JP2001244566A - Semiconductor optical element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical element wherein reduction of manufacturing cost and improvement of yield are enabled, and a manufacturing method of the device. SOLUTION: In the semiconductor optical element wherein an active layer 6, a light confinement layer 8 of a second conductivity type and an electrode 11 are formed in this order on a substrate 1 of a first conductivity type, the light confinement layer is constituted of a stripe-shaped current injection window layer 8b and current block layers 8a which are formed on both sides of the current injection window layer and have electric resistance higher than that of the current injection window layer. A current from the electrode is constricted by the current block layers and injected into the active layer from the current injection window layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor optical device suitably used as a light source for optical communication such as gigabit Ethernet, high-speed digital communication, and multi-wavelength optical communication, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a semiconductor laser has a current confinement structure for injecting a current into a narrow region of an active layer in order to keep the oscillation threshold current value and the operating current low. FIG.
It is a typical perspective view showing the appearance of the conventional semiconductor laser. The semiconductor laser 50 includes an n-type buffer layer 52, an n-type optical confinement layer 53, and a GR
An IN layer 54, an active layer 55, a GRIN layer 56, a current injection window layer 57, a current block layer 58, a p-type light confinement layer, a contact layer 60, and a p-side electrode 61 are sequentially formed. An n-side electrode 62 is formed on the other surface. Here, the light confinement layer functions to confine light generated by the recombination of electrons and holes near the active layer, and the GRIN layer gradually changes the refractive index to concentrate light on the active layer. It works to increase.

[0003] For example, as disclosed in Japanese Patent Application Laid-Open No. 8-222800,
_2. An insulating film such as SiN or a pn inversion block layer provided to have a reverse bias is used for the injected current. Therefore, the current injected from the p-side electrode cannot flow through the current blocking layer 58, but is confined by the current blocking layer 58, flows through the current injection window layer 57, and is injected into the active layer 55. Thereby, the threshold current value of the semiconductor laser can be reduced.

Next, the semiconductor laser 50 is, for example, shown in FIG.
Are manufactured by the steps shown in the schematic cross-sectional view of FIG. First, an n-type buffer layer 5 is formed on one surface of an n-type substrate 51.
2. n-type optical confinement layer 53, GRIN layer 54, active layer 5
5, a GRIN layer 56, and a p-type current injection window layer 57 are grown sequentially (FIG. 8A). Next, an etching mask 63 is formed on the current injection window layer 57 by photolithography (FIG. 8B), and the current injection window layer 57 is etched to expose the GRIN layer 56 (FIG. 8C). Next, an insulating film such as SiO ₂ is deposited on both sides of the remaining current injection window layer 57 to form a current blocking layer.
(D)), the etching mask 63 is removed (FIG. 8)
(E)). Then, on the current injection window layer 57 and the current block layer 58, the p-type optical confinement layer 59 and the contact layer 6 are formed.
0 and a p-side electrode 61 are sequentially formed, and an n-type electrode 62 is formed on the other surface of the n-type substrate 51 (FIG. 8F).

[0005]

However, in the conventional method, in order to form a current confinement structure, steps such as deposition of an insulating film, photolithography, and etching are required, thereby reducing the manufacturing cost and improving the yield. It was difficult to make it. Further, since the width of the current injection window layer is determined by the resolution of photolithography, it is difficult to form a current injection window layer of 5 μm or less, and it is difficult to improve the current density to the active layer. There were also problems.

Accordingly, it is an object of the present invention to solve the above-mentioned problems and to provide a semiconductor optical device capable of reducing the manufacturing cost and improving the yield, and a method of manufacturing the same.

[0007]

In order to solve the above-mentioned problems, a semiconductor optical device according to the present invention is provided on a first conductivity type substrate.
In a semiconductor optical device in which an active layer, a second conductivity type light confinement layer, and an electrode are formed in this order, the light confinement layer is a stripe-shaped current injection window layer, and both sides of the current injection window layer. And a current blocking layer having a higher electric resistance than the current injection window layer, wherein the current from the electrode is confined by the current blocking layer and injected into the active layer from the current injection window layer. I do.

In the semiconductor optical device of the present invention, since the light confinement layer has the current injection window layer and the current blocking layer, it is possible to confine the current from the electrode by the light confinement layer. Therefore, unlike the related art, it is not necessary to newly form an insulating film as a current blocking layer, so that the manufacturing process can be further simplified.

Further, the semiconductor optical device of the present invention has a ridge portion composed of a second conductivity type cladding layer interposed between the light confinement layer and the electrode, and the light confinement layer has a current just below the ridge portion. A layer composed of an injection window layer and a current blocking layer formed on both sides of the ridge portion and having a higher resistance than the current injection window layer can be used.

Further, in the semiconductor optical device of the present invention, it is preferable that the light confinement layer uses a binary or ternary compound made of a group III-V compound semiconductor of the periodic table containing at least Al. For example, AlAs, AlGaAs, A
lGaN, AlInAs and the like.
s is preferred.

In the semiconductor optical device of the present invention, it is preferable that the oxygen atom concentration in the current blocking layer is higher than the oxygen atom concentration in the current injection window layer. Oxygen atoms in the optical confinement layer form a deep level and compensate for the hole level, which has the effect of lowering the carrier concentration and increasing the electrical resistance of the optical confinement layer. Control of electric resistance with the layer becomes easy.

Further, another semiconductor optical device according to the present invention has a first
In a semiconductor optical device in which an active layer, a second conductivity type light confinement layer, and an electrode are formed in this order on a conductivity type substrate, the light confinement layer has a stripe-shaped high refractive index layer, A low-refractive-index layer formed on both sides of the high-refractive-index layer and having a lower refractive index than the high-refractive-index layer. Characterized by being injected into the layer. The light confinement layer
By having the stripe-shaped high refractive index layer and the low refractive index layer, the semiconductor optical element has a horizontal refractive index distribution, so that a semiconductor optical device of a refractive index guide type can be manufactured.

In another semiconductor optical device of the present invention, it is preferable that the light confinement layer is made of a group III-V compound semiconductor of the periodic table containing at least Al.

Further, in another semiconductor optical device of the present invention, it is preferable that the oxygen atom concentration in the refractive index layer is higher than the oxygen atom concentration in the high refractive index layer.

The method for manufacturing a semiconductor optical device according to the present invention comprises:
In a method for manufacturing a semiconductor optical device in which an active layer, a second confinement type light confinement layer, and an electrode are formed in this order on a conductive type substrate, an active layer is formed on the substrate, and A light confinement layer is formed on the active layer, and a current injection window layer is formed on the light confinement layer in a region shielded by ion implantation through a stripe-shaped mask. A current blocking layer having a higher electric resistance than the current injection window layer is formed on both sides, and the electrodes are formed at least on the current injection window layer.

According to the above method, the ion-implanted region of the optical confinement layer has a higher electrical resistance than the non-ion-implanted region. Becomes a current blocking layer. On the other hand, a region in the optical confinement layer where ions are not implanted becomes a low-resistance current injection window layer. Therefore, the current from the electrode confined by the current blocking layer flows through the current injection window layer and is injected into the active layer. Furthermore, by using the ion implantation method, 5 μm, which was difficult in the conventional photoengraving, was used.
A fine current block layer and a current injection window layer having a width of not more than m can be formed.

Further, in the manufacturing method of the present invention, a ridge portion composed of a cladding layer of the second conductivity type is formed between the light confinement layer and the electrode, and then ion implantation is performed on the light confinement layer using the ridge portion as a mask. Thus, a current injection window layer can be formed in a region shielded by the ridge portion, and a current blocking layer having higher resistance than the current injection window layer can be formed on both sides of the current injection window layer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to a semiconductor laser using AlInAs for an optical confinement layer as an example. Embodiment 1 FIG. This embodiment is an example in which the present invention is applied to a stripe type semiconductor laser diode. Figures 1 and 2
1 is a schematic perspective view showing a structure of a stripe type semiconductor laser diode A, FIG. 1 shows a partial structure, and FIG. 2 shows an entire structure. Stripe type semiconductor laser diode A
Is an n-type InP single crystal semiconductor substrate 1 as shown in FIG.
N-type InP buffer layer 2, n-type AlGaInAs BDR layer 3, n-type AlI
nAs light confinement layer 4, n-type AlGaInAs GRIN
Layer 5, active layer 6 of MQW structure of AlGaInAs, intrinsic AlGaInAs GRIN layer 7, current blocking layer 8a, current injection window layer 8b, p-type InP cladding layer 9, p-type InGaAs contact layer 10, p-side electrode 11
And an n-side electrode 12 formed on the other surface of the n-type InP single-crystal semiconductor substrate 1.

Here, the current blocking layer 8a and the current injection window layer 8b are common in that they are both made of p-type AlInAs and also serve as an optical confinement layer, but the current block layer 8a is higher than the current injection window layer 8b. The difference is that it has an oxygen atom concentration. In addition, as shown in FIG.
a is formed on both sides of the current injection window layer 8b extending in a stripe shape in the laser resonance direction.

Next, a method of manufacturing the stripe type semiconductor laser diode A will be described with reference to FIG. On the n-type InP single crystal semiconductor substrate 1, n
Type InP buffer layer 2 (0.3 to 1.0 μm), n-type A
lGaInAs BDR layer 3 (0.05 to 0.1 μm)
m) and n-type AlInAs optical confinement layer 4 (0.05
0.1 μm), n-type AlGaInAs GRIN layer 5
(0.05-0.10 μm), MQ of AlGaInAs
Active layer 6 of W structure, intrinsic AlGaInAsGRI
N layer 7 (0.05-0.10 μm) and p-type AlI
The nAs light confinement layer 8 (0.05 to 0.07 μm) is epitaxially grown (FIG. 3A). Note that n-type A
The lGaInAs BDR layer 3 has a role of alleviating band discontinuity between the n-type InP buffer layer 2 and the n-type AlInAs light confinement layer 4.

Next, oxygen atoms are ion-implanted into the p-type AlInAs optical confinement layer 8 by using an ion implantation apparatus through a striped metal mask so as to shield the region where the current injection window layer is to be formed (FIG. 3 (b)). As a result, in the p-type AlInAs optical confinement layer 8, the region into which oxygen atoms have been implanted becomes the current blocking layer 8a, and the region into which oxygen atoms have not been implanted becomes the current injection window layer 8b.

Subsequently, the p-type AlInAs light confinement layer 8
And a p-type InP light confinement layer 9 (1.0-1.
6 μm), p-type InGaAs contact layer 10 (0.2
.About.0.4 .mu.m) after epitaxial growth.
Au and Zn are added on the nGaAs contact layer 10 by 0.3.
0.5 μm is deposited to form a p-side electrode, and Au, Ge, and Ni are deposited on the back surface of the n-type InP single crystal semiconductor substrate
0.5 μm is deposited to form an n-side electrode (FIG. 3C).
Then, for the cleavage, die bonding, bonding, and the like, a stripe-type semiconductor laser diode A is manufactured using a conventionally known method.

In the laser diode A, the holes injected from the p-side electrode 11 are narrowed by the current blocking layer 8a, and the electrons injected from the n-side electrode 12 recombine with the light emitted by the active layer 6 to have a certain current value. Exceeding the (oscillation threshold) leads to laser oscillation.

Helium, argon, oxygen and the like can be used as the atoms to be ion-implanted, but it is preferable to use oxygen. With a small amount of implantation, the electrical resistance of the implanted region can be increased.

Further, by using the ion implantation method,
It is possible to increase the electric resistance of the region by implanting ions into a region having a width of 5 μm or less. Therefore, a fine current block layer and a current injection window layer having a width of 5 μm or less can be formed, so that the density of current injection into the active layer can be further increased and the threshold current can be reduced.

Here, the concentration of oxygen atoms to be ion-implanted into the p-type AlInAs optical confinement layer changes the concentration of Zn as a dopant and the concentration of oxygen in the p-type AlInAs layer, and changes the concentration of carriers in the p-type AlInAs layer. The change was examined by examining it. Here, the Zn concentration and the oxygen concentration were measured by secondary ion mass spectrometry (SIMS).

As a result, in the undoped AlInAs optical confinement layer, oxygen atoms mixed during crystal growth were 5 ×.
It was found that there was about 10 ¹⁸ cm ^-3, and the deep level generated by the mixed oxygen atoms was about 30% of the mixed oxygen atom concentration. The deep level due to the oxygen atom is Z
Compensating the hole level generated by n doping, and the Zn concentration C _Zn doped in AlInAs is usually
Since it is 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ ,
It has been found that when the oxygen atom concentration Co in the ion-implanted region in the undoped AlInAs optical confinement layer is 10 times or more the Zn concentration, a higher electric resistance can be obtained than in the region not ion-implanted. It is considered that the electric resistance of the AlInAs optical confinement layer is increased because part of Al is chemically bonded to oxygen to form an oxide by the injection of oxygen atoms.

The oxygen atom concentration Co of the current block layer into which oxygen atoms have been ion-implanted is 2 to 10 times, more preferably 5 to 10 times, the oxygen atom concentration of the current injection window layer not implanted with ions. 5 × 10 ¹⁸ cm ⁻³ ≦ Co ≦ 5
It is preferably in the range of × 10 ¹⁹ cm ^-3 . When the concentration of oxygen atoms is 5 × 10 ¹⁸ cm ⁻³ or less, the resistance is not higher than that of the current injection window layer because the concentration of oxygen is almost the same as the concentration of oxygen mixed during crystal growth. Further, the oxygen concentration is 5 × 10 ¹⁹ cm ^−3.
If ion implantation is performed as described above, annealing treatment is required to reduce damage to generated lattice defects and crystals such as amorphous, and the number of steps increases, which is not preferable.

When oxygen atoms are ion-implanted into the current blocking layer 8a, the oxygen concentration is 10 to 30% higher than that of the current injection window layer 8b.
The refractive index decreased. As a result, the light confinement layer 8 has a refractive index distribution in which the refractive index increases in the region of the current injection window layer 8b in the horizontal direction, and it is possible to provide a refractive index guide type laser diode. In this case, the oxygen atom concentration of the current blocking layer is 2 to 10 times, more preferably 5 to 10 times, or 5 × 10 ¹⁸ cm ⁻³ ≦ Co ≦ 5
It is preferably in the range of × 10 ¹⁹ cm ^-3 . If the oxygen atom concentration is smaller than 5 × 10 ¹⁸ cm ^{−3, the} decrease in the refractive index is small, and if the oxygen atom concentration is larger than 5 × 10 ¹⁹ cm ⁻³ , an annealing process is required and the number of steps is increased.

Embodiment 2 FIG. This embodiment is an example in which the present invention is applied to a ridge-type semiconductor laser. A method for manufacturing the ridge type semiconductor laser B will be described with reference to FIGS. On the n-type InP single crystal semiconductor substrate 21, an n-type InP was formed in the same manner as in Example 1 by using a metal organic chemical vapor deposition method.
Buffer layer 22 (0.3 to 1.0 μm), n-type AlGa
InAs BDR layer 23 (0.05 to 0.1 μm), n
Type AlInAs light confinement layer 24 (0.05 to 0.1 μm)
m), n-type AlGaInAs GRIN layer 25 (0.0
5 to 0.20 μm), an active layer 26 having an MQW structure of AlGaInAs, an intrinsic AlGaInAs GRIN layer 27 (0.05 to 0.20 μm), a p-type AlInAs optical confinement layer 28 (0.05 to 0.1 μm), and p-type InP cladding layer 29 (1.0 to 1.60 μm), p-type InGaAsP BDR layer 30 (0.1 μm), p-type I
nGaAs contact layer 31 (0.2 to 0.4 μm),
A p-type InP cap layer 35 (0.1 μm) is sequentially epitaxially grown (FIG. 4A).

Next, the p-type InP cap layer 35 is removed, and an insulating film 36 having a stripe width corresponding to the ridge width is formed.
(SiO ₂ or SiN) 4 (b). Then p
Dry etching is performed halfway between the p-type InGaAs contact layer 31 and the p-type InP cladding layer 29 (FIG. 4).
(C)). Thereafter, the p-type InP cladding layer 29 is formed with hydrochloric acid +
Etch with phosphoric acid (1: 3-5) to form p-type AlInA
The p-type InP cladding layer 29, the p-type InGaAsP BDR layer 30, and the p-type InG
A ridge portion composed of the aAs contact layer 31 is formed (FIG. 5A).

Next, using the ridge portion as a mask, p-type AlI
Oxygen atoms are ion-implanted into the nAs layer, and a low-resistance current injection window layer 28b is provided in a region shielded by the ridge portion, and a current blocking layer having a higher electrical resistance than the current injection window layer 28b is provided in a region exposed on the surface. 28a (FIG. 5)
(B)). Then, the insulating film 36 is removed with buffered hydrofluoric acid, and the insulating film 32 made of SiO _{2 is} formed on the entire surface of the substrate.
And open a window on the ridge (Fig. 5
(C)). Then, electrodes are deposited on the front surface and the back surface of the substrate to form a p-side electrode 33 and an n-electrode 34, respectively (FIG. 6).

The holes injected from the p-side electrode 33 are confined by the current blocking layer 28a, and recombine with the electrons injected from the n-side electrode 34 in the active layer 6 to exceed a certain current value (oscillation threshold). And laser oscillation.

The ridge type semiconductor laser B according to the present embodiment has a light confinement layer having a current injection window layer and a current block layer, as in the case of the stripe type semiconductor laser diode A of the first embodiment. Thus, the current from the electrode can be confined by the light confinement layer, and the same effect as in the first embodiment can be obtained. Further, in the ridge type semiconductor laser B according to the present embodiment, since the light confinement layer close to the active layer is used as the current blocking layer, the flow of holes in the lateral direction can be suppressed, and the density of injected holes into the active layer can be reduced. The threshold current can be reduced.
In addition, since the light density can be concentrated on the bottom of the ridge, the aspect ratio can be easily controlled.

[0035]

According to the semiconductor optical device of the present invention, the light confinement layer has a stripe-shaped current injection window layer, a current blocking layer formed on both sides of the current injection window layer and having a higher electric resistance than the current injection window layer. Therefore, it is not necessary to separately provide an insulating film as a current blocking layer in order to form a current confinement structure as in the prior art, and a more inexpensive semiconductor optical device can be provided.

Further, the semiconductor optical device of the present invention has a ridge portion composed of a cladding layer of the second conductivity type interposed between the light confinement layer and the electrode, and the light confinement layer has a current just below the ridge portion. Since it is composed of an injection window layer and a current blocking layer formed on both sides of the ridge portion and having a higher resistance than the current injection window layer, the current spreading in the lateral direction can be suppressed, and the ridge having a lower threshold current value can be suppressed. Semiconductor optical device.

Further, in the semiconductor optical device of the present invention, since the light confinement layer is made of a group III-V compound semiconductor of the periodic table containing at least Al, a semiconductor optical device having a high light density can be provided.

In the semiconductor optical device according to the present invention, the concentration of oxygen atoms in the current blocking layer is made higher than the concentration of oxygen atoms in the current injection window layer. Resistance can be controlled accurately.

In another semiconductor optical device according to the present invention, a light confinement layer has a stripe-shaped high refractive index layer and a low refractive index having a lower refractive index than the high refractive index layer formed on both sides of the high refractive index layer. And the current from the electrode is confined by the low-refractive-index layer and injected from the high-refractive-index layer into the active layer. Can be provided.

In another semiconductor optical device of the present invention, the light confinement layer is made of a group III-V compound semiconductor of the periodic table containing at least Al, so that the refractive index can be easily controlled. A waveguide type semiconductor light emitting device can be provided.

In another semiconductor optical device according to the present invention, the concentration of oxygen atoms in the low-refractive-index layer is higher than the concentration of oxygen atoms in the high-refractive-index layer. The refractive index distribution can be controlled accurately.

Further, according to the method of manufacturing a semiconductor optical device of the present invention, a current injection window layer is formed on a region confined by ion implantation on a light confinement layer through a stripe-shaped mask and the current injection window layer is formed. Since a current blocking layer having a higher electric resistance than the current injection window layer is formed on both sides of the window layer, it is not necessary to form an insulating film as a current blocking layer as in the related art, and the ion implantation amount is further reduced. Therefore, an annealing process for reducing crystal damage is not required, and the manufacturing cost can be reduced. In addition, since a current injection window layer that is fine and highly accurate can be manufactured by ion implantation, a semiconductor optical device having a single transverse mode oscillation and a low threshold current value can be provided.

Further, according to the method of manufacturing a semiconductor optical device of the present invention, a ridge portion is formed between a light confinement layer and an electrode, and then ions are implanted into the light confinement layer using the ridge portion as a mask. A current injection window layer is formed in the shielded region, and a current blocking layer having a higher resistance than the current injection window layer is formed on both sides of the current injection window layer, so that current spreading in the floor direction is suppressed. Thus, a ridge-type semiconductor optical device having a lower threshold current value can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a partial structure of a stripe type semiconductor optical device according to the present invention.

FIG. 2 is a schematic perspective view showing the entire structure of a stripe-type semiconductor optical device according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a step of manufacturing a stripe-type semiconductor optical device according to the present invention.

FIG. 4 is a schematic cross-sectional view (No. 1) showing a step of manufacturing a ridge-type semiconductor optical device according to the present invention.

FIG. 5 is a schematic cross-sectional view (2) showing a step of manufacturing a ridge-type semiconductor optical device according to the present invention.

FIG. 6 is a schematic cross-sectional view (No. 3) showing a step of manufacturing the ridge-type semiconductor optical device according to the present invention.

FIG. 7 is a schematic perspective view showing the structure of a conventional stripe-type semiconductor optical device.

FIG. 8 is a schematic perspective view showing a manufacturing process of a conventional stripe-type semiconductor optical device.

[Explanation of symbols]

1,21 n-type InP single crystal semiconductor substrate, 2,22 n-type InP buffer layer, 3,23 n-type AlGaInAs
BDR layer, 4,24 n-type AlInAs optical confinement layer, 5,
25 n-type AlGaInAs GRIN layer, 6, 26
Active layer having MQW structure of AlGaInAs, 7,2
7 Intrinsic AlGaInAs GRIN layer, 8,28 p
-Type AlInAs optical confinement layer, 8a, 28a current blocking layer, 8b, 28b current injection window layer, 9,29 p-type InP cladding layer, 10,31 p-type InGaAs contact layer, 11,33 p-side electrode, 12,34 n Side electrode, 30p type InGaAsP BDR layer, 32, 36
Insulating film, 35p-type InP cap layer, A stripe type semiconductor laser diode, B ridge type semiconductor laser.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Takiguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Mitsubishi Electric Corporation (reference) 5F073 AA07 AA13 AA74 BA01 CA15 CB19 DA14 EA23

Claims (9)

[Claims] An active layer formed on a substrate of a first conductivity type;
In a semiconductor optical device in which a conductive light confinement layer and an electrode are formed in this order, the light confinement layer has a stripe-shaped current injection window layer,
A current blocking layer formed on both sides of the current injection window layer and having a higher electric resistance than the current injection window layer, and the current from the electrode is constricted by the current blocking layer to the active layer from the current injection window layer. A semiconductor optical device characterized by being injected. 2. A ridge portion comprising a second conductivity type cladding layer interposed between the light confinement layer and the electrode, wherein the light confinement layer includes a current injection window layer immediately below the ridge portion, 2. The semiconductor optical device according to claim 1, comprising a current blocking layer formed on both sides of the ridge portion and having a higher resistance than the current injection window layer. 3. The semiconductor optical device according to claim 1, wherein the optical confinement layer is made of a group III-V compound semiconductor of the periodic table containing at least Al. 4. The semiconductor optical device according to claim 1, wherein the oxygen atom concentration in the current blocking layer is higher than the oxygen atom concentration in the current injection window layer. 5. An active layer, comprising: a first conductive type substrate;
In a semiconductor optical device in which a conductive type optical confinement layer and an electrode are formed in this order, the optical confinement layer is a stripe-shaped high refractive index layer, and a high refractive index formed on both sides of the high refractive index layer. A low-refractive-index layer having a lower refractive index than the layer, wherein current from the electrode is confined by the low-refractive-index layer and injected into the active layer from the high-refractive-index layer. . 6. The semiconductor optical device according to claim 5, wherein the optical confinement layer is made of a group III-V compound semiconductor of the periodic table containing at least Al. 7. The semiconductor optical device according to claim 5, wherein the oxygen atom concentration in the low refractive index layer is higher than the oxygen atom concentration in the high refractive index layer. 8. An active layer, a second conductive type substrate, and a second conductive type substrate.
In a method for manufacturing a semiconductor optical device in which a conductive type optical confinement layer and an electrode are formed in this order, forming an active layer on the substrate, and forming an optical confinement layer on the active layer, On the light confinement layer, a current injection window layer is provided in a region which is ion-implanted through a stripe-shaped mask and shielded by the mask, and both sides of the current injection window layer have higher electric resistance than the current injection window layer. Forming a current blocking layer, and further forming the electrode on at least a current injection window layer. 9. A ridge portion comprising a second conductivity type cladding layer is formed between the light confinement layer and the electrode, and then ion-implanted into the light confinement layer using the ridge portion as a mask to be shielded by the ridge portion. 9. The method according to claim 8, wherein a current injection window layer is formed in the region, and a current blocking layer having higher resistance than the current injection window layer is formed on both sides of the current injection window layer.