JPH06196809A - Semiconductor optical device and manufacture thereof - Google Patents

Abstract

(57) [Summary] [Object] To obtain a semiconductor laser having an active layer formed on a flat surface having no step and having a thin laser emitting end face side and a thick laser inside and a manufacturing method thereof. [Structure] Two stripe-shaped SiO 2 films 9 are formed in parallel on a GaAs substrate 1 in a region located inside a laser resonator formed on the GaAs substrate 1 at regular intervals. The AlGaAs cladding layer 2a is formed by the layer-epitaxy mode metal-organic vapor phase epitaxy method, and then the normal mode metal-organic vapor phase epitaxy method A
lGaAs active layers 30a (near the end faces) and 30b (inside the laser) are formed, and further, AlGaAs clad layers 4a and 4a are formed by metal-organic vapor phase epitaxy in the atomic layer epitaxy mode.
The GaAs clad layer 5a is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device and a method for manufacturing the same, and more particularly to improvements in a semiconductor laser, a semiconductor laser with an optical modulator, and a method for growing a semiconductor growth layer in a superluminescent diode. Is.

[0002]

2. Description of the Related Art When a predetermined region on a semiconductor substrate is covered with a SiO2 film or a SiN film and the semiconductor layer is epitaxially grown by a metal organic chemical vapor deposition method in this state, the source gas supplied onto the semiconductor substrate is heated on the substrate. The raw material gas which is decomposed and epitaxially grown as it is, and is supplied onto the SiO2 film (or SiN film) does not react on the SiO2 film,
It diffuses on the film (or SiN film) and moves to a portion where the semiconductor substrate is exposed, and is thermally decomposed on the semiconductor substrate to epitaxially grow. Due to such a property, the growth rate of the semiconductor layer is different between the position near the SiO2 film and the SiN film on the semiconductor substrate and the position apart from the SiN film, and a difference in the layer thickness of the semiconductor layer occurs. It is known that regions having different band gaps are formed in a growing semiconductor layer because of different crystal compositions. Conventionally, the element structure in a semiconductor optical device, that is, the layer thickness and composition of a semiconductor layer grown on a substrate have been controlled by utilizing the above phenomenon.

FIG. 12 shows SiO2 utilizing the above characteristics.
Produced by epitaxially growing an AlGaAs layer and a GaAs layer on a GaAs substrate with a film.
FIG. 3 is an exploded perspective view showing a structure of a conventional semiconductor laser disclosed in Japanese Patent Laid-Open Publication No. JP-A-2003-242, where A in the drawing shows a state after epitaxy growth, and B in the drawing are formed in parallel with each other on a semiconductor substrate at regular intervals. Two striped SiO2 films 9
The grown portion that has undergone crystal growth during the period, that is, the portion that is inside the laser chip is taken out and shown. In the figure, 1 is a GaAs substrate, 2 is an Alx Ga1-x As clad layer (0 <x <1), and 3a and 3b are Alz Ga1-z As.
Active layers (0 <z <1, x> z), 4 are Alx Ga1-x A
s clad layer (0 <x <1), 5 is a GaAs contact layer, and 9 is a SiO2 film. As you can see from this figure,
The thickness of the AlzGa1-z As active layer 3b grown inside the laser chip is Alz grown near the end face of the laser chip.
It can be seen that it is thicker than that of the Ga1-z As active layer 3a.

FIG. 13 is a perspective view showing a GaAs substrate with an SiO2 film used in manufacturing the semiconductor laser shown in FIG. 12, and in the drawing, 10 is a stripe on the surface of the GaAs substrate 1 sandwiched by the SiO2 films 9. It is a department.

The manufacturing process will be described below. As shown in FIG. 13, the SiO2 film 9 is formed in the vicinity of both end surfaces of the substrate and in the central stripe portion 10. Such SiO
2 When an AlGaAs layer and a GaAs layer are grown on a GaAs substrate with a film by using the low pressure metal organic vapor phase epitaxy,
As described above, AlGaAs and GaAs grow on the exposed portion of the GaAs substrate 1, but the SiO2 film 9
Does not grow up. That is, of the trimethylgallium, trimethylaluminum, and arsine supplied in the gas state, those directly supplied to the surface of the GaAs substrate 1 are:
It is thermally decomposed as it is and epitaxially grown, but Ga
Trimethylgallium, trimethylaluminum, and arsine supplied to the surface of the SiO2 film 9 on the As substrate 1 do not grow epitaxially on the SiO2 film 9, and GaAs
The substrate 1 is moved to the exposed portion, and epitaxial growth is performed there. Therefore, the surface of the GaAs substrate 1 slightly separated from the SiO2 film 9, that is, the stripe portion 1 is more than the surface of the GaAs substrate 1 sufficiently separated from the SiO2 film 9.
The amount of gallium (Ga), aluminum (Al), and arsenic (As) contributing to epitaxial growth on the 0 surface increases, and the growth rate increases accordingly. And
Due to this difference in growth rate, the thickness of the active layer is thin near the end face and thick inside the laser chip.

Next, the reason why the active layer of this semiconductor laser is thin near the end face and thick inside the laser chip will be described. From the viewpoint of high-power operation and life of the laser, it is advantageous to reduce the thickness of the active layer. That is, AlGa
In a semiconductor laser using an As-based material or an AlGaInP-based material, the generated laser light is absorbed near the end face and generates heat during high-power operation, and the end face of the active layer is exposed to the Catastr
There is a case where the laser emitting end face is destroyed due to damage called ophic optical damage (hereinafter referred to as COD). On the other hand, the layer thickness of the active layer near the end face is thinned to about 0.03 μm. By doing so, the amount of light that leaks from the active layer to the cladding layers 2 and 4 increases, the emission spot on the end face increases, the light density on the end face of the laser decreases, end face destruction is suppressed, and high output operation becomes possible. You can Also in the life test, it is known that when the thickness of the active layer near the end face is reduced to reduce the light density of the end face, the end face deterioration mode is suppressed and the life becomes long. On the other hand, the oscillation threshold current of the laser largely changes depending on the layer thickness of the active layer, and normally the layer thickness of the active layer is less than 0.
The oscillation threshold current becomes the lowest when it is set to about 1 μm. Therefore, if the thickness of the active layer is reduced to about 0.03 μm, the oscillation threshold current will increase. Therefore, from such a point, in the semiconductor laser, the layer thickness of the active layer is thinned to about 0.03 μm near the end face and 0.1 μm inside the chip.
The thickness is moderately increased to obtain low threshold and high output characteristics.
The layer thickness of the active layer near the end face is 0.1 μm to 0.03 μm.
By reducing the thickness to μm, the full angle at half maximum in the direction perpendicular to the joining of the radiation beams is narrowed from 40 ° to about 16 °, and there is also an advantage that a narrow radiation beam can be obtained.

On the other hand, FIG. 14 shows a fiber gyro and an OT.
Non-excitation absorption, which is a type of conventional super luminescent diode (hereinafter referred to as SLD) used as a light source in the optical measurement field of DR (Optical Time-Domain Reflectometry) and a light source of LAN (Local Area Network) It is a figure which shows the structure of type | mold SLD, FIG.14 (a) is the cross-sectional schematic diagram, FIG.14 (b) is the upper surface schematic diagram. In the figure, 101 is an n-type GaAs substrate, 102 is an n-type AlGaAs cladding layer having an Al composition ratio of 0.48, and 103 is Al.
AlGaAs active layer with a composition ratio of 0.05, 104 is Al
P-type AlGaAs cladding layer having a composition ratio of 0.48, 10
5 is an n-type GaAs cap layer, 106 is an n-side electrode, 10
7 is a P-side electrode, 108 is a Zn diffusion P-type region (excitation region), 109 is a non-injection region (non-excitation region), 111 is a front end face, and 112 is a rear end face.

Next, the operation will be described. The Zn diffusion P-type region 108 is a current injection region, and when a current is injected into the Zn diffusion P-type region 108, the Zn diffusion P-type region 10
8 is the excitation region, and the other regions are the non-excitation regions. Then, it is generated in the excitation region 108, and the rear end surface 112 of the resonator is generated.
The light propagating toward the excitation region 10 is absorbed while passing through the non-excitation region 109, is reflected by the rear end surface 112, and is excited by the excitation region 10.
The intensity of the light that re-enters 8 is reduced. As a result, the effective reflectance is reduced, oscillation in the Fabry-Perot mode is suppressed, and light with a broad spectrum width required for optical measurement or the like is emitted without laser oscillation.

[0009]

In the conventional semiconductor laser shown in FIG. 12, the semiconductor layer is formed under reduced pressure metal-organic vapor phase epitaxy with the SiO2 film 9 formed in a predetermined region on the semiconductor substrate 1 as described above. By epitaxially growing using the method, the layer thickness of the active layer 3 in the semiconductor layer obtained is
Although it was made thin at the end face and thick inside the chip, a layer thickness difference is formed over the entire semiconductor layer that grows during this epitaxial growth, so that not only the active layer but also the clad layer has an end face and a chip. A layer thickness difference is formed between the inside and the inside. For example, the layer thickness of the active layer 3 inside the chip is 0.1 μm, and the layer thickness of the active layer near the end face is 0.03 μm.
When grown under such conditions, the lower clad layer 2 has a layer thickness of 1.5 μm inside the chip and a layer thickness of 0.45 μm near the end face, and a large step is formed in the formed layer. It Therefore, the active layer 3 grows on the lower clad layer 2 having such a step, and the step is formed on the active layer 3 itself, so that the laser beam is distorted downward and emitted. There was a problem. Further, since light is guided in the stepped active layer, there is a problem that a loss occurs at the step.

On the other hand, the conventional super luminescent diode shown in FIG. 14 has a problem that it cannot absorb light sufficiently at the time of high output and laser oscillation occurs, so that a broad emission spectrum cannot be obtained. It was Moreover, since the width of the emission spectrum is limited by the composition of the active layer,
There is a problem that it is difficult to realize a very broad spectrum width required by OTDR or the like.

The present invention has been made to solve the above problems, and a semiconductor laser capable of producing a layer thickness difference only in a desired layer among semiconductor layers formed on a substrate and a semiconductor laser thereof. The purpose is to obtain a manufacturing method.

Further, another object of the present invention is to collectively form a semiconductor laser and an optical modulator by epitaxially growing a semiconductor layer on the semiconductor substrate on which the SiN film and the SiO2 film are partially formed as described above. It is an object of the present invention to obtain a modulator-equipped semiconductor laser and a method of manufacturing the same, in which a step difference between the optical modulator and the semiconductor laser can be made smaller than that of the conventional semiconductor laser.

Further, another object of the present invention is to provide an SLD and a method for manufacturing the same which can obtain a broad spectrum without lasing even at a high output and can realize a very broad spectrum width as compared with the conventional one. The purpose is to get.

[0014]

A semiconductor laser and a method of manufacturing the same according to the present invention include a semiconductor layer formed by a metal organic chemical vapor deposition method on a semiconductor substrate having a SiO2 film or a SiN film partially formed on the surface thereof. When epitaxial growth is performed, a layer that does not cause a layer thickness difference in the layer is grown in the atomic layer epitaxy mode (hereinafter referred to as ALE mode), and the layer thickness difference is generated in the layer. The growth of the layer for which is desired is performed in a normal growth mode in which a plurality of source gases forming the semiconductor layer are mixed and supplied.

Further, in the semiconductor laser and the method for manufacturing the same according to the present invention, only the active layer is grown in the normal growth mode of the above-mentioned metal organic chemical vapor deposition method, and the layer disposed below the active layer is formed of the metal organic metal. It is designed to grow in the ALE mode of the vapor phase growth method.

Further, in the DFB laser and the method for manufacturing the same according to the present invention, only the optical guide layer formed on the active layer is grown in the normal growth mode of the above-mentioned metal organic chemical vapor deposition method to obtain the active layer and the active layer. Each layer formed below the layer is grown in the ALE mode of the metal organic chemical vapor deposition method.

Further, according to the present invention, there is provided a semiconductor laser with an optical modulator and a method for manufacturing the same. When the optical modulator and the semiconductor laser are collectively formed by epitaxy growth, the optical guide layer disposed below the active layer is grown in the ALE mode of the metal-organic chemical vapor deposition method. The layers other than the guide layer are grown in the normal growth mode of the metal organic chemical vapor deposition method.

Further, in the SLD and the manufacturing method thereof according to the present invention, a SiO2 film or a Si film is formed on a semiconductor substrate in a predetermined region on the rear end face side of a resonator formed on the semiconductor substrate.
After the N film is partially formed, a semiconductor layer including an active layer is epitaxially grown by a metal organic chemical vapor deposition method to form a large bandgap on the light emitting surface side of the active layer in the light propagation direction, and the rear end surface is formed. The side has a small band gap, and a current injection region, that is, an excitation region is formed above the active layer portion where the band gap is increased.

[0019]

According to the present invention, the growth of the layer in which the layer thickness difference is desired is grown by the ordinary metal organic vapor phase method, and the layer in which the layer thickness difference is not desired is controlled by the organic metal vapor deposition method. Since the growth is performed in the ALE mode of the metal vapor phase epitaxy method, a layer thickness difference can be generated only in a desired layer among the semiconductor layers epitaxially grown on the semiconductor substrate.

Further, in the present invention, a layer thickness difference is generated in the active layer, and the active layer and the layer disposed below the active layer are formed to have a uniform layer thickness. Without being formed, it is possible to prevent the distortion and loss of the laser beam from increasing.

Further, in the present invention, since the layer thickness difference is generated only in the optical guide layer of the DFB laser and the layers other than the optical guide layer are formed to have a uniform layer thickness, the active layer is formed on the step. It is possible to prevent the distortion and loss of the laser beam from increasing without being formed, and in addition, since the distance between the diffraction grating and the active layer is large in the thick part of the optical guide layer, the light guided through the active layer is Since the degree of coupling between the diffraction grating and the diffraction grating is weak, and the distance between the diffraction grating and the active layer is large, the degree of coupling between the light guided through the active layer and the diffraction grating becomes strong in the thin portion of the light guide layer. The light intensity distribution in the laser chip can be made uniform by adjusting the portion where the layer thickness of the light guide layer is changed.

Further, according to the present invention, since the light guide layer of the semiconductor laser with an optical modulator can be formed to have a uniform layer thickness, the step difference at the coupling portion between the semiconductor laser and the optical modulator is reduced and the light is propagated to the modulator. The coupling loss of the generated light can be reduced.

Further, in the present invention, since the relatively large band gap portion and the relatively small band gap portion are formed in the active layer of the SLD along the cavity direction, the band gap of the non-excitation region is set to the excitation region. It can be made larger than that, and the absorption of light in the non-excitation region becomes large,
The effective reflectance can be reduced, and as a result, laser oscillation can be suppressed and a broad emission spectrum can be obtained.

[0024]

EXAMPLES Example 1. FIG. 3 is an exploded perspective view showing the structure of the semiconductor laser according to the first embodiment of the present invention, in which A in the drawing shows a state after epitaxial growth and B in the drawing is
This shows the portion grown on the surface of the substrate sandwiched by the two SiO2 films 9, that is, the inside of the laser chip. In the figure, the same reference numerals as those in FIG. 12 denote the same or corresponding portions, and 2a denotes an Alx Ga1-x As clad layer (0 <x <
1), 4a is Alx Ga1-x As clad layer, 5a is G
aAs contact layer, 30a and 30b are Alz Ga1-z
As active layer (0 <z <1, z <x). As can be seen from the figure, in this semiconductor laser, the active layer 30b grown inside the laser chip is formed to have a larger layer thickness than the active layer 30a grown near the end face of the laser chip,
Other layers, that is, the cladding layers 2a and 4a and the contact layer 5
a is formed in a uniform layer thickness in the entire laser chip.

Next, the manufacturing process will be described. First, the difference in the growth mechanism between the ordinary metal-organic chemical vapor deposition method and the ALE mode metal-organic chemical vapor deposition method will be described by taking GaAs growth as an example. In normal metal organic vapor phase epitaxy,
Trimethylgallium (hereinafter referred to as TMG), which is a raw material of Ga, and arsine (AsH3), which is a raw material of As, are simultaneously sent to the reaction chamber, and Ga and As are deposited on the GaAs substrate by a thermal decomposition reaction in the reaction chamber. At the same time, they are deposited and crystal growth proceeds. On the other hand, in the ALE mode metal organic chemical vapor deposition method, as shown in FIG. 1, TMG, H2, AsH3
Are intermittently and alternately supplied into the reaction chamber, and when the pressure, temperature, etc. in the reaction chamber at this time are set within a predetermined range, As atoms and Ga atoms are alternately adsorbed to the GaAs substrate 1a one atomic layer at a time. To go. FIG. 2 schematically shows this state, in which AsH3 is first supplied, and only one atomic layer of As atoms is adsorbed on the GaAs substrate 1a, and then H2 is supplied to leave AsH3 remaining near the substrate 1a. Then, when TMG is supplied, Ga is adsorbed to form an atomic layer of Ga on the atomic layer of As atoms previously formed by adsorbing As atoms. Then, this process is repeated and crystal growth proceeds.

Here, SiO is formed on a part of the GaAs substrate 1a.
If a 2 film or SiN film is formed, GaAs
Ga atoms and As atoms are alternately adsorbed by one atomic layer in the exposed portion, but neither Ga atom nor As atom is adsorbed on the SiO2 film or SiN film, and only the exposed portion of GaA. The crystal growth proceeds. At this time, in the portion where GaAs is exposed, the growth proceeds in the same manner one atomic layer at a portion near or away from the SiO2 film or SiN film, so that it is separated from the vicinity of the SiO2 film or SiN film. There is no difference in the layer thickness between the crystal layers grown in the raised portion. This is except during the formation of one atomic layer
This is because the material gas, that is, TMG and AsH3, is blown off from the substrate.

In manufacturing the semiconductor laser of this embodiment shown in FIG. 3, the same Si as the conventional one shown in FIG. 14 is used.
On the GaAs substrate 1 with the O2 film 9, first, the lower clad layer 2a is crystallized to be flat by the ALE mode metal-organic vapor phase epitaxy method, and then the active layer 30a (near the end face) is formed by the ordinary metal vapor phase epitaxy method. ), 30b (inside the laser). In this ordinary metal vapor deposition method, as described above,
Since the amount of the raw material gas that contributes to the reaction is different between the portion close to the SiO2 film 9 and the portion distant from the SiO2 film 9, the layer thickness near the end face of the laser chip, that is, the layer thickness of the active layer 30a becomes thin and the layer of the active layer 30b becomes thin. The thickness becomes thicker. Then, after this, the upper clad layer 4a and the contact layer 5a are crystal-grown by the ALE mode metal-organic vapor phase epitaxy.

As described above, in the manufacturing process of the semiconductor laser of this embodiment, the lower cladding layer 2a is flatly crystallized by the ALE mode metal-organic vapor phase epitaxy, and then the active layer 30a is formed.
Since (30b) is crystal-grown by the normal metal vapor deposition method, the active layer 30a (30b) can be formed on the flat surface with a desired layer thickness difference, and the active layers 30a, 3
The loss of light guided through 0b is reduced, and the laser beam is also emitted downward without distortion. Further, since the upper clad layer 4a and the contact layer 5a are also grown in the layers without causing a layer thickness difference, the flatness of the entire laser chip is excellent, and post-processes such as formation of electrodes can be performed easily and accurately. be able to.

In the above embodiment, the upper clad layer 4a,
Although the contact layer 5a was grown in the ALE mode, the growth of the contact layer 5a by a normal metal vapor phase epitaxy does not significantly affect the laser characteristics.

Example 2. In the first embodiment, the active layer 3
Although 0a and 30b are composed of one AlGaAs layer, this active layer may be composed of an AlGaAs-based multiple quantum well layer in which GaAs layers and AlGaAs layers are alternately formed by a normal metal organic chemical vapor deposition method. In this case as well, only the active layer can have a desired film thickness difference, the same effect as in the first embodiment can be obtained, and in this case, the layer thickness of the multiple quantum well layer becomes thin near the end face. Equivalently, the band cap near the end face becomes large, and there is no such thing as absorbing the light generated inside the chip.
A window structure is formed, and as a result, the effect of preventing end face deterioration and COD can be further improved.

Example 3. FIG. 4 is a sectional perspective view for each step showing a manufacturing process of a semiconductor laser with an optical modulator according to a third embodiment of the present invention. In the figure, 11 is an InP substrate, 12 is an InGaAsP optical guide layer, and 13 is InGa.
As / InGaAsP multiple quantum well active layer, 14 is In
The upper cladding layer of P, 19 is a diffraction grating, and 20 is a SiN2 film. The region where the diffraction grating 19 and the SiN2 film 20 are formed on the InP substrate 11 in FIG. 4 (a) is the region where the semiconductor laser is formed, and the region in front of which nothing is formed is the optical modulator. Is a region where is formed.

FIG. 5 is a schematic side view showing the structure of a semiconductor laser with an optical modulator manufactured through the manufacturing process shown in FIG. 4. In the figure, the same reference numerals as in FIG. 4 indicate the same or corresponding portions. , 15 are InGaAsP cap layers, 16
Is a light modulator electrode, 17 is a semiconductor laser electrode, and 18 is a groove for separating the light modulator and the semiconductor laser.

The manufacturing process will be described below. First, FIG.
As shown in (a), a diffraction grating 19 is formed in a part of a region on the InP substrate 11 where a semiconductor laser is to be formed, and further,
A SiN2 film 20 is formed so as to sandwich the diffraction grating 19. Next, as shown in FIG. 4 (b), the InGaAsP optical guide layer 12 is flatly grown by the ALE mode metal-organic vapor phase epitaxy method, and then InGaAs / InGaAsP is grown by the ordinary metal-organic vapor phase epitaxy method. The multiple quantum well active layer 13 and the InP upper cladding layer 14 are crystal-grown. Then, after this, InGaAs on the InP upper clad layer 14 is formed.
After crystal growth of the P cap layer by the ALE mode metal-organic vapor phase epitaxy method or the usual metal-organic vapor phase epitaxy method,
A predetermined portion of this is removed to form a separation groove 18, and electrodes 16 and 1 are formed on the InGaAsP cap layer 15a on the optical modulator side and the InGaAsP cap layer 15b on the semiconductor laser side.
7 is formed, the InGaAs / InGaA shown in FIG.
The optical modulator side of the sP multiple quantum well active layer 13 is thin and the semiconductor laser side is thick, and the band gap of the multiple quantum well active layer 13 on the optical modulator side is smaller than the band gap of the multiple quantum well active layer 13 on the laser side. It is possible to obtain a semiconductor laser with an optical modulator, which is capable of modulating the increased light generated by the optical modulator on the semiconductor laser side without absorption loss.

As described above, in the manufacturing process of the semiconductor laser with an optical modulator of the present embodiment, the InGaAsP optical guide layer 12 is crystal-grown by the ALE mode metal-organic vapor phase epitaxy.
InGaAs / InGaAsP multiple quantum well active layer 1
3, since the InP upper clad layer 14 is crystal-grown by the usual metal organic chemical vapor deposition method, as shown in FIG.
When the nGaAsP optical guide layer 12 is grown, the InP substrate 1
The growth rate in the region close to the SiN2 film 20 on 1 and the region apart from the SiN2 film 20 is almost the same, and the InGaAsP optical guide layer 12
Grows flat in the layer without causing a layer thickness difference, and
nGaAs / InGaAsP multiple quantum well active layer 13,
During the growth of the InP upper clad layer 14, the region near the SiO2 film 20 has a higher growth rate than the region away from the SiO2 film 20, and these layers are formed thin on the optical modulator side and thick on the semiconductor laser side. It Therefore, conventionally, in this type of semiconductor laser with an optical modulator, the crystal growth of the semiconductor layer on the substrate has always been performed by using the ordinary metal organic chemical vapor deposition method. Therefore, as shown in FIG. In addition to the layer thickness difference formed in the light guide layer 12 and the active layer 13 formed on the step, a coupling loss occurs when the light generated in the laser section is propagated to the optical modulator section. However, the semiconductor laser with an optical modulator according to the present embodiment can solve such a problem. Although the active layer is formed in the multiple quantum well structure in the above-mentioned embodiment, the same effect as that in the above-mentioned embodiment can be obtained when the active layer is formed of a normal single layer.

Example 4. FIG. 7 is a sectional view showing the structure of a distributed feedback semiconductor laser (hereinafter referred to as a DFB laser) according to the fourth embodiment of the present invention.
1 is a GaAs substrate, 22 is an AlGaAs cladding layer, 2
3 is an AlGaAs active layer, 24 is an AlGaAs optical guide layer, 25 is a GaAs contact layer, 26 is a diffraction grating, 2
Reference numeral 7 is a laser emitting end face coated with a non-reflective coating, and 28 is a back face coated with a high reflectance. The above Al
The GaAs light guide layer 24 is formed thin on the laser emission end face 27 side and thick on the back face 28 side.

This DFB laser is provided in a predetermined region on the side corresponding to the rear end face side of the laser resonator on the GaAs substrate 21,
Similar to the GaAs substrate 11 shown in FIG. 4, two stripe-shaped SiO2 films are formed in parallel with each other at regular intervals along the light guiding direction of the resonator, and then the GaAs is formed.
An AlGaAs clad layer 22 and an AlGaAs active layer 23 are formed on the substrate 21 by ALE mode metal organic chemical vapor deposition.
To a uniform layer thickness, and then an AlGaAs optical guide layer 24 is formed by a normal metal organic chemical vapor deposition method. After that, GaA is formed by an ALE mode metal organic chemical vapor deposition method.
The s contact layer 25 is formed to have a uniform layer thickness.

On the other hand, FIG. 8 is a sectional view showing the structure of a conventional DFB laser. In the figure, the same reference numerals as those in FIG. 7 indicate the same or corresponding portions, and this conventional DFB laser is formed on a GaAs substrate 21. All the layers are formed by a normal metal organic chemical vapor deposition method without forming the SiO2 film as described above, and each layer is formed to have a uniform layer thickness. Generally, in a DFB laser, the intensity distribution of light in the laser chip changes depending on the strength of the coupling between the light propagating in the active layer and the diffraction grating. Since one end surface is originally coated non-reflective and the other end is coated with high reflectance, the light intensity distribution in the axial direction in the laser chip is not uniform, which deteriorates the laser characteristics.

D of this embodiment formed as described above
In the FB laser, the thick portion 24 of the light guide layer 24
In a, since the distance between the diffraction grating 26 and the active layer 23 is large, the degree of coupling between the light and the diffraction grating is weak and the light guide layer 2
In the thin portion 24b of No. 4, since the distance between the diffraction grating 26 and the active layer 23 is short, the degree of coupling between light and the diffraction grating is strong, and the degree of coupling between the light propagating in the active layer and the diffraction grating is large. It will change locally. Therefore, by adjusting the degree of change in the layer thickness of the light guide layer 24, the light distribution in the laser chip can be made uniform and the laser characteristics can be improved.

In the first to fourth examples, the ALE mode growth was performed when the layer thickness difference was not made. However, by increasing the pressure in the reaction tube in the normal growth mode, this layer thickness is increased. You can grow without any difference, and the effect is AL
Although a little inferior to the growth by the E mode, almost the same effect can be expected.

Example 5. 9A and 9B are views showing the structure of an SLD according to a fifth embodiment of the present invention, FIG. 9A being a schematic sectional view and FIG. 9B being a schematic top view. In addition, FIG.
FIG. 10A is a sectional view for each step showing the manufacturing process of the SLD shown in FIG. 9. In these figures, 31 is an n-type GaAs substrate,
32 is an n-type AlGaAs clad layer having an Al composition ratio of 0.48, and 33 is a GaAs layer and an AlG having an Al composition ratio of 0.2.
GaAs / AlGaAs multiple quantum well active layer composed of aAs layer, 34 is P-type AlGaA with Al composition ratio of 0.48
s clad layer, 35 n-type GaAs cap layer, 36 n-side electrode, 37 P-side electrode, 38 Zn diffused P-type region (excitation region), 39 ridge, 40 SiO2 film, 41
Is a light emitting end face, 42 is a rear end face, and 43 is a non-injection region (non-excitation region). Here, the layer thickness of the GaAs well layer 33a of the GaAs / AlGaAs multiple quantum well active layer is relatively thicker in the region B in the figure than in the region A.

The manufacturing process will be described below. First, FIG.
As shown in (a), after the SiO2 film is formed on the n-type substrate 31, the SiO 2 film is formed by an ordinary photolithography and etching technique.
By removing a predetermined portion of the iO2 film, a rectangular SiO2 film 40 of about 200 μm × 300 μm is formed at a distance of about 200 μm in a predetermined region on the rear end face side with respect to the light emitting end face.
011> direction. Next, as shown in FIG. 10 (b), the n-type cladding layer 32 and the multiple quantum well active layer 3 are formed.
The 3, P-type clad layer 34 and the n-type GaAs cap layer 35 are formed in this order by metal organic chemical vapor deposition.
At this time, in the region B sandwiched by the SiO2 film 40, SiO
2 The reaction raw material reaching the film 40 diffuses from the SiO2 film 40 to the surface of the n-type substrate 31 and contributes to the growth.
The layer thickness of each growth layer is relatively thicker than in the region A where the iO2 film 40 is not provided. Assuming that the layer thickness of the layer grown in the region B of the GaAs well layer 33a in the GaAs / AlGaAs multiple quantum well active layer is about 50% thicker than the layer thickness of the layer grown in the region A. If the layer thickness is 40 Å, the region B has a layer thickness of about 60 Å.

Next, as shown in FIG. 10C, Zn is selectively diffused into a striped region having a width of about 6 μm along the <110> direction on the upper surface of the n-type GaAs cap layer 35, A Zn-diffused P-type region 38 whose bottom is diffused to a depth reaching the P-type AlGaAs cladding layer 4 is formed. Here, the diffusion region 38 is formed to have a length from a position about 300 μm away from the end of the region B on the rear end face side to the end of the region A on the light emission face side. Next, as shown in FIG. 10D, the Zn diffusion P-type region 38 formed in the above step has a thickness of 3 μm.
The n-type GaAs cap layer 35 is selectively removed by etching so as to form a stripe-shaped ridge 39 having a width of about the same, and the P-type cladding layer 34 is further etched to a predetermined depth. Then, after this, the P-side electrode 3 is formed on the ridge 39.
7. When the n-side electrode 36 is formed on the back surface of the substrate, the SLD shown in FIG. 9 is obtained.

Next, the operation will be described. As described above, the GaAs / AlGaAs multiple quantum well active layer 33
The thickness of the GaAs well layer 33a is thicker in the region B than in the region A. When the layer thickness of the region A is 40 angstroms, the region B becomes 60 angstroms. The effective bandgap of the quantum well layer depends on the layer thickness of the well layer, and the bandgap of the active layer in the GaAs / AlGaAs multiple quantum well active layer 33 in the regions A and B is
In each region A, Eg1 = 1.53 eV (wavelength 810
in the region B, Eg2 = 1.49 eV (wavelength 8)
30 nm). Then, of the excitation region where the current is injected, that is, the light generated in the region A of the Zn diffusion P-type region 38 (that is, the light of the wavelength corresponding to the band gap Eg1 of the active layer of the region A) , Front end face 41 of region A
The light propagating toward the region B travels while being amplified by stimulated emission and is extracted from the end face 41, while the light propagating toward the rear end face 42 of the region B is a region of the active layer 33 in the region B. Since the bandgap Eg2 of B is smaller than the bandgap Eg1 of the region A, the non-injection region (non-excitation region) 43 receives large absorption. Therefore, even at the time of high output, the ratio of the light that propagates to the rear end face 42 and is reflected, then propagates in the region B again and re-enters the Zn diffusion P-type region 38 that is the excitation region, that is, the effective reflectance. Can be made small enough to be ignored. On the other hand, the excitation region Z
Of the light generated in the region B of the n-diffused P-type region 38 (that is, the light having the wavelength corresponding to the bandgap Eg2 of the active layer in the region B), the one propagating toward the front end face 41 is the region B. Since the bandgap Eg1 of the region A is larger than the bandgap Eg2 of the region B while being amplified in the region A and propagating through the active layer 33 in the region A, almost no amplification or absorption is received, and the bandgap Eg1 goes toward the rear end face 42. The propagating light is absorbed while propagating in the non-excited region.

Therefore, in the SLD of this embodiment, laser oscillation does not occur even at a high output, and light having a broad spectrum width can be emitted. Further, the light extracted from the front end face 11 is Zn as the excitation region as described above.
Light having a short wavelength corresponding to a wide band gap Eg1 generated in the active layer 33 in the region A of the diffusion P-type region 38,
Narrow band gap E generated in the active layer 33 in the region B
Light with a long wavelength corresponding to g2 is combined, and the wavelength width is wider than in the case of the conventional active layer with a single composition (that is, with a single bandgap), which is necessary for optical measurement. It is possible to obtain light with a very wide spectrum width.

Example 6. FIG. 11 is a schematic top view showing the structure of the SLD according to the sixth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 9 denote the same or corresponding portions, and 38a denotes a Zn diffused P-type region. .

The basic layer structure of this SLD is basically the same as that of the SLD of the fifth embodiment, and the Zn diffusion P-type region 38a, which becomes an excitation region when a current is injected, has a band gap of the active layer. Is small, that is, it is formed so as not to reach above the region B where the film thickness is formed thick.

In the SLD of this embodiment, the spectrum width of the emitted light is slightly narrower than that of the SLD of Embodiment 5, but the activity in the excitation region is the same as in the fifth embodiment. Since the bandgap Eg1 of the layer is larger than the bandgap Eg2 in the non-excitation region, the layer is sufficiently absorbed in the non-excitation region, and as a result, laser oscillation can be surely suppressed even at high output.

Example 7. In the fifth and sixth embodiments, the active layer is composed of multiple quantum well layers, but in the seventh embodiment, the active layer is composed of a single layer of InGaAs having a thickness of about 300 to 2000 angstroms. Similar to the sixth embodiment, a SiO2 film is formed on a predetermined region on the rear end face side on a substrate, and an SLD is formed of an InGaAsP-based material by the same method (manufacturing process) as in the fifth and sixth embodiments. To do.

In this case, the InGaAs active layer grown in the region sandwiched by the SiO 2 films is the InGaAs active layer grown in the other region.
InG is formed to be thicker than the GaAs active layer, and the In ratio in the inside grows in other regions.
The number is larger than that of the aAs active layer. This is due to the fact that among the III group growth species (or source gas) reaching the SiO2 film, I
This is because the growth species (or source gas) of n has a larger diffusion distance than that of Ga.

Therefore, in the SLD of this embodiment, the bandgap of the active layer grown in the region sandwiched by the SiO 2 films is similar to that of the SLDs of the fifth and sixth embodiments.
The deviation of the active layer grown in other regions is also reduced, and laser oscillation can be reliably suppressed even at high output.

In the fifth to seventh embodiments, the layers other than the active layer may be formed in the ALE mode of the metal organic chemical vapor deposition method. In this case, the layers other than the active layer are formed. Since it is formed to have a uniform layer thickness, the step difference in the chip is reduced, and the loss when light propagates in the active layer can be reduced.

In the above embodiment, the AlGaAs-based material or the InGaAsP-based material was used, but the present invention uses another AlGaInP-based material that lattice-matches the GaAs substrate or another AlGaInAs that lattice-matches the InP substrate.
Semiconductor lasers or SLDs made of system materials
It goes without saying that it can also be applied to.

[0053]

As described above, according to the present invention, a layer for which a layer thickness difference is desired to be formed in the layer is grown by an ordinary metal organic chemical vapor deposition method, and the layer thickness difference is formed in the layer. Since the layers not to be attached are grown in the ALE mode of the metal organic chemical vapor deposition method, each layer is formed to have a preferable layer thickness in terms of laser characteristics, and a semiconductor laser having excellent operation characteristics can be obtained. There is.

Further, according to the present invention, a difference in layer thickness is caused in the active layer, and the active layer and the layer disposed under the active layer are formed to have a uniform layer thickness. There is an effect that it is possible to obtain a semiconductor laser which is not formed in the above manner and in which the distortion and loss increase of the laser beam are suppressed.

Further, according to the present invention, a layer thickness difference is generated only in the light guide layer, and the layers other than the light guide layer are formed to have a uniform layer thickness to form the DFB laser. Is not formed on the steps, distortion and loss increase of the laser beam can be prevented, and the DFB laser having a uniform light intensity distribution in the laser chip can be obtained.

Further, according to the present invention, since the light guide layer is formed to have a uniform layer thickness, the step difference at the coupling portion between the semiconductor laser and the optical modulator is reduced, and the light propagated to the optical modulator is reduced. There is an effect that it is possible to obtain a semiconductor laser with an optical modulator in which the coupling loss of the above phenomenon occurs.

Further, according to the present invention, a portion having a relatively large band gap and a portion having a relatively small band gap are formed in the active layer of the SLD along the cavity direction.
The band gap of the non-excitation region can be made larger than the band gap of the excitation region, the absorption in the non-excitation region becomes large, and the effective reflectance can be reduced, and as a result, an SLD with a broad emission spectrum can be obtained. There is.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method for supplying a source gas in an atomic layer epitaxy mode of a metal organic chemical vapor deposition method used in the present invention.

FIG. 2 is a diagram for explaining a growth mechanism of an epitaxy layer in the atomic layer epitaxy mode.

FIG. 3 is an exploded perspective view showing the structure of the semiconductor laser according to the first embodiment of the present invention.

FIG. 4 is a sectional view for each step showing a manufacturing process of a semiconductor laser with an optical modulator according to a third embodiment of the present invention.

5 is a schematic side view showing the structure of a semiconductor laser with an optical modulator obtained in the manufacturing process shown in FIG.

FIG. 6 is a schematic side view showing the structure of a conventional semiconductor laser with an optical modulator.

FIG. 7 is a sectional view showing the structure of a DFB laser according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view showing the structure of a conventional DFB laser.

FIG. 9 is a schematic sectional view and a schematic top view showing the configuration of an SLD according to a fifth embodiment of the present invention.

10A to 10D are cross-sectional views for each manufacturing step showing the manufacturing process of the SLD shown in FIG.

FIG. 11 is a schematic top view showing the structure of the SLD according to the sixth embodiment of the present invention.

FIG. 12 is an exploded perspective view showing the structure of a conventional semiconductor laser.

13 is a view showing a semiconductor substrate with a SiO2 film used when manufacturing the semiconductor laser shown in FIG.

FIG. 14 is a schematic sectional view and a schematic top view showing a conventional SLD.

[Explanation of symbols]

1, GaAs substrate 2, 2a, 4, 4a AlGaAs clad layer 3a, 3b, 30a, 30b AlGaAs active layer 5, 5a GaAs contact layer 9 SiO2 film 10 stripe portion 11 InP substrate 12 InGaAs light guide layer 13 InGaAs / InGaAsP multiple quantum Well active layer 14 InP upper clad layer 15a, 15b InGaAsP cap layer 16 Optical modulator electrode 17 Semiconductor laser electrode 18 Groove for separating optical modulator and laser 19 Diffraction grating 20 SiO2 film 21 GaAs substrate 22 AlGaAs clad layer 23 AlGaAs Active layer 24 AlGaAs optical guide layer 25 GaAs contact layer 26 Diffraction grating 27 Non-reflective coating laser emission surface 28 High-reflectance coating back surface 31,101 n-type GaAs substrate 2,102 n-type AlGaAs clad layer 33 GaAs / AlGaAs multiple quantum well layer 34,104 p-type AlGaAs clad layer 35,105 n-type GaAs cap layer 36,106 n-side electrode 37,107 p-side electrode 38,108 Zn diffusion p Type region (excitation region) 39 Ridge 40 SiO2 film 41 Light emission end face 42 Rear end face 43 Non-injection region (non-excitation region) 109 Non-injection region (non-excitation region) 111 Front end face 112 Rear end face

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[Procedure amendment]

[Submission date] July 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

Therefore, in the SLD of this embodiment, laser oscillation does not occur even at a high output, and light having a broad spectrum width can be emitted. Furthermore, light extracted from the front end surface 4 1 is the excitation region as described above Zn
Light having a short wavelength corresponding to a wide band gap Eg1 generated in the active layer 33 in the region A of the diffusion P-type region 38,
Narrow band gap E generated in the active layer 33 in the region B
Light with a long wavelength corresponding to g2 is combined, and the wavelength width is wider than in the case of the conventional active layer with a single composition (that is, with a single bandgap), which is necessary for optical measurement. It is possible to obtain light with a very wide spectrum width.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0057

[Correction method] Change

[Correction content]

Further, according to the present invention, a portion having a relatively large band gap and a portion having a relatively small band gap are formed in the active layer of the SLD along the cavity direction.
Smaller than the band gap of the excitation region a band gap of the non-excitation region Kudeki and absorption in the non-excitation region is increased, it is possible to reduce the effective reflectivity, thereby making it possible to obtain the SLD of broad emission spectrum effective.

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Claims (14)

[Claims] 1. A predetermined portion on a semiconductor substrate along a light guide direction of light of a laser resonator formed on the semiconductor substrate.
Two stripe-shaped SiO2 films or SiN films are formed in parallel with each other at a predetermined interval, and in this state, a semiconductor layer having a multi-layer structure including at least an active layer is epitaxially grown on the semiconductor substrate by a metal organic chemical vapor deposition method. In the method for manufacturing a semiconductor laser for forming the laser resonator, a layer which does not cause a layer thickness difference in the semiconductor layer of the multilayer structure is grown in an atomic layer epitaxy mode. Of manufacturing a semiconductor laser. 2. The method for manufacturing a semiconductor laser according to claim 1, wherein among the semiconductor layers of the multilayer structure, a layer disposed below the active layer is epitaxially grown in an atomic layer epitaxy mode. A method for manufacturing a characteristic semiconductor laser. 3. A stripe-shaped SiO2 film formed on a semiconductor substrate at a position corresponding to the inside of the resonator of the laser resonator formed on the semiconductor substrate, the SiO2 films being in the form of two stripes along the light guiding direction of the laser resonator. SiN films are formed in parallel with each other with a predetermined interval, and then a semiconductor layer having a multi-layer structure including at least an active layer is epitaxially grown on the semiconductor substrate by a metal organic chemical vapor deposition method to form the active layer. In the method for manufacturing a semiconductor laser in which the layer thickness near the laser cavity end face is thin and the layer thickness near the laser cavity interior is thick, in the semiconductor layer of the multilayer structure, a layer thickness difference occurs in the layer. A method for manufacturing a semiconductor laser, which comprises growing an undesired layer in an atomic layer epitaxy mode. 4. The method for manufacturing a semiconductor laser according to claim 3, wherein a layer disposed below the active layer among the semiconductor layers having the multilayer structure is epitaxially grown in an atomic layer epitaxy mode. A method for manufacturing a semiconductor laser, comprising: 5. A semiconductor laser in which a semiconductor layer having a multi-layered structure including an active layer is epitaxially grown on a semiconductor substrate to form a laser resonator, wherein the active layer has a layer thickness near an end facet of the laser resonator. A semiconductor laser, wherein the semiconductor laser is formed so as to be thin and have a large layer thickness in the vicinity of the inside of the laser resonator, and the layer disposed below the active layer is formed to have a uniform layer thickness. 6. A stripe-shaped SiO2 film or SiN film on one side of a semiconductor substrate in which a laser resonator is to be formed, and which has two stripes along the light guide direction of the laser resonator.
Films are formed in parallel with each other with a predetermined space, and then a semiconductor layer having a multilayer structure including an active layer is formed on the semiconductor substrate.
A laser resonator is formed on the semiconductor substrate in a region sandwiched by the two stripe-shaped SiO2 films or SiN films by epitaxial metal growth by metalorganic vapor phase epitaxy, and the SiO2 film or the SiO2 film on the semiconductor substrate is formed. A method of manufacturing a semiconductor laser with an optical modulator, comprising: an optical modulator that absorbs and modulates laser light oscillated by the laser resonator on the other side on which no SiN film is formed. A method of manufacturing a semiconductor laser, characterized in that, of the layers, a layer in which a layer thickness difference is not desired to be produced is grown in an atomic layer epitaxy mode. 7. The method for manufacturing a semiconductor laser according to claim 6, wherein a layer disposed below the active layer among the semiconductor layers having the multi-layer structure is epitaxially grown in an atomic layer epitaxy mode. A method for manufacturing a semiconductor laser, comprising: 8. A two-striped SiO2 film or SiN film along a light guide direction of the laser resonator in a region where the laser resonator is formed on one side of the semiconductor substrate.
Films are formed in parallel with each other with a predetermined space, and a semiconductor layer having a multi-layer structure including an active layer is epitaxially grown on the semiconductor substrate to absorb and modulate a laser resonator and laser light oscillated by the laser resonator. In the semiconductor laser with an optical modulator, the optical modulator and the optical modulator are collectively formed, and the layer disposed below the active layer is formed to have a uniform layer thickness. Semiconductor laser. 9. A lower clad layer, an active layer, and an optical guide layer are epitaxially grown on a semiconductor substrate in this order, the upper surface of the optical guide layer is shaped into a diffraction grating, and then a contact layer is epitaxially formed on the optical guide layer. A method of manufacturing a distributed feedback semiconductor laser that grows, wherein one end of a laser resonator formed on the semiconductor substrate and corresponding to a rear end face side of the laser resonator Two stripes of Si along the waveguiding direction
An O2 film or a SiN film is formed in parallel with each other at a predetermined interval, and in this state, the lower clad layer, the active layer, and the optical guide layer are epitaxially grown on the semiconductor substrate by a metal organic chemical vapor deposition method. A method of manufacturing a characteristic distributed feedback semiconductor laser. 10. The method of manufacturing a distributed feedback semiconductor laser according to claim 9, wherein the lower cladding layer and the active layer are epitaxially grown in an atomic layer epitaxy mode. 11. A current injection region is formed in a predetermined portion on one side of a semiconductor layer having a multi-layer structure including an active layer formed on a semiconductor substrate, and the current injection region is used as an excitation region, and the other semiconductor layer is formed. In the method for manufacturing a super luminescent diode having a non-excitation region as a region, a predetermined number along a light guide direction is provided on a semiconductor substrate on a side corresponding to a rear end face side of a resonator formed on the semiconductor substrate. A step of forming two stripe-shaped SiO2 films or SiN films of a length parallel to each other at a predetermined interval; and a multi-layered semiconductor layer including the active layer on the semiconductor substrate by metal organic chemical vapor deposition. The process of epitaxial growth and the stripe-shaped current of a predetermined length from the end on the side that becomes the light emission end face of the semiconductor layer of the multilayer structure including the active layer formed on the semiconductor substrate toward the inside of the resonator Method for producing a super luminescent diode, characterized in that it comprises a step of forming the incoming region. 12. The method for manufacturing a superluminescent diode according to claim 11, wherein the stripe-shaped current injection region is formed in a region of the semiconductor layer sandwiched between the two stripe-shaped SiO 2 films or SiN films. A method for manufacturing a super luminescent diode, which is characterized in that it is formed so as to reach the grown semiconductor layer. 13. A current injection region is formed in a predetermined portion on one side of a semiconductor layer having a multilayer structure including an active layer formed on a semiconductor substrate, and the current injection region is used as an excitation region, and the other semiconductor layer is formed. In the superluminescent diode having the region as a non-excitation region, the active layer has a large bandgap on the light emitting surface side of the resonator formed of the semiconductor layer and a small rear end surface side opposite to the light emitting surface. A super luminescent diode formed in a band gap, wherein the current injection region is formed on an active layer having the large band gap. 14. The superluminescent diode according to claim 13, wherein a part of the current injection region is formed over the active layer having the small bandgap. Nesting diode.