JPH11204773A - Waveguide type semiconductor optical integrated element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve characteristics by reducing absorption loss in a waveguide in a waveguide type semiconductor optical element, and realize an optical module and optical communication system at a low cost by using the element. SOLUTION: In a waveguide type semiconductor optical integrated element containing a light emitting part and a passive optical waveguide part, film thickness of an active layer 1 of the light emitting part is constant, and width of the active layer is at most 5 μm. The film thickness of a core layer of the passive optical waveguide part is modulated in a tapered shape 2 so as to be thinned along the direction of light propagation. The width of the core layer is greater than that of the active layer, and the active layer 1 of the light emitting part and the core layer of the passive optical waveguide part are collectively formed by selective growth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a waveguide type semiconductor optical integrated device, and more particularly to a waveguide type semiconductor optical integrated device suitably used for an optical module for optical communication and an optical communication system, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Cost reduction of access optical communication systems
It is important to reduce the price of the optical module. Light module
In order to reduce the price of the lens, the optical system using the conventional lens system
System, not semiconductor laser and optical waveguide or optical fiber
It is effective to directly connect However, the conventional structure
Spot size of the semiconductor laser (light intensity is 1 / e
^TwoIs about 2 μm, which is widely used
1.3 μm Zero-dispersion optical fiber
There is a big difference. For this reason, the direct combination of the two
Has a large coupling loss of about 10 dB, which is a serious problem.
I was In addition, a planar optical circuit (PLC: planar
Normally used in light-wave circuits
The optical spot size is 8 even in the quartz optical waveguide
This difference in light spot size is about μm larger.
Is a problem.

In order to reduce the coupling loss due to such mode mismatch, it is effective to increase the light spot size of the semiconductor laser. However, in a semiconductor laser, the smaller the light confinement of the optical waveguide, that is, the larger the light spot size, the higher the oscillation threshold value and the lower the luminous efficiency. In order to increase the light spot size without sacrificing the laser oscillation characteristics, a light spot size conversion optical waveguide made of a semiconductor may be integrated and its thickness or width may be modulated in a tapered shape in the optical axis direction. (Hereinafter, this is referred to as SSC-LD).

[0004] A method of manufacturing an SSC-LD in which the thickness of an optical waveguide is modulated in the optical axis direction to convert the light spot size is disclosed in Japanese Patent Application Laid-Open No. 7-283490. FIG. 2 shows a structural diagram of this. Here, the active layer 1 and the core layer of the tapered waveguide 2 are collectively formed by changing the pattern of the growth blocking film by selective MOVPE. Further, the thickness of the optical waveguide and the energy band gap are changed in the optical axis direction by devising the pattern of the growth blocking film to form a tapered waveguide. In this structure, a coupling loss with a flat-end optical fiber of 4 dB or less is obtained.

A structure for changing the thickness of the optical waveguide and the energy band gap in the optical axis direction by the selective MOVPE is as follows.
It is disclosed in JP-A-5-29602. FIG. 3 is a schematic diagram showing the result of performing selective MOVPE by changing the gap width of the growth blocking film 10.

In both Japanese Patent Application Laid-Open Nos. 7-283490 and 5-29602, after forming a waveguide by semiconductor etching, current blocking layers 3, 4 and a cladding layer 5 are grown. Complete the device.

[0007]

By the way, the selection MOV
In PE, the actual thickness of the optical waveguide changes smoothly even if one of the growth blocking film width and the gap width is suddenly changed in the optical axis direction. Similarly, the band gap energy gradually changes at the boundary between the active layer 1 and the core layer of the tapered waveguide 2, thereby causing absorption loss due to the inter-band transition in the tapered waveguide 2. Increase in absorption loss is due to increase in threshold current,
Not only does the slope efficiency drop, but the high temperature operating characteristics also drop significantly.

In order to solve this problem, an active layer 1 and a core layer of the tapered waveguide 2 are formed by crystal growth in different steps, and a structure for realizing the SSC-LD is disclosed in the document ELECT.
RONICS LETTERS Vol. 31, N
o. 21, page 1838. Since the tapered waveguide formed by this structure has a small absorption loss at the laser oscillation wavelength, it realizes excellent oscillation characteristics such as a threshold current at room temperature of 5.6 mA, a slope efficiency of 0.41 W / A, and a maximum oscillation temperature of 135 ° C. doing. Further, by expanding the light spot size due to the integration of the tapered waveguide, the coupling loss with the flat end optical fiber of 1.8 dB and good coupling characteristics are also realized.

However, in this structure, since the active layer and the tapered waveguide layer are formed by different crystal growth, the manufacturing process becomes complicated. For this reason, there is a concern that sufficient reproducibility and uniformity of characteristics cannot be obtained when the element is put into practical use.

An object of the present invention is to provide a laser which oscillates with a low threshold current and a high slope efficiency, has excellent high-temperature operation characteristics, reproducibility, uniformity of characteristics, and can be manufactured by a simple process.
An object of the present invention is to provide a waveguide type semiconductor optical integrated device including a C-LD. Another object is to realize an inexpensive optical module and an optical communication system using the element.

[0011]

According to the present invention, a selective MOV is provided.
The following solution using PE reduces absorption loss in a passive waveguide, and realizes a waveguide type semiconductor optical integrated device having an excellent light emission characteristic with an enlarged light spot size.

According to a first aspect of the present invention, in a waveguide type semiconductor optical integrated device including a light emitting section and a passive optical waveguide section, the active layer of the light emitting section has a constant thickness, and the active layer width is 5 μm or less. The thickness of the core layer of the passive optical waveguide portion is modulated in a tapered shape so as to become thinner in the light propagation direction, and the width of the core layer is wider than the width of the active layer. The problem is solved by a waveguide type semiconductor optical integrated device characterized in that the active layer of the portion and the core layer of the passive optical waveguide portion are collectively formed by selective growth.

[0013] In a second aspect of the present invention, the width of the core layer of the passive optical waveguide portion is tapered in a region in contact with the active layer of the light emitting portion. The problem is solved by a waveguide type semiconductor optical integrated device.

According to a third aspect of the present invention, there is provided the waveguide type semiconductor optical integrated device according to the first or second aspect, wherein the active layer of the light emitting section and the core layer of the passive optical waveguide section are quantum well layers. The element solves the problem.

According to a fourth aspect of the present invention, there is provided a waveguide type semiconductor optical integrated device according to any one of the first and second aspects, wherein the light emitting section and the passive optical waveguide section are of an embedded type. Solve.

According to a fifth aspect of the present invention, there is provided the first to fourth aspects, further including at least one selected from a distributed feedback semiconductor laser, a distributed reflection semiconductor laser, an optical modulator, a photodetector, an optical switch, and an optical waveguide. The problem is solved by the waveguide type semiconductor optical integrated device according to any one of the above.

According to Solution 6 of the present invention, a growth inhibiting film used as a mask for selective growth is formed on a semiconductor substrate in a pair of stripes, and (a) the gap between the growth inhibiting films in the light emitting portion is 5 μm or less. The gap between the growth blocking film in the passive optical waveguide is wider than the gap width in the light emitting portion. (B) The width of the growth blocking film in the passive optical waveguide is narrower than the width of the growth blocking film in the light emitting portion, and light propagates. A waveguide-type semiconductor including a step of forming the active layer of the light-emitting portion and a core layer of the passive waveguide in a gap portion of the growth-blocking film by collective selective growth. The problem is solved by a method for manufacturing an optical integrated device.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a waveguide type semiconductor optical integrated device according to the sixth aspect, wherein the selective growth is formed by selective MOVPE.

According to Solution 8 of the present invention, the waveguide type semiconductor optical integrated device according to Solution 6 or 7, wherein selective growth is performed so that the active layer of the light emitting section and the core layer of the passive waveguide have a quantum well structure. To solve the problem.

[0020] According to the solution 9 of the present invention, the waveguide according to any one of the solutions 1 to 5, wherein the side walls of the optical waveguide of the light emitting portion and the passive optical waveguide portion formed by selective growth are (111) crystal planes. The problem is solved by the type semiconductor optical device.

According to a tenth aspect of the present invention, there is provided the waveguide according to any one of the first to fifth aspects, wherein the light emitting portion and the optical waveguide of the passive optical waveguide portion have two or more electrode structures for applying current or voltage. The problem is solved by the integrated semiconductor optical device.

According to a solution 11 of the present invention, the problem is solved by the waveguide type semiconductor optical integrated device according to any one of the solutions 1 to 5, wherein the operating wavelength is 0.3 to 1.7 μm.

In the solution means 12 of the present invention, the solution means 1 to 1
The problem is solved by an optical module characterized in that the optical module is formed by using at least one waveguide-type semiconductor optical integrated device according to any one of (5).

According to the solution means 13 of the present invention, the solution means 1
The problem is solved by an optical communication system characterized by using at least one waveguide type semiconductor optical integrated device according to any one of the above (5).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In the waveguide type semiconductor optical integrated device of the present invention, the thickness of the active layer of the light emitting section is constant, and the thickness of the core layer of the passive optical waveguide section is along the direction of light propagation. Since the light is modulated so as to be tapered, the spot size of the light from the light emitting portion is enlarged in the passive optical waveguide portion. Here, thinning in a tapered shape means not only linearly thinning but also smooth thinning without discontinuous change. The passive optical waveguide portion in which the core layer is tapered and thus thin is also referred to as a tapered waveguide hereinafter.

The active layer of the light emitting portion and the core layer of the tapered waveguide are formed by selective growth, particularly preferably by MOVPE. The pattern of the growth blocking film, which is a mask used for selective growth, is formed to have a gap width of 5 μm or less at the portion where the active layer is formed, and the active layer is formed with a gap width at the region where the core layer of the tapered waveguide is formed. The width is wider than the region, and the width of the growth blocking film in the passive optical waveguide is narrower than the width of the growth blocking film in the light emitting portion, and is narrower in the light propagation direction. By doing so, the width of the active layer becomes 5 μm or less, and the width of the core layer is formed wider than the width of the active layer.

In the method of changing the gap width shown in the conventional example, a waveguide is formed by performing selective MOVPE and then etching the semiconductor. However, due to the migration of the raw material species moving on the growth inhibiting film, as shown in FIG.
It rises up to about 2 μm, and the optical characteristics and the like at this portion deteriorate. Therefore, in this manufacturing method, it is necessary to provide a relatively wide gap, avoiding the raised area, and form the active layer 1, the tapered waveguide 2, and the like in the center. For this reason, Japanese Unexamined Patent Application Publication No.
In the manufacturing method of forming a waveguide by etching a semiconductor as disclosed in Japanese Unexamined Patent Application Publication No. 5-29602 and Japanese Unexamined Patent Application Publication No. 5-29602, a gap width of about 10 μm or more is required. But,
When the gap width is increased, the change in film thickness is caused not by the effect of migration but by the effect of gas phase diffusion, so that a steep band gap energy shift cannot be realized and SSC-
A low-loss tapered waveguide required by LD cannot be realized.

On the other hand, in the present invention, since the gap width of the growth blocking film is narrowed to 5 μm or less, the shape directly formed in the gap is such that the protrusion near the side face shown in FIG. Becomes The protrusion on the side surface is mainly due to migration, and this becomes dominant to form a waveguide.

Considering that the supply amount of the raw material supplied to the gap is constant, the cross-sectional area of the waveguide formed in this portion is constant. For example, if the gap is 1.5 μm to 3
When the thickness is increased to μm, as shown in FIG. 5, the thickness to be selectively grown changes from 0.3 μm to about 0.15 μm.
In the selective MOVPE growth in this case, since it is hard to be affected by the concentration gradient due to the vapor phase diffusion, a steep change in the waveguide thickness by changing the gap width becomes possible.

Further, if a quantum well structure is adopted for the waveguide, the bandgap energy changes to a higher energy side as the thickness of the waveguide decreases, so that the bandgap wavelength is sharply shortened simultaneously with the thickness of the optical waveguide layer. The wavelength can be increased, and the absorption loss in the tapered waveguide 2 can be reduced. This reduction in the absorption loss greatly contributes to the improvement of the characteristics of the SSC-LD, and can realize good oscillation characteristics and high-temperature operation characteristics. Further, the effect on the active layer 1 due to the widening of the gap width is extremely small, and good optical gain characteristics can be realized at the same time. For this reason, even if the tapered waveguide 2 is integrated, an SSC-LD having excellent characteristics comparable to a semiconductor laser alone can be obtained by the present invention.

FIG. 6 shows a measurement result of a change in photoluminescence wavelength (hereinafter, referred to as PL wavelength) when selective MOVPE is performed by actually changing the gap width in the optical axis direction. Note that the PL wavelength corresponds to the band gap. Here, the width of the growth blocking film was changed to 50 μm in the light emitting portion, and the width in the passive optical waveguide portion was tapered from 50 μm to 4 μm. In order to realize a steep PL wavelength change, the gap width was increased from 1.5 μm to 3 μm. Also, for comparison, the PL wavelength change when the growth blocking film width is the same pattern and the gap width is constant is also shown. It can be seen that in the growth blocking film pattern according to the present invention in which the gap width is widened, a steep PL wavelength change can be obtained in the tapered waveguide region near the active layer as compared with the conventional pattern having a constant gap width.

FIG. 7 shows the result of plotting the difference between the PL wavelengths. In the tapered waveguide region near the light emitting section,
The PL wavelength of 45 nm can be shortened by increasing the gap width, and the PL wavelength change due to the gap width change occurs sharply within a range of several μm from the boundary between the light emitting portion and the tapered waveguide portion. I understand. As shown here, a rapid band gap energy shift can be obtained without being affected by gas phase diffusion by increasing the gap width, which is the phenomenon discovered by the present inventors for the first time.

As described above, in the waveguide type semiconductor optical integrated device of the present invention, the thickness of the active layer of the light emitting portion and the thickness of the core layer of the tapered waveguide portion are sharply changed, and the band gap energy shift is abrupt. SSC having good oscillation characteristics without absorption loss due to inter-band transition
-A waveguide type semiconductor optical integrated device having an LD portion is obtained.

At the same time, according to the manufacturing method of the present invention, it is not necessary to form a waveguide by etching a semiconductor layer or the like, which has been conventionally performed, and a waveguide having excellent uniformity and reproducibility can be formed.

Next, the active layer of the light emitting portion and the tapered waveguide in the waveguide type semiconductor optical integrated device of the present invention will be described while explaining the pattern of the growth inhibiting film used in the selective growth in the manufacturing method of the present invention. The shape of the core layer will be further described.

FIG. 14 shows an example of a pattern of a growth blocking film used in the selective growth in the present invention. In the figure,
La is the length of the light emitting portion, and Lt is the length of the tapered waveguide. Incidentally, the growth blocking film has a pair of stripes in the portion where the light emitting portion and the tapered waveguide are formed as shown in this figure, and when the light emitting portion and the tapered waveguide end are cut out by cleavage or the like, It is not always necessary for the light emitting portion and the tapered waveguide to be formed outside, that is, portions that are cut out and become unnecessary, and are not necessarily in a stripe shape, and the present invention includes such a form.

The gap Gp-a in the light emitting portion of the growth blocking film forming a pair is set to 5 μm or less. The width of the active layer of the light emitting unit is determined by the gap Gp-a. The lower limit of the gap Gp-a may be set to a width that is equal to or greater than the level at which light emission occurs in the active layer, and is usually 0.1 μm or more.

The gap Gp-t at the tapered waveguide portion of the growth blocking film forming a pair is set wider than the gap Gp-a. The gap Gpt may be wider than 5 μm. Here, in a region of the light emitting portion in contact with the active layer (distance from the active layer is in a range of 0 to L1), the gap Gpt is sharply expanded in a tapered shape. If the length L1 is too long, a rapid change in film thickness may not be obtained.
m or less, preferably 50 μm or less. In this case, the “tapered shape” means that it spreads smoothly, but does not mean that it spreads only linearly.

As shown in FIG. 15, L1 may be set to 0. Even if L1 is set to 0, it is not formed such that the width of the active layer and the core layer changes steeply as the width becomes discontinuous by selective growth. However, in order to prevent scattering loss due to mode mismatch, L1 is set to 5 μm. Above, preferably 10μ
m or more.

Further, the width of the growth blocking film in the tapered waveguide portion is narrowed in the light propagation direction so that the thickness of the formed tapered waveguide is reduced in the light propagation direction. Set as follows. As shown in FIG. 14, even if the width decreases gradually at a distance L2 from the active layer, as shown in FIG. 16, the outside of the growth inhibiting film changes linearly. You can set
As shown in FIG. 7, the gap between the tapered waveguide portions may gradually widen in the light propagation direction. In addition, the gap or the width of the growth inhibiting film may not only change linearly or polygonally as described above, but may also change gradually in a curved shape. In any case, the thickness of the grown core layer may be modulated in a tapered shape so as to become thinner in the light propagation direction.

The width Wa of the active layer portion of the light emitting portion of the growth blocking film in FIG. 14 is constant in the region where the active layer is formed, and is appropriately changed according to the required thickness of the active layer. I do.

Further, the width Wt of the growth blocking film on the output end side of the tapered waveguide is appropriately adjusted according to the film thickness required on the output end side.

In the waveguide type semiconductor optical integrated device of the present invention, the SSC-LD portion is the most characteristic portion as described above. In addition to the SSC-LD, a distributed feedback semiconductor laser,
Other optical functional elements such as distributed reflection type semiconductor lasers, optical modulators, photodetectors, optical switches, and optical waveguides are integrated on the same substrate to achieve higher functionality and higher integration. Good.

[0044]

The present invention will be described in more detail with reference to the following examples.

(First Embodiment) FIG. 1 shows an SSC-LD which is an embodiment of the waveguide type semiconductor optical integrated device of the present invention. The active layer 1 having the InGaAsP / InGaAsP MQW structure has a gap width of 1.5 μm, and the core layer of the simultaneously formed tapered waveguide 2 has a gap width of 3 μm.
It is formed directly on the part that is spread out. The width of the waveguide increases from 1.5 μm to 3 μm over a length of 30 μm near the boundary between the active layer 1 and the core layer of the tapered waveguide 2, thereby suppressing scattering loss (mode conversion loss) due to mode mismatching. The structure is adopted. The thickness of the waveguide at the emission end is the active layer 1
The light spot size is increased here, the aspect ratio is improved, and good coupling characteristics with the optical fiber can be realized. This semiconductor laser employs a structure having an oscillation wavelength of 1.3 μm.

The manufacturing process will be described with reference to FIGS. As shown in FIG. 8A, first, a 100 nm thick S is formed on a (001) plane of an n-InP substrate by a thermal CVD method.
A growth stop film 10 made of an iO ₂ film is deposited. Subsequently, a resist pattern used for selective MOVPE is formed by a photolithography process. The growth inhibition film 10 is etched with the diluted hydrofluoric acid, and a substrate used for growth is completed. The pattern of the growth blocking film 10 is the same as the shape shown in FIG. 14, and the width of the growth blocking film in the light emitting section is 50 μm (=
Wa) constant, 50 μm to 4 μm in the passive optical waveguide section
(= Wt). Further, the width of the gap 11 of the growth blocking film 10 is 1.5 μm (= G
pa) Constant, at the boundary between the passive optical waveguide portion and the light emitting portion, the width of the gap portion 11 is 1.5 μm over a length of 30 μm (= L1).
From 3 μm (= Gp−t).

Using this substrate, by selective MOVPE,
The n-InP cladding layer is 100 nm, and the first SCH layer made of InGaAsP having a wavelength composition of 1.13 μm is 60 n.
An m, MQW layer, a second SCH layer made of InGaAsP having a wavelength of 1.13 μm and a p-InP cladding layer of 60 nm are epitaxially grown in order. The crystals of those layers do not grow on the growth-blocking film 10 but grow selectively on the n-InP substrate in the gaps between them. In addition, those layers have the largest thickness in the light emitting portion of the wide portion of the growth blocking film 10, and become thinner as the distance from the laser active layer 1 increases in the region where the width of the growth blocking film becomes narrower. The MQW layer has seven 1.4 μm wavelength composition InG
aAsP well layer and 1.13 μm sandwiched between the well layers
The active layer 1 was composed of a barrier layer of m-wavelength composition InGaAsP, the thickness of the well layer was 7 nm, and the thickness of the barrier layer was 15 nm.

After the active layer 1 and the tapered waveguide 2 are collectively formed as described above, the growth stopper film 10 made of a SiO ₂ film is removed with hydrofluoric acid, and the process up to FIG. 8B is completed.

Thereafter, a SiO ₂ film is deposited again on the entire surface,
Next, by a self-alignment process, the SiO ₂ film is left only on the top of the directly formed waveguide, and the S
By removing the iO ₂ film with hydrofluoric acid, a growth stop film 10b for buried growth is formed as shown in FIG. Subsequent steps will be described with reference to FIG.

Next, MOVPE growth is performed again using the growth blocking film 10b as a mask, and the p-InP current blocking layer 3 is 0.7 μm and the n-InP current blocking layer 4 is 0.1 μm.
7 μm are sequentially formed.

Next, the p-InP cladding layer 5 is formed on the entire surface after removing the growth inhibiting film 10b. The p-InP cladding layer 5 is 5 μm thicker than a normal LD structure so that a part of the light field does not reach the electrode due to the increase in the spot size. After the growth of the p-InP cladding layer 5,
The p-InGaAs contact layer 6 is grown to have a structure that makes it easy to make ohmic contact with the electrode.

Subsequently, an SiO ₂ film is formed on the entire surface, and the SiO ₂ film is patterned by a photolithography process to form openings so that current flows only in the active layer 1. After forming the p-electrode 7 and the n-electrode 9 made of TiAu on both surfaces, 430
Electrode alloying at a temperature of ° C. completes the device shown in FIG.

The device was cut out from the wafer with the length of the LD part being 300 μm and the length of the tapered waveguide 2 being 200 μm, and the characteristics were evaluated. FIG. 9 shows the IL characteristics when a high reflection coating of 95% is applied to the end face of the LD section. The threshold current at room temperature was as low as 8 mA, and good oscillation characteristics of 24.5 mA were realized even at 85 ° C. The external differential quantum efficiencies were as good as 0.46 W / A and 0.36 W / A for the cases of 25 ° C. and 85 ° C., respectively.
The driving current at the time of high-temperature operation, which is important as a characteristic of the LD used in the subscriber system, is as low as 56 mA in the case of 11 mW at 85 ° C., for example.

The reason that such excellent oscillation characteristics were obtained is that a steep PL wavelength change was obtained by enlarging the waveguide width, whereby the absorption loss in the tapered waveguide 2 could be greatly reduced. In addition, the mode conversion loss and the scattering loss due to the roughness of the waveguide side wall were not caused by the selective MOVPE.

FIG. 10 shows a far radiation pattern of the element. 12. Horizontal and vertical radiation angles are 10.8 ° and 13.
A narrow value of 5 ° was realized. This is about 1/3 of the emission angle of 35 ° obtained by a normal LD.

FIG. 11 shows the results of a coupling experiment performed with a normal single mode fiber having a spot size of 10 μm. As a minimum coupling loss, 2.7 dB was obtained. The position tolerance at which the coupling loss increases by 1 dB is 1.8.
Good coupling characteristics that can be adequately applied to passive alignment, which is an inexpensive mounting method with μm, are also realized. Considering that the coupling loss obtained by a semiconductor laser having a normal structure having a large mode mismatch with an optical fiber is 10 dB, an improvement of coupling characteristics of 7 dB or more can be realized by the integration of the tapered waveguide 2. Was.

Embodiment 2 FIG. 12 shows an SSC according to the present invention.
-The LD 12 is mounted on a PLC (planar optical circuit) substrate 15 by passive alignment. Passive alignment mounting uses the electrode pattern attached to the device and the PLC
This is a technique for aligning the pattern of the substrate with the substrate by image recognition, thereby arranging the element on the PLC substrate 15. This is a method of coupling the element and the waveguide without adjusting the optical axis, which has been conventionally performed. It is drawing attention as a significant reduction in cost.

A Y-branch 14 is formed on the PLC substrate 15, and the SSC-LD 12 is mounted on one of the Y-branches 14, and the light receiving element 16 is mounted on the other. PL
The coupling loss between the waveguide 13 of the C substrate 15 and the SSC-LD 12 was 4 dB, and the excess loss due to the passive alignment mounting could be suppressed to only 1.3 dB. The semiconductor laser according to the present invention is excellent in high-temperature operation characteristics due to the reduction of the absorption loss in the tapered waveguide 2, so that the temperature control conventionally performed by the semiconductor laser is unnecessary. For this reason, the optical module 17 can be configured at very low cost.

(Embodiment 3) FIG. 13 shows a configuration in which the optical module 17 on which the element of the present invention shown in Embodiment 2 is mounted is adopted in an optical communication system. The head office and the subscriber are connected by one optical fiber 19 through an optical coupler 18 having 8 to 32 branches. Since the present invention makes it possible to realize an inexpensive optical module 17, the total cost of the optical communication system can be reduced.

In the embodiment described above, the laser structure is the Fabry-Perot structure. However, a passive waveguide is provided between the LD portion as the light emitting portion and the tapered waveguide 2, and a DBR laser structure in which a diffraction grating is formed there. It is good. Also, L
A DFB laser structure in which a diffraction grating is formed in the portion D may be used. A DFB laser and a modulator may be formed on the same substrate, and the gap width of the modulator portion may be widened to form a modulator integrated light source that reduces the absorption loss.

Further, in the above-described embodiment, the MQW is
Although it is made of nGaAsP / InP-based material,
AlGaAs / GaAs-based material, AlGaInP / Ga
InP-based materials, ZnSe-based, GaN-based, and other compound semiconductor materials may be used.

[0062]

According to the present invention, since the film thickness and band gap of the active layer of the light emitting portion and the core layer of the passive optical waveguide portion are sharply changed, the portion close to the light emitting region of the passive optical waveguide portion is provided. Absorption loss caused by band-to-band transition can be greatly reduced, laser oscillation with low threshold current and high slope efficiency, excellent high-temperature operation characteristics, reproducibility, uniformity of characteristics, and can be manufactured by a simple process. Further, it is possible to provide a waveguide type semiconductor optical integrated device including an SSC-LD capable of realizing a good coupling loss with a single mode fiber by enlarging an optical spot size.

Further, according to the present invention, etching of a waveguide shape is not required, and a low threshold current and a low threshold current can be obtained by a simple process.
Waveguide-type semiconductor light including SSC-LD that oscillates with high slope efficiency, has excellent high-temperature operation characteristics, reproducibility, and uniformity of characteristics, and realizes good coupling loss with single mode fiber by expanding the light spot size. A method for manufacturing an integrated device can be provided.

Further, according to the present invention, a waveguide-type semiconductor optical integrated device having higher function and higher integration can be realized by combination with another optical functional device.

Further, according to the present invention, the cost of the optical module and the subscriber optical communication system can be reduced.

[Brief description of the drawings]

FIG. 1 is a structural diagram of an SSC-LD according to an embodiment of the present invention.

FIG. 2 is a structural diagram of a conventional SSC-LD.

FIG. 3 is a structural diagram of a selective growth layer for explaining a conventional technique.

FIG. 4 is a sectional view of a selective growth layer for explaining a conventional technique.

FIG. 5 is a cross-sectional view of a selective growth layer for explaining the effect of the present invention.

FIG. 6 is a PL wavelength profile diagram for explaining the effect of the present invention.

FIG. 7 is a PL wavelength profile diagram for explaining the effect of the present invention.

FIG. 8 is a diagram for explaining a manufacturing process of the SSC-LD according to the present invention.

FIG. 9 is a diagram for explaining an embodiment of the present invention.

FIG. 10 is a diagram for explaining an embodiment of the present invention.

FIG. 11 is a diagram for explaining an embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration wp of an optical module for describing an example of the present invention.

FIG. 13 is a diagram showing a configuration of an optical communication system for explaining an embodiment of the present invention.

FIG. 14 is an example of a pattern of a growth blocking film used in the present invention.

FIG. 15 is an example of a pattern of a growth blocking film used in the present invention.

FIG. 16 is an example of a pattern of a growth blocking film used in the present invention.

FIG. 17 is an example of a pattern of a growth blocking film used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 active layer 2 tapered waveguide 3 p-InP current blocking layer 4 n-InP current blocking layer 5 p-InP cladding layer 6 p-InGaAs contact layer 7 p electrode 8 n-InP substrate 9 n electrode 10 growth inhibiting film 11 gap Part 12 SSC-LC 13 waveguide 14 Y branch 15 PLC substrate 16 light receiving element 17 optical module 18 optical coupler 19 optical fiber

Claims (13)

[Claims] 1. A waveguide-type semiconductor optical integrated device including a light emitting section and a passive optical waveguide section, wherein the active layer of the light emitting section has a constant thickness, the active layer width is 5 μm or less, The thickness of the core layer in the waveguide section is modulated in a tapered shape so as to become thinner in the light propagation direction, and the width of the core layer is wider than the active layer width. A waveguide type semiconductor optical integrated device, wherein the core layer of the optical waveguide portion is formed by collective selective growth. 2. The waveguide type semiconductor optical integrated device according to claim 1, wherein the width of the core layer of the passive optical waveguide portion changes in a tapered shape in a region in contact with the active layer of the light emitting portion. . 3. The integrated semiconductor optical device according to claim 1, wherein the active layer of the light emitting section and the core layer of the passive optical waveguide section are quantum well layers. 4. The waveguide type semiconductor optical integrated device according to claim 1, wherein said light emitting section and said passive optical waveguide section are of a buried type. 5. The semiconductor device according to claim 1, further comprising at least one selected from a distributed feedback semiconductor laser, a distributed reflection semiconductor laser, an optical modulator, a photodetector, an optical switch, and an optical waveguide. Waveguide type semiconductor optical integrated device. 6. A pair of stripe-shaped growth inhibiting films used as a mask for selective growth on a semiconductor substrate,
(A) the gap between the growth blocking films in the light emitting portion is 5 μm or less;
The gap between the growth blocking film in the passive optical waveguide is wider than the gap width in the light emitting portion. (B) The width of the growth blocking film in the passive optical waveguide is narrower than the width of the growth blocking film in the light emitting portion, and light propagates. A waveguide-type semiconductor including a step of forming the active layer of the light-emitting portion and a core layer of the passive waveguide in the gap portion of the growth-blocking film by collective selective growth. A method for manufacturing an optical integrated device. 7. The method according to claim 6, wherein the selective growth is performed by selective MOVPE. 8. The selective growth is performed so that the active layer of the light emitting section and the core layer of the passive waveguide have a quantum well structure.
Or a method of manufacturing a waveguide-type semiconductor optical integrated device according to item 7. 9. The waveguide type semiconductor optical device according to claim 1, wherein the side walls of the light guide of the light emitting portion and the passive light guide portion formed by the selective growth have a (111) crystal plane. 10. The waveguide-type semiconductor optical integrated device according to claim 1, wherein the light-emitting portion and the optical waveguide of the passive optical waveguide portion have two or more electrode structures for applying current or voltage. 11. The waveguide type semiconductor optical integrated device according to claim 1, wherein an operating wavelength is 0.3 to 1.7 μm. 12. An optical module comprising at least one waveguide type semiconductor optical integrated device according to claim 1. Description: 13. An optical communication system using at least one waveguide-type semiconductor optical integrated device according to claim 1. Description: