0.8 to 0.9 by using a GaInNP quantum well layer containing nitrogen. Has increased. Thereby, high-temperature operation and high-output operation are improved.

[0004]

However, the inventor of the present application has found that it is difficult to sufficiently increase the luminous efficiency in a semiconductor light emitting device in which a GaInNP layer is directly formed on an AlGaInP layer. 8 was proposed. In the structure of FIG. 8, the n-GaAs substrate 2
1 on the n-GaAs buffer layer 22, n-
(Al _x1 Ga _1-x1 ) _0.51 In _0.49 P cladding layer (0 <x1
≦ 1) 23, n- (Al _x2 Ga _{1 -x2} ) _0.51 In _0.49 P guide layer (0 <x2 <x1 ≦ 1) 24, multiple quantum well structure
(MQW) 25, p- (Al x2 Ga 1-x2) 0.51 In 0.49 P guiding layer _{26, p- (Al x1 Ga 1} -x1) 0.51 In 0.49 P cladding layer 27, p-GaAs contact layer 28 is formed ing. Further, the multiple quantum well portion 25 includes the guide layer 24,
A structure in which a Ga _0.51 In _0.49 P intermediate layer 31 is inserted at each boundary between an (Al _x2 Ga _{1 -x2} ) _0.51 In _0.49 P barrier 29 having the same composition as 26 and a Ga _0.51 In _0.49 N _0.01 P _0.99 active layer 30. It has become. In FIG. 8, an SiO ₂ layer 32 as an insulating film and a p-side electrode 33 are further formed on the contact layer 28.
Are formed, and an n-side electrode 34 is formed on the back surface of the element.

In the semiconductor laser device shown in FIG.
_0.51 In _0.49 N _0.01 P _0.99 Active layer 30 and (Al _x2 Ga
_1-x2 ) _0.51 In _0.49 P barrier layer 29 or (Al _x2 Ga
_1-x2 ) _0.51 In _{0.49 At} each boundary between the P guide layers 24 and 26, Ga which is a III-V group semiconductor containing no Al and N is used.
By inserting the _0.51 In _0.49 P intermediate layer 31,
Ga _0.51 In _0.49 N _0.01 P _0.99 active layer 3 with good crystallinity
0 can be obtained, and the luminous efficiency of the multiple quantum well structure can be increased.

The group V element is composed of As or P II
When nitrogen (N) is introduced as a group V constituent element into an IV group semiconductor material, a large bowing occurs with respect to the nitrogen composition of the forbidden band width. For this reason, a relatively small nitrogen composition reduces the forbidden band width. At this time, the forbidden band width is reduced mainly on the conduction band side. In particular, when Al is not included as a group III element, the band edge of the valence band shifts to a lower energy side by introducing nitrogen. Therefore, a GaInNP active layer and a G
The band diagram of the aInP intermediate layer is as shown in FIG. 1A (type II). Therefore, particularly in the low injection region, the overlap integral between the conduction band electrons and the valence band holes is small, and there is a problem that the luminous efficiency is low.

An object of the present invention is to provide an AlGaInNP-based semiconductor light emitting device capable of improving luminous efficiency.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, Ga _x is formed on a GaAs substrate.
In _1-x N _y and the light emitting layer composed of P _1-y mixed crystal semiconductor, (Al _z
Ga1 _-z ) _{wIn1 -w} P-cladding layer or optical waveguide layer or barrier layer, and Al and N-free III- layer laminated between the light emitting layer and the cladding layer or optical waveguide layer or barrier layer. A semiconductor light emitting device having an intermediate layer made of a group V semiconductor, wherein the intermediate layer lattice-matches with a GaAs substrate, and the light emitting layer has a compressive strain with respect to the GaAs substrate. .

According to a second aspect of the present invention, a light emitting layer comprising a Ga _x In ₁ -xN _y P _{1 -y} mixed crystal semiconductor and a (Al _z Ga _{1 -z} ) _w In _{1 -w a} P cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer, the III-V semiconductor not containing Al and N. Wherein the intermediate layer lattice-matches with the GaAs substrate, and the light-emitting layer has a tensile strain with respect to the GaAs substrate.

[0010] According to a third aspect of the invention, in the semiconductor light-emitting device according to claim 1 or claim 2 wherein, the Delta] E _N and the amount of change in the energy level of the valence band due to the addition of nitrogen, Delta] E _strain Is the amount of change in the energy level of the valence band due to strain, and ΔE _v is the amount of change in the energy level of the valence band due to changing the group III element composition from the lattice matching condition. Ga _x In _1-x N _y P
_The light-emitting layer made of the _1-y mixed crystal semiconductor has ΔE _N + ΔE _strain +
It is characterized by having a composition satisfying ΔE _v > 0.

Further, the invention according to claim 4 provides a light emitting layer comprising a Ga _x In ₁ -xN _y P _{1 -y} mixed crystal semiconductor on a GaAs substrate, and (Al _z Ga _{1 -z} ) _w In _{1 -w a} P cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer, the III-V semiconductor not containing Al and N. Wherein the light emitting layer is doped with a p-type impurity.

Further, according to a fifth aspect of the present invention, a light emitting layer comprising a Ga _x In _1-x N _y P _1-y mixed crystal semiconductor and a (Al _z Ga _1-z ) _w In _{1 -w a} P cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer, the III-V semiconductor not containing Al and N. Wherein the intermediate layer provided at least on the n-type cladding layer side is doped with an n-type impurity.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The semiconductor light emitting device according to the first embodiment of the present invention includes a light emitting layer made of a Ga _x In _1-x N _y P _1-y mixed crystal semiconductor and a (Al _z Ga _1-z ) _w In on a GaAs substrate. _1-w P
A cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer made of a group III-V semiconductor not containing Al and N, laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer. Here, the intermediate layer lattice-matches with the GaAs substrate, and the light emitting layer has a compressive strain with respect to the GaAs substrate.

As a theory of band offset in a heterostructure made of a compound semiconductor, Harrison's strong coupling theory is widely known. Further, the band edge shift amount Δ of the conduction band and the valence band when compressive strain is applied to the compound semiconductor layer Δ
E _c and ΔE _v are represented by the following equations.

[0015]

ΔE _c = −2a {(C ₁₁ −C ₁₂ ) / C ₁₁ } ε ΔE _v = 2a ′ {(C ₁₁ −C ₁₂ ) / C ₁₁ } ε−b {(C ₁₁ + 2C
₁₂ ) / C ₁₁ } ε

Here, a is the hydrostatic deformation potential of the conduction band, a 'is the hydrostatic deformation potential of the valence band, b is the axial deformation potential, ε is the lattice strain, and C ₁₁ and C ₁₂ are the elastic constants. .

FIG. 2A shows GaAs obtained from the above-mentioned Harrison theory and energy level shift due to compression strain.
The energy levels E _c and E _v of the conduction band and the valence band when compressive strain Ga _x In _1-x P is formed on the substrate are shown. The parameter of the strain amount is the Ga composition amount x.
From FIG. 2A, the Ga composition x is changed to the lattice matching condition x =
By making the film smaller than 0.52 so that the film has a compressive strain, the energy level E _v of the valence band becomes GaAs.
It can be seen that the energy shifts to a higher energy side than in the case of lattice matching with the s substrate. Therefore, GaAs is used as the intermediate layer.
When Ga _0.5 In _0.5 P lattice-matched to s is used and compressive strain GaInNP is used as the light emitting layer, the shift amount of the valence band edge due to the introduction of nitrogen is compensated as shown in FIG. Thus, valence band discontinuity with the GaInP intermediate layer is reduced. Thereby, leakage of holes from the GaInNP light emitting layer to the GaInP intermediate layer can be reduced, and the light emission efficiency can be improved.

The semiconductor light emitting device according to the second embodiment of the present invention comprises a light emitting layer made of a Ga _x In ₁ -xN _y P _{1 -y} mixed crystal semiconductor on a GaAs substrate, and (Al _z Ga _{1 -z} ) _w In _1-w P
A cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer made of a group III-V semiconductor not containing Al and N, laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer. Here, the intermediate layer lattice-matches with the GaAs substrate, and the light emitting layer has a tensile strain with respect to the GaAs substrate.

With respect to the energy levels at the lower end of the conduction band and the upper end of the valence band based on the vacuum level of the compound semiconductor,
For example, in the document `` Appl.Phys.Lett., Vol. 60, No. 5, pp. 630-632
(1992) ". The band edge shift amounts ΔE _c and ΔE _v of the conduction band and the valence band when a tensile strain is applied to the compound semiconductor layer are expressed by the following equations.

[0020]

ΔE _c = −2a {(C ₁₁ −C ₁₂ ) / C ₁₁ } ε ΔE _v = 2a ′ {(C ₁₁ −C ₁₂ ) / C ₁₁ } ε + b {(C ₁₁ + 2C
₁₂ ) / C ₁₁ } ε

FIG. 2B shows a tensile strain G on a GaAs substrate.
The results of determining the energy levels E _c and E _v of the conduction band and the valence band when a _x In _1-x P is formed are shown. The parameter of the strain amount is the Ga composition amount x. FIG.
From (b), Ga composition x is changed to lattice matching condition x = 0.5.
It can be seen that when the value is larger than 2 and the film has a tensile strain, the energy level E _v of the valence band shifts to a higher energy side than when the film is lattice-matched with the GaAs substrate. Therefore, when Ga _0.5 In _0.5 P lattice-matched to GaAs is used for the intermediate layer and tensile strain GaInNP is used for the light emitting layer, as shown in FIG. 1C, the valence band edge due to the introduction of nitrogen is reduced. The shift amount is compensated, and the valence band discontinuity with the GaInP intermediate layer is reduced. Therefore, the GInNP light emitting layer
Hole leakage into the aInP intermediate layer can be reduced, and luminous efficiency can be improved.

In the case of tensile strain, unlike the case of compressive strain, as can be seen from FIG. 2 (b), the lower end of the conduction band is also shifted to the higher energy side. If the lower end of the conduction band of the tensile strained GaInNP light emitting layer is higher than the lower end of the conduction band of the lattice-matched GaInP intermediate layer, the confinement of electrons decreases, and conversely, the lower end of the conduction band of the tensile strained GaInNP light emitting layer. However, it is necessary to control the amount of tensile strain and the nitrogen composition so as to be located below the lower end of the conduction band of the lattice-matched GaInP intermediate layer.

In the semiconductor light emitting devices of the first and second embodiments, the light emitting layer made of a Ga _x In ₁ -xN _y P _{1 -y} mixed crystal semiconductor has a composition satisfying the following expression. Good to have.

[0024]

ΔE _N + ΔE _strain + ΔE _v > 0

Here, ΔE _N is the amount of change in the energy level (level) E _v of the valence band due to the addition of nitrogen, ΔE _N
E _strain is the change in energy level (level) E _v of the valence band due to the application of strain, and ΔE _v is the energy level (level) of the valence band due to changing the group III element composition from the lattice matching condition. ) _{Ev is} the amount of change.

When the GaInNP light emitting layer satisfies the above formula (Equation 3), a heterostructure is formed with the lattice-matched GaInP intermediate layer, and the band diagram becomes as shown in FIG. ). In this case, both the conduction band electrons and the valence band holes are concentrated in the GaInNP light emitting layer, so that the light emitting efficiency of the device can be improved.

The semiconductor light emitting device according to the third embodiment of the present invention comprises a light emitting layer made of a Ga _x In ₁ -xN _y P _{1 -y} mixed crystal semiconductor on a GaAs substrate, and (Al _z Ga _{1 -z} ) _w In _1-w P
A cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer made of a group III-V semiconductor not containing Al and N, laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer. Here, the light emitting layer is doped with a p-type impurity.

Generally, when a semiconductor layer is doped with a p-type impurity, the Fermi level (E _fp ) of the semiconductor layer shifts to a lower energy side. In the heterojunction, since the junction is performed so that the Fermi levels match, the injected carrier density is Ga
In a region lower than the p-type doping concentration of the InNP light emitting layer, the upper end of the valence band of the GaInNP light emitting layer shifts to a higher energy side than in the case of non-doping. for that reason,
The top of the valence band of the GaInNP light emitting layer and lattice-matched GaIn
Band discontinuity with the energy level at the upper end of the valence band of the P intermediate layer is reduced. That is, the upper end of the valence band of the GaInNP light emitting layer is located above the energy level of the upper end of the valence band of the lattice-matched GaInP intermediate layer (FIG. 1 (e)). Therefore, in the low implantation region of the p-type impurity,
Leakage of holes from the GaInNP light emitting layer to the GaInP intermediate layer can be reduced, thereby improving luminous efficiency.

The semiconductor light emitting device according to the fourth embodiment of the present invention comprises a light emitting layer made of a Ga _x In _{1 -x} N _y P _{1 -y} mixed crystal semiconductor on a GaAs substrate, and (Al _z Ga _{1 -z} ) _w In _1-w P
A cladding layer or an optical waveguide layer or a barrier layer, and an intermediate layer made of a group III-V semiconductor not containing Al and N, laminated between the light emitting layer and the cladding layer or the optical waveguide layer or the barrier layer. Here, the intermediate layer provided at least on the n-type cladding layer side is doped with an n-type impurity.

Generally, when an n-type impurity is doped into a semiconductor layer, the Fermi level (E _fn ) of the semiconductor layer shifts to a higher energy side. In the heterojunction, since the junction is performed so that the Fermi levels match, the injected carrier density is Ga
In a region lower than the n-type doping concentration of the InN intermediate layer, the upper end of the valence band of the GaInP intermediate layer shifts to a lower energy side as compared with the case of non-doping. Therefore, G
The valence band discontinuity between the upper end of the valence band of the aInP intermediate layer and the GaInNP light emitting layer is reduced. That is, Ga
The upper end of the valence band of the InP intermediate layer is located below the energy position of the upper end of the valence band of the GaInNP light emitting layer (FIG. 1 (f)). Therefore, in the low implantation region, Ga
Hole leakage from the InNP light emitting layer to the GaInP intermediate layer can be reduced, thereby improving luminous efficiency.

[0031]

EXAMPLE 1 FIG. 3 is a view showing a semiconductor light emitting device (semiconductor laser device) of Example 1, and Example 1 (FIG. 3) is a semiconductor light emitting device according to a second embodiment of the present invention. This is a specific example. FIG.
Referring to FIG. 2, an n-type GaAs substrate 101 has an n-type Ga
As buffer layer 102, n-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P cladding layer 103, non-doped (Al _0.5 Ga _0.5 )
_0.5 In _0.5 P lower optical waveguide layer 104, non-doped Ga _0.5
In _0.5 P intermediate layer 105a, non-doped Ga _0.6 In _0.4
N _0.01 P _0.99 light emitting layer 106, non-doped Ga _0.5 In _0.5
P intermediate layer 105b, non-doped (Al _0.5 Ga _0.5 ) _0.5 I
n _0.5 P upper optical waveguide layer 107, p-type (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P cladding layer 108, p-type Ga _0.5 In _0.5 P spike prevention layer 109, p-type GaAs contact layer 110
Are sequentially stacked.

Here, as the crystal growth method of each layer, a metal organic chemical vapor deposition method was used. In addition, n-type (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P cladding layer 103 has a layer thickness of 1 μm, and non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P lower optical waveguide layer 1.
04 has a thickness of 0.1 μm and is undoped Ga _0.5 In _0.5 P
The thickness of the intermediate layer 105a is 2 nm, and undoped Ga _0.6 I
The layer thickness of the n _0.4 N _0.01 P _0.99 light emitting layer 106 is 30 nm, and the layer thickness of the non-doped Ga _0.5 In _0.5 P intermediate layer 105 b is 2 n.
m, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer thickness of the upper optical waveguide layer 107 is 0.1 μm, p-type (Al _0.7 Ga _0.3 )
The thickness of the _0.5 In _0.5 P cladding layer 108 is 1 μm, and the p-type G
The thickness of the a _0.5 In _0.5 P spike prevention layer 109 is 50 n.
The layer thickness of the m, p type GaAs contact layer 110 is 0.5 n
m.

Then, the p-type GaAs contact layer 110
Is etched in a stripe shape having a width of 5 μm, an SiO ₂ insulating film 111 is deposited on the surface of the laminated structure, and a p-type Ga film is formed by a photolithography process and etching.
The SiO ₂ insulating film 111 on the As contact layer 110 was removed to form a current injection region, and a p-side ohmic electrode 112 was further deposited thereon. An n-side ohmic electrode 113 was formed on the back surface of the n-type GaAs substrate 101.

In the semiconductor laser device of FIG. 3, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 containing Al as a constituent element
And P optical waveguide layer 104 and 107, an undoped Ga _0.6 In _0.4 N _0.01 between the P _{of 0.99} emitting layer 106, an undoped Ga _0.5 an In containing no Al and N as constituent elements _0.5 P intermediate layer 105a containing N as a constituent element , 105b are inserted. Thereby, non-doped Ga _0.6 In _0.4 N _0.01
By improving the crystallinity of the P _0.99 light emitting layer 106, the luminous efficiency of the light emitting layer is improved.

Further, the non-doped Ga _0.5 In _0.5 P intermediate layers 105a and 105b have a composition lattice-matched to the GaAs substrate 101, and have a non-doped Ga _0.6 I
The n _0.4 N _0.01 P _0.99 light emitting layer 106 has a tensile strain of 0.6% with respect to the substrate 101. Lattice-matched Ga
Nitrogen (N) is added to the _0.5 In _0.5 P intermediate layers 105a and 105b.
%, The forbidden band width is reduced by about 150 meV, and the energy level at the upper end of the valence band is reduced by about 18 meV level Δ
It decreases by E _N (ΔE _N = 18 meV). On the other hand, GaIn
When the composition of P is changed to have a tensile strain,
(That is, for example, when Ga _0.6 In _0.4 P is used),
From FIG. 2B, the energy level at the upper end of the valence band of Ga _0.6 In _0.4 P is about 34 meV compared to Ga _0.5 In _0.5 P.
Rise (ΔE _strain + ΔE _v = 34 meV). Therefore,
ΔE _N + ΔE _strain + ΔE _v > 0 is satisfied, and the upper end of the valence band of the non-doped Ga _0.6 In _0.4 N _0.01 P _0.99 light-emitting layer 106 is the non-doped Ga _0.5 In _0.5 P intermediate layer 105.
a and 105b are located above the upper end of the valence band (FIG. 1 (d)).

In addition, non-doped Ga _0.6 In _0.4 N _0.01 P
The energy level at the bottom of the conduction band of the _0.99 light-emitting layer 106 is lower by about 80 meV than the bottom of the conduction band of the non-doped Ga _0.5 In _0.5 P intermediate layers 105a and 105b (FIG. 1D). Thereby, the non-doped Ga _0.5 In _0.5 P intermediate layer 105
a, 105b and non-doped Ga _0.6 In _0.4 N _0.01 P _0.99
The DH structure (double hetero junction structure) of the light emitting layer 106 is of type I. Therefore, both the conduction band electrons and the valence band holes are non-doped Ga _0.6 In _0.4 N _0.01 P _0.99 light emitting layer 106
Luminous efficiency is improved.

As described above, in the first embodiment, since Ga _0.5 In _0.5 P lattice-matched to GaAs is used as the intermediate layer and tensile strain GaInNP is used as the light emitting layer,
The shift amount of the valence band edge due to the introduction of (N) is compensated, and the valence band discontinuity with the GaInP intermediate layer is reduced, whereby the holes from the GaInNP light emitting layer to the GaInP intermediate layer are reduced. Can be reduced, and luminous efficiency can be improved.

Example 2 FIG. 4 is a view showing a semiconductor light emitting device (semiconductor laser element) according to Example 2 of the present invention. Example 2 (FIG. 4) is a specific example of the first embodiment of the present invention. It has become. In FIG.
Structures other than the light emitting layer were formed in the same manner as in Example 1. That is, referring to FIG. 4, non-doped (Al _0.5 Ga
_0.5 ) _0.5 In _0.5 P On the lower optical waveguide layer 104, the layer thickness is 2n.
m non-doped Ga _0.5 In _0.5 P intermediate layer 105a, non-doped Ga _0.45 In _0.55 N _0.01 P _0.99 light-emitting layer 201 with a thickness of 30 nm, non-doped Ga _0.5 In _0.5 P with a thickness of 2 nm
Intermediate layer 105b, non-doped (Al _0.5 Ga _0.5 ) _0.5 In
_0.5 P upper optical waveguide layers 107 are sequentially stacked.

In the semiconductor laser device of FIG. 4, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 containing Al as a constituent element
P optical waveguide layers 104 and 107 and non-doped Ga _0.45 In _0.55 N _0.01 P _0.99 light emitting layer 201 containing N as a constituent element
, The non-doped Ga _0.5 In _0.5 P intermediate layers 105 a and 105 b containing no Al and N as constituent elements provide non-doped Ga _0.45 In _0.55 N _0.01 P
The crystallinity of the _0.99 light-emitting layer 201 is improved, and the luminous efficiency is improved.

Further, the non-doped Ga _0.5 In _0.5 P intermediate layers 105a and 105b have a composition that lattice-matches with the GaAs substrate 101, and the non-doped Ga _0.45 I
The n _0.55 N _0.01 P _0.99 light emitting layer 201 has a compressive strain of about 0.5% with respect to the substrate. Lattice matched Ga _0.5
When 1% of N is introduced into In _0.5 P, the forbidden band width is about 150
The energy level at the top of the valence band is reduced to about 18
The level is reduced by ΔE _{N for} the level of meV (ΔE _N = 18me
V). On the other hand, when the composition of GaInP is changed to have a compressive strain (that is, for example, Ga _0.45 In
_0.55 P), from FIG. 2A, Ga _0.45 In
The energy level at the top of the valence band of _0.55 P is Ga _0.5 In
Approximately 33 meV increase compared to _0.5 P (ΔE _strain + Δ
E _v = 33 meV). Therefore, ΔE _N + ΔE _strain + ΔE _v
> 0, and non-doped Ga _0.45 In _0.55 N
_The upper end of the valence band of the _0.01 P _0.99 light emitting layer 201 is positioned higher than the upper end of the valence band of the non-doped Ga _0.5 In _0.5 P intermediate layers 105a and 105b (FIG. 1D).

Further, non-doped Ga _0.45 In _0.55 N _0.01
The energy level at the bottom of the conduction band of the P _0.99 light-emitting layer 201 is
Non-doped Ga _0.5 In _0.5 P intermediate layers 105a, 105b
(FIG. 1 (d)). Therefore,
Non-doped Ga _0.5 In _0.5 P intermediate layers 105a, 105b
And non-doped Ga _0.45 In _0.55 N _0.01 P _0.99 light emitting layer 20
The DH structure (double heterojunction structure) of No. 1 is of type I. Therefore, both the conduction band electrons and the valence band holes are concentrated in the non-doped Ga _0.45 In _0.55 N _0.01 P _0.99 light emitting layer 201, so that the luminous efficiency is improved.

As described above, in Example 2, since Ga _0.5 In _0.5 P lattice-matched to GaAs was used as the intermediate layer and compression-strained GaInNP was used as the light emitting layer,
The shift amount of the valence band edge due to the introduction of (N) is compensated, and the valence band discontinuity with the GaInP intermediate layer is reduced, whereby the holes from the GaInNP light emitting layer to the GaInP intermediate layer are reduced. Can be reduced, and luminous efficiency can be improved.

Example 3 FIG. 5 is a view showing a semiconductor light emitting device (semiconductor laser device) according to Example 3 of the present invention. Example 3 (FIG. 5) is a specific example of the third embodiment of the present invention. It has become. In FIG.
Structures other than the light emitting layer were formed in the same manner as in Example 1. That is, referring to FIG. 5, non-doped (Al _0.5 Ga
_0.5 ) _0.5 In _0.5 P On the lower optical waveguide layer 104, the layer thickness is 2n.
m non-doped Ga _0.5 In _0.5 P intermediate layer 105a, 30 nm thick Mg doped Ga _0.5 In _0.5 N _0.01 P _0.99 light emitting layer 301, 2 nm thick non-doped Ga _0.5 In _0.5 P intermediate layer 105b, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5
The P upper optical waveguide layer 107 is stacked. Where Mg
Doped Ga _0.5 In _0.5 N _0.01 P _0.99 Mg of light emitting layer 301
The doping concentration was 2 × 10 ¹⁸ cm ⁻³ .

When Ga _0.5 In _0.5 N _0.01 P _0.99 is doped with Mg as a p-type impurity, the Fermi level shifts to a lower energy side. In the heterojunction, since the junction is made so that the Fermi levels match, in a region where the injected carrier density is lower than the Mg doping concentration, the Mg doped G
The upper end of the valence band of the a _0.5 In _0.5 N _0.01 P _0.99 light emitting layer 301 is shifted to a higher energy side than in the case of non-doped Ga _0.5 In _0.5 N _0.01 P _0.99 . Thereby, the valence band discontinuity at the upper end of the valence band of the Mg-doped Ga _0.5 In _0.5 N _0.01 P _0.99 light emitting layer 301 with the non-doped Ga _0.5 In _0.5 P intermediate layer 105 is reduced. That is, the upper end of the valence band of the Mg-doped Ga _0.5 In _0.5 N _0.01 P _0.99 light-emitting layer 301 is positioned higher than the energy level of the upper end of the valence band of the non-doped Ga _0.5 In _0.5 P intermediate layer 105 (see FIG. 1 (e)). Therefore, especially in the low implantation region, Mg
Hole leakage from the doped Ga _0.5 In _0.5 N _0.01 P _0.99 light-emitting layer 301 to the non-doped Ga _0.5 In _0.5 P intermediate layers 105a and 105b can be reduced, and luminous efficiency can be improved.

Example 4 FIG. 6 is a view showing a semiconductor light emitting device (semiconductor laser device) according to Example 4 of the present invention. Example 4 (FIG. 6) is a specific example of the fourth embodiment of the present invention. It has become. In FIG.
The structure other than the vicinity of the light emitting layer was formed in the same manner as in Example 1. That is, referring to FIG. 6, non-doped (Al _0.5
On the Ga _0.5 ) _0.5 In _0.5 P lower optical waveguide layer 104, a 2 nm-thick Si-doped Ga _0.5 In _0.5 P intermediate layer 401, a 30 nm-thick non-doped Ga _0.5 In _0.5 N _0.01 P _0.99 light-emitting layer 402, and a layer thickness 2 nm non-doped Ga _0.5 In _0.5 P
Intermediate layer 105b, non-doped (Al _0.5 Ga _0.5 ) _0.5 In
_{The 0.5P} upper optical waveguide layer 107 is laminated. here,
The Si doping concentration of the Si-doped Ga _0.5 In _0.5 P intermediate layer 401 was 5 × 10 ¹⁸ cm ⁻³ .

Ga _0.5 In _0.5 P is replaced with Si which is an n-type impurity.
Doping, the Fermi level shifts to a higher energy side. In the heterojunction, since the junction is performed so that the Fermi levels coincide with each other, in a region where the injected carrier density is lower than the Si doping concentration, Si-doped Ga _0.5 In
_The upper end of the valence band of the _0.5 P intermediate layer 401 is non-doped Ga _0.5
It shifts to a lower energy side as compared with the case of In _0.5 P. Thereby, the Si-doped Ga _0.5 In _0.5 P intermediate layer 4
The upper end of the valence band of 01 is undoped Ga _0.5 In _0.5 N _0.01
Valence band discontinuity with the P _0.09 light-emitting layer 402 is reduced. That is, the Si-doped Ga _0.5 In _0.5 P intermediate layer 4
The upper end of the valence band of 01 is undoped Ga _0.5 In _0.5 N _0.01
It is located below the energy position at the upper end of the valence band of the P _0.09 light emitting layer 402 (FIG. 1 (f)). Therefore, especially in the low implantation region, the non-doped Ga _0.5 In _0.5 N _0.01
Hole leakage from the P _0.09 light-emitting layer 402 to the Si-doped Ga _0.5 In _0.5 P intermediate layer 401 can be reduced, and luminous efficiency can be improved.

[0047]

As described above, according to the first aspect of the present invention, Ga _x In _{1 -x} N _y P is formed on a GaAs substrate.
_A light-emitting layer made of a _1-y mixed crystal semiconductor, and (Al _z Ga _1-z ) _w In
_1-w P-cladding layer or optical waveguide layer or barrier layer, and intermediate layer made of a III-V semiconductor not containing Al and N, laminated between the light-emitting layer and the cladding layer or optical waveguide layer or barrier layer Wherein the intermediate layer is lattice-matched to a GaAs substrate, and the light-emitting layer is GaAs.
Since the s-substrate has a compressive strain, leakage of holes from the light-emitting layer to the intermediate layer can be reduced, and luminous efficiency can be improved.

According to the second aspect of the present invention, Ga
A light emitting layer made of a Ga _x In _1-x N _y P _1-y mixed crystal semiconductor, an (Al _z Ga _1-z ) _w In _1-w P cladding layer, an optical waveguide layer or a barrier layer on an As substrate; A semiconductor light-emitting device comprising: a light-emitting layer and a cladding layer or an optical waveguide layer or a barrier layer, which are stacked between the light-emitting layer and the cladding layer or the optical waveguide layer or the barrier layer. Since the light emitting layer is lattice-matched with the GaAs substrate and has a tensile strain with respect to the GaAs substrate, leakage of holes from the light emitting layer to the intermediate layer can be reduced, and luminous efficiency can be improved. it can.

According to a third aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, Δ Δ
The E _N and the amount of change in the energy level of the valence band due to the addition of nitrogen, a Delta] E _strain and the amount of change in the energy level of the valence band due to the addition of distortion, the group III element composition of Delta] E _v When the amount of change in the energy level of the valence band due to the change from the lattice matching condition is expressed as Ga _x In _1-x
The light-emitting layer made of the N _y P _1-y mixed crystal semiconductor has ΔE _N + ΔE
_{Since the} composition has a composition that satisfies _strain + ΔE _v > 0, when a heterostructure is formed by the GaInNP light emitting layer and the lattice-matched GaInP intermediate layer, the band diagram becomes Type I, and the conduction band electrons and the valence band. Holes are concentrated in the GaInNP light emitting layer, and the luminous efficiency of the device can be improved.

According to the fourth aspect of the present invention, Ga
_{Since the x} In _1-x N _y P _1-y light emitting layer is doped with a p-type impurity, GaInN is used in a region where the injected carrier density is lower than the p-type doping concentration of the GaInNP light emitting layer.
The upper end of the valence band of the P light emitting layer is shifted to a higher energy side than in the case of non-doping, and therefore, it is necessary to reduce the leakage of holes from the p-type doped GaInNP light emitting layer to the GaInP intermediate layer in the low injection region. As a result, luminous efficiency can be improved.

According to the fifth aspect of the present invention, since the n-type impurity is doped in at least the intermediate layer provided on the n-type cladding layer side, the injected carrier density is lower than the n-type doping concentration of the intermediate layer. In the lower region, the upper end of the valence band of the intermediate layer shifts to the lower energy side as compared with the non-doped region.
Hole leakage from the NP light-emitting layer to the n-type doped intermediate layer can be reduced, and luminous efficiency can be improved.

[Brief description of the drawings]

FIG. 1 shows a GaInP intermediate layer and a GaI of each semiconductor light emitting device.
FIG. 4 is a diagram illustrating a band diagram of an nNP light emitting layer.

FIG. 2 is a diagram showing energy levels of a conduction band and a valence band of a Ga _x In _1-x P layer on a GaAs substrate.

FIG. 3 is a diagram showing a semiconductor light emitting device according to Embodiment 1 of the present invention.

FIG. 4 is a diagram showing a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a semiconductor light emitting device according to a fourth embodiment of the present invention.

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

FIG. 8 is a diagram showing a conventional semiconductor light emitting device.

[Explanation of symbols]

Reference Signs List 101 n-type GaAs substrate 102 n-type GaAs buffer layer 103 n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5
P cladding layer 104 non-doped (Al _0.5 Ga _0.5 ) _0.5
In _0.5 P Lower optical waveguide layers 105a, 105b Non-doped Ga _0.5 In _0.5
P intermediate layer 106 Non-doped Ga _0.6 In _0.4 N _0.01
P _0.99 Emission layer 107 Non-doped (Al _0.5 Ga _0.5 ) _0.5
In _0.5 P Upper optical waveguide layer 108 p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5
P cladding layer 109 p-type Ga _0.5 In _0.5 P spike prevention layer 110 p-type GaAs contact layer 111 SiO ₂ insulating film 112 p-side ohmic electrode 113 n-side ohmic electrode 201 non-doped Ga _0.45 In _0.55 N
_0.01 P _0.99 Light-emitting layer 301 Mg-doped Ga _0.5 In _0.5 N _0.01
P _0.99 Light-emitting layer 401 Si-doped Ga _0.5 In _0.5 P intermediate layer 402 Non-doped Ga _0.5 In _0.5 N _0.01
P _0.09 light emitting layer

Claims (5)

[Claims] 1. A Ga _x In _{1 -x} N _y P on a GaAs substrate.
_A light-emitting layer made of a _1-y mixed crystal semiconductor, and (Al _z Ga _1-z ) _w In
_1-w P-cladding layer or optical waveguide layer or barrier layer, and intermediate layer made of a III-V semiconductor not containing Al and N, laminated between the light-emitting layer and the cladding layer or optical waveguide layer or barrier layer Wherein the intermediate layer is lattice-matched to a GaAs substrate, and the light-emitting layer is GaAs.
A semiconductor light emitting device having a compressive strain with respect to an s substrate. 2. A Ga _x In _{1 -x} N _y P on a GaAs substrate.
_A light-emitting layer made of a _1-y mixed crystal semiconductor, and (Al _z Ga _1-z ) _w In
_1-w P-cladding layer or optical waveguide layer or barrier layer, and intermediate layer made of a III-V semiconductor not containing Al and N, laminated between the light-emitting layer and the cladding layer or optical waveguide layer or barrier layer Wherein the intermediate layer is lattice-matched with a GaAs substrate, and the light-emitting layer is GaAs.
A semiconductor light emitting device having a tensile strain with respect to a substrate. 3. The semiconductor light emitting device according to claim 1, wherein ΔE _N is a change amount of an energy level of a valence band caused by adding nitrogen, and ΔE _strain is a value obtained by applying strain. Ga _x In _1-x N _{y where} ΔE _v is the change in the energy level of the valence band due to the change in the group III element composition from the lattice matching condition, A semiconductor light emitting device, wherein a light emitting layer made of a P _1-y mixed crystal semiconductor has a composition satisfying ΔE _N + ΔE _strain + ΔE _v > 0. 4. A method according to claim 1, wherein a Ga _x In _{1 -x} N _y P
_A light-emitting layer made of a _1-y mixed crystal semiconductor, and (Al _z Ga _1-z ) _w In
_1-w P-cladding layer or optical waveguide layer or barrier layer, and intermediate layer made of a III-V semiconductor not containing Al and N, laminated between the light-emitting layer and the cladding layer or optical waveguide layer or barrier layer Wherein the light emitting layer is doped with a p-type impurity. 5. A method according to claim 5, wherein Ga _x In _{1 -x} N _y P is formed on a GaAs substrate.
_A light-emitting layer made of a _1-y mixed crystal semiconductor, and (Al _z Ga _1-z ) _w In
_1-w P-cladding layer or optical waveguide layer or barrier layer, and intermediate layer made of a III-V semiconductor not containing Al and N, laminated between the light-emitting layer and the cladding layer or optical waveguide layer or barrier layer A light emitting device comprising: an n-type impurity doped in at least an intermediate layer provided on an n-type cladding layer side;