JP3255111B2 - Semiconductor laser and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and a method for manufacturing the same, and a semiconductor optical integrated device, an optical module, and an optical communication system.

[0002]

2. Description of the Related Art In order to reduce the cost of an access optical communication system, it is essential to realize a low-cost optical module. In order to reduce the cost of the optical module, it is considered essential to realize a semiconductor laser having excellent temperature characteristics that does not require the conventional temperature control. In order to reduce the temperature dependence of the threshold current and the drive current, a current constriction structure with a small leakage current even at a high temperature is required. Further reduction of sorting costs
For this purpose , an element structure having excellent in-plane distribution uniformity and reproducibility of oscillation characteristics is required.

Hitherto, a thyristor structure in which p-type and n-type semiconductors are alternately sandwiched has been widely used as a current confinement layer of a semiconductor laser. However, when a leakage current enters the block layer, the thyristor is turned on, and has a disadvantage that the thyristor does not function as a current confinement layer.

It is known that thyristor turn-on can be improved by increasing the n-doping concentration of the block layer or increasing the thickness of the current confinement layer. However, increasing the n-doping concentration causes a decrease in the refractive index, which affects the light propagating in the waveguide, disturbs the field distribution, and reduces the coupling efficiency to the optical fiber or the waveguide. I will. In addition, in order to increase the thickness of the block layer functioning as a current confinement layer, a deep mesa is required for forming a waveguide, and there is a large variation in a mesa-shaped wafer and uniform oscillation characteristics cannot be obtained. There are many.

In order to overcome the problems in the current confinement layer having the thyristor structure, studies have been made on an embedded semiconductor laser using a high-resistance layer as the current confinement layer.

FIG. 2 shows the structure of a conventional semiconductor laser using a high-resistance semiconductor layer. High resistance I on n-InP substrate 3
After growing the nP layer 10 and forming a groove by etching, a double hetero (DH) including an InGaAsP active layer is formed.
The structure is grown, and the active layer 1 is embedded in the trench. At the time of crystal growth, a liquid phase epitaxial growth method (LPE: liquid phase epitaxy) is used, and an active layer is formed in a crescent shape. From this, BC
It is often called a crescent structure. Due to the growth mechanism peculiar to LPE, the active layer 1 does not come into contact with the high-resistance InP layer 10 inside the groove, and effectively narrows the current to realize high-output operation. Furthermore, the introduction of the high-resistance InP layer 10 has the advantage that the parasitic capacitance is reduced and good high-frequency response characteristics can be obtained.

When the high-resistance InP layer 10 is doped with Fe, Fe acts as an acceptor so that injected electrons are captured, but holes are not captured, but recombine with electrons and flow as current. It has been pointed out that the effect of double injection is lost. In order to prevent this, a structure in which an n-type InP layer is inserted between the p-type InP substrate and the high-resistance InP layer to suppress the leakage current has been studied. In the case of an InGaAsP / InP semiconductor laser having a wavelength of 1.3 μm, the maximum is 180 mW. Light output has been reported (H. Hori
kawa et al., Applied Physics Letters, 54, 1989, p.
1077). When the InP substrate is of the n-type, the high-resistance InP layer is originally sandwiched between the n-type InPs, so that it is not necessary to add a new layer.

FIG. 3 shows a high-resistance buried (SI-BH) structure in which a high-resistance InP layer 10 is buried and grown in a double hetero (DH) structure etched by mesa. This structure is a metal organic phase growth method (MOVP
E: Metal organic vapor phase epitaxy), which can be grown, has been actively researched and developed as a powerful embedded structure. The above
Similarly, it has been made an attempt to suppress the leakage current by inserting an n-type InP layer between the high-resistance layer and the p-InP layer and.

[0009]

From the viewpoint of the maximum light output, the BC structure shown in FIG. 2 has obtained better results than the SI-BH structure shown in FIG. This is because the p-type substrate can be used for the BC structure, the contact resistance can be reduced, and the crystallinity of the high-resistance layer is excellent by growing the high-resistance layer on a flat substrate. However, the BC structure can be manufactured only by LPE, and has a disadvantage that it is impossible to increase the area of the wafer. further,
Since an active layer is formed in the V-groove, it is difficult to form a diffraction grating, and a DFB-LD (Distributed-FeedBack-Laser-Diode)
Is difficult to manufacture.

On the other hand, a device structure for improving the light output characteristics of the SI-BH structure is disclosed in Japanese Patent Application Laid-Open No. 60-22199.
No. 7). This is shown in FIG. This element structure is formed as follows. First, n-In
After growing the semi-insulating high-resistance layer 10 on the P substrate 3, the active layer 1
A groove is formed by etching the high-resistance layer in the portion where the layer is grown. Next, an n-InP layer 9 is selectively formed only in the groove, an active layer 1 is grown on the upper portion, an oxide film is removed, and the entire surface is buried with a clad layer 5. Then, a cap layer 6 is formed.

Here, in order to effectively trap the injected electrons in the semi-insulating high-resistance layer 10 and to sufficiently function the high-resistance layer as a current confinement layer, at least 1 μm is required.
m is required. Therefore, it is necessary to selectively grow the active layer 1 in a groove having a step of 1 μm or more.

When an active layer is selectively grown inside the groove, a flat layer structure cannot be obtained because crystals also grow on the side surfaces of the groove. Therefore, in order to obtain an active layer having excellent optical characteristics, it is necessary to form the active layer above the groove as shown in FIG. On the other hand, when forming the active layer on the top of the groove,
Since an n-InP layer 9 having a thickness of 1 μm or more is grown and an active layer is formed thereon, it is easily expected that it is difficult to control the position of the active layer. In particular, when a multiple quantum well (MQW) structure is adopted for the active layer, the photoluminescence spectrum is broadened due to a change in film thickness due to a change in the position of the active layer, and it is extremely difficult to obtain an active layer suitable for a semiconductor laser. Becomes A similar device structure is disclosed in Japanese Patent Application Laid-open Nos.
76089), it is considered that a thick semi-insulating high-resistance layer is required in all structures, and it is extremely difficult to form a good active layer and thereby realize a semiconductor laser having excellent oscillation characteristics. .

Therefore, it has been extremely difficult to stably exhibit excellent characteristics with a semiconductor laser having such a buried structure.

In order to improve the quality of the active layer and the controllability of the film thickness, it is important to reduce the depth of the groove. For that purpose, unlike a semi-insulating high-resistance layer, a current confinement layer that functions sufficiently even with a thin film is required.

References (Japan Journal Applied Physics, Volume 63, p. 1896, 199)
7 years), a 20 nm thick AlAs
A laser structure that oscillates at a wavelength of 1.65 μm using a thin film obtained by oxidizing the above is shown.

FIG. 5 shows this laser structure. This structure has an active layer 1 and an active layer 1 formed on the entire surface of an n-InP substrate 3.
An AlAs layer 23 is provided, and the AlAs layer is selectively oxidized to form a current confinement layer, so that the current is concentrated on the unoxidized AlAs layer . This is because when AlAs is used as a film material for forming the insulating oxide film, As is replaced with O by oxidation to become Al ² O ^X , which shows the electrical characteristics of the insulating film close to alumina. This insulating oxide film does not require a thick film used for a semi-insulating high-resistance layer, and if it has a thickness of several tens of nm, it functions sufficiently as a current confinement layer.

However, in this structure, since the current confinement width is adjusted by changing the oxidation time, there is a problem in the characteristics distribution on the wafer surface and the reproducibility of the characteristics. Further, unlike a normal buried type semiconductor laser, the active layer is continuous in the lateral direction and the current flowing there is only constricted by the insulating oxide film, so that the current confinement is effectively performed. In addition to this, the absorption loss is large in a region where no current is injected, and the threshold current has a high value of ² kA / cm ² .

Accordingly, an object of the present invention is to provide a semiconductor laser having a structure capable of growing a high-quality active layer, thereby oscillating a laser with a low threshold current and a high slope efficiency, and having excellent high-temperature operating characteristics and uniformity of characteristics. Is to provide. Also,
It is an object of the present invention to provide a method for manufacturing such a semiconductor laser with a simple process and with good reproducibility. Another object of the present invention is to realize an inexpensive and high-performance optical module and an optical communication system using the element.

[0019]

According to the present invention, a structure suitable for selective growth is formed by the following means to realize a semiconductor laser having good oscillation characteristics.

According to the present invention, there is provided a semiconductor laser in which the semiconductor active layer is buried by a crystal having a band gap larger than that of the active layer in both the thickness direction and the lateral direction. The constriction layer is formed on the semiconductor substrate
It is formed of an insulating oxide film having a thickness of 0.1 μm or less, and is formed on a semiconductor substrate in a gap between these current confinement layers.
The first conductive type semiconductor layer, the active layer and the second conductive type semiconductor
The present invention relates to a semiconductor laser in which a double hetero structure including a layer is formed .

The present invention also relates to a semiconductor active layer in the thickness direction.
And the band gap is larger than the active layer
Having a structure buried by various crystals, on both sides of the active layer
Current constriction layer formed on the substrate is made of an insulating film
A method of manufacturing a semiconductor laser, comprising: a step of forming a film capable of being insulated on a first conductivity type semiconductor substrate; a step of forming a growth stop film in two adjacent stripes; Etching a non-formed region between the growth inhibiting films to remove at least the insulative film in the region to form a groove; and forming a first conductive type semiconductor layer, a semiconductor active layer, Selectively forming a double hetero structure including a conductive type semiconductor layer in the trench, forming a second conductive type semiconductor layer on the entire surface, and forming the insulative film.
Selectively oxidized and insulated to have a thickness of 0.1 μm or less
The present invention relates to a method for manufacturing a semiconductor laser including at least a step of forming a current confinement layer .

Further, according to the present invention, there is provided a step of forming a film capable of being insulated on a first conductivity type semiconductor substrate, a step of forming a growth stop film in two adjacent stripes, and a step of forming the growth stop film. Etching a region between the growth blocking films which has not been formed, removing at least the insulative film in the region to form a groove, and forming a first conductive type semiconductor layer, a semiconductor active layer, and a second conductive type. Selectively forming a double hetero structure including a type semiconductor layer in the trench, forming a second conductivity type semiconductor layer on the entire surface, and selectively oxidizing the insulable film to insulate it. The present invention relates to a method for manufacturing a semiconductor laser having at least steps.

According to the present invention, there is also provided a semiconductor integrated device having the structure of the semiconductor laser, wherein at least one of a distributed feedback semiconductor laser, a distributed reflection semiconductor laser, an optical modulator, a photodetector, an optical switch, and an optical waveguide is provided. The present invention relates to a semiconductor optical integrated device comprising: The present invention also provides a semiconductor integrated device having the structure of the semiconductor laser,
The semiconductor optical integrated device, wherein the semiconductor active layer and the passive optical waveguide are formed at the same time, and the thickness of the core layer of the passive optical waveguide portion is modulated in a tapered shape along the direction in which light propagates. .

According to the present invention, there is provided a semiconductor integrated device having the structure of the semiconductor laser, wherein the active layer is divided into two or more regions, and an independent electrode is formed in each region. And a semiconductor optical integrated device.

The present invention also relates to an optical module formed by using at least one semiconductor optical integrated device.

The present invention also relates to an optical communication system formed by using a plurality of the optical modules.

In the present invention, the thickness of the current confinement layer needs to be 0.1 μm or less.
0.1 μm is preferable, and 0.02 to 0.05 μm
Is more preferable.

The semiconductor optical integrated device of the present invention preferably has an operating wavelength of 0.3 to 1.7 μm.

[0029]

FIG. 6 shows a basic configuration diagram of an embodiment of the present invention. An insulating film 2 having a thickness of 0.1 μm or less functioning as a current confinement layer is formed on an n-InP substrate 3.
The n-InP layer 9, the active layer 1, and the p-type
The -InP layer 11 is formed in this order. A p-InP clad layer 5 is formed on the entire surface so as to cover the n-InP layer 9, the active layer 1, the p-InP layer 11, and the insulating film 2.

In the present invention, the insulating film 2 is made of Al and Sb.
It is preferable that the crystal comprises at least one of the following.
Further, it is preferable that the insulating film is a layer made of a crystal containing at least one of Al and Sb and insulated by oxidation.

As described above, the current confinement layers formed on both sides of the active layer 1 are composed of an insulating film, and the thickness of the insulating film is 0.1 μm or less, so that the active layer 1 can be effectively formed. Current injection can be performed. Also, when fabricating the element structure of the present invention, unlike the case of fabricating a conventional structure,
Since the etching depth of the portion where the active layer 1 is selectively grown may be small, the controllability of the layer thickness is improved, and a high quality crystal having a desired layer thickness can be formed.
In addition, in the structure of the present invention, the leak path width d which causes a leak current can be extremely narrowed to 0.1 μm or less.

As a result, oscillation characteristics such as a reduction in threshold current and an improvement in slope efficiency can be significantly improved. Note that, for example, when a layer obtained by oxidizing AlAs to be insulated as an insulating film functioning as a current confinement layer is used, the current confinement layer becomes Al ₂ O _X and the refractive index becomes 1.
There is a concern that the film thickness will be close to 5, but the film thickness is 0.1 μm.
If m or less, the effect on light propagating through the active layer is small, and it is considered that scattering loss and coupling loss do not increase.

In one embodiment of the method for manufacturing a semiconductor laser according to the present invention, a crystal layer to be insulated by oxidation is formed on a substrate, and only a portion of the crystal layer immediately below an active layer to be formed later is removed. After the formation of the layer, the crystal layers on both sides thereof are selectively oxidized. Thus, the progress of oxidation of the crystal layer always stops near the active layer from which the crystal layer has been removed. As a result, a narrow current injection region width, which cannot be obtained by the conventional structure, can be formed with good reproducibility. Further, it is not necessary to precisely control the oxidation time, which has been conventionally performed, and it is possible to provide a laser structure having excellent uniformity of oscillation characteristics with good reproducibility.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional structural view of a semiconductor laser according to a first embodiment of the present invention. Active layer 1
Is InG designed to have an oscillation wavelength of 1.3 μm.
It has an MQW structure of aAsP / InGaAsP, and is formed in a portion having a gap width of 1.5 μm. AlAs / In
The insulating film 2 formed by thermally oxidizing the AlAs superlattice layer is
It is formed at a distance of 0.1 μm from the active layer 1 toward the n-InP substrate 3.

A method of manufacturing a semiconductor laser having the structure shown in FIG. 1 will be described with reference to FIG.

First, an AlAs / InAlAs superlattice layer made of 4 cycles of 5 nm thick AlAs and 1 nm thick InAlAs on the (001) plane of the n-InP substrate 3 by gas source MBE (GS-MBE). After growing 24,
An n-InP buffer layer 4 having a thickness of 50 nm is grown.

On this substrate, a thickness of 10 was formed by thermal CVD.
A growth inhibition film 12 made of a 0 nm SiO ₂ film is deposited. Subsequently, by the photolithography process, the selective MOV
A resist pattern used for PE is formed. The growth inhibition film 12 is etched with the diluted hydrofluoric acid, and a substrate used for selective growth is completed (FIG. 7A). The pattern of the growth inhibiting film 12 was formed so that the growth inhibiting film 12 having a width of 50 μm was opposed in the <110> direction, and the width of the gap between the two growth inhibiting films 12 was 1.5 μm. The active layer 1 is selectively formed on the gap.

The AlAs /
In order to remove the InAlAs superlattice layer 24 by etching, the substrate is etched with a mixed solution of hydrogen bromide, hydrogen peroxide and water. This etching is performed to a depth of 80 nm completely penetrating the AlAs / InAlAs superlattice layer 24. In this case, the growth prevention film 12 serves as a mask, and the Al in a portion where this mask is not formed is used.
The As / InAlAs superlattice layer 24 is completely removed (FIG. 7B).

The n-InP layer 9 (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ ) is formed in the gap of the substrate by selective MOVPE.
Is InGaAs having a thickness of 200 nm and a wavelength composition of 1.13 μm.
The first SCH layer made of sP is formed to a thickness of 60 nm and a thickness of 6 n.
MQW active layer 1, 1.13 μm consisting of seven periods of an InGaAsP well layer having a wavelength composition of 1.4 μm and an InGaAsP barrier layer having a thickness of 15 nm and having a composition of 1.13 μm.
A second SCH layer made of InGaAsP having a wavelength composition is formed to a thickness of 60 nm and a p-InP layer 11 (carrier concentration 5 ×
10 ¹⁷ cm ⁻³ ) is epitaxially grown to 100 nm. These crystal layers are not grown on the growth blocking film 12 but are selectively grown on the n-InP substrate 3 in the gap portion where the AlAs / InAlAs superlattice layer 24 is removed (FIG. 7C). .

Growth inhibition film 12 used for selective MOVPE
Is removed with diluted hydrofluoric acid, and a p-InP cladding layer 5 (carrier concentration of 1 × 10 ¹⁸ cm ⁻³ ) is formed on the entire surface to a thickness of 2 μm.
An m, p-InGaAs cap layer 6 is grown to a thickness of 0.3 μm (FIG. 7D).

Subsequently, etching is performed using a mixed solution of hydrogen bromide, aqueous hydrogen peroxide and water as an etchant to form a double mesa having a width of 20 μm centering on the active layer 1. The etching depth is 4 μm, and AlAs / In
The AlAs superlattice layer 24 is completely penetrated (FIG. 7E). The wafer is put into a thermal oxidation furnace and held for 5 hours, and only the AlAs / InAlAs superlattice layer 24 is selectively oxidized to achieve insulation.

Subsequently, an oxide film 7 is formed on the entire surface and is patterned by a photolithography process to form an active layer 1.
The gap is formed so that the current flows only through the MQW layer (FIG. 1). After forming the p-electrode 8 and the n-electrode 13 made of TiAu on both surfaces, the electrodes are alloyed at 430 ° C. to complete the device.

The semiconductor laser was cleaved so as to have a cavity length of 300 μm, and a high reflection coating of 95% was applied to the end face of the semiconductor laser to evaluate the characteristics. The threshold current at room temperature is as low as 3 mA, and 8 mA even at 85 ° C.
And good oscillation characteristics. The external differential quantum efficiency is 25
0.5 W / A for the case of 85 ° C.
It was very good at 0.47 W / A.

Such good oscillation characteristics were obtained because the AlAs / InAlAs superlattice layer 24 disposed near the active layer was insulated by oxidation, so that the leakage current not contributing to the oscillation characteristics was greatly reduced. Because he did. Also, in the current constriction structure using the conventional thyristor, the leakage current increases at high temperatures, which causes a decrease in slope efficiency and a tendency to saturate the optical output. In the structure of the present invention, the current confinement is performed by the insulating film. As a result, no deterioration in characteristics at high temperatures, which was conventionally observed, was observed, and good temperature characteristics were also realized at the same time.

In the manufacturing method of the present invention, the width of the active layer mainly depends on the width of the gap between the growth blocking films. As a result, a very uniform oscillation characteristic of 0.2 mA as the standard deviation of the threshold current distribution and 0.02 W / A as the standard deviation of the slope efficiency distribution could be realized on the entire surface of the 2-inch substrate.

(Embodiment 2) Next, an element (SSC-L) in which a tapered waveguide having a changed waveguide thickness is integrated in the same resonator.
An example in which D) is manufactured will be described. This element structure is shown in FIG. The manufacturing process is almost the same as that of the first embodiment, except that the tapered waveguide portion whose waveguide thickness becomes thinner toward the emission end and the semiconductor laser portion are collectively formed.

The AlAs / InAlAs superlattice layer 24 is formed only in the gap where the MQW active layer 1 and the tapered waveguide layer are formed.
Are removed, and both are collectively formed by selective MOVPE.

FIG. 8 shows the pattern of the growth blocking film 12 used for the selective growth. Semiconductor laser length is 300μ
m, and the length of the tapered waveguide portion was 200 μm. The growth blocking film width in the semiconductor laser portion is 50 μm, and the growth blocking film width in the tapered waveguide portion is 5 μm from 50 μm toward the emission end.
The pattern was narrowed to μm. By adopting a pattern in which the width of the growth blocking film 12 is reduced toward the emission end, a taper structure in which the growth rate of the gap portion is reduced and the thickness of the waveguide becomes thinner toward the emission end is formed. Can be included. Further, since the side surface of the tapered waveguide has a (111) crystal plane, a waveguide having a low scattering loss can be obtained.

After the active layer 1 and the tapered waveguide layer are formed at once, the SSC-
LD can be manufactured. Note that the p-electrode 8 is formed up to the light emitting portion and a part of the tapered waveguide, and has a structure in which current is injected into a part of the tapered waveguide, thereby preventing an increase in absorption loss.

The threshold currents at 25 ° C. and 85 ° C. are 4
A low characteristic of mA and 12 mA was realized. 10 at 85 ° C
The drive current of mW is as low as 40 mA, and an optical module that does not require temperature control can be realized. Due to the integration of the tapered waveguide, the emission angle is 33 ° (‖) of a normal semiconductor laser,
Good coupling characteristics were realized at the same time, with a minimum coupling loss of 1.5 dB with a single mode fiber having a narrow spot size of 10 μm and a diameter as narrow as 35 ° (⊥) to 10 ° (‖, ⊥).

Embodiment 3 An element (EM) in which a distributed feedback semiconductor laser having a diffraction grating and an electroabsorption modulator are integrated
L: modulator integrated light source). This element structure is shown in FIG. The major difference from the first embodiment is that the pattern of the growth blocking film 12 used for the selective MOVPE is different.

FIG. 10 shows a mask pattern used for forming the active layer 1 and the absorbing layer at one time. The active layer and the absorption layer, which are light-emitting portions, are cascaded and formed on the same substrate. The light emitted from the active layer is almost 100% coupled to the absorption layer, and the intensity is modulated by changing the voltage applied to the absorption layer. The absorption layer has an MQW structure like the active layer. The resonator length of the distributed feedback semiconductor laser section was 300 μm, and the length of the modulator section was 200 μm.
The width of the growth blocking film is 50 μm in the distributed feedback semiconductor laser section where the diffraction grating 14 is formed on the substrate, and 30 μm in the modulator section.
m. The active layer 1 and the absorption layer are collectively formed by selective MOVPE in a gap having a width of 1.5 μm. The wavelength shift due to the change in the growth blocking film width was 70 nm, and the wavelength shift was designed to be suitable for an electroabsorption modulator. After the selective MOVPE, an EML was manufactured by the same device manufacturing process as in Example 1.

The EML manufactured according to this example oscillated at a threshold current of 3 mA. The extinction ratio when 2 V was applied to the absorption layer was as good as 20 dB. A good eye opening was obtained even at 2.5 Gb modulation. When a normal fiber transmission experiment of 600 km was performed using the integrated device, a small value of 0.5 dB was obtained as a power penalty.

(Embodiment 4) FIG.
FIG. 2 is a configuration diagram of an optical module in which an SC-LD 17 is passively mounted on a PLC substrate 15. In passive alignment mounting, the electrode pattern attached to the element and the P
By matching the pattern of the LC substrate (Planar Lightwave Circuit) with the image recognition,
This is a technique of connecting the element and the waveguide without adjusting the optical axis, which has been conventionally performed, and greatly reduces the mounting cost. PLC substrate 15
Is formed with a Y-branch waveguide 18, one of which is mounted with an SSC-LD 17 and the other with a light receiving element 19 mounted thereon.

The waveguide 16 of the PLC substrate 15 and the SSC-L
The coupling loss with D17 was 4 dB, and the excess loss due to 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 a reduction in leakage current, so that the temperature control conventionally performed by the semiconductor laser is unnecessary.
For this reason, it has become possible to configure the optical module at very low cost.

(Embodiment 5) FIG. 13 shows a configuration in which the optical module 20 mounted with the element manufactured in Embodiment 4 is adopted in an optical communication system. The head office and each subscriber are connected by one optical fiber 22 through a star coupler 21 having 8 to 32 branches. The present invention makes it possible to realize an inexpensive optical module 20, so that the total cost of the optical communication system can be kept low.

(Other Embodiments) The semiconductor laser of the present invention may have a DBR laser structure in which a semiconductor laser portion and a Bragg waveguide on which a diffraction grating is formed are integrated. Further, a distributed feedback semiconductor laser structure in which a diffraction grating is formed in the semiconductor laser unit may be used.

In the above embodiment, the AlAs / InAlAs superlattice layer is adopted as the layer to be insulated by oxidation, but may be made of AlAsSb or another crystal containing Al or Sb.

Further, in the above embodiment, the MQW is set to In
It is made of GaAsP / InP-based material.
lGaAs / GaAs-based material, AlGaInP / GaI
Other compound semiconductor materials such as an nP-based material, a ZnSe-based material, and a GaN-based material may be used.

The embedded structure according to the present invention has a
The present invention can be applied not only to a single element such as a Perot type semiconductor laser, a semiconductor laser amplifier, and a distributed feedback type semiconductor laser but also to various structures such as a modulator integrated light source and a distributed Bragg reflection type semiconductor laser.

[0063]

According to the present invention, the current confinement layer has a thickness of 0.
Good oscillation characteristics can be realized by employing an insulating thin film of 1 μm or less, particularly a crystalline thin film that can be insulated by thermal oxidation or the like. The current confinement layer made of the insulating thin film can be uniformly and reproducibly arranged in the vicinity of the active layer, so that the width of the current injection region can be controlled with high precision, and the leak path width that causes a leakage current is extremely narrow. And a high quality active layer can be grown. As a result, laser oscillation can be performed with a low threshold current and a high slope efficiency, and a semiconductor laser having excellent high-temperature operation characteristics and uniformity in characteristics can be provided with a simple process with good reproducibility. Also, by using the semiconductor laser of the present invention,
An inexpensive and high-performance optical module and optical communication system can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of one embodiment of a semiconductor laser of the present invention.

FIG. 2 is a structural diagram of a conventional semiconductor laser having a buried crescent (BC) structure.

FIG. 3 is a structural diagram of a conventional semiconductor laser having a high resistance buried (SI-BH) structure.

FIG. 4 is a structural view of a conventional semiconductor laser.

FIG. 5 is a structural view of a conventional semiconductor laser.

FIG. 6 is a diagram showing a basic structure of a semiconductor laser of the present invention.

FIG. 7 is a diagram for explaining a method of manufacturing a semiconductor laser according to the present invention.

FIG. 8 is a view showing a mask pattern used for manufacturing an SSC-LD according to the present invention.

FIG. 9 is a diagram showing a structure of an SSC-LD according to the present invention.

FIG. 10 is a diagram showing a mask pattern used for manufacturing a modulator integrated light source according to the present invention.

FIG. 11 is a diagram showing a structure of a modulator integrated light source according to the present invention.

FIG. 12 is a diagram showing a configuration of an optical module of the present invention.

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

[Explanation of symbols]

 Reference Signs List 1 active layer 2 insulating film 3 n-InP substrate 4 n-InP buffer layer 5 p-InP clad layer 6 p-InGaAs cap layer 7 oxide film 8 p electrode 9 n-InP layer 10 high resistance layer 11 p-InP layer 12 Growth blocking film 13 n electrode 14 diffraction grating 15 PLC substrate 16 waveguide 17 SSC-LD 18 Y branch waveguide 19 light receiving element 20 optical module 21 star coupler 22 optical fiber 23 AlAs layer 24 AlAs / InAlAs super lattice layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-75009 (JP, A) JP-A-1-220492 (JP, A) JP-A-63-120491 (JP, A) JP-A-9-09 186400 (JP, A) JP-A-9-223842 (JP, A) JP-A-8-37341 (JP, A) JP-A-5-114767 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A semiconductor active layer has a structure in which the semiconductor active layer is buried with crystals having a band gap larger than that of the active layer in both the thickness direction and the lateral direction, and a current confinement layer formed on both sides of the active layer is insulated. A method of manufacturing a semiconductor laser comprising a film, comprising: forming a film capable of being insulated on a first conductivity type semiconductor substrate; and forming a growth inhibiting film in two adjacent stripes. Forming a groove by etching a region between the growth blocking films where the growth blocking film is not formed, and removing at least the insulative film in the region, forming a groove; A semiconductor active layer, a step of selectively forming a double hetero structure including a second conductivity type semiconductor layer in the trench, a step of forming a second conductivity type semiconductor layer over the entire surface, and selectively forming the insulable film. Oxidized to insulation and thickness A method for manufacturing a semiconductor laser, comprising at least a step of forming the current confinement layer having a thickness of 0.1 μm or less. 2. A step of forming a film capable of being insulated on a first conductivity type semiconductor substrate, a step of forming a growth inhibiting film in two adjacent stripes, and wherein the growth inhibiting film is not formed. Etching a region between the growth inhibiting films to remove at least the insulative film in the region to form a groove; a first conductive semiconductor layer, a semiconductor active layer, and a second conductive semiconductor layer Selectively forming a double hetero structure in the trench portion, forming a second conductivity type semiconductor layer on the entire surface, and selectively oxidizing the insulable film to insulate it. A method for manufacturing a semiconductor laser, comprising: Wherein said insulated available film, Al and at least a semiconductor laser manufacturing method according to claim 1 or 2, wherein comprising a crystal containing one of Sb. Wherein after the step of growing a second conductivity type semiconductor layer on the entire surface, a semiconductor laser manufacturing method according to claim 1, wherein a step of forming a Daburumesa about said semiconductor active layer.