JP2001326423A - Semiconductor optical element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ridge-waveguide semiconductor optical element that has a single wavelength property and can carry out high-speed and low-threshold operation, and a method for manufacturing the semiconductor light element. SOLUTION: A stripe-like region extending in the waveguide direction is formed on the surface of a buried layer for burying diffraction grating, a second conductivity type cladding layer is formed directly above the stripe-like region while the second conductivity type cladding layer perpendicular to the buried layer, a second conductivity type contact layer is formed on the cladding layer, and a ridge where a section shape in the width wise direction is in a rectangular shape is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor optical device used as a light source for an optical communication system, and more particularly, to a ridge waveguide type semiconductor optical device having a distributed feedback type waveguide structure and a method of manufacturing the same. .

[0002]

2. Description of the Related Art Gigabit Ethernet (registered trademark),
Semiconductor optical devices for light sources used in high-speed digital communication and optical communication systems such as wavelength-division multiplexing optical communication are required to have high-speed operation and single wavelength characteristics in order to cope with an increase in communication capacity. A semiconductor optical device having a ridge waveguide structure includes:
Although excellent in high-speed switching characteristics, single wavelength characteristics are not sufficient. Therefore, for example, a semiconductor optical device having a ridge waveguide structure having a distributed feedback waveguide structure excellent in single wavelength characteristics has been studied.

Here, in the distributed feedback waveguide structure, light generated by radiative recombination in the active layer is reflected by a diffraction grating formed in the vicinity of the active layer, and reciprocates in the element to produce a laser. Leading to oscillation. At this time, when the period の of the diffraction grating is an integral multiple of (resonance wavelength / 2), the phases of the light reflected by the diffraction grating are added to have a large reflection action, and function as a waveguide mirror. Further, a single wavelength corresponding to the pitch interval of the diffraction grating is obtained as the oscillation wavelength.

FIG. 4 is a schematic perspective view showing an example of the structure of a conventional semiconductor optical device having a ridge waveguide structure having a distributed feedback waveguide structure. A conventional semiconductor optical device is an n-type In
N-type In formed on one surface of P single crystal substrate 51
P buffer layer 52, n-type InP light confinement layer 53, I
nGaAsP multiple quantum well active layer 54, p-type InGaAs
sP light confinement layer 55, p-type InP cladding layer 56, p
Grating 57 of p-type InGaAsP, p-type InP buried layer 58, p-type InP cladding layer 59, p-type InG
aAs contact layer 60, insulating layer 61, p-side electrode 62
And an n-side electrode 63 formed on the other surface.

Here, the ridge portion is, for example, disclosed in
As disclosed in Japanese Patent No. 242034, it is formed using wet etching. That is, p-type I
nP cladding layer 59 and p-type InGaAs contact layer 6
0 is epitaxially grown on the diffraction grating 11 and the p-type InP cladding layer 59 and the p-type In
A ridge portion is formed by removing the GaAs contact layer 60 by wet etching.

[0006]

However, in the conventional method, the ridge has a mesa shape due to the low processing accuracy of etching, and it has been difficult to uniformly control the width of the ridge. Therefore, there are problems that the shape of the waveguide is not constant, the unity of the oscillation wavelength becomes insufficient, and it is difficult to keep the oscillation threshold current value and the operating current low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and to provide a ridge waveguide type semiconductor optical device having a single wavelength, capable of high-speed operation and low threshold operation, and a method of manufacturing the same. Aim.

[0008]

According to the present invention, there is provided a method for manufacturing a semiconductor optical device, comprising: a ridge waveguide type having an active layer, a buried layer for embedding a diffraction grating, and a ridge portion on a substrate of a first conductivity type. Forming the ridge portion, forming a stripe-shaped region extending in the waveguide direction on the surface of the buried layer, and forming a second conductive type clad layer immediately above the stripe-shaped region. Is formed perpendicular to the buried layer, and then a contact layer of the second conductivity type is formed on the cladding layer.

According to the manufacturing method of the present invention, an insulating layer is formed on the surface of the buried layer, a mask having a desired pattern is formed on the insulating layer, and the mask is shielded by the mask. By removing the insulating layer other than the above, the buried layer is exposed to form a groove extending in the waveguide direction, and the groove is used as the above-mentioned stripe region.

The semiconductor optical device of the present invention is a ridge waveguide type semiconductor optical device having an active layer, a buried layer for embedding a diffraction grating, and a ridge portion on a substrate of a first conductivity type. A ridge portion formed of a second conductivity type cladding layer and a second conductivity type contact layer, which are formed on the surface of the buried layer and are stacked in this order immediately above a stripe-shaped region extending in the waveguide direction; Has a rectangular cross-sectional shape in the width direction.

Further, in the semiconductor optical device according to the present invention, the stripe-shaped region is formed of a concave groove formed in an insulating layer formed on a surface of the buried layer.

Further, the semiconductor optical device of the present invention is characterized in that it has an insulating layer which is in contact with both side surfaces of the ridge portion and covers the upper surface of the semiconductor optical device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a semiconductor optical device according to the present invention will be described in detail below using a semiconductor laser as an example. The semiconductor optical device according to the present invention is not limited to a semiconductor laser. Embodiment 1 FIG. The manufacturing process of the semiconductor laser according to the present embodiment will be described with reference to FIGS. On one surface of the n-type InP single crystal substrate 1, n is formed by an organic metal growth method.
InP buffer layer 2 (0.3-1.0 μm), n-type AlGaInAs BDR layer 3 (0.3-1.0 μm)
m), n-type AlInAs optical confinement layer 4 (0.05-
0.1 μm), n-type AlGaInAs GRIN layer 5
(0.75-1.25 μm), AlGaInAs strained multiple quantum well (MQW) active layer 6, AlGaInAs G
RIN layer 7 (0.75-1.25 μm), p-type AlIn
As light confinement layer 8 (0.05-0.1 μm), p-type I
nP cladding layer (0.05-0.1 μm) and p
InGaAsP ESL (Etching Stop)
Per layer (0.05 μm) is epitaxially grown (FIG. 1A). Note that n-type AlGaIn
The As BDR layer 3 has a role of alleviating a band discontinuity between the n-type InP buffer layer 2 and the n-type AlInAs optical confinement layer 4.

Next, the p-type InGaAsP ESL1
In a region where no diffraction grating is formed, for example, SiO ₂
And an insulating film such as SiN _X is formed. Next, a resist is applied on the entire surface, and the diffraction grating pattern is exposed by the two-beam interference exposure method, and then developed to form a resist pattern having a line and space cycle equal to the diffraction grating cycle Λ, and etching is performed using the resist pattern as a mask. After that, the resist and the insulating film are removed, and a cycle of p-type InGaAsP is formed.
Is formed (FIG. 1B). Next, a buried layer 12 made of p-type InP is formed on the diffraction grating 11 by burying growth (FIG. 1C).

Next, on the buried layer 12, for example, S
After forming the insulating film 13 made of iC, a resist mask is patterned on the insulating layer 13 and the insulating layer other than the one shielded by the resist mask is removed to form a concave groove having a predetermined width W in the waveguide direction. (FIG. 2 (a)). Next, the insulating film 1
3 as a selective growth mask, a p-type InP cladding layer 14 (1.4-1.6 μm) and a p-type InGaAs
A ridge is formed by epitaxially growing the s-contact layer 15 (0.5-0.7 μm).

Next, the p-type InGaAs contact layer 15
The p-side electrode 16 made of Au-Zn, n-type In
An n-side electrode made of Au-Ge-Ni is formed on the other surface of the P single crystal substrate 1 by vapor deposition to complete a semiconductor laser (FIG. 2C). Note that cleavage, die bonding, bonding, and the like can be performed using a conventionally known method.

The active layer used in this embodiment has a thickness of 1.3.
Any known material used for semiconductor lasers in the μm band can be used, but AlG having excellent temperature characteristics can be used.
It is preferable to use a multiple quantum well layer made of aInAs.

The diffraction grating can be formed by etching a p-type clad layer formed on the active layer. Also,
The buried layer can be formed using a material having a different refractive index from the p-type clad layer. For example, the active layer has Al
When a multiple quantum well layer made of GaInAs is used, the combination of the material constituting the diffraction grating and the material used for the buried layer may be AlInAs / AlGaInAs, InP
/ AlGaInAs, AlGaInAs / InGaAs
P, AlInAs / InGaAsP, AlInAs / I
nP, InGaAsP / InGaAsP or the like can be used. It is preferable to use AlGaInAs having a different Al mixed crystal ratio from the active layer for the diffraction grating, and it is preferable to use InP having a large light confinement effect for the buried layer.

The p-type cladding layer grown on the buried layer can be formed by selecting a material having the same or smaller refractive index as the material of the buried layer. Is preferred. The crystallinity of the p-type clad layer to be grown can be improved.

In the present embodiment, a groove formed in an insulating layer above a buried layer is used as a stripe region, and a cladding layer and a contact layer are grown in the groove, so that a ridge having a uniform width is formed. A part can be formed. As a result, in a ridge waveguide type semiconductor laser having a distributed feedback waveguide structure, the size of the waveguide can be controlled. As a result, the ridge waveguide type semiconductor laser can be improved in unity of oscillation wavelength, can operate at high speed, and can operate at a low threshold.

Embodiment 2 FIG. FIG. 3 is a perspective view showing the structure of the semiconductor laser according to the present embodiment. p-side electrode 1
6 has the same structure as that of the first embodiment except that it has an insulating layer 17 made of, for example, polyimide, which is in contact with both side surfaces and covers the upper surface of the semiconductor laser. Further, it can be manufactured by using the same method as that of the first embodiment except that the upper surface of the p-side electrode 16 is buried with polyimide other than the upper surface.

First, an n-type InP
On one surface of the single crystal substrate 1, an n-type InP buffer layer 2 (0.3-1.0 μm), an n-type AlGaInAs B
DR layer 3 (0.3-1.0 μm), n-type AlInAs optical confinement layer 4 (0.05-0.1 μm), n-type AlGa
InAs GRIN layer 5 (0.75-1.25 μm),
AlGaInAs strained MQW active layer 6, AlGaInA
s GRIN layer 7 (0.75-1.25 μm), p-type A
lInAs light confinement layer 8 (0.05-0.1 μm),
p-type InP cladding layer (0.05-0.1 μm) and p-type InGaAsP ESL (Etching S
A top layer (0.05 μm) is epitaxially grown. Note that n-type AlGaInAs B
The DR layer 3 includes the n-type InP buffer layer 2 and the n-type AlIn
It has a role of alleviating the band discontinuity between As light confinement layer 4.

Next, the p-type InGaAsP ESL1
In a region where no diffraction grating is formed, for example, SiO ₂
And an insulating film such as SiN _X is formed. Next, a resist is applied on the entire surface, and the diffraction grating pattern is exposed by the two-beam interference exposure method, and then developed to form a resist pattern having a line and space cycle equal to the diffraction grating cycle Λ, and etching is performed using the resist pattern as a mask. After that, the resist and the insulating film are removed, and a cycle of p-type InGaAsP is formed.
Is formed. Next, p is placed on the diffraction grating 11.
A buried layer 12 of type InP is formed by buried growth.

Next, on the buried layer 12, for example, S
After forming the insulating film 13 made of iC, a resist mask is patterned on the insulating layer 13 and the insulating layer other than the one shielded by the resist mask is removed to form a concave groove having a predetermined width W in the waveguide direction. . Next, using the insulating film 13 as a selective growth mask, the p-type InP cladding layer 14 is formed on the surface of the groove.
A ridge is formed by epitaxially growing (1.4-1.6 μm) and the p-type InGaAs contact layer 15 (0.5-0.7 μm).

Next, the p-type InGaAs contact layer 15
The p-side electrode 16 made of Au-Zn, n-type In
On the other surface of P single crystal substrate 1, an n-side electrode made of Au-Ge-Ni is formed by vapor deposition. Next, the p-side electrode 1
The semiconductor laser is completed by embedding the upper surface of the semiconductor laser other than the upper surface of 6 with polyimide. Note that cleavage, die bonding, bonding, and the like can be performed using a conventionally known method.

By embedding polyimide other than the upper surface of the ridge portion with polyimide, the capacitance of the semiconductor laser can be reduced. Thereby, high frequency characteristics such as modulation characteristics, relaxation frequency, and cutoff frequency can be improved.

[0027]

As described above, the method of manufacturing a semiconductor optical device according to the present invention provides a method of manufacturing a semiconductor optical device in which a second conductive type clad layer and a second conductive type clad layer are formed immediately above a stripe region formed on a buried layer in which a diffraction grating is buried. Since the conductive type contact layer and the buried layer are grown vertically, a ridge portion having an upright shape and a uniform width can be formed. This allows
A ridge waveguide type semiconductor optical device having a distributed feedback type waveguide structure can be manufactured with good reproducibility.

In the method of manufacturing a semiconductor optical device according to the present invention, since the concave groove formed in the insulating layer above the buried layer is used as a stripe-shaped region, the width of the ridge can be easily controlled. .

Further, in the semiconductor optical device of the present invention, the ridge portion is formed on the surface of the buried layer, and the cladding layer of the second conductivity type is laminated in this order immediately above the stripe-shaped region extending in the waveguide direction; Since the ridge portion has a rectangular cross-sectional shape in the width direction of the second conductive type contact layer, the unity of the oscillation wavelength is improved, and a high-speed operation and a low threshold operation are possible.

Further, in the semiconductor optical device of the present invention, since the concave groove provided in the insulating layer formed on the surface of the buried layer is used as a stripe region, the width of the charge injection region immediately below the ridge portion is reduced. Control becomes easy.

Further, since the semiconductor optical device of the present invention has an insulating layer which is in contact with both side surfaces of the ridge portion and covers the upper surface of the semiconductor optical device, the high frequency characteristics of the semiconductor optical device can be improved.

[Brief description of the drawings]

FIGS. 1A and 1B are a schematic cross-sectional view and a schematic perspective view (part 1) showing a manufacturing process of a semiconductor optical device according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view (2) showing a step of manufacturing the semiconductor optical device according to the first embodiment of the present invention.

FIG. 3 is a schematic perspective view showing a structure of a semiconductor optical device according to a second embodiment of the present invention.

FIG. 4 is a schematic perspective view showing the structure of a conventional semiconductor optical device.

[Explanation of symbols]

1 n-type InP single crystal substrate, 2 n-type InP buffer layer, 3 n-type InGaAsP BDR layer, 4 n
-Type AlInAs optical confinement layer, 5 n-type AlGaIn
As GRIN layer, 6 AlGaInAs multiple quantum well active layer, 7 AlGaInAs GRIN layer, 8
p-type AlInAs optical confinement layer, 9,14 p-type In
P cladding layer, 10 p-type InGaAsP ESL,
11 diffraction grating, 12 p-type InP buried layer, 1
3,18 insulating layer, 15p-type InGaAs contact layer, 16p-side electrode, 17n-side electrode.

Claims (5)

[Claims] 1. A method for manufacturing a ridge waveguide type semiconductor optical device having an active layer, a buried layer for embedding a diffraction grating, and a ridge on a substrate of a first conductivity type, wherein the ridge is formed. At this time, a stripe-shaped region extending in the waveguide direction is formed on the surface of the buried layer, and a cladding layer of the second conductivity type is formed immediately above the stripe-shaped region perpendicularly to the buried layer. A method for manufacturing a semiconductor optical device, comprising forming a conductive contact layer on the cladding layer. 2. An insulating layer is formed on the surface of the buried layer when forming the stripe-shaped region, a mask having a desired pattern is formed on the insulating layer, and the insulating layer other than the masked by the mask is removed. 2. The method according to claim 1, wherein the buried layer is exposed to form a groove extending in the waveguide direction, and the groove is used as the stripe-shaped region. 3. A ridge waveguide type semiconductor optical device having an active layer, a buried layer for embedding a diffraction grating, and a ridge on a substrate of a first conductivity type, wherein the ridge is a surface of the buried layer. A second conductive type clad layer and a second conductive type contact layer laminated in this order immediately above a stripe-shaped region formed in the waveguide direction and a second conductive type contact layer, and the ridge portion has a rectangular cross-sectional shape in the width direction. A semiconductor optical device, characterized in that: 4. The semiconductor optical device according to claim 3, wherein said stripe-shaped region comprises a concave groove provided in an insulating layer formed on a surface of the buried layer. 5. The semiconductor optical device according to claim 3, further comprising an insulating layer in contact with both side surfaces of said ridge portion and covering an upper surface of said semiconductor optical device.