JP2001358409A - Semiconductor optical device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical device which has a light source for long wavelength (1 μm band) suitable for optical communication wherein control of wavelength of oscillation light is easy, stable oscillation wavelength can be obtained and reliability is excellent, and to provide a method of manufacturing the device. SOLUTION: In this semiconductor optical device and its manufacturing method, a quantum well active layer which includes an InxGa1-xNyAs1-y (0<x<=1, 0<y<=1) quantum well layer and GaNzAs1-z (0<z<=1) barrier layers which are adjacent to the upper part and the lower part of the quantum well layer is arranged on a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device useful as a semiconductor laser or the like and a method for manufacturing the same, and more particularly to a semiconductor optical device suitable for an optical communication system and a method for manufacturing the same.

[0002]

2. Description of the Related Art A long-wavelength semiconductor laser conventionally used as an optical communication system has an InP clad layer and a GaInAsP active layer formed on an InP substrate. Therefore, there is a problem that the temperature characteristics are poor and the characteristics are degraded during high-temperature operation. Therefore, in order to extend the life of the laser diode and reduce the production cost, it has been essential to develop a semiconductor laser having good temperature characteristics.

In order to solve the problem in high-temperature operation,
Many proposals have been made so far. For example, JP
No. 0-270798 discloses In _0.1 Ga _0.9 N _0.03 As _0.97 lattice-matched with a GaAs substrate or having tensile strain.
Bulk active layer or _{In 0. 06 Ga 0.94 N 0.04 As} 0.96
There is disclosed a semiconductor light emitting device in which a GaAs spacer layer is inserted into upper and lower layers of a quantum well active layer and an emission wavelength is 1.3 μm. In the semiconductor light emitting device, the cladding layer is made of AlGaAs or GaInP, so that the band discontinuity of the conduction band can be increased and the temperature characteristics can be improved. Furthermore, by inserting a GaAs spacer layer, the cladding layer can be formed on the cladding layer. Mirror growth of the active layer is possible, which can contribute to quality improvement of the active layer.

[0004]

However, in the semiconductor light emitting device disclosed in Japanese Patent Application Laid-Open No. Hei 10-270798,
There is a phenomenon that it is difficult to obtain a stable oscillation wavelength. In addition, it is difficult to obtain a specific wavelength (particularly, a long wavelength) with the semiconductor light emitting device, and there is a problem in terms of wavelength controllability.
Therefore, there has been a demand for the development of a semiconductor optical device capable of avoiding such phenomena and problems.

Thus, the present invention has been made in view of the above-mentioned problems, and it is easy to control the wavelength of oscillation light, and
It is an object of the present invention to provide a semiconductor optical device having a long-wavelength light source (1 μm band) suitable for optical communication having a stable oscillation wavelength and excellent reliability, and a method of manufacturing the same.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that Ga is formed on the upper and lower layers of a well layer made of InGaNAs having a compressive strain.
It has been found that by manufacturing a quantum well active layer including a barrier layer made of NAs and having a tensile strain, an excellent semiconductor optical device exhibiting a desired effect can be obtained.

That is, the inventors of the present invention disclosed in the above-mentioned Japanese Patent Application Laid-Open
As a result of repeated tests on the semiconductor light emitting device disclosed in Japanese Unexamined Patent Publication (Kokai) No.-270798, the change in band gap energy at the boundary between the InGaNAs active layer and the GaAs spacer layer is moderately inclined. It has been found that a specific wavelength cannot be stably obtained due to poor steepness.

[0008] The inventors of the present invention have further studied diligently, considering that development of a quantum well structure capable of maintaining the sharpness of the well-type potential is indispensable in order to solve the above-mentioned problem. Advanced. As a result, the following solution has been found and the present invention has been completed. (1) In forming a quantum well active layer, the interface between the well layer and the barrier layer can be easily formed only by adjusting the addition amount of indium, and the steepness of the well-type potential in the quantum well structure is improved. What you can do. Japanese Patent Application Laid-Open No. 10-27
In the semiconductor light-emitting device disclosed in Japanese Patent No. 0798, indium and nitrogen are added at the same time, so that the well-type potential at the interface between the well layers becomes gentle, and it is difficult to control the wavelength. In addition, when a plurality of well layers are formed, such as a multi-quantum well active layer, the adjustment is time-consuming and cumbersome. Therefore, in order to improve the steepness of the well-type potential and increase the efficiency of the work, the well layer and the barrier layer having a good interface can be formed simply by adjusting the presence or absence of indium in the presence of nitrogen. It can be formed. (2) By forming a GaNAs barrier layer having tensile strain in the lower and upper layers of the InGaNAs well layer, the composition ratio and critical thickness of indium in the well layer are increased while controlling the generation and propagation of misfit transition. What you can do. If the composition ratio of indium is increased, the compressive strain increases, and the lattice constant mismatches at the boundary, causing misfit transition, thereby limiting the composition ratio of indium. On the other hand, in order to prevent the propagation of misfit transition in the barrier layer, it is necessary to increase the crystal strength of the barrier layer. Thus, the present inventors have proposed Ga
As a result of repeated studies on how the critical film thickness of the well layer changes when nitrogen is added to the As barrier layer, the presence of nitrogen in the GaAs barrier layer can increase the critical film pressure. It has been found that the composition ratio of indium can be further increased (see FIG. 6). For example, FIG.
Is about 7 nm, the barrier layer without addition of nitrogen has the X value of 0.33 and reaches the critical thickness.
The value increased to 0.53, and as a result, a favorable result was obtained in which the indium composition ratio could be increased by about 0.2. Therefore, the present invention enhances the crystallinity of the barrier layer, while controlling the occurrence of misfit transition to increase the composition ratio of indium, the upper layer and the lower layer of the well layer have a strain opposite to the compressive strain, That is, a nitrogen-containing barrier layer having a tensile strain was formed. (3) In the composition of the well layer made of InGaNAs,
When the composition ratio of indium is increased and the composition ratio of nitrogen is decreased, a well layer having a compressive strain can be formed while maintaining good crystallinity. From the viewpoint of increasing the wavelength, it is preferable to increase both the composition ratio of indium and nitrogen. However, since the atomic radii of arsenic (As), which is a group V element, and nitrogen are greatly different, if the composition ratio of nitrogen is increased, heat It becomes metastable (unstable) mechanically and its crystallinity is greatly reduced. When the composition ratio of nitrogen is increased, G
The band offset of the valence band becomes smaller than that of aAs, and holes cannot be effectively confined in the active layer. Therefore, it is not suitable for a semiconductor laser requiring a high carrier density in the active layer. Therefore, the present invention
The composition ratio of indium was increased from the viewpoint of obtaining good crystallinity and being usable in a semiconductor laser requiring a high carrier concentration.

That is, the present invention relates to In _x Ga _{1 -x} N _y As
A quantum well active layer including a _1-y (0 <x ≦ 1, 0 <y ≦ 1) well layer and a GaN _z As _1-z (0 <z ≦ 1) barrier layer above and below the well layer A semiconductor optical device device characterized by having a substrate on a substrate.

In a preferred embodiment of the semiconductor optical device according to the present invention, the substrate is made of GaAs; the quantum well active layer has two or more well layers; An aspect characterized by including a layer having a lower refractive index than the quantum well active layer above and below the quantum well active layer, respectively, of the layers having a lower refractive index than the quantum well active layer. An embodiment in which the lower layer of the well active layer is a first conductivity type cladding layer and the upper layer of the quantum well active layer is a second conductivity type cladding layer; Is Al
_p Ga _1-p As (0 <p ≦ 1), and / or the second conductivity type cladding layer is Al _q Ga _1-q As (0 <q ≦ 1); An embodiment in which the well active layer has a lower light guide layer on the first conductivity type clad layer side and / or an upper light guide layer on the second conductivity type clad layer side; wherein the lower light guide layer is Al _r Ga _1-r As (0 ≦ r <
1) and / or the upper light guide layer is Al _s Ga _1-s A
s (0 ≦ s <1);
l _p Ga _1-p As the (0 <p ≦ 1) and the Al composition ratio p of the first conductivity type cladding layer _{Al r Ga 1-r As (} 0 ≦ r <1)
An aspect in which the Al composition ratio r of the lower light guide layer has a relationship of p>r; the above-mentioned Al _q Ga _1-q As
(0 <q ≦ 1) Al composition ratio q of the second conductivity type cladding layer
And the Al _s Ga _{1 -s} As (0 ≦ s <1) and the Al composition ratio s of the upper optical guide layer have a relationship of q>s; the semiconductor optical device device emits semiconductor light. An aspect characterized by being an element; an aspect characterized in that the semiconductor light emitting element is a semiconductor laser; an aspect characterized by an emission wavelength of the semiconductor light emitting element being 1 to 2 μm; An embodiment is characterized in that the device is a semiconductor light receiving element.

The present invention also provides a method for forming a substrate, comprising the steps of:
_x Ga _1−x N _y As _1−y (0 <x ≦ 1, 0 <y ≦ 1) well layer and GaN _z As _1−z (0 <z
.Ltoreq.1) A method for manufacturing a semiconductor optical device, comprising a step of forming a quantum well active layer including a barrier layer, wherein the barrier formed as a lower layer of the well layer in the step of forming the quantum well active layer. Adding nitrogen at the beginning of the formation of the layer, ending the addition of nitrogen at the end of the formation of the barrier layer formed as an upper layer of the well layer, and adding indium during the formation of the well layer; There is provided a method for manufacturing a semiconductor optical device, wherein indium is not added during formation of a layer.

In a preferred embodiment of the method for manufacturing a semiconductor optical device according to the present invention, in the step of forming the quantum well active layer, indium is added twice or more while nitrogen is added. There is an embodiment characterized in that the well layer is formed as described above.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and manufacturing method of a semiconductor optical device according to the present invention will be described below in detail. A semiconductor optical device device according to the present invention includes a substrate and In _x Ga ₁ -xN _y As _{1 -y} (0 <x ≦
1,0 <y ≦ 1) a well layer, and a quantum well active layer including a GaN _z As _1-z (0 <z ≦ 1) barrier layer as an upper layer and a lower layer, respectively. The semiconductor optical device of the present invention may appropriately have layers usually formed in the semiconductor optical device in addition to these layers.

In this specification, the expression “B layer formed on the A layer” refers to the case where the B layer is formed such that the bottom surface of the B layer is in contact with the upper surface of the A layer. , One or more layers are formed on the upper surface, and a layer B is further formed on that layer. The above expression also includes the case where the upper surface of the A layer and the bottom surface of the B layer are partially in contact with each other and one or more layers exist between the A layer and the B layer in other portions. Specific aspects are apparent from the following description of each layer and specific examples of the examples.

FIG. 1 is a perspective view showing an example of a semiconductor optical device according to the present invention. FIG. 1A shows a so-called ridge waveguide type semiconductor laser (hereinafter referred to as “ridge waveguide type laser”). As can be understood from FIG. 1A, in the ridge waveguide type laser, a first conductivity type cladding layer 12 and an active layer 13 are formed in this order on a substrate 11, and a second conductive type cladding layer 12 is further formed on the active layer 13. A mold first cladding layer 14, a cap layer 15, and a protective film 16 are formed in this order, and then a second conductivity type second cladding layer 17 is formed in a ridge shape. A contact layer 18 is formed on the surface of the second ridge-shaped second conductive type second cladding layer 17, and electrodes 19 and 20 are formed on the surface of the contact layer 18 and the surface of the substrate 11 as shown in the figure.

FIG. 1B shows a semiconductor laser having a so-called self-aligned inner stripe structure (hereinafter referred to as "self-aligned laser"). FIG.
As understood from (b), in the self-aligned laser, the first conductive type clad layer 22, the active layer 23, the second conductive type first clad layer 24, and the cap layer 2 are formed on the substrate 21.
5 is formed, and a current blocking layer 26 having an opening 32 and a protective film 27 are further formed on the cap layer 25, and then a second cladding layer 28 of the second conductivity type and a contact layer 29 are formed.
Is formed, and the surface of the contact layer 29 and the substrate 21 are formed.
Electrodes 30 and 31 are sequentially formed on the surface.

In FIG. 1, if the substrates 11 and 21 constituting the semiconductor optical device of the present invention can grow a crystal having a double hetero structure on them, the conductivity and the material thereof are not limited. Is not particularly limited. Preferred is a conductive substrate. Specifically, GaAs, InGaAs, and IGaAs suitable for growing a crystal thin film on a substrate
It is preferable to use a crystal substrate of nP, GaP, ZnSe, ZnO, Si, Al ₂ O ₃ or the like, particularly a crystal substrate having a zinc blende structure, more preferably GaAs, InGaAs, InP, and most preferably GaAs. In that case,
The substrate crystal growth plane is preferably a low-order plane or a plane crystallographically equivalent thereto, and most preferably a (100) plane.

In this specification, the (100) plane is not necessarily strictly a (100) just plane, but includes a case having an off-angle of about 30 ° at the maximum. 30 ° off-angle limit
Or less, more preferably 16 ° or less. The lower limit is preferably 0.5 ° or more, more preferably 2 ° or more, and 6
And more preferably 10 ° or more.

On the substrates 11 and 21, the thickness of the substrate is usually set at 0.
It is preferable to form a buffer layer of about 2 to 2 μm.

The active layers 13 and 23 are provided on the substrates 11 and 21.
Is formed. The compound semiconductor layer
Layers having a lower refractive index than the active layer are included above and below the active layer. Among them, the layer on the substrate side functions as a first conductivity type cladding layer, and the other layer on the epitaxial side functions as a second conductivity type cladding layer. The magnitude relationship between the refractive indices can be adjusted by appropriately selecting the material composition of each layer according to a method known to those skilled in the art. For example, Al _x Ga _1-x A
s, (Al _x Ga _1-x ) _0.5 In _0.5 P, Al _x Ga _1-x N
The refractive index can be adjusted by appropriately changing the Al composition such as (0 <x ≦ 1). However, in order to maintain good crystallinity of the active layer, Al _x Ga _{1 -x} As must be used. Is preferred.

The first conductivity type cladding layers 12 and 22 are formed of a material having a smaller refractive index than the active layers 13 and 23 in order to confine light. For example, first conductivity type InP, G
aInP, AlGaInP, AlInP, AlGaAs
s, AlGaAsP, AlGaInAs, GaInAs
P, GaN, AlGaN, AlGaInN, BeMgZ
nSe, MgZnSSe, CdZnSeTe, ZnO,
General group III-V and group II-VI semiconductors such as MgZnO and MgO can be used, and AlGaAs, GaIn
P and AlGaInP are preferable, and Al _p Ga _1-p As (0
<P ≦ 1) is more preferable.

The lower limit of the carrier concentration of the first conductivity type cladding layers 12 and 22 is preferably 1 × 10 ¹⁷ cm ⁻³ or more,
× 10 ¹⁷ cm ^-3 or more is more preferable, and 5 × 10 ¹⁷ cm ^-3
The above is more preferred. The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less, more preferably 2 × 10 ¹⁹ cm ⁻³ or less, and 5 ×
It is more preferably 10 ¹⁸ cm ^-3 or less.

The first conductivity type cladding layers 12 and 22 may be composed of a single layer or may be composed of two or more layers. When it is composed of a single layer, the lower limit of the thickness is 0.1.
4 μm or more is preferable, 0.6 μm or more is more preferable, and 0.7 μm or more is further preferable. Further, the upper limit of the thickness is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably 2 μm or less.

When the first conductivity type cladding layers 12 and 22 are composed of two or more layers, GaInP, AlG
a cladding layer made of aInP or AlInP, and a first conductivity type AlGaAs or AlGa
An embodiment in which a cladding layer made of AsP is formed can be exemplified. At this time, the thickness of the layer on the active layer side is preferably reduced, and the lower limit of the thickness is 0.01 μm.
m or more, more preferably 0.05 μm or more.
The upper limit is preferably 0.5 μm or less, and 0.3 μm
The following is more preferred. The lower limit of the carrier concentration of the cladding layer on the substrate side is preferably 2 × 10 ¹⁷ cm ⁻³ or more, more preferably 5 × 10 ¹⁷ cm ⁻³ or more. The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less, and 5 × 10 ¹⁹ cm ^−3.
The following is more preferred.

The active layers 13 and 23 are made of In _x Ga _{1 -x} N _y A
s _1-y well layer and GaN _z As adjacent above and below the well layer
It has a quantum well structure including a _1-z barrier layer.

The active layers 13 and 23 are made of In _x Ga _{1 -x} N _y A
s _1-y (0 <x ≦ 1, 0 <y ≦ 0.02) A well layer, and GaN _z As as an upper layer and a lower layer of the well layer, respectively.
There is no particular limitation as long as the quantum well structure includes a _1-z (0 <z ≦ 1) barrier layer, and the active layer may include two or more well layers.

The active layer 23 in the self-aligned laser shown in FIG. 1B has a double quantum well (DQW) structure. Specifically, the double quantum well (DQW) structure has a barrier layer (non-doped) 52, a well layer (non-doped) 5
3, a structure in which a barrier layer (non-doped) 54, a well layer (non-doped) 55, and a barrier layer (non-doped) 56 are sequentially stacked. In addition to the double quantum well (DQW) structure, for example, as in a ridge waveguide type laser shown in FIG. 1A, a well layer 43 and a barrier layer 4 sandwiching the well layer from above and below are provided.
It may be a single quantum well structure (SQW) composed of 2,44. In addition, a multi-quantum well structure (not shown) having three or more well layers and barrier layers sandwiched between them, and barrier layers stacked above the uppermost well layer and below the lowermost well layer, respectively. It does not matter.

Although the well layer and the barrier layer inside the active layer are usually undoped, the barrier layer may be doped (usually p-type) in order to realize high-speed response.

The composition of the In _x Ga _{1 -x} N _y As _{1 -y} well layer is as follows:
In order to obtain good crystallinity, to prevent the band offset of the valence band from being reduced, and to effectively confine carriers (holes) in the active layer, InGaNA is used.
In the s composition, increase the composition ratio of In as much as possible,
It is preferable to reduce the composition ratio of N as much as possible.
The lower limit of the composition ratio of In in the In _x Ga _1-x N _y As _1-y well layer is larger than 0, preferably 0.2 or more, more preferably 0.3 or more. The upper limit is 1 or less,
0.7 or less is preferable, and 0.6 or less is more preferable.

N in the In _x Ga _{1 -x} N _y As _{1 -y} well layer
The lower limit of the composition ratio is larger than 0, preferably 0.001 or more, more preferably 0.003 or more, and 0.005 or more.
The above is more preferred. The upper limit is 1 or less, preferably 0.3 or less, and more preferably 0.05 or less.

The thickness of the In _x Ga _{1 -x} N _y As _{1 -y} well layer is as follows:
The lower limit is preferably one atomic layer or more, more preferably 2 nm or more, and even more preferably 4 nm or more. The upper limit is 30 nm
Or less, more preferably 20 nm or less, and 10 n
m or less is more preferable.

It should be noted that when a well layer made of InGaNAs of the present invention contains an element having a significantly different lattice constant in both group III and group V, a natural superlattice is easily formed. It is also possible to use an off substrate.

The composition of the GaN _z As _{1 -z} barrier layer of the present invention comprises Ga, N and As. Although N is contained to enhance the crystallinity of the barrier layer and increase the critical thickness of the well layer, the lower limit of the composition ratio of N is set to be larger than 0 and 0.001 or more for thermodynamic stability. Preferably, 0.0
03 or more is more preferable, and 0.005 or more is still more preferable. The upper limit of the N composition ratio is 1 or less, and 0.3
The following is preferable, and 0.05 or less is more preferable.

The lower limit of the thickness of the GaN _z As _{1 -z} barrier layer is preferably one atomic layer or more, more preferably 2 nm or more, in order to satisfactorily confine carriers in the active layer and obtain steepness of the well-type potential. Preferably, 4 nm or more is most preferable. The upper limit is preferably 30 nm or less, and 20 n
m or less, more preferably 10 nm or less.

The active layers 13 and 23 may have lower light guide layers 41 and 51 between the first conductive type cladding layers 12 and 22. The composition of the lower light guide layers 41 and 51 is as follows:
The material is not particularly limited as long as the light is confined in the active layers 13 and 23, but may be composed of Al _r Ga _{1 -r} As (0 ≦ r <1). The first conductivity type cladding layers 12 and 22 are Al _p Ga _1-p As (0 <p ≦ 1), and the lower light guide layers 41 and 51 are Al _r Ga _1-r As (0 ≦ r <1).
When each is formed by p, p between the Al composition ratio of both layers
> R.

The lower limit of the thickness of the lower light guide layers 41 and 51 is preferably 2 nm or more, more preferably 4 nm or more.
6 nm or more is more preferable. The upper limit is preferably 200 nm or less, more preferably 100 nm or less, and 50 nm or less.
The following are more preferred.

The active layers 13 and 23 of the present invention further include a second
Upper light guides 45 and 57 may be provided between the conductive type first cladding layers 14 and 24. Upper light guide layer 4
The composition of 5,57 is not particularly limited as long as it can focus light into the active layer _{13,23, Al s Ga 1-s} As
The composition may be such that (0 ≦ s <1). Also, the second
The conductive type first cladding layer is formed of Al _q Ga _{1 -q} As (0 <q ≦
1), the upper light guiding layer _{Al s Ga 1-s As (} 0 ≦ s <
When each is formed in 1), it can be formed so as to have a relationship of q> s between the Al composition ratios of both layers.

The lower limit of the thickness of the upper light guide layers 45 and 57 is preferably 2 nm or more, more preferably 4 nm or more.
6 nm or more is more preferable. The upper limit is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less.

On the active layers 13 and 23, a second conductivity type clad layer is formed. The number of layers of the second conductivity type cladding layer of the present invention is not particularly limited as long as carriers (electrons and holes) can be confined in the active layer. When the second conductivity type cladding layer is a single layer, the thickness of the layer is preferably about 0.5 to 4 μm, more preferably about 1 to 3 μm. The second conductivity type cladding layer may be composed of a plurality of layers, and it is preferable to form two or more second conductivity type cladding layers from the viewpoint of confining light in the active layer. In the following description, a preferred embodiment having two layers of a second conductive type first clad layer and a second conductive type second clad layer in order from the one closer to the active layers 13 and 23 will be described as an example.

The second conductive type first cladding layers 14 and 24 are
It is formed of a material having a lower refractive index than the active layers 13 and 23. As a material of the second conductive type first cladding layers 14 and 24, for example, a second conductive type InP, GaInP, AlGa
InP, AlInP, AlGaAs, AlGaAsP,
AlGaInAs, GaInAsP, GaN, AlGa
N, AlGaInN, BeMgZnSe, MgZnSS
e, CdZnSeTe, ZnO, MgZnO, MgO, and other general III-V and II-VI group semiconductors can be used, and AlGaAs, GaInP, AlGaIn
P is preferred, AlGaAs is more like this, Al
_q Ga _1-q As (0 <q ≦ 1) is more preferable.

The lower limit of the carrier concentration of the second conductive type first cladding layers 14 and 24 is preferably 1 × 10 ¹⁷ cm ⁻³ or more, more preferably 3 × 10 ¹⁷ cm ⁻³ or more, and 5 × 10 ¹⁷ cm ^−3.
cm ^-3 or more is more preferable. The upper limit is 5 × 10 ¹⁸ cm ^-3
Is preferably 3 × 10 ¹⁸ cm ⁻³ or less, more preferably 2 × 10 ¹⁸ cm ⁻³ or less.

The thickness of the second conductive type first cladding layer is preferably at least 0.01 μm, more preferably at least 0.05 μm, even more preferably at least 0.07 μm, as the lower limit.
The upper limit of the thickness is preferably 0.5 μm or less, and 0.4 μm
The following is more preferable, and the size is more preferably 0.2 μm or less.

The second conductive type first clad layers 14 and 24 are
It is formed on the active layers 13 and 23. In a preferred embodiment of the present invention, the refractive index of the second conductive type first cladding layers 14 and 24 is smaller than the refractive index of the first conductive type cladding layers 12 and 22. By adopting such an embodiment, the light distribution (near-field image) can be controlled so that light effectively seeps from the active layer to the light guide layer side. Further, since the optical waveguide loss from the active region (the portion where the active layer is present) to the impurity diffusion region can be reduced, the laser characteristics and the reliability in high-power operation can be improved.

The second conductive type cap layers 15 and 25 can be formed on the second conductive type first cladding layers 14 and 24. By forming the cap layers 15 and 25, at the time of regrowing a second-conductivity-type second clad layer described later at least in the opening, a high-resistance layer that increases the passage resistance at the regrowth interface is generated. It can be easily prevented. Further, the cap layers 15 and 25 may function as an etching stop layer.

The material of the cap layers 15 and 25 is not particularly limited as long as it is hardly oxidized or easy to clean even if oxidized. Specifically, the content of easily oxidizable elements such as Al is low (about 0.3 or less) III
-V group compound semiconductor layers. It is preferable that light from the active layer is not absorbed by selecting a material and a thickness. The material of the cap layers 15 and 25 is generally selected from materials having a larger band gap than the material of the active layer. Even if the material has a small band gap, the material has a thickness of 50 nm or less, and more preferably 30 n.
m or less, and most preferably 10 nm or less, can be used because light absorption can be substantially ignored.

In order to improve the controllability of the process, the second
It is preferable that the lower part of the conductive type clad layer be the second conductive type first clad layers 14 and 24. In a self-aligned laser (see FIG. 1B), when the current blocking layer 26 formed on the second conductive type first cladding layer is removed by etching, the current blocking layer 26 and the second conductive type One or more etching stop layers may be inserted at the interface with the mold first cladding layer 24.

The current blocking layer 26 of the self-aligned laser shown in FIG. 1B is formed on the second conductivity type first cladding layer 24 and has an opening 32. Basically,
A current is injected from the opening 32 into the active layer.

The material of the current block layer 26 is not particularly limited as long as it is a semiconductor having advantages such as heat dissipation, cleavage, and low contact resistance. For example, AlGa
Semiconductor materials such as As or AlGaAsP, or AlGaInP or AlInP can be given.

The conductivity type of the current blocking layer 26 is not particularly limited. Specifically, the first conductivity type or high resistance (impurities (O,
(Cr, Fe, etc.) or any combination of the two, and may be formed from a plurality of layers having different conductivity types or compositions.

If the thickness of the current blocking layer 26 is too small, the current blocking function becomes insufficient, so the lower limit is 0.1 μm.
It is preferably at least 0.3 μm. On the other hand, if the thickness is too large, the passage resistance increases, so the upper limit is preferably 2 μm or less, more preferably 1 μm or less.

The refractive index of the current blocking layer 26 is made lower than the refractive index of a second-conductivity-type second cladding layer 28 to be described later narrowed between the current blocking layers 26 (actual refractive index guide structure). By controlling such a refractive index,
The operating current can be reduced as compared with the conventional loss guide structure. The lower limit of the refractive index difference between the current blocking layer 26 and the second conductivity type second cladding layer 28 is preferably at least 0.001, more preferably at least 0.003, and 0.007.
The above is more preferred. The upper limit is preferably 1.0 or less, more preferably 0.5 or less, and still more preferably 0.1 or less.

In the ridge waveguide type laser according to the embodiment of the present invention, the second layer is formed on the cap layer 15 and a part of the protective film 16.
The conductive type second cladding layer 17 is selectively grown (FIG. 1).
(A)). When the second conductive type second cladding layer 17 of the ridge waveguide type laser overlaps a part of the protective film 16, it is possible to improve the control of the light distribution that seeps near the boundary between the protective film 16 and the ridge bottom. This is preferable. On the other hand, in the self-aligned laser, the current blocking layer 26
A second conductive type second cladding layer 28 is formed as an upper layer so as to reach the inside of the opening 32 and a part of the current blocking layer 26 (see FIG. 1B).

The lower limit of the carrier concentration of the second conductive type second cladding layers 17 and 28 is preferably 3 × 10 ¹⁷ cm ⁻³ or more, more preferably 5 × 10 ¹⁷ cm ⁻³ or more, and more preferably 7 × 10 ¹⁷ cm ^−3.
cm ^-3 or more is more preferable. The upper limit of concentration is 1 × 10 ¹⁹
cm ^-3 or less, more preferably 5 × 10 ¹⁸ cm ^-3 or less, and most preferably 3 × 10 ¹⁸ cm ^-3 or less.

The lower limit of the thickness of the second conductive type second clad layers 17 and 28 is 0 in consideration of the fact that if the thickness is too small, the light confinement will be insufficient, and if the thickness is too large, the passage resistance will increase. It is preferably at least 0.5 μm, more preferably at least 1.0 μm. The upper limit is preferably 3.0 μm or less,
2.0 μm or less is more preferable.

After forming the second conductive type second cladding layers 17 and 28 and before forming an electrode further, in order to reduce the contact resistance with the electrode material, a low-resistance (high carrier concentration) contact layer 18 is formed. 29 is preferably formed. In particular, after the contact layers 18 and 29 are formed over the entire surface of the uppermost layer on which the electrodes 19 and 30 are to be formed,
Preferably, 9, 30 are formed.

At this time, the material of the contact layers 18 and 29 is usually selected from materials having a smaller band gap than that of the cladding layer, and has a low resistance and a suitable carrier density in order to obtain ohmic contact with the metal electrode. Is preferred. The lower limit of the carrier density is preferably 1 × 10 ¹⁸ cm ⁻³ or more, more preferably 3 × 10 ¹⁸ cm ⁻³ or more, and 5 × 10 ¹⁸ cm ^−3.
cm ^-3 or more is most preferable. The upper limit is 2 × 10 ²⁰ cm ^-3
It is preferably at most 5 × 10 ¹⁹ cm ⁻³ , more preferably at most 3 × 10 ¹⁹ cm ⁻³ . The thickness of the contact layer is preferably 0.1 to 10 μm, and 1 to 8 μm
Is more preferable, and 2 to 6 μm is most preferable.

Next, the opening 32 formed in the current block layer 26 in the self-aligned laser will be described.

When the opening 32 of the current block layer 26 is smaller on the lower side (active layer side) than on the upper side (contact layer side), the passage resistance can be reduced (the operating voltage and the heat generation can be reduced). This is preferable from the viewpoint of (1). Further, by forming the current blocking layer 26 near the end face, it is possible to suppress current injection to the end of the active layer. This allows
Deterioration (particularly end surface deterioration) in the end region can be reduced.

The opening 32 of the current block layer 26 may be a stripe-shaped opening extending to both ends, or extending to one end but extending to the other end. The opening may not be provided. If the opening is a striped opening extending to both ends,
The control of light in the end window structure region becomes easier, and the spread of light in the lateral direction on the end face can be reduced. On the other hand, if the opening is formed in a portion that is somewhat inside from the end face, current can be made non-injected near the end face, preventing recombination of current at the end face and preventing the cladding layer etc. Can be minimized. It is preferable that the structure of the opening is appropriately determined according to the purpose of use while taking such advantages into consideration.

The direction of the off angle depends on the current blocking layer 2
6 is preferably within ± 30 ° from a direction perpendicular to a direction (longitudinal direction) in which the opening 32 formed in the substrate 6 extends.
A direction within 7 ° is more preferable, and a direction within ± 2 ° is most preferable. When the plane orientation of the substrate is (100), the direction of the opening is [0-11] or a direction equivalent thereto, and the off-angle direction is within ± 30 ° from the [011] direction or a direction equivalent thereto. Is preferred, ± 7 °
Direction is more preferable, and a direction within ± 2 ° is most preferable.

In the present specification, the “[01-1] direction” refers to the distance between the (100) plane and the (01-1) plane in general III-V and II-VI semiconductors. [01-1] direction is defined such that the (11-1) plane present in the group V is a plane in which a group V or group VI element appears.

For the same reason, when a wurtzite type substrate is used, the direction in which the opening 32 extends is, for example, [11-20] or [1-10] on the (0001) plane.
0] is preferred. HVPE (Hydride Vapor Phase Epit
axy) may be in either direction, but MOVPE is more preferably in the [11-20] direction.

In designing the semiconductor optical device of the present invention, first, the thickness of the active layer and the composition of the cladding layer are determined in order to obtain a desired vertical spread angle. Normally, when the vertical divergence angle is reduced, light seepage from the active layer to the cladding layer is promoted, the light density at the end face is reduced, and the COD level at the emission end face can be improved. Therefore, when high output operation is required, it is set relatively narrow, but the lower limit is to suppress the increase in oscillation threshold current due to the reduction of light confinement in the active layer and the decrease in temperature characteristics due to carrier overflow. There are restrictions on doing so. As the limit, the lower limit is preferably 15 ° or more, more preferably 17 ° or more, and most preferably 19 ° or more. The upper limit is preferably 33 ° or less, more preferably 31 ° or less, and even more preferably 30 ° or less.

Next, when the vertical divergence angle is determined, the structural parameters that largely govern the high output characteristics are the distance dp between the active layer and the current blocking layer and the width at the bottom of the opening (hereinafter referred to as “opening width”) W Becomes The second conductive type first cladding layer 2 is provided between the active layer 23 and the current blocking layer 26.
When only 4 exists, dp is the thickness of the second conductive type first cladding layer 24. When the active layer 23 has a quantum well structure, the distance between the active layer closest to the current block layer 26 and the current block layer 26 is dp.

The upper limit of dp is preferably 0.5 μm or less, more preferably 0.4 μm or less, and 0.3 μm or less.
The following are more preferred. The lower limit is preferably at least 0.03 μm, more preferably at least 0.05 μm, and 0.07 μm
The above is the most preferable. However, the purpose of use (where to set the spread angle, etc.), material system (refractive index, resistivity, etc.)
If the values are different, the above-mentioned optimum range is slightly shifted. It should also be noted that this optimum range affects each of the above structural parameters.

The upper limit of the opening width W at the bottom of the opening is 1
It is preferably at most 00 μm, more preferably at most 50 μm. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more,
Most preferably, it is 2 μm or more. Further, in order to make the transverse mode a single mode (transverse light intensity distribution of a single peak), W cannot be made too large from the viewpoint of cutoff of a higher-order mode and prevention of spatial hole burning. The upper limit of W is preferably 7 μm or less,
5 μm or less is more preferable, and 3 μm or less is further preferable.

To realize a high output operation, it is effective to increase the opening width W at the bottom of the opening from the viewpoint of reducing the light density at the end face. However, in order to reduce the operating current, the opening width is reduced. Is preferable from the viewpoint of reducing the waveguide loss. Therefore, the opening width W2 near the center serving as the gain region
Is relatively narrow, and the opening width W1 near the end is relatively wide, so that a low operation current and a high output operation can be realized at the same time, and high reliability can be secured. 4 (a)). That is, the end (cleavage plane) width W
For 1, the upper limit is preferably 1000 μm or less, more preferably 500 μm or less. The lower limit is preferably 2 μm or more, more preferably 3 μm or more. The upper limit of the center width W2 is 1
It is preferably at most 00 μm, more preferably at most 50 μm. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more,
Most preferably, it is 2 μm or more. Edge width W1
The upper limit of the difference between the width W2 and the center width W2 is preferably 1000 μm or less, and more preferably 500 μm or less. The lower limit is preferably 0.2 μm or more, more preferably 0.5 μm or more.

In order to make the transverse mode a single mode, the upper limit of the end width W1 is preferably 10 μm or less, more preferably 7 μm or less. The upper limit of the center width W2 is preferably 7 μm or less, more preferably 5 μm or less. The upper limit of the difference between the end width W1 and the center width W2 is preferably 5 μm or less, more preferably 3 μm or less, and 2 μm or less.
μm or less is most preferred. 0.2 μm for lower limit
Or more, more preferably 0.5 μm or more.

In order to achieve a laser with a nearly circular beam while maintaining high reliability, it is necessary to control the above dp and W within an appropriate range with good controllability.

It is effective to reduce the aperture width in order to realize a beam close to a circle. However, if the aperture width is reduced, the injection current density is not preferable from the viewpoint of suppressing bulk deterioration. Therefore, by reducing the width of the central portion W2, which is the gain region, to a relatively large value and the portion near the end portion to a relatively small value, beam spot reduction and low operating current can be realized at the same time, and high reliability is secured. (Fig. 4
(B)). That is, the upper limit of the end portion (cleavage plane) width W1 is preferably 10 μm or less, and preferably 5 μm.
Or less, more preferably 3 μm or less, most preferably. The lower limit is preferably 0.5 μm or more, more preferably 1 μm or more. Center width W
As for 2, the upper limit is preferably 100 μm or less, more preferably 50 μm or less. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more, and most preferably 2 μm or more. The upper limit of the difference between the end width W1 and the center width W2 is preferably 100 μm or less, more preferably 50 μm or less. The lower limit is preferably 0.2 μm or more, more preferably 0.5 μm or more.

The length of the above-mentioned gradually increasing portion, gradually decreasing portion, and end may be designed in accordance with desired characteristics. However, the length of the gradually decreasing portion is 5 to 5 from the viewpoint of reducing the waveguide loss.
10 μm is preferable, and 10 to 50 μm is more preferable.
The length of the end portion is preferably from 5 to 30 μm, more preferably from 10 to 20 μm, from the viewpoint of cleavage accuracy. However, if necessary, the window may be manufactured as follows. (1) The opening width or length of the end portion, the gradually increasing portion or the gradually decreasing portion is asymmetric on both sides of the chip. (2) An area in which the width of the end is constant is not set, but is gradually increased or decreased to the end. (3) One side of the end face (normally, high-output light extraction (front end face)
Side), the opening width of which gradually increases or decreases. (4) The width of the end opening differs between the front end face and the rear end face. (5) A combination of some of the above (1) to (4).

In addition, it is not possible to suppress the bulk deterioration due to the current injection into the opening near the end face and to reduce the recombination current at the end face without providing an electrode near the end face. This is effective from the viewpoint of producing a laser having a spot diameter.

The method for manufacturing the semiconductor optical device of the present invention is not particularly limited. What is manufactured by any method is included in the scope of the present invention as long as it satisfies the requirements of claim 1 described above.

In manufacturing the semiconductor optical device of the present invention, a conventionally used method can be appropriately selected and used. The method of growing the crystal is not particularly limited. For the crystal growth of the double hetero structure and the selective growth of the current block layer, the metal organic chemical vapor deposition (MOC)
A known growth method such as a VD method, a molecular beam epitaxy method (MBE method), a hydride or halide vapor phase growth method (VPE method), and a liquid phase growth method (LPE method) can be appropriately selected and used. Details of this manufacturing method and other manufacturing methods can be understood from the following examples and related technical documents.

In a preferred method of manufacturing a semiconductor optical device according to the present invention, a step of forming a substrate comprises the steps of: In _x Ga ₁ -xN _y A
A quantum well active layer including a s _1-y (0 <x ≦ 1, 0 <y ≦ 1) well layer and a GaN _z As _1-z (0 <z ≦ 1) barrier layer above and below the well layer Forming a quantum well active layer, wherein the step of forming a quantum well active layer starts adding nitrogen at the start of forming a barrier layer formed as a lower layer of the well layer, and is formed as an upper layer of the well layer. At the end of the formation of the barrier layer, the addition of nitrogen is terminated, and indium is added during the formation of the well layer, and indium is not added during the formation of the barrier layer.

FIG. 5 shows the relationship between the amounts of indium and nitrogen added and the process of forming each layer. In FIG. 5, there is a portion where the ratio of the addition amount is intentionally changed in order to clarify the timing of adding the indium and the nitrogen, but the actual addition amounts are the well layer and the barrier described in this specification. It is determined based on the ratio of layers. As shown in FIG. 5, in the manufacturing method of the present invention, nitrogen is added to the light guide layer (G).
After the formation of the barrier layer (B1), the addition is started after the formation of the barrier layer (B1), and the addition is completed so that the addition is completed after the formation of the barrier layer (B3) which is the uppermost layer of the well layer in the quantum well active layer. The light guide layer (G2) in the upper layer is not added. On the other hand, indium is added in the well layers (W1 and W2), and the barrier layers (B1 to B3) and the light guide layers (G
1, G2) does not add. By selecting the addition ratio of indium and the step of adding indium, the interface between the well layer and the barrier layer can be easily formed, and the steepness of the well-type potential can be improved.

Although the specific growth conditions and the like of each layer vary depending on the composition of the layer, the growth method, the shape of the device, and the like, when growing a III-V compound semiconductor layer using the MOCVD method, a double heterostructure is used. Means a growth temperature of about 600 to 750 ° C. (A
It is preferable to carry out at a growth temperature of about 500 to 600 ° C. (in the case of InGaNAs).

Particularly, the portion selectively grown using the protective film is A
When Al is contained like lGaAs and AlGaInP,
It is very preferable to introduce a small amount of HCl gas during the growth, because the deposition of poly on the mask can be prevented. If the Al composition is higher, or the mask width or the mask area ratio is larger, and other growth conditions are constant, poly deposition is prevented and selective growth is performed only on the exposed portion of the semiconductor surface (selective mode). The amount of HCl introduced required for this increases. On the other hand, if the introduction amount of the HCl gas is too large, the growth of the AlGaAs layer does not occur, and the semiconductor layer is etched instead (etching mode). The amount of HCl introduced required to enter the etching mode increases. For this reason, the optimal amount of HCl introduced largely depends on the supply mole number of the group III raw material containing Al such as trimethylaluminum. Specifically, the ratio of the number of moles of HCl supplied and the number of moles of group III raw material containing Al (HCl / I
The lower limit of (Group II) is preferably 0.01 or more, more preferably 0.05 or more, and most preferably 0.1 or more. The upper limit is preferably 50 or less, more preferably 10 or less, and 5 or less.
The following are most preferred. However, when the compound semiconductor layer containing In is selectively grown (in particular, HCl is introduced), it is easy to control the composition.

The protective films 16 and 27 used for forming the mesa-shaped opening of the self-aligned laser and the selective growth of the ridge of the ridge waveguide laser are preferably made of a dielectric material. Film, SiO ₂ film, SiON
Film, Al ₂ O ₃ film, ZnO film, SiC film, and amorphous Si. The protective films 16 and 27
It is used when a groove is formed by selective regrowth using MOCVD or the like as a mask.

The semiconductor optical device of the present invention can be used for all semiconductor light emitting elements and semiconductor light receiving elements. Examples of the semiconductor light emitting element include a semiconductor laser (LD) and a light emitting diode (LED), and more specifically, a communication signal light source (1-2 μm band using InGaNAs as an active layer) laser or a fiber excitation pump. In particular, long wavelength (1 μm) light sources (such as near 980 nm using an InGaAs strained quantum well active layer / GaAs substrate, near 1480 nm using an InGaAsP strained well active layer / InP substrate) and communication semiconductor laser devices such as lasers.
A semiconductor laser used for a communication system requiring an m-band and high-output operation can be given. Also, among communication lasers, a laser having a nearly circular shape is effective in increasing the coupling efficiency with a fiber. Further, a laser having a single far-field image can be used as a laser suitable for a wide range of applications such as information processing and optical communication. Further, as a semiconductor light receiving element, a PIN photodiode (PI
N-PD), avalanche photodiode (AP)
D) and the like.

[0081]

The present invention will be described in more detail with reference to specific examples. Materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

Example 1 In this example, a ridge waveguide type laser was manufactured by forming layers in the order shown in FIG.
2 (a) to 2 (c), there are portions where the dimensions are intentionally changed in order to make it easier to grasp the structure, but the actual dimensions are as described in the following text.

First, the thickness is 350 μm and the surface is (100)
N-type GaAs (n = 1 × 10¹⁸cm^-3) Substrate 1
01 on the n-type A having a thickness of 2.0 μm by MOCVD.
l_{0. 35}Ga_0.65As (Si-doped: n = 1 × 10¹⁸cm
^-3) Was formed. Next
Then, a GaAs light guide having a thickness of 10 nm is formed by MOCVD.
Layer (non-doped) 131, 8 nm thick GaN_0.01A
s_0.99Barrier layer (non-doped) 132, 7 nm thick I
n_0.35Ga_0.65N_0.01As_0.99Well layer (non-doped) 1
33, 8 nm thick GaN_0.01As_0.99Barrier layer (non
Doped 134, 7 nm thick In_0.35Ga_0.65N_0.01
As_0.99Well layer (non-doped) 135, 8 nm thick G
aN_0.01As_0.99Barrier layer (non-doped) 136, thickness
10 nm GaAs optical guide layer (non-doped) 137
Double quantum well (DQW) active layer 103
Formed. Next, the thickness is 0.1 μm by MOCVD.
P-type Al_0.35Ga_0.65As (Zn doped: p = 1 × 1
0¹⁸cm^-3), A p-type cladding layer 104 having a thickness of 0.
01 μm p-type GaAs (Zn doped: p = 1 × 10 ¹⁸
cm^-3) The surface protection layer 105 is sequentially laminated to form a double hetero
The structure was formed (FIG. 2A).

In the MOCVD method, trimethyl gallium (TMG) and trimethyl indium (TMI) were used as group III raw materials, arsine and dimethylhydrazone (DMHy) were used as group V raw materials, and hydrogen was used as a carrier gas. At this time, in the MOCVD method, dimethylhydrazone (DMHy) starts to be added at the time of forming the GaN _0.01 As _0.99 barrier layer 132 after the GaAs light guide layer 131 is formed, and forms the GaN _0.01 As _0.99 barrier layer (non-doped) 136. The addition was terminated at the end, and was not added when the GaAs light guide layer (non-doped) 137 was formed. In addition, trimethyl indium (TMI) is
_0.35 Ga _0.65 N _0.01 As _0.99 is added only when the well layers 133 and 135 are formed.

Next, a SiNx protective film 106 having a thickness of 100 nm is deposited on the surface of the double hetero substrate by plasma CVD, and [0-1] is formed by photolithography.
1] Stripe-shaped opening 10 whose longitudinal direction is in direction B
7 (the p-type GaAs surface protective layer 105 was exposed). The width of the stripe-shaped opening 107 is 2 μm,
The horizontal space interval between the stripe-shaped openings 107 was about 250 μm.

An MO is formed in the above-mentioned stripe-shaped opening 107.
By selective growth using the CVD method, a 1.8 μm thick p
Type Al _0.4 Ga _0.6 As (Zn doped: p = 1 × 10 ¹⁸ c
m ⁻³ ) p-type cladding layer 108 and a thickness of 0.5 μm
m p-type GaAs (Zn doped: p = 2 × 10 ¹⁹ c
m ⁻³ ) (FIG. 2)
(B)).

In the above MOCVD method, III
Group materials include trimethylgallium (TMG), triethylgallium (TEG), and trimethylaluminum (TG).
MA), arsine was used as the group V raw material, and hydrogen was used as the carrier gas. Dimethyl zinc (DEZ) was used as the p-type dopant, and disilane was used as the n-type dopant.

Thereafter, the p-side electrode 110 was deposited and the substrate was thinned to 100 μm, and then the n-side electrode 111 was deposited and alloyed (FIG. 2C). The wafer thus fabricated was cut into chip bars so as to form (primary cleavage) a laser light emitting end face. The resonator length at this time was 250 μm. After applying an asymmetric coating of 10% of the front end face-90% of the rear end face, chips were separated by secondary cleavage. After assembling the chip by junction down, current-light output and current-voltage characteristics were measured at 25 ° C. by continuous conduction (CW).

The oscillation wavelength of the laser device thus manufactured was about 1.3 μm, the threshold current was 30 mA on average, and the slope efficiency was 0.55 mW / mA on average, and the characteristics were very good. High reliability (70 ° C, 3mW
Stable operation for more than 3000 hours at high temperature and high output)
Was obtained. In addition, since the ridge is formed in the opening for current injection by selective growth, the uniformity of the device structure can be improved, and the above-described semiconductor laser device can be manufactured with high yield. Well layer I
By further increasing the n composition or the N composition, for example, to In _0.4 Ga _0.6 N _0.03 As _0.97 , the oscillation wavelength can be extended to the 1.5 μm band.

(Example 2) The thickness was 350 μm and the surface was (1).
N-type GaAs as the (00) plane (n = 1 × 10 ¹⁸ cm ⁻³ )
2.0 μm thick on the substrate 201 by MOCVD.
N-type Al _0.35 Ga _0.65 As (Si-doped: n = 1 × 1
An n-type cladding layer 202 of 0 ¹⁸ cm ^-3 ) was laminated. Next, GaAs having a thickness of 10 nm is formed by MOCVD.
s light guide layer (non-doped) 231, Ga having a thickness of 7 nm
N _0.01 As _0.99 barrier layer (non-doped) 232, thickness 6
In _0.35 Ga _0.65 N _0.01 As _0.99 well layer (non-doped) 233 nm, GaN _0.01 As _0.99 barrier layer (non-doped) 234 having a thickness of 8 nm, In _0.35 Ga having a thickness of 7 nm
_0.65 N _0.01 As _0.99 well layer (non-doped) 235, 8 nm thick GaN _0.01 As _0.99 barrier layer (non-doped) 2
A double quantum well (DQW) active layer 203 was formed by laminating a GaAs light guide layer (non-doped) 237 having a thickness of 36 nm and a thickness of 10 nm. Then, a thickness of 0.
1 μm p-type Al _0.35 Ga _0.65 As (Zn doped: p =
1 × 10 ¹⁸ cm ⁻³ ) p-type cladding layer 204, 0.01 μm-thick p-type GaAs (Zn doped: p = 1 ×
10 ¹⁸ cm ⁻³ ) A double hetero structure was formed by sequentially laminating the surface protective layer 205 (FIG. 3A).

In the MOCVD method, the group III raw materials include trimethylgallium (TMG) and triethylgallium (T
EG) and trimethylindium (TMI) and arsine and dimethylhydrazone (DMHy) as group V raw materials.
And hydrogen as a carrier gas. At this time, dimethylhydrazone (DMH) is used in the MOCVD method.
y) shows that after forming the GaAs light guide layer 231, GaN
_The addition is started at the time of forming the _0.01 As _0.99 barrier layer 232 and the GaN _0.01 As _0.99 barrier layer (non-doped) 236 is formed.
At the end of the formation of the GaAs light guide layer (non-doped) 237. Trimethylindium (TMI) is In _0.35 Ga _0.65
N _0.01 As _0.99 was added only when the well layers 233 and 235 were formed.

Next, an SiN _x protective film having a thickness of 100 nm was deposited on the surface of the double hetero substrate by plasma CVD, and a stripe-like protective film 206 having a [011] A direction as a longitudinal direction was formed by photolithography. . The width of the striped SiN _x protective film 206 is 2 μm.
m, and the horizontal space interval between the stripe-shaped protective films 206 was about 250 μm.

The above-mentioned striped SiN _x protective film 20
6 was selectively grown on both sides by MOCVD to form a 0.6 μm thick n-type Al _0.4 Ga _0.6 As (Si-doped: n
= 1 × 10 ¹⁸ cm ⁻³ ) and an n-type GaAs surface protective layer (Si doped: n = 1 × 10 ¹⁸ cm ⁻³ ) 208 having a thickness of 0.01 μm (FIG. 3)
(B)). At this time, sidewalls made of the (111) B plane (the B plane means the As plane) were formed on both sides of the SiN _x protective film 206. By selecting the stripe direction of the SiN _x protective film 206 in the [011] A direction, lateral growth on the protective film could be suppressed and the facet surface of the side wall could be made very flat.

Next, the striped SiN _x protective film 20 is formed.
6 was removed by etching. At this time, the SiN _x film 206 was removed by wet etching using a buffered hydrofluoric acid solution or dry etching using a gas such as SF ₆ or CF ₄ . Thereafter, a 2.0 μm-thick p-type Al _0.35 Ga _0.65 As (Zn-doped:
p-type second cladding layer 2 consisting of p = 1 × 10 ¹⁸ cm ⁻³ )
09 and a 3.0 μm-thick p-type GaAs (Zn-doped:
A contact layer 210 consisting of p = 2 × 10 ¹⁹ cm ⁻³ ) was grown.

Thereafter, the p-side electrode 211 was deposited and the substrate was thinned to 100 μm, and then the n-side electrode 212 was deposited and alloyed (FIG. 3C). The wafer thus fabricated was cut into chip bars so as to form (primary cleavage) a laser light emitting end face. The resonator length at this time was 250 μm. After applying an asymmetric coating of 10% of the front end face-90% of the rear end face, chips were separated by secondary cleavage. After assembling the chip by junction down, current-light output and current-voltage characteristics were measured at 25 ° C. by continuous conduction (CW).

The laser device thus manufactured had an oscillation wavelength of about 1.3 μm, a threshold current of 27 mA on average, and a slope efficiency of 0.6 mW / mA on average. The characteristics were very good. In addition, it was found that high reliability (stable operation at 3000 ° C. or more at a high temperature of 70 ° C. and a high output of 3 mW) was obtained. Further, since the current block layer is formed by selective growth, the uniformity of the device structure can be improved, and the above-described semiconductor laser device can be manufactured with a high yield.

In the above MOCVD method, III
Group materials include trimethylgallium (TMG), triethylgallium (TEG), and trimethylaluminum (TMG).
A), arsine and dimethylhydrazine (DMHy) were used as group V raw materials, and hydrogen was used as a carrier gas. Also, dimethyl zinc (DE
Z), disilane was used as the n-type dopant. further,
During the growth of the n-type Al _0.4 Ga _0.6 As block layer, Si
HCl to prevent poly deposition on the Nx protective film.
Gas may be introduced. In this case, when growing the ridge, HCl gas is used at a molar ratio of HCl / III group of 0.05-1.
It is preferable that it is about.

Further, after the selective growth, the protective film is removed without exposing the wafer to the atmosphere, and thereafter, the second conductive type second cladding layer is formed without exposing the wafer to the atmosphere to thereby re-use the wafer. Oxidation of the growth surface (the bottom surface of the opening and the surface of the current block layer) can be prevented, so that the reliability of the device can be further improved.

Comparative Example GaN _0.01 As of 8 nm Thickness
_A laser device was manufactured in the same manner as in Example 1 except that the _0.99 barrier layers (non-doped) 132, 134, and 136 were replaced with GaAs layers (non-doped) having a thickness of 8 nm. As described above), the efficiency was reduced (2/3 or less). The element life was very short (100 hours or less). A possible cause is that misfit dislocations propagated in the active layer.

[0100]

According to the present invention, a GaI having a compressive strain in which the composition ratio of In is increased and the composition ratio of N is decreased, according to the present invention.
By manufacturing a quantum well active layer including an nNAs well layer and a GaNAs barrier layer having a tensile strain, a semiconductor optical device having excellent high-temperature characteristics and reliability can be provided. This semiconductor optical device is particularly useful as a long wavelength light source (1 μm band) suitable for optical communication. Further, according to the method for manufacturing a semiconductor optical device of the present invention, the interface between the well layer and the barrier layer can be easily formed only by adjusting the addition amount of indium, and the sharpness of the well-type potential in the quantum well structure can be improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of a semiconductor optical device according to the present invention.

FIG. 2 is a process diagram illustrating an example of a manufacturing process of the semiconductor optical device device of the present invention.

FIG. 3 is a process diagram illustrating an example of another manufacturing process of the semiconductor optical device device of the present invention.

FIG. 4 is a top view of one embodiment of the semiconductor optical device device of the present invention.

FIG. 5 is an explanatory diagram showing the amounts of nitrogen and indium added in the process of manufacturing the semiconductor optical device of the present invention.

FIG. 6 shows the critical thickness of the well layer and the X of the In _x Ga ₁ -xN _0.01 As _0.99 well layer in the semiconductor optical device of the present invention.
FIG. 4 is an explanatory diagram showing a relationship with a value.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Substrate 12 1st conductivity type clad layer 13 Active layer 14 2nd conductivity type 1st clad layer 15 Cap layer 16 Protective film 17 2nd conductivity type 2nd clad layer 18 Contact layer 19 Electrode 20 Electrode 21 Substrate 22 1st conductivity type Cladding layer 23 Active layer 24 Second conductivity type first cladding layer 25 Cap layer 26 Current blocking layer 27 Protective film 28 Second conductivity type second cladding layer 29 Contact layer 30 Electrode 31 Electrode 32 Opening 41 Lower light guide layer 42 Barrier layer 43 Well layer 44 Barrier layer 45 Upper light guide layer 51 Lower light guide layer 52 Barrier layer 53 Well layer 54 Barrier layer 55 Well layer 56 Barrier layer 57 Upper light guide layer 101 Substrate 102 N-type cladding layer 103 Active layer 104 p-type first cladding layer 105 a surface protective layer 106 SiN _x protective film 107 opening 08 p-type second cladding layer 109 contact layer 110 p-side electrode 111 n-side electrode 131 light guide layer 132 barrier layer 133 well layer 134 barrier layer 135 well layer 136 barrier layer 137 light guide layer 201 substrate 202 n-type cladding layer 203 activity Layer 204 p-type first cladding layer 205 GaAs surface protection layer 206 SiN _x protection film 207 current blocking layer 208 GaAs surface protection layer 209 p-type second cladding layer 210 contact layer 211 p-side electrode 212 n-side electrode 231 light guide layer 232 Barrier layer 233 Well layer 234 Barrier layer 235 Well layer 236 Barrier layer 237 Light guide layer G Light guide layer B Barrier layer W Well layer

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5F041 AA14 AA43 CA04 CA05 CA34 CA35 CA36 CA65 CB03 5F049 MA04 MA07 MB07 PA04 QA08 5F073 AA13 AA45 AA74 CA17 DA05 DA35

Claims (16)

[Claims] 1. Inx Ga _{1 -x} N _y As _{1 -y} (0 <x ≦ 1,
0 <y ≦ 1) a well layer and Ga adjacent above and below the well layer
A semiconductor optical device device comprising a quantum well active layer including a N _z As _1-z (0 <z ≦ 1) barrier layer on a substrate. 2. The semiconductor optical device according to claim 1, wherein said substrate is made of GaAs. 3. The semiconductor optical device according to claim 1, wherein the quantum well active layer has two or more well layers. 4. The semiconductor optical device according to claim 1, further comprising a layer having a lower refractive index than said quantum well active layer, above and below said quantum well active layer. apparatus 5. A layer having a lower refractive index than the quantum well active layer, a layer below the quantum well active layer is a first conductivity type cladding layer, and a layer above the quantum well active layer is a first conductive type cladding layer. 2. A cladding layer of a second conductivity type.
5. The semiconductor optical device according to any one of items 1 to 4. 6. The first conductivity type cladding layer is formed of Al _p Ga.
_{1-p As (0 <p} ≦ 1), and / or said second conductivity type cladding layer Al _q Ga _1-q As of claim 5, wherein the (0 <q ≦ 1) is Semiconductor optical device. 7. The quantum well active layer has a lower light guide layer on the side of the first conductivity type clad layer and / or an upper light guide layer on the side of the second conductivity type clad layer. The semiconductor optical device according to claim 5. 8. The light guide layer according to claim 1, wherein the lower light guide layer is Al _r Ga _{1 -r} As.
(0 ≦ r <1), and / or the upper light guide layer is made of Al
8. The semiconductor optical device according to claim 7, wherein _s Ga _{1 -s} As (0 ≦ s <1). 9. The Al composition ratio p of the Al _p Ga _1-p As (0 <p ≦ 1) first conductivity type cladding layer and the Al _r Ga
9. The semiconductor optical device device according to claim 8, wherein the Al composition ratio r of the lower optical guide layer of _1-r As (0 ≦ r <1) has a relationship of p> r. 10. The Al _q Ga _{1 -q} As (0 <q ≦ 1)
The Al composition ratio q of the second conductivity type cladding layer and the Al _s G
9. The semiconductor optical device device according to claim 8, wherein a _1-s As (0 ≦ s <1) and the Al composition ratio s of the upper optical guide layer have a relationship of q> s. 11. The semiconductor optical device according to claim 1, wherein said semiconductor optical device is a semiconductor light emitting device. 12. The semiconductor optical device according to claim 11, wherein said semiconductor light emitting device is a semiconductor laser. 13. The light emitting wavelength of the semiconductor light emitting element is 1 to 1.
13. The semiconductor optical device according to claim 11, wherein the thickness is 2 [mu] m. 14. The semiconductor optical device according to claim 1, wherein said semiconductor optical device is a semiconductor light receiving element. 15. A process for forming a substrate, wherein In _x Ga ₁ -xN
A quantum well including a _y As _1-y (0 <x ≦ 1, 0 <y ≦ 1) well layer and a GaN _z As _1-z (0 <z ≦ 1) barrier layer above and below the well layer A method for manufacturing a semiconductor optical device device comprising a step of forming an active layer, wherein in the step of forming the quantum well active layer, the addition of nitrogen is started at the start of forming a barrier layer formed as a layer below the well layer. At the end of the formation of the barrier layer formed as the upper layer of the well layer, the addition of nitrogen is terminated, and indium is added during the formation of the well layer, and indium is not added during the formation of the barrier layer. A method for manufacturing a semiconductor optical device, comprising: 16. The method according to claim 15, wherein in the step of forming the quantum well active layer, two or more well layers are formed by adding indium two or more times while adding nitrogen. The manufacturing method of the semiconductor optical device device described in the above.