JP2000114665A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element easy to assemble using a GaAs substrate with good characteristics, and capable of emitting light in a long-wavelength band. SOLUTION: In a semiconductor laser with a SCH structure using an n-type GaAs substrate 1 as a substrate, a (BxGa1-x)yIn1-yAs active layer 4, where 0<x<=1, 0<y<=1,xy≠ 1, is used as an active layer. In the (BxGa1-x)yIn1-yAs active layer 4, x and y are so selected that the (BxGa1-x)yIn1-yAs active layer 4 is conformed in grating with the n-type GaAs substrate 1. An n-type AlGaAs clad layer 2 and p-type AlGaAs clad layer 6 are used as clad layers. An n-type (ByGa1-u)vIn1-vAs optical waveguide layer 3 and p-type An n-type (ByGa1-u)vIn1-vAs optical waveguide layer 5, where 0<u<=1, 0<v<=1, uv≠1, are used as optical waveguide layers.

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, and more particularly, to a semiconductor light emitting device which emits infrared light of about 0.88 .mu.m to several .mu.m.

[0002]

2. Description of the Related Art Conventionally, InGaAs has been used as a semiconductor laser capable of emitting light in a long wavelength band in the infrared region of about several μm.
sP-based semiconductor lasers are known. Generally, this In
In a GaAsP-based semiconductor laser, a laser structure is formed by growing an InGaAsP-based semiconductor such as InGaAsP or InP on an InP substrate.

[0003]

However, InG
Since the characteristic temperature of an aAsP semiconductor laser is small,
The upper limit of the temperature at which continuous oscillation is possible is lower than that of a GaAs-based semiconductor laser or the like. Therefore, this InGaAsP-based semiconductor laser requires control of the operating temperature to stabilize the operation.

[0004] InGaAsP semiconductor lasers are
In general, since the semiconductor laser is manufactured on an InP substrate, the substrate cost is higher than that of a semiconductor laser manufactured on an easily available GaAs substrate such as an AlGaAs semiconductor laser or an AlGaInP semiconductor laser. Further, for example, when a plurality of semiconductor lasers having different emission wavelength bands are considered to be integrated on the same substrate, the I / O fabricated on the InP substrate is considered.
An nGaAsP-based semiconductor laser cannot be matched with another semiconductor laser manufactured on a GaAs substrate. Therefore, it is desired to realize a semiconductor laser capable of emitting light in a long wavelength band using a material system capable of growing crystals on a GaAs substrate, instead of an InGaAsP-based semiconductor laser manufactured on an InP substrate.

Under these circumstances, GaAs and G have recently been developed.
The relationship between the composition ratio of nitrogen (N) and band gap in GaNAs, which is a mixed crystal with aN, is large, and bowing (b)
GaAs and G
Quaternary mixed crystal GaInNA obtained by adding InAs to aN
There has been a report on a semiconductor laser that emits light in the infrared region using a material system that lattice-matches with a GaAs substrate by using s for the active layer.

However, in the case of this quaternary mixed crystal of GaInNAs, it is difficult to grow the crystal while properly incorporating N in the crystal. Therefore, a semiconductor laser using this GaInNAs for the active layer has a thickness of 1.4 μm. There is a problem that it is difficult to make the wavelength longer than this. In general, Ga
It is said that it is difficult to control the crystal growth of a mixed crystal having two or more group V elements such as InNAs.

Therefore, an object of the present invention is to provide a G
An object of the present invention is to provide a semiconductor light emitting device that can be easily manufactured using an aAs substrate and that can emit light in a long wavelength band and that can achieve good characteristics.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems of the prior art, the present inventors have made intensive studies. The outline is shown below.

FIG. 1 shows the relationship between the lattice constant and band gap of typical group III-V compound semiconductors and their mixed crystals. In FIG. 1, the horizontal axis represents the lattice constant (Å), and the vertical axis represents the band gap (eV). As shown in FIG. 1, GaAs has a lattice constant of 5.6533 °,
The band gap is 1.42 eV. On the other hand, GaAs
BAs in which all the group III elements of the above are replaced with boron (B)
In InAs, the lattice constant is 4.777 °, the band gap is 1.46 eV, and InAs in which all the group III elements of GaAs are replaced with indium (In),
Lattice constant 6.0584 °, band gap 0.36
eV. When the electronegativity of each group III element is compared, the electronegativity of Al is 1.5, the electronegativity of Ga is 1.6, and the electronegativity of In is 1.7, B has an electronegativity of 2.0, and B has a higher electronegativity than other group III atoms.

In FIG. 1, focusing on the relationship between the lattice constant and the band gap in a mixed crystal of GaAs and BAs, when the lattice constant changes from a value corresponding to BAs to a value corresponding to GaAs, it corresponds to the change. It can be seen that the band gap changes while drawing a downwardly convex arc-shaped locus. This is due to the large electronegativity of B, and is generally called the bowing effect. FIG. 2 shows the result of calculating the relationship between the B composition ratio x of B _x Ga _1-x As and the band gap. In FIG. 2, the horizontal axis represents the B composition ratio x in B _x Ga _{1 -x} As, and the vertical axis represents the band gap (eV). FIG.
From the graph, it can be seen that the graph of the B composition ratio xvs band gap in B _x Ga _{1 -x} As shows that the bowing increases greatly in the direction in which the band gap decreases.

On the other hand, although the band gap of the mixed crystal of InAs and BAs is not so large as that of the mixed crystal of GaAs and BAs, the mixed crystal of InAs and BAs can be obtained by selecting the mixed crystal ratio. It is possible to grow while lattice-matching on a GaAs substrate. Figure 3 shows the results obtained by calculating the relationship between the B composition ratio x and the band gap of the B _y In _1-y As. 3, the horizontal axis represents the B composition ratio y in B _y an In _1-y As, the vertical axis represents band gap (eV). Incidentally, B composition ratio y when the lattice constant of the B _y In _1-y As is consistent with the lattice constant of GaAs is y = 0.316.

A quaternary mixed crystal of BGaInAs containing GaAs, InAs and BAs as constituent elements is shown in FIG.
As indicated by the hatched area, the lattice constant and the band gap can be changed over a wide range from a value corresponding to BAs to a value corresponding to InAs, respectively. In particular, this BGaInAs can be obtained by selecting a mixed crystal ratio as shown by a broken line a in FIG.
aAs can be made to match the lattice constant.
The band gap is changed from the value corresponding to GaAs to B _0.316 I
It can be arbitrarily changed to a value corresponding to n _0.684 As. This band gap corresponds to about 0.88 μm to 2.5 μm in terms of wavelength. Therefore, it is considered that BGaInAs is promising as a material for an active layer of a semiconductor light emitting device capable of emitting light in a long wavelength band.

Since BGaInAs contains only one group V element, it is considered that the control of crystal growth is easier than that of a mixed crystal containing two kinds of V group elements such as GaInNAs. Thus, it can be said that it is effective to use BGaInAs for the active layer of a semiconductor light emitting device capable of emitting light in a long wavelength region. In the crystal growth of BGaInAs, for example, metal organic chemical vapor deposition (M
OCVD) method can be used. In this case, for example, trimethylgallium is used as a group III Ga source, trimethylindium is used as an In source, triethylboron is used as a B source, and arsine is used as a group V source. Here, the reason why triethylboron is used as a raw material for B is that since triethylboron is in a liquid state, it is considered to be compatible with other organic metal raw materials and to have good controllability. Of course, trimethylboron or diborane may be used as a raw material of B instead of triethylboron. As a crystal growth method, a molecular beam epitaxy (MBE) method may be used instead of the MOCVD method.

Here, when considering the crystal growth of BGaInAs on a GaAs substrate, it is desirable to suppress the deviation of the lattice constant between BGaInAs and GaAs. By the way, conventionally, an AlGaAs-based semiconductor laser that realizes a strained quantum well structure by using GaInAs for an active layer is known.
In this semiconductor laser, Ga _0.7 In _0.3 As
May be used. The lattice constant of Ga _0.7 In _0.3 As is 0.3 × 6.0584 + 0.7 × 5.6533 = 5.7.
748 (Å), in this case, Ga _0.7 In with respect to the GaAs substrate.
The magnitude of the lattice mismatch of _0.3 As Δa / a (≡ (a ₂ −a
₁ ) / a ₁ , where a ₁ is the lattice constant of the substrate and a ₂ is the lattice constant of the semiconductor layer) is about 2 × 10 ⁻² . Therefore,
As for BGaInAs, if the magnitude of the lattice mismatch Δa / a with respect to the GaAs substrate can be kept within the range of ± 2 × 10 ⁻² , a semiconductor light emitting device using this BGaInAs for the active layer is manufactured on the GaAs substrate. It is thought that it is possible. At this time, in order to obtain a higher quality semiconductor light emitting device, BGaIn with respect to the GaAs substrate is used.
It is preferable to keep the magnitude Δa / a of the lattice mismatch of As within ± 1 × 10 ^−2.
More preferably, s is lattice matched with the GaAs substrate.

Here, BGaInAs is represented by the general formula (B _x G
a _1-x ) _y In _1-y As (B _x G)
a _1−x ) _y In _1−y As is Δa /
If there is a lattice mismatch of a = + 2 × 10 ⁻² ,

[0016]

(Equation 1)

Thus, x and y are

[0018]

(Equation 2)

The following relationship is satisfied. On the other hand, (B _x Ga _1-x )
_y In _1−y As is Δa / a = −2 with respect to the GaAs substrate
If there is a lattice mismatch of × 10 ^-2 ,

[0020]

(Equation 3)

Thus, x and y are

[0022]

(Equation 4)

The following relationship is satisfied. Therefore, in order to keep the magnitude Δa / a of the lattice mismatch of (B _x Ga _{1 -x} ) _y In _{1 -y} As with respect to the GaAs substrate within the range of ± 2 × 10 ^-2 ,

[0024]

(Equation 5)

X and y may be selected so as to satisfy the relationship (condition). In addition, (B _x G
a _1−x ) _y In _1−y As lattice mismatch magnitude Δa / a of As
In order to fall within the range of ± 1 × 10 ^-2 ,

[0026]

(Equation 6)

X and y may be selected so as to satisfy the relationship (condition), and (B _x Ga _{1 -x} ) _y In _{1 -y} As is expressed as G
For lattice matching with the aAs substrate,

[0028]

(Equation 7)

X and y may be selected so as to satisfy the relationship (condition).

Further, (B _x Ga _{1 -x} ) _y In is added to the active layer.
_{When 1-y} As is used, AlGaAs,
AlGaInP, GaAs, InGaAsP or B
The laser structure may be formed using a material having a larger band gap than the active layer, such as GaInAs. Any of these materials can be lattice-matched to a GaAs substrate, and can form a heterojunction with good crystallinity.

Further, (B _x Ga _{1 -x} ) _y In is added to the active layer.
_When a semiconductor light emitting device using _1-y As is fabricated on a GaAs substrate and the field of view is changed to change the emission wavelength, (B _x Ga _{1 -x} ) _y In is used for the active layer.
_It is necessary that _1-y As be a mixed crystal of at least three elements. Of the constituent elements of (B _x Ga _{1 -x} ) _y In _{1 -y} As, GaInAs using GaAs and InAs can change (B _x Ga _{1 -x} ) _y In by changing the mixed crystal ratio.
It is possible to change the band gap in a range substantially similar to the case of _1-y As. However, GaInA
In the case of s, the emission wavelength is determined when the lattice constant is matched with that of GaAs. On the other hand, in the case of (B _x Ga _{1 -x} ) _y In _{1 -y} As containing the constituent element, the mixed crystal ratio ( By selecting (composition), there is an advantage that the emission wavelength can be changed while the lattice constant is matched with that of GaAs. In general, a group III-V compound semiconductor containing In has a lower optimum growth temperature than a group III-V compound semiconductor not containing In. In addition, at a temperature higher than the growth temperature, In is removed from the crystal. It is known that the elimination degrades the crystallinity. However, in the case of (B _x Ga _{1 -x} ) _y In _{1 -y} As containing B as a constituent element, the optimal growth temperature is set to In because the addition of B suppresses the elimination of In from the crystal. Not containing III
It can be pulled up to almost the same degree as that of a -V compound semiconductor, and the crystallinity can be improved. From the above, when (B _x Ga _{1 -x} ) _y In _{1 -y} As is used for the active layer, it can be said that it is desirable to use a ternary mixed crystal or a quaternary mixed crystal containing at least BAs as a component.

The present invention has been devised based on the results of the above study by the present inventors.

[0033] That is, in order to achieve the above object, the present invention is a semiconductor light emitting device having a sandwiched by n-type cladding layer and p-type cladding layer an active layer on a substrate and the active layer (B _x Ga _1-x ) _y In _1-y As (where 0 <x ≦ 1, 0 <y ≦ 1, xy ≠ 1).

In the present invention, a GaAs substrate is typically used as the substrate. In this case, x and y in (B _x Ga _{1 -x} ) _y In _{1 -y} As constituting the active layer
Is preferably selected so as to satisfy the condition such that the magnitude of the lattice mismatch Δa / a with respect to the GaAs substrate falls within the range of ± 2 × 10 ⁻² , and more preferably the lattice mismatch with respect to the GaAs substrate. Is selected so as to satisfy the condition such that the magnitude Δa / a of the image is within the range of ± 1 × 10 ⁻² . Note that (B _x Ga _{1 -x} ) _y In constituting the active layer
_When x and y in _1-y As are selected so as to satisfy the conditions, the active layer lattice-matches with the GaAs substrate.

In the present invention, (B _x Ga _{1 -x} ) _y In _{1 -y} As which is lattice-matched to the substrate is preferably used for the active layer. (B _x Ga _{1 -x} ) _y In _{1 -y} As may be used. Note that this active layer may have a quantum well structure such as a single quantum well structure or a multiple quantum well structure. When (B _x Ga _{1 -x} ) _y In _{1 -y} As, which has lattice mismatch with the substrate, is used as the active layer, strain is applied to the active layer. When strain is applied to the active layer, the magnitude of the strain is preferably set, for example, within a range of ± 2%, and more preferably, within a range of ± 1.5%. When strain is applied to the active layer, the thickness of the active layer is set to be equal to or less than the critical thickness.

In the present invention, the n-type cladding layer and the p-type cladding layer are typically lattice-matched with the substrate. As the material of the n-type clad layer and the p-type clad layer, those having a larger band gap than the active layer and a low refractive index are used. Specifically, as a material of the n-type clad layer and the p-type clad layer, for example, AlGa
A III-V group compound semiconductor such as As, AlGaInP, GaAs, InGaAsP, or BGaInAs is used. Any of these materials can be lattice-matched to a GaAs substrate.

In the present invention, a first optical waveguide layer is provided between the active layer and the n-type cladding layer to separate the carrier confinement region and the light confinement region, and the active layer and the p-type cladding layer are provided. A second optical waveguide layer may be provided between the layers. These first and second optical waveguide layers are typically lattice matched to the substrate. As a material of the first optical waveguide layer and the second optical waveguide layer, the band gap is larger than the active layer and the refractive index is lower, and the band gap is smaller than the n-type cladding layer and the p-type cladding layer and the refractive index is high. Rate. As such a material, for _{example, B u Ga 1-u)} v In 1-v As ( however, 0 <u
≦ 1, 0 <v ≦ 1, uv ≠ 0). In this case, (B _x Ga _{1 -x} ) _y In _{1 -y} A lattice-matched to the substrate with the active layer.
with s, it is preferable to use the first to the substrate and lattice-matched to the optical waveguide layer and the second optical waveguide layer _{(B u Ga 1-u)} v In 1-v As, in some cases, the active layer (B _x Ga _1-x ) _y In _1-y
With As, the first optical waveguide layer and the second optical waveguide layer may be used _{(B u Ga 1-u)} v In 1-v As the substrate lattice-matched. The first optical waveguide layer and the second optical waveguide layer include, for example, AlGaAs, AlGaIn
A group III-V compound semiconductor, such as P, GaAs, and InGaAsP, which can be lattice-matched with a GaAs substrate, may be used.

According to the present invention configured as described above, since the active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As, an emission wavelength of about 0.88 μm to several μm can be obtained. A semiconductor light emitting device capable of emitting light in such a long wavelength band can be easily manufactured using a GaAs substrate as a substrate. Also, by arbitrarily selecting the mixed crystal ratio of (B _x Ga _{1 -x} ) _y In _{1 -y} As used for the active layer, the active layer can be lattice-matched to the substrate.
This active layer can be strained. Further, since a large band gap difference can be obtained between the active layer and the n-type clad layer and the p-type clad layer, the conventional InG
A higher characteristic temperature can be realized as compared with the aAsP-based semiconductor light emitting device.

[0039]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 4 is a sectional view of a semiconductor laser according to one embodiment of the present invention. This semiconductor laser is a buried ridge type semiconductor laser of a refractive index guided type. Also, this semiconductor laser has a SCH (Separate Confinement Het).
erostructure) structure.

As shown in FIG. 4, in this semiconductor laser, for example, an n-type GaAs substrate 1 is used as a substrate. Then, on this n-type GaAs substrate 1, an n-type A
lGaAs cladding layer 2, n-type _{(B u Ga 1-u)} v In
_1-v As optical waveguide layer 3 (where 0 <u ≦ 1, 0 <v ≦
1, uv ≠ 1), (B _x Ga _1-x ) _y In _1-y As active layer 4 (where 0 <x ≦ 1, 0 <y ≦ 1, xy ≠ 1),
p-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 5, p-type AlGaAs cladding layer 6 and the p-type GaAs cap layer 7 is provided by sequentially stacking. p-type AlGaAs
Upper part of clad layer 6 and p-type GaAs cap layer 7
Have a ridge stripe shape extending in one direction.

An n-type GaAs current confinement layer 8 is buried in both sides of the ridge stripe portion, thereby forming a current confinement structure, and corresponding to the ridge stripe portion in a direction parallel to the junction (lateral direction). A step-like refractive index distribution is created in which the refractive index of the portion where the refractive index is high is high and the refractive index of the portions corresponding to both sides is low.

The p-type GaAs cap layer 7 and the n-type Ga
A p-side electrode 9 such as a Ti / Pt / Au electrode is provided on the As current confinement layer 8. On the other hand, n-type G
On the back surface of the aAs substrate 1, for example, AuGe / Ni / Au
An n-side electrode 10 such as an electrode is provided.

The n-type AlGaAs cladding layer 2 and the n-type (B
_u Ga _1-u ) _v In _1-v As optical waveguide layer 3 and n-type Ga
For example, Si or S is used as a donor in the As current confinement layer 8 as a donor.
e is doped, p-type _{(B u Ga 1-u)} v In 1-v As
The optical waveguide layer 5, the p-type AlGaAs cladding layer 6, and the p-type GaAs cap layer 7 have, for example, Zn as an acceptor.
Alternatively, Mg is doped. An example of the thickness of each semiconductor layer forming the laser structure is n-type AlG
The thickness of aAs cladding layer 2 is 2 [mu] m, n-type (B _u Ga
_1-u ) _v In _1-v As The optical waveguide layer 3 has a thickness of 50 nm,
The thickness of the (B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 is 10
nm, p-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 5
Is 50 nm, the thickness of the p-type AlGaAs cladding layer 6 is 2 μm, and the thickness of the p-type GaAs cap layer 7 is 0.5 μm.
μm.

This embodiment having the above-described structure is characterized in that a laser structure is formed using (B _x Ga _{1 -x} ) _y In _{1 -y} As for the active layer. Further, in the semiconductor laser according to this embodiment,
(B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 is an n-type GaAs
This (B _x Ga _1-x ) is lattice-matched with the s substrate 1.
The composition of the _y In _1-y As active layer 4 is selected. That is, _{x and y in the} (B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 are as follows:

[0046]

(Equation 8)

Have been chosen to satisfy Here, x and y were selected so as to satisfy the condition (B _x Ga _{1 -x} )
_{In the y} In _1-y As active layer 4, as shown by a broken line a in FIG. 1, the band gap has an arbitrary value within a range from a value substantially corresponding to GaAs to a value corresponding to B _0.316 In _0.684 As. Can be set to This band gap is about 0.88 μm to 2.5 μm in terms of wavelength.
Is equivalent to Therefore, in this embodiment, the values of x and y in the (B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 are selected so as to obtain a desired emission wavelength while satisfying the above conditions. Is done. In addition, 0.88 μm to 2.5
The wavelength range of 1.3 μm and 1.55 μm used in optical communication using a glass fiber for the transmission line are used.
Since the m-band is covered, this semiconductor laser can be used as a light source for optical communication.

[0048] n-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 3 and the p-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 5, (B _x Ga _1-x ) _y In _1-y As active layer 4 has a larger band gap and a lower refractive index. These n-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 3 and the p-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 5, n-type GaAs made from those substrate 1 and the lattice-matched, thus, these n-type _{(B u Ga 1-u)} v I
n _1-v As optical waveguide layer 3 and p-type (B _u Ga _1-u ) _v I
u and v in the n _1-v As optical waveguide layer 5 are:

[0049]

(Equation 9)

Are selected so as to satisfy the following relationship.

The n-type AlGaAs cladding layer 2 and the p-type AlGaAs cladding layer 6 are made of, for example, Al _0.45 Ga _0.55
Consists of As. These n-type AlGaAs cladding layers 2
The p-type AlGaAs cladding layer 6 is formed of an n-type ( _BuG
a _1-u ) _v In _{1 -v} As optical waveguide layer 3 and p-type (B _u G)
a _1-u ) _v In _1-v As optical waveguide layer 5 has a larger band gap and a lower refractive index than n-type GaAs.
Lattice matching with s substrate 1.

Next, a method of manufacturing the semiconductor laser according to the embodiment will be described. In this embodiment, for example, an MOCVD method is used as a crystal growth method of each semiconductor layer forming a laser structure. At this time, III
Gallium (TMG) as a raw material for group Ga
With trimethylaluminum (TM
A) using trimethyl indium (TM) as a raw material of In
I) using triethylboron (TEB) as a raw material for B
And arsine (AsH ₃ ) as a raw material of the group V As.

First, as shown in FIG. 5, on an n-type GaAs substrate 1, an n-type AlGaAs cladding layer 2 and an n-type ( _BuG)
a _1-u ) _v In _{1 -v} As optical waveguide layer 3, (B _x Ga _{1 -x} )
_y In _1-y As active layer 4, p-type _{(B u Ga 1-u)} v In
_{A 1-v} As optical waveguide layer 5, a p-type AlGaAs cladding layer 6, and a p-type GaAs cap layer 7 are sequentially grown by MOCVD.

Here, n-type (B _u Ga _1-u ) _v In _1-v
As optical guide layer 3, a layer containing _{(B x Ga 1-x)} y In 1-y As active layer 4 and p-type _{(B u Ga 1-u)} v In 1-v As optical guide layer 5 is In However, each of these layers is B
And the desorption of In from the crystal can be suppressed by the effect of adding B. Therefore, the growth temperature of these In-containing layers is raised to about the same as the growth temperature of the In-free layers (the n-type AlGaAs cladding layer 2, the p-type AlGaAs cladding layer 6, and the p-type GaAs cap layer 7). Is possible. In this embodiment, the n-type AlGaAs cladding layer 2 and the n-type (B
_{u Ga 1-u) v In} 1-v As optical guide layer 3, (B _x Ga
_{1-x) y In 1-} y As active layer 4, p-type (B _u Ga _{1-u)
The v} In _1-v As optical waveguide layer 5, the p-type AlGaAs cladding layer 6 and the p-type GaAs cap layer 7 are, for example, 760 ° C.
The crystal is grown at a constant growth temperature of 820 ° C. or lower, specifically, for example, 780 ° C.

Next, as shown in FIG. 6, an SiO ₂ film or SiN film is formed on the entire surface of the p-type GaAs cap layer 7 by the CVD method.
After forming the _x film, the film is patterned into a stripe shape having a predetermined width extending in one direction, thereby forming a mask 11.
To form Next, using the mask 11 as an etching mask, the p-type AlGaAs cladding layer 6 is etched to a depth in the thickness direction. Thereby, the p-type AlGa
The upper layer portion of the As cladding layer 6 and the p-type GaAs cap layer 7 are patterned into a predetermined ridge stripe shape.

Next, as shown in FIG. 7, using the mask 11 as a growth mask, an n-type GaAs current confinement layer 8 is grown by MOCVD so as to bury the portions on both sides of the ridge stripe portion. Thereafter, the mask 11 is removed by etching.

Next, as shown in FIG. 4, a p-side electrode 9 is formed on the p-type GaAs cap layer 7 and the n-type GaAs current confinement layer 8 by a vacuum evaporation method or a sputtering method, and the n-type GaAs substrate 1 is formed. The n-side electrode 10 is formed on the back surface of the substrate. Thus, the intended semiconductor laser is manufactured.

According to this embodiment configured as described above, (B _x Ga _{1 -x} ) _y In _{1 -y} As is used as the active layer.
By using the active layer 4, a semiconductor laser capable of emitting light in a long wavelength band can be easily manufactured using the easily available n-type GaAs substrate 1. Also,
(B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 is made of n-type GaAs.
The emission wavelength can be arbitrarily set within a range from 0.88 μm in the near infrared region to 2.5 μm in the mid infrared region while lattice-matching with the s substrate 1.

According to this embodiment, the (B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 is used as the active layer, and the n-type AlGaAs is used as the n-type clad layer and the p-type clad layer.
By using the s cladding layer 2 and the p-type AlGaAs cladding layer 6, a large band gap difference between the active layer and the cladding layer can be obtained, and the conventional typical long-wavelength semiconductor laser, InGaAsP-based laser, is used. A higher characteristic temperature can be realized as compared with a semiconductor laser. Further, n-type AlGaAs cladding layer 2, n-type (B _u Ga
_1-u ) _v In _1-v As optical waveguide layer 3, (B _x Ga _{1 -x} ) _y
In _1-y As active layer 4, p-type _{(B u Ga 1-u)} v In
_{Since the 1-v} As optical waveguide layer 5 and the p-type AlGaAs cladding layer 6 are both lattice-matched to the n-type GaAs substrate 1, a stable and high-quality heterojunction can be obtained, and a semiconductor with good operating characteristics can be obtained. A laser can be realized.

Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the numerical values, materials, structures, and the like described in the embodiments are merely examples, and the present invention is not limited thereto. Specifically, in the above-described embodiment, the (B _x Ga _{1 -x} ) _y In _{1 -y} As active layer 4 that is lattice-matched to the n-type GaAs substrate 1 is used. B _x Ga _1-x ) _y In _1-y As active layer 4
May have lattice mismatch with the n-type GaAs substrate 1. Further, the active layer may have a multiple quantum well structure.

In the above-described embodiment, the laser structure is formed by using AlGaAs for the n-type clad layer and the p-type clad layer. This is because the n-type clad layer and the p-type clad layer are formed of AlGaInP. , GaAs,
The laser structure may be formed using a group III-V compound semiconductor that can be lattice-matched with a GaAs substrate such as InGaAsP or BGaInAs. Further, as the material of the optical waveguide _{layer, (B u Ga 1-u} ) v In
AlGaAs, AlGaInP, Ga instead of _1-v As
As or InGaAsP may be used.

In the above-described embodiment, the MOCVD method is used for crystal growth of the semiconductor layer forming the laser structure. However, the MBE method may be used.

In the above embodiment, the conductivity types of the substrate and the semiconductor layer forming the laser structure may be reversed.

In the above-described embodiment, the case where the present invention is applied to a semiconductor laser having an SCH structure has been described. However, the present invention relates to a DH (Double Heterostruc
ture) structure. Further, the laser structure and the waveguide type are not limited to the buried ridge structure and the refractive index waveguide type shown in the above-described embodiment. For example, the present invention relates to a BH (Buried Heterostructure) structure and a SAN (SAN). Se
It is also possible to apply the present invention to a semiconductor laser having another structure such as an (lf Aligned Narrow stripe) structure or a gain guided semiconductor laser. Further, the present invention can be applied to a light emitting diode other than the semiconductor laser.

[0065]

As described above, according to the present invention, since the active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As, a long wavelength of about 0.88 μm to several μm is obtained. A semiconductor light emitting element capable of emitting light in a band can be easily manufactured by using GaAs as a substrate. Also, by arbitrarily selecting the composition of (B _x Ga _{1 -x} ) _y In _{1 -y} As constituting the active layer, the active layer can be lattice-matched to the substrate, or the active layer can be strained. Is also possible. Also, a large band gap difference between the active layer, the n-type cladding layer and the p-type cladding layer can be obtained,
A higher characteristic temperature can be realized as compared with a conventional InGaAsP-based semiconductor light emitting device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the relationship between the lattice constant and band gap of typical group III-V compound semiconductors and their mixed crystals.

FIG. 2 is a graph showing a relationship between a B composition ratio x and a band gap in B _x Ga _1-x As.

3 is a graph showing the relationship between the B composition ratio x and the band gap in the B _y In _1-y As.

FIG. 4 is a sectional view of a semiconductor laser according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining the method for manufacturing the semiconductor laser according to one embodiment of the present invention;

FIG. 6 is a cross-sectional view for explaining the method for manufacturing the semiconductor laser according to one embodiment of the present invention;

FIG. 7 is a cross-sectional view for explaining the method for manufacturing the semiconductor laser according to one embodiment of the present invention.

[Explanation of symbols]

1 ... n-type GaAs substrate, 2 ... n-type AlGaAs
Cladding layer, 3 · · · n-type _{(B u Ga 1-u)} v In 1-v
As optical waveguide layer, 4 ... (B _x Ga _1-x ) _y In _1-y A
s active layer, 5 · · · p-type _{(B u Ga 1-u)} v In 1-v A
s optical waveguide layer, 6... p-type AlGaAs cladding layer, 7
... p-type GaAs cap layer, 8 ... n-type GaAs
Current confinement layer, 9 ... p-side electrode, 10 ... n-side electrode

Claims (13)

[Claims] 1. A semiconductor light emitting device having a structure in which an active layer is sandwiched between an n-type cladding layer and a p-type cladding layer on a substrate, wherein the active layer is (B _x Ga _{1 -x} ) _y In _{1 -y} As ( Here, 0 <x ≦ 1, 0 <y ≦ 1, xy ≠ 1). 2. The semiconductor light emitting device according to claim 1, wherein said substrate is a GaAs substrate. 3. The semiconductor light emitting device according to claim 1, wherein said active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As lattice-matched to said substrate. 4. The semiconductor light emitting device according to claim 1, wherein said active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As having lattice mismatch with respect to said substrate. 5. The semiconductor light emitting device according to claim 1, wherein said n-type cladding layer and said p-type cladding layer are made of AlGaAs. 6. The semiconductor light emitting device according to claim 1, wherein said n-type cladding layer and said p-type cladding layer are made of AlGaInP. 7. The semiconductor light emitting device according to claim 1, wherein said n-type cladding layer and said p-type cladding layer are made of GaAs. 8. The semiconductor light emitting device according to claim 1, wherein said n-type cladding layer and said p-type cladding layer are made of InGaAsP. 9. The semiconductor light emitting device according to claim 1, wherein said n-type cladding layer and said p-type cladding layer are made of BGaInAs. 10. A semiconductor device comprising: a first optical waveguide layer between the active layer and the n-type cladding layer; and a second optical waveguide layer between the active layer and the p-type cladding layer. The semiconductor light-emitting device according to claim 1, wherein: 11. The first optical waveguide layer and the second optical waveguide layer _{(B u Ga 1-u)} v In 1-v As ( where
11. The semiconductor light emitting device according to claim 10, wherein 0 <u ≦ 1, 0 <v ≦ 1, uv ≠ 1). 12. The active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As lattice-matched to the substrate, and the first optical waveguide layer and the second optical waveguide layer are and lattice-matched _{(B u Ga 1-u)} v in 1-v semiconductor light emitting device according to claim 11, characterized in that it consists of as. 13. The first optical waveguide layer and the second optical waveguide, wherein the active layer is made of (B _x Ga _{1 -x} ) _y In _{1 -y} As having lattice mismatch with the substrate. layers are the substrate lattice-matched _{(B u Ga 1-u)} v in 1-v as
12. The semiconductor light emitting device according to claim 11, comprising: