JP2004039717A - Semiconductor distribution bragg reflector, surface luminescence type semiconductor laser, surface luminescence type semiconductor laser array, optical communication system, optical write-in system, and optical pick-up system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor distribution Bragg reflector with the number of lamination layers made fewer than that of AlGaAs material especially in wavelength bands shorter than 0.78 μm and suitable for practical use. <P>SOLUTION: In the semiconductor distribution Bragg reflector having periodical changes in refraction factor and for reflecting incident light by a lightwave interference, a layer having a small refraction factor is composed of Al<SB>x</SB>Ga<SB>1-x</SB>P (0<x≤1) and a layer having a larg refraction factor is composed of Al<SB>y</SB>Ga<SB>1-y</SB>P (0≤y<x≤1). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor distributed Bragg reflector, a surface emitting semiconductor laser, a surface emitting semiconductor laser array, an optical communication system, an optical writing system, and an optical pickup system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a surface emitting semiconductor laser emits light in a direction perpendicular to a substrate, and has a lower cost and higher performance than an edge emitting semiconductor laser. It is used in consumer applications such as light sources for home use.
[0003]
The surface-emitting type semiconductor laser has a structure in which an active region including an active layer for generating laser light is sandwiched between reflectors. As the reflecting mirror, a semiconductor distributed Bragg reflecting mirror in which low refractive index layers and high refractive index layers are alternately stacked is widely used. As the material of the semiconductor distributed Bragg reflector, a material that does not absorb the light generated from the active layer (generally, a material having a wider band gap than the active layer) and is lattice-matched to the substrate to prevent lattice relaxation from being used is used. Can be
[0004]
By the way, the reflectivity of the reflecting mirror needs to be extremely high at 99% or more, and the reflectivity can be increased by increasing the number of layers. However, when the number of layers increases, it becomes difficult to manufacture a surface-emitting type semiconductor laser. For this reason, it is preferable that the refractive index difference between the low refractive index layer and the high refractive index layer is large. AlGaAs-based materials are often used because AlAs and GaAs are terminating substances, and the lattice constant is almost the same as that of GaAs as the substrate, the refractive index difference is large, and high reflectance can be obtained with a small number of stacked layers. Have been.
[0005]
In order to lower the threshold value, a current narrowing structure is used. Japanese Patent Application Laid-Open No. Hei 7-240506 discloses a structure using a resonator using a semiconductor distributed Bragg reflector made of AlAs / GaAs and a current narrowing structure in which a high resistance layer is formed by ion implantation. Japanese Patent No. 2917971 discloses a surface using a resonator using a semiconductor distributed Bragg reflector made of AlGaAs / GaAs and a current narrowing structure using an oxide film obtained by selectively oxidizing a part of Al (Ga) As. A light emitting semiconductor laser is shown. Here, oxidation by steam supply at a high temperature is used for the oxidation. The oxidation by steam supply at high temperature_xO_yIn addition, it becomes a perfect insulator as described above, the distance between the active layer and the narrow layer can be strictly controlled by crystal growth, and the current path can be made extremely narrow. It is suitable for low power consumption and has been widely used recently.
[0006]
Japanese Patent No. 2917971 utilizes the fact that the oxidation rate sharply increases as the Al composition of AlGaAs increases, and only the layer to be oxidized is oxidized by making the Al composition of the layer to be oxidized larger than the others. Like that. Thus, a structure in which the current is narrowed by selective oxidation can be obtained. For this reason, the Al composition of the AlGaAs layer of the low refractive index layer of the semiconductor distributed Bragg reflector is smaller than the Al composition of the Al (Ga) As oxide layer (that is, the Ga composition is increased). Japanese Patent No. 2917971 discloses that a layer to be selectively oxidized contains Al._yGa_1-yAs (y = 0.97) was used, and the low refractive index layer of the semiconductor distributed Bragg reflector was made of Al._xGa_1-xAs (x = 0.92) is used.
[0007]
As described above, from the viewpoint of the reflector and the current confinement structure, a distributed Bragg reflector (DBR) having a reflection band in the 0.78 μm band, 0.85 μm band, 0.98 μm band using an AlGaAs-based material, and A surface-emitting type semiconductor laser in the same wavelength band using this as a resonator mirror has achieved a practical level of performance.
[0008]
On the other hand, a surface emitting semiconductor laser that oscillates in a wavelength band of 0.6 μm is expected as a light source for optical communication using a plastic fiber (POF: Plastic Optical Fiber) and for optical writing and reproduction of laser printers, CDs, DVDs, and the like. ing. The low-loss region of the inexpensive acrylic plastic fiber is in the red wavelength band, and optical communication using POF is expected to be an extremely low-cost optical communication system.
[0009]
In the wavelength band of 0.6 μm, an AlGaInP-based material on a GaAs substrate is used, and an edge emitting laser has a track record. The AlGaInP-based material is the largest direct-transition type material among the III-V semiconductors except for the AlGaInN-based material, and has a maximum band gap energy of about 2.3 eV (wavelength 540 nm). In order to manufacture a semiconductor laser, a structure is required in which a carrier and light are confined in an active layer (light-emitting layer) using a cladding layer (made of a material having a larger band gap than the active layer). However, the AlGaInP-based material has a small band offset ratio of the conduction band when a heterojunction is formed, and a small band discontinuity (△ Ec) between the active layer (light emitting layer), the cladding layer, and the conduction band. ) Easily overflows from the active layer to the cladding layer, and there is a problem that the temperature dependence of the oscillation threshold current of the semiconductor laser is large and the temperature characteristics are poor. The surface emission type is particularly severe because the carrier density required for laser operation is higher than that of the edge emission type.
[0010]
Further, there is a limitation in forming a semiconductor distributed Bragg reflector (DBR) using an AlGaAs-based material practically used in the 0.78 μm band, the 0.85 μm band, and the 0.98 μm band. For example, Japanese Patent Application Laid-Open No. 2000-196189 discloses an example of a red surface emitting semiconductor laser. This red surface emitting type semiconductor laser has a wavelength of 0.6 μm band, and an Al composition of 0.5 or more is generally used to avoid light absorption, and the difference in refractive index between the low refractive index layer and the high refractive index layer is reduced. Since it cannot be made large, the number of layers increases. That is, the difference in the refractive index between the low refractive index layer and the high refractive index layer is half that of the DBR in the 0.98 μm band, the number of layers is doubled, and the resistance rise and the heat radiation are poor. Problems arise. Further, in practice, a sufficiently high reflectivity cannot be obtained even if the number of layers is increased due to fluctuations in the film thickness of each layer, and a wavelength range in which a high reflectivity is narrowed. Become smaller. This has a greater effect as the wavelength becomes shorter.
[0011]
Also, studies have been made on using an AlGaInP-based material as a material capable of obtaining a large difference in the refractive index between the low refractive index layer and the high refractive index layer of the DBR (Appl. Phys. @ Lett., Pp. Schneider et al.). 60 (15), {13} April $ 1992, $ P1830 "). Specifically, (Al_yGa_1-y)_{0 . 5}In_0.5P / Al_0.5In_0.5The use of P (y = about 0.2) has been studied. However, this material system is a material system in which the lattice constant changes greatly due to a slight deviation of the composition, and it is difficult to strictly control the supply amount of In. It is difficult. In addition, a method of reducing the resistance by inserting a composition gradient layer between the low refractive index layer and the high refractive index layer is usually used, but it is difficult to control this without changing the lattice constant. Furthermore, as the number of constituent elements of the mixed crystal increases and the composition of the mixed crystal approaches the center, the thermal resistance increases. Therefore, it cannot be said that the material is preferable for the DBR in terms of heat radiation. For this reason, AlGaAs-based materials are mainly used in research and development of surface emitting semiconductor lasers in the wavelength band of 0.6 μm.
[0012]
Further, heat is generated mainly on the active layer and the reflecting mirror, and on the side (main surface) where the crystal is grown. In order to actively dissipate heat, a method of mounting the main surface on a heat sink or the like and extracting light from the substrate side is conceivable. However, in the wavelength of 0.6 μm band, this is not possible because it is absorbed by GaAs of the substrate. .
[0013]
Japanese Patent Application Laid-Open No. 10-200202 proposes a surface-emitting type semiconductor laser using a GaInP substrate to suppress the overflow of the carrier and formed of a material system lattice-matched to the substrate. In this surface-emitting type semiconductor laser, an AlInP / GaInP-based reflecting mirror is used. However, the GaInP substrate is extremely difficult to manufacture, and high-quality crystal growth cannot be obtained thereon. Further, the reflecting mirror is a ternary system and has a large thermal resistance. Practical application is difficult, for example, it is difficult to control the composition gradient layer.
[0014]
For these reasons, at a wavelength of 650 nm at which the absorption loss of the POF is at the bottom, a continuous operation could be finally achieved at room temperature at present (see KD Choquette et al., “Electronics Letters, # 6”).^thJuly 1995, Vol. 31 No. 14, ΔP1145 ”) to some extent.
[0015]
For the above reasons, a surface emitting semiconductor laser having a wavelength band shorter than 0.78 μm has not been put to practical use.
[0016]
[Problems to be solved by the invention]
The present invention provides a semiconductor distributed Bragg reflector, a surface-emitting type semiconductor laser, a surface-emitting type semiconductor laser array, a light-emitting device, and a semiconductor distributed Bragg reflector suitable for practical use, in which the number of layers is smaller than that of an AlGaAs-based material particularly in a wavelength band shorter than 0.78 μm. It is an object to provide a communication system, an optical writing system, and an optical pickup system.
[0017]
That is, the present invention increases the reflectance with a small number of stacked layers, reduces heat generation, and improves heat dissipation, thereby realizing a practical semiconductor Bragg reflector, a surface emitting semiconductor laser, and a surface emitting semiconductor laser array. And an optical communication system, an optical writing system, and an optical pickup system.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a semiconductor distributed Bragg reflector in which the refractive index changes periodically and the incident light is reflected by light wave interference._xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yIt is characterized by being composed of P (0 ≦ y <x ≦ 1).
[0019]
According to a second aspect of the present invention, in a semiconductor distributed Bragg reflector formed by laminating two types of semiconductor layers having different refractive indexes, two types of semiconductor layers having different refractive indexes are different from a layer having a lower refractive index. The layer having a large refractive index and the layer having a small refractive index are Al_xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yP (0 ≦ y <x ≦ 1), and a semiconductor layer having a refractive index between the two semiconductor layers having different refractive indexes is provided between the two semiconductor layers having different refractive indexes. It is characterized by:
[0020]
According to a third aspect of the present invention, there is provided an active region including at least one active layer for generating laser light on a semiconductor substrate, and upper and lower portions provided above and below the active region for obtaining laser light. In a surface emitting semiconductor laser having a resonator structure including a reflecting mirror and a lower reflecting mirror, the semiconductor distributed Bragg reflecting mirror according to claim 1 or 2 is used for the upper reflecting mirror and / or the lower reflecting mirror. It is characterized by.
[0021]
According to a fourth aspect of the present invention, there is provided an active region including at least one active layer for generating a laser beam on a semiconductor substrate, and upper and lower portions provided above and below the active region for obtaining the laser beam. In a surface emitting semiconductor laser having a resonator structure including a reflecting mirror and a lower reflecting mirror, the active region is made of a material lattice-matched to GaAs (thickness which does not cause misfit dislocation due to lattice distortion even if not completely lattice-matched). The upper reflecting mirror and / or the lower reflecting mirror are made of a material lattice-matched to GaP (misfit dislocation due to lattice strain even if not completely lattice-matched). The thickness is not more than the critical film thickness, which is a thickness that does not cause the generation of the semiconductor distributed Bragg reflector.
[0022]
The invention according to claim 5 provides a step of growing a first semiconductor distributed Bragg reflector on a first GaP substrate, a step of growing an active region on a GaAs substrate, and a step of growing a second semiconductor on a second GaP substrate. Crystal growing a distributed Bragg reflector, bonding the active region to the first semiconductor distributed Bragg reflector, removing the GaAs substrate, and bonding the active region to the second semiconductor distributed Bragg reflector; It is characterized by having.
[0023]
According to a sixth aspect of the present invention, there is provided a first semiconductor distributed Bragg reflector made of a material lattice-matched to GaP, an active region made of a material lattice-matched to GaAs, and a material lattice-matched to GaAs. And a second distributed Bragg reflector made of semiconductor.
[0024]
Further, according to the present invention, a step of crystal-growing a first semiconductor distributed Bragg reflector on a GaP substrate, a step of crystal-growing a second semiconductor distributed Bragg reflector and an active region on a GaAs substrate, Bonding the region and the first semiconductor Bragg reflector to each other.
[0025]
According to an eighth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth or sixth aspect, the active region made of a material lattice-matched to GaAs and the semiconductor distributed Bragg reflector made of a material lattice-matched to GaP are provided. And a part of a semiconductor distributed Bragg reflector made of a material lattice-matched to GaAs is formed between the semiconductor distributed Bragg reflector made of a material lattice-matched to the GaP and a material lattice-matched to the GaAs. And a part of the semiconductor distributed Bragg reflector.
[0026]
According to a ninth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth or eighth aspect, the semiconductor substrate is a GaP substrate, and light is extracted from the GaP substrate side. It is characterized by being constituted so that.
[0027]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth, eighth or ninth aspect, AlAs containing Al and As as main components is selectively oxidized. It is characterized by having a current narrowing layer.
[0028]
According to an eleventh aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, or tenth aspect, the active region includes at least Ga, In, and P. , The wavelength is shorter than 0.78 μm.
[0029]
According to a twelfth aspect of the present invention, there is provided a surface-emitting type semiconductor laser array comprising the surface-emitting type semiconductor laser according to the eleventh aspect.
[0030]
According to a thirteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or the surface described in the twelfth aspect. An optical transmission module using a light emitting semiconductor laser array as a light source.
[0031]
According to a fourteenth aspect of the present invention, there is provided a surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a twelfth aspect. An optical transceiver module, wherein a light emitting semiconductor laser array is used as a light source.
[0032]
According to a fifteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspect, or a surface according to the twelfth aspect. An optical communication system in which a light emitting semiconductor laser array is used as a light source.
[0033]
According to a sixteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a twelfth aspect. An optical writing system is characterized in that a light emitting semiconductor laser array is used as a light source.
[0034]
According to a seventeenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a surface emitting semiconductor laser according to the twelfth aspect. An optical pickup system is characterized in that a light emitting semiconductor laser array is used as a light source.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0036]
First embodiment
The semiconductor distributed Bragg reflector (DBR) according to the first embodiment of the present invention is a semiconductor distributed Bragg reflector whose refractive index changes periodically and reflects incident light by light wave interference, and has a small refractive index. Layer is Al_xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yIt is characterized by being composed of P (0 ≦ y <x ≦ 1).
[0037]
AlGaP-based DBRs have not been studied because a material capable of laser oscillation could not be grown on a GaP substrate. However, an AlGaP-based material having AlP or GaP as a terminating substance has a lattice constant close to that of GaP regardless of the Al composition, and allows a crystal to grow on a GaP substrate and has a large refractive index difference. This is the same tendency as an AlGaAs-based material having AlAs and GaAs as termination materials. Specifically, the lattice constants are GaP: 5.4495 Å, AlP: 5.4625 Å, GaAs: 5.65325 Å, and AlAs: 5.6611 Å. The refractive indexes (at the band gap wavelength) are GaP: 3.452, AlP: 3.03, GaAs: 3.655, and AlAs: 3.178. Therefore, it is considered that the AlGaP-based material is suitable as the material of the semiconductor distributed Bragg reflector similarly to the AlGaAs-based material. Further, since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, it transmits light in a wavelength band longer than about 0.55 μm. Therefore, the entire composition range of AlGaP can be used in a wavelength band longer than 0.55 μm, and in particular, a semiconductor distributed Bragg reflector more suitable than an AlGaAs-based material can be formed in a wavelength band shorter than 0.78 μm.
[0038]
Second embodiment
The semiconductor distributed Bragg reflector according to the second embodiment of the present invention is a semiconductor distributed Bragg reflector formed by laminating two types of semiconductor layers having different refractive indexes. And the layer with a large refractive index, and the layer with a small refractive index is Al_xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yP (0 ≦ y <x ≦ 1), and a semiconductor layer having a refractive index between the two semiconductor layers having different refractive indexes is provided between the two semiconductor layers having different refractive indexes. It is characterized by: Specifically, a semiconductor layer Al having a refractive index between two types of semiconductor layers having different refractive indexes_zGa_1-zP (0 ≦ y <z <x ≦ 1) is provided.
[0039]
In the second embodiment, in a semiconductor distributed Bragg reflector formed by laminating two types of semiconductor layers having different refractive indices, the two types of semiconductor layers having different refractive indices are different in refractive index from a layer having a lower refractive index. A layer having a large refractive index and a layer having a small refractive index is Al_xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yP (0 ≦ y <x ≦ 1), and a semiconductor layer having a refractive index between the two semiconductor layers having different refractive indexes is provided between the two semiconductor layers having different refractive indexes. Thus, when electricity is passed through the reflecting mirror, band discontinuity between a layer having a small refractive index and a layer having a large refractive index can be smoothed, and a high resistance can be suppressed. Note that the Ga composition z of the semiconductor layer having a refractive index between two kinds of semiconductor layers having different refractive indexes may be changed stepwise or continuously.
[0040]
Third embodiment
A surface emitting semiconductor laser according to a third embodiment of the present invention includes an active region including at least one active layer for generating laser light on a semiconductor substrate, and upper and lower portions of the active region for obtaining laser light. In the surface-emitting type semiconductor laser having a resonator structure including an upper reflecting mirror and a lower reflecting mirror provided in the semiconductor device, the upper reflecting mirror and / or the lower reflecting mirror may have the semiconductor distribution according to the first or second embodiment. It is characterized in that a Bragg reflector is used.
[0041]
Since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, the AlGaP-based material transmits light having a wavelength longer than about 0.55 μm and emits light at a wavelength shorter than 0.78 μm such as the 0.6 μm band. Since a material that does not cause absorption can be used for a semiconductor distributed Bragg reflector (also simply referred to as a reflector), and a large difference in refractive index can be obtained, a high reflectance of 99% or more can be obtained more easily than using an AlGaAs-based material. As a result, the number of layers can be reduced to about half. Thereby, the resistance can be reduced.
[0042]
Further, the thermal conductivity of the related materials is GaAs: 0.54 Wcm, respectively.^-1K^-1, AlAs: 0.91 Wcm^-1K^-1, GaP: 1.1 Wcm^-1K^-1, AlP :: 0.9 Wcm^-1K^-1It is. As described above, since the thermal conductivity of the AlGaP-based material is higher than that of the AlGaAs-based material, the heat radiation is improved, the temperature rise during operation can be suppressed, the threshold value and the output can be increased, and the temperature characteristics can be further improved. I do. The effect of heat conduction is effective not only in the 0.6 μm band but also in other wavelength ranges (long wavelength bands such as the 0.78 μm, 0.85 μm, 0.98 μm, 1.3 μm, and 1.55 μm bands). .
[0043]
Fourth embodiment
A surface emitting semiconductor laser according to a fourth embodiment of the present invention includes an active region including at least one active layer that generates laser light on a semiconductor substrate, and upper and lower portions of the active region for obtaining laser light. In the surface-emitting type semiconductor laser having a resonator structure including an upper reflecting mirror and a lower reflecting mirror, the active region is made of a material lattice-matched with GaAs, and the upper reflecting mirror and / or the lower reflecting mirror are provided. The reflector is a semiconductor distributed Bragg reflector made of a material lattice-matched to GaP.
[0044]
Many materials capable of crystal growth on a GaP substrate are indirect transition materials, and it is difficult to obtain a material that enables laser oscillation. However, a material capable of crystal growth on a GaAs substrate with a thickness equal to or less than the critical film thickness is used. Are materials that can be formed with sufficient quality as an active layer of a semiconductor laser, such as GaAs, AlGaAs, GaInP, AlGaInP, GaPAs, GaInPAs, GaInAs, GaInNAs, GaNAs, GaInNAsSb, and GaAsSb. When these active layers are used and a reflecting mirror is formed on a GaP substrate using an AlGaP-based material which is a material capable of growing a crystal with a thickness equal to or less than a critical film thickness, compared with a conventional AlGaAs-based reflecting mirror, A surface-emitting type semiconductor laser having high thermal conductivity and improved heat dissipation and good temperature characteristics can be realized. Further, since the AlGaP-based material has a wider gap than the AlGaAs-based material, especially when the wavelength is shorter than 780 nm, a large difference in refractive index can be obtained, a high reflectance can be easily obtained with a small number of layers, and the absorption can be improved. Is reduced, and a low-threshold, high-output surface-emitting type semiconductor laser can be obtained. In this case, examples of the material of the active layer include GaInP, AlGaInP, AlGaAs, GaAsP, and AlGaInAs.
[0045]
Fifth embodiment
The method for manufacturing a surface emitting semiconductor laser according to the fifth embodiment of the present invention includes the steps of: growing a first semiconductor distributed Bragg reflector on a first GaP substrate; and growing an active region on a GaAs substrate. Crystal growing a second semiconductor distributed Bragg reflector on the second GaP substrate, bonding the active region to the first semiconductor distributed Bragg reflector and removing the GaAs substrate, removing the active region and the second semiconductor distributed Bragg reflector, Bonding a Bragg reflector.
[0046]
An AlGaP-based material having AlP or GaP as a terminating substance used for the first and second reflecting mirrors has a lattice constant close to that of GaP and can be crystal-grown on a GaP substrate, and has a large refractive index difference. This is the same tendency as an AlGaAs-based material having AlAs and GaAs as termination materials. Further, for example, in the wavelength band of 0.6 μm, an active region including an active layer can be formed of an AlGaInP-based material that can grow on a GaAs substrate without misfit dislocations. Then, a surface-emitting type semiconductor laser can be formed by bonding them. After bonding one semiconductor distributed Bragg reflector and the active region, the GaAs substrate is removed by etching or the like. As a method of bonding, the surfaces can be cleaned and bonded, and heat treatment can be performed at a high temperature such as 600 ° C. for bonding.
[0047]
Sixth embodiment
A surface emitting semiconductor laser according to a sixth embodiment of the present invention comprises a first semiconductor distributed Bragg reflector made of a material lattice-matched to GaP, an active region made of a material lattice-matched to GaAs, and a semiconductor substrate. A second semiconductor distributed Bragg reflector made of a material lattice-matched to GaAs.
[0048]
GaP has approximately twice the thermal conductivity as GaAs and has good heat dissipation. Therefore, heat generated during operation can be well released, and the temperature characteristics are improved. In addition, many materials capable of crystal growth on a GaP substrate are indirect transition materials, and it is difficult to obtain a material capable of laser oscillation. However, a material capable of laser oscillation is easily provided on a GaAs substrate. It can be formed. That is, an active region made of a material lattice-matched to GaAs can be easily formed on a GaAs substrate.
[0049]
As described above, as the first and second semiconductor distributed Bragg reflectors, it is preferable to use a material crystal-grown on a GaP substrate, but it is preferable to use one or both of the first and second reflectors. Even if the active region and the active region are both crystal-grown on a GaAs substrate and bonded to a GaP substrate, there is an effect of heat dissipation by the GaP substrate.
[0050]
Seventh embodiment
The method for manufacturing a surface emitting semiconductor laser according to the seventh embodiment of the present invention includes a step of growing a first semiconductor distributed Bragg reflector on a GaP substrate and a method of forming the second semiconductor distributed Bragg reflector on a GaAs substrate. The method is characterized in that the method includes a step of crystal growing a region and a step of bonding the active region and the first semiconductor distributed Bragg reflector.
[0051]
An AlGaP-based material having AlP or GaP as a terminating substance used for the first reflecting mirror has a lattice constant close to that of GaP and can grow a crystal on a GaP substrate, and has a large refractive index difference. This is the same tendency as an AlGaAs-based material having AlAs and GaAs as termination materials. Further, for example, in the wavelength band of 0.6 μm, an active region including an active layer can be formed of an AlGaInP-based material that can grow on a GaAs substrate without misfit dislocations. The second semiconductor distributed Bragg reflector can be formed on the GaAs substrate by using an AlGaAs-based material continuously with the active region. Then, the surface emitting semiconductor laser can be formed by bonding them. As a method of bonding, the surfaces can be cleaned and bonded, and heat treatment can be performed at a high temperature such as 600 ° C. for bonding.
[0052]
Eighth embodiment
The surface-emitting type semiconductor laser according to the eighth embodiment of the present invention is the same as the surface-emitting type semiconductor laser according to the fourth or sixth embodiment, except that an active region made of a material lattice-matched to GaAs and a material lattice-matched to GaP are used. A semiconductor distributed Bragg reflector made of a material lattice-matched to GaAs is formed between the semiconductor distributed Bragg reflector and a semiconductor distributed Bragg reflector made of a material lattice-matched to GaP. And a part of a semiconductor distributed Bragg reflector made of a material lattice-matched to the semiconductor.
[0053]
If the wafer bonding interface is near the active layer, the heat generated in the active layer and the confined light act to activate the crystal defects due to the difference in lattice constant between the GaP-based material and the GaAs-based material. This may affect the layers and reduce reliability. As in the eighth embodiment, an AlGaAs-based reflecting mirror lattice-matched to a GaAs substrate is provided between the wafer bonding interface and the active layer, and the active layer and the bonding interface are kept away from each other to prevent the above-mentioned influence from being exerted. be able to.
[0054]
Ninth embodiment
A surface emitting semiconductor laser according to a ninth embodiment of the present invention is the surface emitting semiconductor laser according to the fourth, sixth or eighth embodiment, wherein the semiconductor substrate is a GaP substrate, and light is extracted. It is characterized in that it is configured to be made from the GaP substrate side.
[0055]
The GaP substrate is transparent to light in a wavelength band longer than about 0.55 μm, and can extract light. Therefore, a so-called junction-down mounting in which a heat sink or the like is attached to a side where heat is mainly generated becomes possible, so that heat radiation can be extremely improved and temperature characteristics can be improved. In addition, if wiring and the like are formed on the mounting substrate and bonding is performed via solder or the like, wire bonding becomes unnecessary, so that an array element is particularly effective in terms of economy.
[0056]
Tenth embodiment
The surface emitting semiconductor laser according to the tenth embodiment of the present invention is different from the surface emitting semiconductor laser according to the fourth, sixth, eighth or ninth embodiment in that AlAs mainly containing Al and As is selectively used. It is characterized by having a current narrowing layer which is oxidized.
[0057]
Al_xGa_1-xOxidation experiments have shown that the addition of P to As decreases the refractive index and decreases the oxidation rate. It is well known that when Ga or In is added to AlAs, the oxidation rate sharply decreases with an increase in the Ga or In composition, but the behavior when P is added was not known. Therefore, AlAs on a GaAs substrate and GaAs grown on a GaAs substrate via a composition gradient layer are described._0.6P_0.4AlAs on epi substrate_0.6P_0.4And oxidized by steam at high temperature. Each layer was 40 nm thick and was sandwiched between cladding layers. A mesa was formed by etching until a side surface of the layer to be selectively oxidized appeared, and oxidation was performed from the side surface. As a result, AlAs is oxidized by 8 μm in 10 minutes at 440 ° C._xO_yIt became. On the other hand, AlAs_0.6P_0.4Was hardly oxidized even at 500 ° C. for 20 minutes. Therefore, it was found that although P was included, the oxidation rate was reduced even though the group III was only Al. That is, the oxidation rate of the AlGaP-based DBR is much lower than that of AlAs, even if it is AlP. Therefore, it is not necessary to use AlGaAs having an Al composition smaller than the oxide layer for the DBR as in the AlGaAs-based DBR, and AlGaP having a large Al composition can be used. Therefore, the oxidation of the semiconductor distributed Bragg reflector can be suppressed without reducing the refractive index difference of the semiconductor distributed Bragg reflector, and the current narrowing structure by the selective oxidation layer can be realized without increasing the number of layers of the semiconductor distributed Bragg reflector. It is possible to achieve both low power consumption and thinning of the surface emitting semiconductor laser.
[0058]
Eleventh embodiment
The surface emitting semiconductor laser according to the eleventh embodiment of the present invention is the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth or tenth embodiment in which the active region has at least Ga, In, P And the wavelength is shorter than 0.78 μm.
[0059]
Since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, a material that transmits light in a longer wavelength band than about 0.55 μm, and in particular, does not absorb light in a shorter wavelength band than 0.78 μm. Can be used as a reflector, and a large difference in refractive index can be obtained. Therefore, a high reflectance of 99% or more can be easily obtained as compared with the case of using an AlGaAs-based material. A semiconductor distributed Bragg reflector can be formed. Further, since the thermal conductivity of the AlGaP-based material is higher than that of the AlGaAs-based material, the heat radiation is improved, the temperature rise during operation can be suppressed, and the temperature characteristics are improved. An AlGaInP-based material on a GaAs substrate can obtain a wavelength shorter than 0.78 μm from the 0.6 μm band. Therefore, according to the fourth, sixth, eighth, ninth, and tenth embodiments, a surface emitting semiconductor laser using an active region made of an AlGaInP-based material and having a wavelength shorter than 0.78 μm can be reduced. It can be manufactured with threshold value, high output and good temperature characteristics. As the active layer, for example, a GaInP quantum well is used, and AlGaInP can be used as a barrier layer or a spacer (cladding) layer.
[0060]
Twelfth embodiment
The surface emitting semiconductor laser array according to the twelfth embodiment of the present invention is characterized by being constituted by the surface emitting semiconductor laser according to the eleventh embodiment.
[0061]
The surface-emitting type semiconductor laser of the present invention has improved heat generation and heat radiation. Therefore, in the case of an array, characteristic deterioration (threshold increase, output decrease, etc.) due to interference of heat generated by other elements is reduced, A high-performance surface-emitting type semiconductor laser array can be realized. Further, since the influence of heat on other elements can be reduced, there is an advantage that the interval between the elements can be reduced.
[0062]
Thirteenth embodiment
The optical transmission module according to the thirteenth embodiment of the present invention is directed to the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh embodiment, or the surface emitting semiconductor laser according to the twelfth embodiment. It is characterized in that a light emitting semiconductor laser array is used as a light source.
[0063]
The surface-emitting type semiconductor laser of the present invention has improved heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, and has a high output, can perform optical transmission using an acrylic POF, and is a cheap light source. An economical optical transmission module using a light emitting semiconductor laser and a cheap optical fiber, POF, can be realized.
[0064]
Fourteenth embodiment
The optical transceiver module according to the fourteenth embodiment of the present invention includes the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh embodiment, or the surface emitting semiconductor laser according to the twelfth embodiment. It is characterized in that a light emitting semiconductor laser array is used as a light source.
[0065]
The surface-emitting type semiconductor laser of the present invention has improved heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, and has a high output, can perform optical transmission using an acrylic POF, and is a cheap light source. An economical optical transceiver module using a light emitting semiconductor laser and a cheap optical fiber, POF, can be realized.
[0066]
15th embodiment
The optical communication system according to the fifteenth embodiment of the present invention includes the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth or eleventh embodiment, or the surface emitting semiconductor laser according to the twelfth embodiment. It is characterized in that a light emitting semiconductor laser array is used as a light source.
[0067]
The surface-emitting type semiconductor laser of the present invention has improved heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, and has a high output, can perform optical transmission using an acrylic POF, and is a cheap light source. An economical optical communication system using a light emitting semiconductor laser and a cheap optical fiber, POF, can be realized. In addition, since a surface-emitting type semiconductor laser is used, high-speed transmission is possible and extremely economical as compared with a case where an LED is used. Is effective.
[0068]
Sixteenth embodiment
An optical writing system (for example, a laser printer) according to a sixteenth embodiment of the present invention includes the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh embodiment, or The twelfth embodiment is characterized in that the surface emitting semiconductor laser array is used as a light source.
[0069]
The surface-emitting type semiconductor laser is advantageous for low power consumption operation and can reduce a rise in temperature in a box such as a printer. In the case of the surface emitting type, arraying is easy, and since it is formed by a normal semiconductor process, the positional accuracy of the elements is high, and at the same time, writing with a multi-beam becomes easy, and the writing speed is remarkably improved. Even if the writing dot density increases, printing can be performed without reducing the printing speed. In the case of the same writing dot density, the printing speed can be increased.
[0070]
Seventeenth embodiment
The optical pickup system according to the seventeenth embodiment of the present invention is directed to the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh embodiment or the surface emitting semiconductor laser according to the twelfth embodiment. It is characterized in that a light emitting semiconductor laser array is used as a light source.
[0071]
The wavelength of a semiconductor laser used as a light source for optical writing and reproduction on a medium is 0.78 μm for a CD and 0.65 μm for a DVD. The surface-emitting type semiconductor laser consumes about one digit less power than the end-face type semiconductor laser and has a longer power. Therefore, the present invention can reproduce not only a normal optical pickup system but also a 0.65 μm surface-emitting type semiconductor laser according to the present invention. A handy type optical pickup system can be realized as a light source.
[0072]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0073]
First embodiment
FIG. 1 is a view showing a semiconductor distributed Bragg reflector according to a first embodiment of the present invention. In the semiconductor distributed Bragg reflector of the first embodiment, the reflection design wavelength is 650 nm, and AlP and GaP are alternately laminated on an n-GaP substrate with a thickness of 1/4 times the reflection design wavelength in each medium. The resulting AlP / GaP periodic structure was grown by metal organic chemical vapor deposition (MOCVD). Raw materials include TMG (trimethylgallium), TMA (trimethylaluminum), PH₃(Phosphine) and H as an n-type dopant₂Se (hydrogen selenide) was used. Also, the carrier gas contains H₂Was used. Note that an AlGaP linear composition gradient layer having a thickness of 10 nm in which the Al composition is linearly changed from one value to the other value is inserted between AlP and GaP. The thickness is 1/4 times the design wavelength. In the MOCVD method, since the composition of AlGaP can be controlled by changing the supply amount of the raw material, the composition gradient layer can be grown more easily than in the MBE method (molecular beam epitaxy method).
[0074]
Since AlP and GaP have a large difference in refractive index and a large band gap, and AlGaP-based materials do not absorb light in a wavelength band longer than 550 nm, high reflectance can be obtained with a small number of layers even at a wavelength of 650 nm. Furthermore, the resistance could be reduced by inserting the composition gradient layer.
[0075]
Second embodiment
FIG. 2 is a diagram showing a surface emitting semiconductor laser device according to a second embodiment of the present invention.
[0076]
As shown in FIG. 2, the surface emitting semiconductor laser device according to the second embodiment has a periodic structure in which n-AlP and n-GaP are alternately (for example, 24.5) stacked on an n-GaP substrate. An n-semiconductor distributed Bragg reflector (first semiconductor distributed Bragg reflector: also simply referred to as a first reflector) is formed. Then, an n-GaP first cap layer is formed on the first reflecting mirror, and a first reflecting mirror structure is formed. In the first reflector structure, a linear composition gradient layer having a thickness of 20 nm in which the Al composition is linearly changed from one value to the other value is inserted between AlP and GaP. The thickness is set to １ ／ of the oscillation wavelength in the medium including the inclined layer. Specifically, a linear composition gradient layer is formed between AlP and GaP._zGa_1-zP (0 ≦ y <z <x ≦ 1) is provided. By providing this linear composition gradient layer, when electricity flows through the first reflecting mirror structure, the band discontinuity between AlP and GaP can be smoothed, and the increase in resistance can be suppressed. . The composition z of the linear composition gradient layer may be changed stepwise or may be changed continuously. Further, the thickness of the linear composition gradient layer is preferably as large as possible within a range where the reflectance is sufficient. Since AlP has a lattice constant close to that of GaP, it has a thickness equal to or less than the critical film thickness, and the first reflecting mirror structure is a material system substantially lattice-matched to the GaP substrate.
[0077]
On such a first reflecting mirror structure, n-Ga having a tensile strain composition with respect to a GaAs substrate is provided._0.6In_0.4P Second cap layer, lattice matched to GaAs substrate (Al_0.7Ga_0.3)_0.5In_0.5P first spacer (cladding) layer, Ga having a compressive strain composition with respect to the GaAs substrate_0.4In_0.6Lattice matching between the P well layer and the GaAs substrate (Al_0.5Ga_0.5)_0.5In_0.5A quantum well active layer comprising a P barrier layer, (Al_0.7Ga_0.3)_0.5In_0.5A P second spacer (cladding) layer is formed.
[0078]
And furthermore, p-Al_xGa_1-xAs (x = 0.95) and p-Al_yGa_1-yA p-semiconductor distributed Bragg reflecting mirror (second semiconductor distributed Bragg reflecting mirror: also simply referred to as a second reflecting mirror) having a periodic structure in which As (y = 0.5) is alternately stacked (for example, 50 periods) is formed. ing. In this second reflecting mirror, p-Al_xGa_1-xAs (x = 0.95) and p-Al_yGa_1-yBetween As (y = 0.5), a linear composition gradient layer having a thickness of 20 nm in which the Al composition is linearly changed from one value to the other value is inserted. The thickness is set to １ ／ of the oscillation wavelength in the medium. Specifically, as the linear composition gradient layer, Al_zGa_1-zAs (0 ≦ y <z <x ≦ 1) is provided.
[0079]
Then, a p-GaAs contact layer is formed on the uppermost portion. Since GaAs has a composition that absorbs oscillation light, it needs to be thin, and the uppermost p-Al_yGa_1-yIt is necessary to make the thickness including As (y = 0.5) and GaAs such that the reflectance does not decrease. The uppermost GaAs layer is a contact layer that makes contact with the electrode. In addition, the thickness between the first and second reflecting mirrors is set to a thickness of one oscillation wavelength (so-called lambda cavity).
[0080]
The surface-emitting semiconductor laser wafer of the second embodiment is manufactured as follows.
[0081]
That is, as shown in FIG. 3A, a first reflecting mirror and an n-GaP first cap layer having a periodic structure in which n-AlP and n-GaP are alternately stacked are formed on an n-GaP substrate. I do.
[0082]
Further, as shown in FIG. 3B, a GaInP etching stop layer, a p-GaAs contact layer, a p-Al_yGa_1-yAs (y = 0.5) and p-Al_xGa_1-xAs (x = 0.95) are alternately laminated to form a second reflecting mirror, and further, (Al)_0.7Ga_0.3)_0.5In_0.5P second spacer (cladding) layer, GaInP / AlGaInP quantum well active layer, (Al_0.7Ga_0.3)_0.5In_0.5P first spacer (cladding) layer, n-Ga_0.6In_0.4A P second cap layer is formed.
[0083]
The crystal growth was performed by the MOCVD method. Raw materials include TMG (trimethylgallium), TMA (trimethylaluminum), TMI (trimethylindium), PH₃(Phosphine), AsH₃(Arsine), H as an n-type dopant₂Se (hydrogen selenide) and CBr as a p-type dopant₄Was used. The carrier gas is H₂Was used. In the MOCVD method, a composition such as a composition gradient layer can be easily formed by controlling the supply amount of a source gas, and thus is suitable as a crystal growth method for a surface emitting semiconductor laser including a DBR. In addition, since high vacuum is not required as in the MBE method and the supply flow rate and supply time of the source gas need only be controlled, mass productivity is excellent.
[0084]
Then, the crystal growth surfaces of the two growth substrates shown in FIGS. 3A and 3B are cleaned and brought into close contact at room temperature, and then H is applied at a high temperature (for example, 600 ° C.).₂Adhere by heat treatment in atmosphere. Thereafter, the GaAs substrate is chemically etched down to the GaInP etching stop layer. When a sulfuric acid-based etchant is used, phosphorus-based materials such as GaInP are not etched, and thus can be controlled. Further, this time, the GaInP etching stop layer is selectively etched with a hydrochloric acid-based etchant. Conversely, when a hydrochloric acid-based etchant is used, the phosphorus-based material is etched, and GaAs or the like is not etched, so that control can be performed. Thereby, the surface of the p-GaAs contact layer can be exposed.
[0085]
As a result, a wafer was formed in which an n-AlGaP-based DBR (first reflecting mirror), an AlGaInP-based active region, and a p-AlGaAs-based DBR (second reflecting mirror) were stacked on the n-GaP substrate.
[0086]
In the second embodiment, the portion outside the current path is changed to proton (H⁺) Irradiation to form an insulating layer (high resistance portion) to form a current narrowing portion. Then, a p-side electrode is formed on the p-contact layer, which is the uppermost layer of the second reflector, excluding the light emitting portion, and an n-side electrode is formed on the back surface of the GaP substrate.
[0087]
The AlGaP-based DBR has a larger band gap of the material than the AlGaAs-based DBR, and in a short wavelength band, can obtain a small absorption and a high reflectance with a small number of layers. Further, the heat conductivity of the GaP substrate is higher than that of the GaAs substrate, and the heat conductivity of the AlGaP-based DBR is higher than that of the AlGaAs-based DBR. The threshold was low, the output was high, and continuous operation was possible up to high temperatures.
[0088]
Surface emitting semiconductor lasers utilizing the wafer bonding technique have been proposed in Japanese Patent Application Laid-Open Nos. 7-335967, 11-103125, 2001-68783, etc., but these are in the 1.3 μm and 1.55 μm bands. In a long wavelength band such as In this wavelength band, the material system on the InP substrate is mainly used as the active layer, but no excellent reflector material is found on the substrate, and the AlGaAs-based material on the GaAs substrate used in the 0.85 μm band or the like is used. Excellent reflector is glued. On the other hand, in the present invention, an AlGaP-based material capable of growing a crystal on a GaP substrate is used for the reflector, and the configuration and operation and effect are different from those of the conventional examples.
[0089]
Third embodiment
FIG. 4 is a view showing a surface emitting semiconductor laser device according to a third embodiment of the present invention.
[0090]
The main difference between the third embodiment and the second embodiment is that the current confinement is performed not by proton irradiation but by selective oxidation of the AlAs layer.
[0091]
That is, in the third embodiment, part of the low refractive index layer closest to the active layer of the p-side DBR is an AlAs layer. Then, a mesa of a predetermined size is formed by exposing at least the side surface of the p-AlAs selectively oxidized layer, and the AlAs that has appeared on the side surface is oxidized from the side surface with water vapor to form an AlAs._xO_yA current narrowing layer was formed. Then, the etched portion is buried with polyimide and planarized, the polyimide on the upper reflector having the p-contact layer and the light-emitting portion is removed, and a p-side electrode is formed on the p-contact layer other than the light-emitting portion. An n-side electrode was formed on the back surface of.
[0092]
In addition, the threshold current was low because the current was narrowed by selective oxidation of the selectively oxidized layer containing Al and As as main components. According to the current narrowing structure using the current narrowing layer made of the Al oxide film in which the selective oxidation layer is selectively oxidized, the current spreading can be suppressed by forming the current narrowing layer close to the active layer, so that it can be exposed to the atmosphere. The carrier can be efficiently confined in a small area that is not present. Further, by oxidizing to form an Al oxide film, the refractive index is reduced, and light can be efficiently confined in a minute region in which carriers are confined by the effect of the convex lens, and the efficiency is extremely improved, and the threshold current is reduced. be able to. In addition, since the current narrowing structure can be easily formed, the manufacturing cost can be reduced.
[0093]
Fourth embodiment
FIG. 5 is a view showing a surface emitting semiconductor laser device according to a fourth embodiment of the present invention.
[0094]
The main difference between the fourth embodiment and the third embodiment is that light is extracted from the GaP substrate. Therefore, different from the third embodiment, the reflectance of the first reflecting mirror is lower than the reflectance of the second reflecting mirror. Further, a light extraction window was formed on the back surface of the GaP substrate, and a non-reflection film was further formed. And mounted on the heat sink by junction down.
[0095]
Conventionally, an AlGaInP red surface emitting semiconductor laser formed on a GaAs substrate cannot have a substrate-side light extraction structure because GaAs absorbs light. However, in the present invention, the substrate is GaP, A light extraction structure became possible, so that junction-down mounting became possible, and heat dissipation was further improved. Therefore, continuous operation was possible up to a higher temperature.
[0096]
In addition, by adopting the substrate-side light extraction structure, when integrated with array elements or other functional elements, soldering is performed on a separate substrate on which a wiring structure has been formed in advance, without using wire bonding to connect to drive circuits and the like. Bonding can be performed via a conductive adhesive such as this, and cost reduction can be achieved.
[0097]
Fifth embodiment
FIG. 6 is a view showing a surface emitting semiconductor laser device according to a fifth embodiment of the present invention.
[0098]
The fifth embodiment differs from the third embodiment mainly in that an AlGaAs-based DBR lattice-matched to the GaAs substrate is formed between the wafer bonding interface and the active layer. That is, in the fifth embodiment, the first reflecting mirror is formed in two stages of the AlGaP-based first reflecting mirror (A) and the AlGaAs-based first reflecting mirror (B). In the fifth embodiment, five pairs of AlGaAs-based DBRs were used. In the fifth embodiment, the AlGaAs-based DBR is made of n-Al_xGa_1-xAs (x = 0.95) and n-Al_yGa_1-yAs (y = 0.5) are alternately stacked, and the uppermost layer (low-refractive index layer) serving as the wafer bonding interface is n-Ga._xIn_1-xP (x = 0.6) was used as a second cap layer. The thickness of the GaP first cap layer, which is the uppermost layer on the GaP substrate, and the thickness of the GaInP second cap layer, which is the uppermost layer of the GaAs substrate, were set to an odd multiple of λ / 4 in total.
[0099]
If the wafer bonding interface is near the active layer, crystal defects due to the difference in lattice constant between the GaP-based material and the GaAs-based material may affect the active layer and reduce the reliability. The effect can be eliminated by providing an AlGaAs-based DBR lattice-matched to the GaAs substrate between the wafer bonding interface and the active layer as in the example.
[0100]
Sixth embodiment
FIG. 7 is a view showing a surface emitting semiconductor laser device according to a sixth embodiment of the present invention.
[0101]
The sixth embodiment differs from the fifth embodiment mainly in that an AlGaP-based DBR lattice-matched to a GaP substrate is also used for the second reflecting mirror.
[0102]
The wafer of the surface emitting semiconductor laser of the sixth embodiment is manufactured as follows.
[0103]
That is, as shown in FIG. 8A, a first reflecting mirror (A) having a periodic structure in which 29.5 pairs of n-AlP and n-GaP are stacked on an n-GaP substrate, One cap layer is formed, and this is referred to as epiwafer 1.
[0104]
As shown in FIG. 8B, a periodic structure having a 19.5 pair of a GaPAs etching stop layer, a p-GaP contact layer, and 19.5 pairs of p-AlP and p-GaP laminated on a p-GaP substrate. 2 Reflector (A) and p-GaP third cap layer are formed, and this is referred to as epiwafer 2.
[0105]
Further, as shown in FIG. 8C, a p-GaInP fourth cap layer and a p-Al_xGa_1-xAs (x = 0.95) and p-Al_yGa_1-yAs (y = 0.5) are alternately stacked in 4.5 pairs to form a second reflecting mirror (B), and further, (Al)_0.7Ga_0.3)_0.5In_0.5P second spacer layer (cladding layer), GaInP / AlGaInP quantum well active layer, (Al_0.7Ga_0.3)_0.5In_0.5P first spacer layer (cladding layer), n-Al_xGa_1-xAs (x = 0.95) and n-Al_yGa_1-yAs (y = 0.5) and a 4.5-pair alternately laminated first reflector (B) and an n-GaInP second cap layer are formed. In the sixth embodiment, a part of the low refractive index layer closest to the active layer of the p-side DBR is an AlAs selective oxidation layer.
[0106]
Note that a composition gradient layer was inserted between the low refractive index layer and the high refractive index layer of each reflecting mirror. The crystal growth was performed by the MOCVD method. Raw materials include TMG (trimethylgallium), TMA (trimethylaluminum), PH₃(Phosphine), AsH₃(Arsine), H as an n-type dopant₂Se (hydrogen selenide), CBr as a p-type dopant₄Was used. The carrier gas is H₂Was used. The MOCVD method is suitable as a crystal growth method for a surface-emitting type semiconductor laser including a DBR because a composition such as a composition gradient layer can be easily formed by controlling the supply amount of a source gas. Further, since the supply flow rate and the supply time of the raw material gas need only be controlled without requiring a high vacuum unlike the MBE method, mass productivity is excellent.
[0107]
In the sixth embodiment, first, the crystal growth surfaces of the two growth substrates of the epi-wafer 1 and the epi-wafer 3 are washed and brought into close contact at room temperature, and then H is heated at a high temperature (for example, 600 ° C.).₂Adhere by heat treatment in atmosphere. After that, the GaAs substrate is chemically etched away until the p-GaInP fourth cap layer appears. When a sulfuric acid-based etchant is used, a phosphorus-based material such as GaInP is not etched, and thus can be controlled. Thereby, the surface of the p-GaInP fourth cap layer appeared.
[0108]
Next, the crystal growth surfaces of the two growth substrates, the bonded wafer and the epi-wafer 2, are cleaned and brought into close contact at room temperature.₂Adhere by heat treatment in atmosphere. After that, the p-GaP substrate of the epiwafer 2 is chemically etched down to the GaPAs etching stop layer. When a hydrochloric acid-based etchant is used, arsenic-based materials such as GaPAs are not etched, and can be controlled. Further, this time, the GaPAs etching stop layer is selectively etched with a sulfuric acid-based etching solution. Conversely, when a sulfuric acid-based etchant is used, the arsenic-based material is etched, and GaP or the like is not etched, so that control can be performed. As a result, the surface of the p-GaP contact layer appeared.
[0109]
Thereby, on the n-GaP substrate, a DBR having a two-stage structure of an n-AlGaP system and an n-AlGaAs system, an AlGaInP-based active region, and a DBR having a two-stage structure of a p-AlGaAs system and a p-AlGaP system are stacked. Thus, a wafer of the surface emitting semiconductor laser shown in FIG. 7 was formed.
[0110]
In the sixth embodiment, a mesa of a predetermined size is formed by exposing at least the side surface of the p-AlAs layer to be selectively oxidized, and the AlAs that appears on the side surface is oxidized from the side surface with water vapor to form an AlAs._xO_yA current narrowing portion was formed. Then, the etched portion is buried and flattened with polyimide, the polyimide on the upper reflector having the p-contact layer and the light-emitting portion is removed, and a p-side electrode is formed on the p-contact layer other than the light-emitting portion. An n-side electrode was formed on the back surface of the substrate.
[0111]
The AlGaP-based DBR has a larger band gap of the material than the AlGaAs-based DBR, and in a short wavelength band, the light absorption is small with a small number of layers and a high reflectance can be obtained. The heat conductivity of the GaP substrate is higher than that of the GaAs substrate, and the heat conductivity of the AlGaP-based DBR is higher than that of the AlGaAs-based DBR. The threshold was small, the output was large, and continuous operation was possible up to high temperatures.
[0112]
In addition, AlAs and GaAs can be said to be suitable for DBR because of a large difference in refractive index between AlGaAs-based DBRs. However, as the wavelength of the laser becomes shorter, it is necessary to increase the Al composition of the high refractive index layer to avoid light absorption. There is. Therefore, for example, at a wavelength of 650 nm, Al_0.5Ga_0.5As is often used. Therefore, the refractive index difference from the low refractive index layer is about half as compared with the combination of AlAs / GaAs, and the number of layers increases to about twice in order to obtain a necessary reflectance. Further, in practice, the film thickness fluctuates as the number of stacked layers increases, and it is difficult to obtain a high reflectance due to absorption since the DBR composition does not completely suppress light absorption. There is a problem that the characteristics of the laser are deteriorated.
[0113]
On the other hand, if an AlGaP-based material is used for the reflecting mirror, it becomes transparent for wavelengths longer than 550 nm, and it becomes possible to use any composition between GaP and AlP at these wavelengths. As a result, a large difference in refractive index can be obtained, crystal growth is easy without increasing the number of layers, and a high reflectance can be easily obtained.
[0114]
Further, in the surface-emitting type semiconductor laser, since the band is discontinuous between the low-refractive-index layer and the high-refractive-index layer constituting the DBR, the resistance tends to be high, so that a composition gradient layer is inserted as shown in the first embodiment. To reduce resistance. According to Sandip et al.'S document "Appl. @ Phys. @ Let. @ Vol.60, No. 5, $ 1992, @ pp630-632", the band discontinuity between AlP and GaP is the same as that of AlAs and GaAs in both the conduction band and the valence band. It is comparable to that of. As described above, when the AlGaP-based material is used for the DBR, the number of stacked layers can be reduced to about half, so that the number of hetero junctions, which is the cause of the increase in resistance, is reduced to about half, the resistance can be reduced, and heat generation in the DBR is reduced. be able to.
[0115]
Seventh embodiment
FIG. 9 is a diagram (top view) showing a surface-emitting type semiconductor laser array (surface-emitting type semiconductor laser array chip) according to a seventh embodiment of the present invention.
[0116]
The surface emitting semiconductor laser array according to the seventh embodiment has ten surface emitting semiconductor lasers according to the sixth embodiment arranged one-dimensionally. However, p and n were reversed for the surface emitting semiconductor laser of the sixth embodiment. In the example of FIG. 9, the surface emitting semiconductor laser of the sixth embodiment is integrated one-dimensionally, but the surface emitting semiconductor laser of the sixth embodiment may be integrated two-dimensionally. That is, the surface-emitting type semiconductor laser array of the seventh embodiment is formed on a p-type GaP semiconductor substrate, and has an n-side individual electrode formed on the upper surface and a p-side common electrode formed on the back surface. Here, the oscillation wavelength of this surface emitting semiconductor laser array was 650 nm. Further, heat generation was reduced and heat radiation was improved, so that there was no adverse effect on adjacent elements.
[0117]
Eighth embodiment
FIG. 10 is a view showing an optical transmission module according to the eighth embodiment, which is a combination of the surface emitting semiconductor laser array chip of the seventh embodiment and an inexpensive acrylic POF (plastic optical fiber). . In the eighth embodiment, laser light from a surface emitting semiconductor laser is input to a POF and transmitted. Here, the acrylic POF has a bottom of absorption loss at a wavelength of 650 nm, and therefore, this wavelength is preferable. In the field of optical communication, parallel transmission using a laser array in which a plurality of semiconductor lasers are integrated has been attempted in order to transmit more data at the same time. As a result, high-speed parallel transmission becomes possible, and more data can be transmitted simultaneously than in the past.
[0118]
In the example of FIG. 10, the surface-emitting type semiconductor laser device and the optical fiber are in one-to-one correspondence, but a plurality of surface-emitting type semiconductor laser devices having different oscillation wavelengths are arranged one-dimensionally or two-dimensionally in an array. By performing wavelength multiplexing transmission, the transmission speed can be further increased.
[0119]
Further, in the eighth embodiment, since the inexpensive surface-emitting type semiconductor laser device according to the present invention and the inexpensive POF are combined, a low-cost optical transmission module can be realized. An optical communication system can be realized. POF is not transparent compared to quartz-based fiber, so it is not suitable for long-distance transmission and has extremely low cost. Therefore, POF is effective for short-distance data communication such as for home use, indoor use in offices, and in equipment. is there.
[0120]
Ninth embodiment
FIG. 11 is a view showing an optical transceiver module according to a ninth embodiment of the present invention, which is a combination of the surface emitting semiconductor laser device, the receiving photodiode, and the acrylic POF of the sixth embodiment. I have.
[0121]
When the surface-emitting type semiconductor laser device according to the present invention is used in an optical communication system, the surface-emitting type semiconductor laser device and the POF are low-cost, so as shown in FIG. It is possible to realize a low-cost optical communication system using an optical transmission / reception module in which a receiving photodiode and a POF are combined. Further, since the POF has a large fiber diameter, is easily coupled with the fiber, and can reduce the mounting cost, an extremely low-cost module can be realized. Further, in the case of the surface emitting semiconductor laser device according to the present invention, since the temperature characteristics are good and the threshold value is low, a system that generates less heat and can be used without cooling to a high temperature without cooling can be realized. .
[0122]
As an optical communication system using the surface emitting semiconductor laser device according to the present invention, transmission between devices such as a computer such as a LAN (Local Area Network) using an optical fiber, data transmission between boards in the device, In particular, it can be used for short-distance communication as an optical interconnection between LSIs and between elements in the LSI.
[0123]
That is, although the processing performance of LSIs and the like has been improved in recent years, the transmission speed of the part connecting them will become a bottleneck in the future. When the signal connection in the system is changed from the conventional electrical connection to the optical interconnection (for example, between the boards of the computer system, between the LSIs in the board, between the elements in the LSI, etc., the optical transmitting module and the optical transmitting and receiving module according to the present invention). ) To enable an ultra-high-speed computer system.
[0124]
When a plurality of computer systems are connected using the optical transmission module and the optical transmission / reception module according to the present invention, an ultra-high-speed network system can be constructed. In particular, a surface-emitting type semiconductor laser device is suitable for a parallel transmission type optical communication system because power consumption can be reduced by orders of magnitude and a two-dimensional array can be easily formed as compared with an edge-emitting type laser.
[0125]
Tenth embodiment
FIG. 12 is a view showing a tenth embodiment of the present invention. That is, FIG. 3 is a diagram showing an optical scanning portion of a laser printer in which a surface emitting semiconductor laser array chip (16-beam VCSEL array) and a photosensitive band drum are arranged in two dimensions of 4 × 4 having a wavelength of 650 nm. FIG. 13 is a diagram (top view) showing a schematic configuration of the surface emitting semiconductor laser array chip in FIG. In the laser printers of FIGS. 12 and 13, by adjusting the lighting timing of the surface-emitting type semiconductor laser array chips arranged two-dimensionally in 4 × 4, on the photosensitive zone in the sub-scanning direction as shown in FIG. It can be understood that the configuration is the same as the case where the light sources are arranged at intervals of 20 μm.
[0126]
In the tenth embodiment, a plurality of beams from a surface-emitting type semiconductor laser array are rotated on a scanning polygon mirror at a high speed using the same optical system to adjust the lighting timing to adjust the timing of lighting on a photosensitive band which is a surface to be scanned. And scans multiple beams at once.
[0127]
According to the tenth embodiment, it is possible to write on the photosensitive belt at intervals of 20 μm in the sub-scanning direction. Note that the interval in the sub-scanning direction corresponds to 1200 DPI (dots / inch). Further, the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light source. With this laser printer, 16 dots could be written simultaneously, and high-speed printing was possible. By increasing the number of arrays, higher-speed printing becomes possible. Further, by adjusting the interval between the surface emitting semiconductor laser elements, the interval in the sub-scanning direction can be adjusted. That is, the density can be made higher than 1200 DPI, and higher quality printing can be performed. In order to increase the density, it is necessary to further narrow the beam diameter using a lens system. However, there is a limit due to the wavelength, and it is preferable that the wavelength of the light source is shorter. Conventionally, a surface-emitting type semiconductor laser has not been able to obtain an element satisfying output and temperature characteristics at a wavelength shorter than 780 nm. However, the present invention has achieved a practical level element in a red (600 nm) wavelength region. It was realized.
[0128]
Although the tenth embodiment shows an example of application to a laser printer, the surface emitting semiconductor laser of the present invention can be applied to an optical pickup system. That is, it can also be used as a light source for recording and reproducing CDs and the like.
[0129]
【The invention's effect】
As described above, according to the first aspect of the present invention, in a semiconductor distributed Bragg reflector whose refractive index changes periodically and reflects incident light by light wave interference, a layer having a small refractive index is made of Al._xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-ySince P (0 ≦ y <x ≦ 1), the reflectance can be increased with a small number of layers, the heat generation can be reduced, and the heat dissipation can be improved. it can. That is, an AlGaP-based material having AlP or GaP as a terminating substance has a large difference in refractive index similarly to an AlGaAs-based material having AlAs or GaAs as a terminating substance, and has a lattice constant close to that of GaP regardless of the Al composition. Crystal growth. Therefore, it is considered that the AlGaP-based material is suitable as a material of the semiconductor distributed Bragg reflector similarly to the AlGaAs-based material. Further, since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, it transmits light in a wavelength band longer than about 0.55 μm. Therefore, the entire composition range of AlGaP can be used in a wavelength band longer than 0.55 μm, and the number of stacked layers can be smaller than that of an AlGaAs-based material in a wavelength band shorter than 0.78 μm. A Bragg reflector can be provided.
[0130]
According to the second aspect of the present invention, in a semiconductor distributed Bragg reflector formed by laminating two types of semiconductor layers having different refractive indices, the two types of semiconductor layers having different refractive indices are layers having a lower refractive index. And a layer having a large refractive index, and a layer having a small refractive index is Al_xGa_1-xP (0 <x ≦ 1), the layer having a large refractive index is Al_yGa_1-yP (0 ≦ y <x ≦ 1), and a semiconductor layer having a refractive index between the two semiconductor layers having different refractive indexes is provided between the two semiconductor layers having different refractive indexes. (Specifically, Al_zGa_1-zP (because the intermediate layer composed of 0 ≦ y <z <x ≦ 1) is provided), and when electricity is passed through the reflecting mirror, the band between the layer having a small refractive index and the layer having a large refractive index is different. The continuity can be smoothed, whereby the increase in resistance is suppressed, and a low-resistance reflector can be provided.
[0131]
According to the third aspect of the present invention, an active region including at least one active layer for generating a laser beam on a semiconductor substrate and upper and lower portions of the active region for obtaining a laser beam are provided. In a surface-emitting type semiconductor laser having a resonator structure including an upper reflector and a lower reflector, the semiconductor Bragg reflector according to claim 1 or 2 is used as the upper reflector and / or the lower reflector. Therefore, the heat radiation is improved, the temperature rise during operation can be suppressed, and a surface emitting semiconductor laser with high output and low threshold current can be provided. That is, since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, it transmits light having a wavelength longer than about 0.55 μm, and particularly uses the AlGaAs-based material in a shorter wavelength band than 0.78 μm. As a result, a high reflectance of 99% or more can be obtained more easily, whereby the number of stacked reflectors can be reduced to about half, resistance can be reduced, and light absorption can be reduced. Further, since the thermal conductivity of the AlGaP-based material is higher than that of the AlGaAs-based material, the heat dissipation is improved, the temperature rise during operation can be suppressed, and a surface-emitting type semiconductor laser with high output and low threshold current can be obtained. Further, temperature characteristics can be improved. The effect of heat conduction is effective not only when the laser wavelength is in the 0.6 μm band but also in other wavelength ranges.
[0132]
According to the fourth aspect of the present invention, an active region including at least one active layer for generating a laser beam, and an upper portion and a lower portion of the active region for obtaining a laser beam are provided on a semiconductor substrate. In a surface emitting semiconductor laser having a resonator structure including an upper reflecting mirror and a lower reflecting mirror, the active region is made of a material lattice-matched to GaAs, and the upper reflecting mirror and / or the lower reflecting mirror is: Since it is a semiconductor distributed Bragg reflector made of a material lattice-matched to GaP (specifically, an AlGaP-based material is used as the reflector material), it is compared with a surface-emitting type semiconductor laser using a conventional AlGaAs-based reflector. As a result, it is possible to realize a surface-emitting type semiconductor laser having a high thermal conductivity and improved heat radiation and excellent temperature characteristics. In addition, since the AlGaP-based material has a wider gap than the AlGaAs-based material, particularly when the wavelength is shorter than 780 nm, high reflectance can be easily obtained with a small number of layers, absorption is reduced, and the threshold is low. And a high output surface emitting semiconductor laser can be obtained.
[0133]
According to the fifth aspect of the present invention, a step of growing a first semiconductor distributed Bragg reflector on a first GaP substrate, a step of growing an active region on a GaAs substrate, and a step of growing a first semiconductor distributed Bragg reflector on a GaAs substrate. (2) the step of growing a semiconductor distributed Bragg reflector; the step of bonding the active region to the first semiconductor distributed Bragg reflector and the step of removing the GaAs substrate; and the step of bonding the active region to the second semiconductor distributed Bragg reflector. Manufacturing a surface emitting semiconductor laser having a higher thermal conductivity and improved heat radiation and better temperature characteristics than a surface emitting semiconductor laser using a conventional AlGaAs-based reflector. it can. In addition, since the AlGaP-based material has a wider gap than the AlGaAs-based material, particularly when the wavelength is shorter than 780 nm, high reflectance can be easily obtained with a small number of layers, absorption is reduced, and the threshold is low. And a high output surface emitting semiconductor laser can be obtained. That is, an AlGaP-based material having AlP or GaP as a terminating material can grow crystals on a GaP substrate with a lattice constant close to that of GaP and have a large refractive index difference, similarly to an AlGaAs-based material having AlAs or GaAs as a terminating material. For example, in the wavelength band of 0.6 μm, an active region including an active layer can be formed of an AlGaInP-based material that can grow on a GaAs substrate without misfit dislocations. By bonding these, the above-mentioned surface-emitting type semiconductor laser can be manufactured.
[0134]
According to the sixth aspect of the present invention, a first semiconductor distributed Bragg reflector made of a material lattice-matched to GaP, an active region made of a material lattice-matched to GaAs, and a lattice matched to GaAs are formed on a semiconductor substrate. And a second semiconductor distributed Bragg reflector made of a material which has a higher thermal conductivity and improved heat radiation compared to a surface emitting semiconductor laser using a conventional AlGaAs-based reflector. And a surface-emitting type semiconductor laser having good characteristics can be realized. In addition, since the AlGaP-based material has a wider gap than the AlGaAs-based material, particularly when the wavelength is shorter than 780 nm, high reflectance can be easily obtained with a small number of layers, absorption is reduced, and the threshold is low. And a high output surface emitting semiconductor laser can be obtained. That is, GaP has approximately twice the thermal conductivity as GaAs and has good heat dissipation. Therefore, heat generated during operation can be well released, and the temperature characteristics are improved. As described above, it is preferable that both semiconductor distributed Bragg reflectors are crystal-grown on a GaP substrate. However, when both the reflector and the active region are crystal-grown on a GaAs substrate and the GaP substrate is bonded, the GaP substrate is bonded. The effect of heat dissipation by the substrate can be obtained.
[0135]
According to the seventh aspect of the present invention, a step of crystal-growing the first semiconductor distributed Bragg reflector on the GaP substrate and a step of crystal-growing the second semiconductor distributed Bragg reflector and the active region on the GaAs substrate are provided. Bonding the active region and the first semiconductor distributed Bragg reflector, so that the thermal conductivity is higher and the heat radiation is higher than that of a surface emitting semiconductor laser using a conventional AlGaAs-based reflector. A surface emitting semiconductor laser with improved temperature characteristics and good characteristics can be manufactured. In addition, since the AlGaP-based material has a wider gap than the AlGaAs-based material, particularly when the wavelength is shorter than 780 nm, high reflectance can be easily obtained with a small number of layers, absorption is reduced, and the threshold is low. And a high output surface emitting semiconductor laser can be obtained. That is, an AlGaP-based material having AlP or GaP as a terminating substance has a lattice constant close to that of GaP and can grow a crystal on a GaP substrate, and has a large refractive index difference. This is the same tendency as AlGaAs-based materials having AlAs and GaAs as termination materials. For example, in the wavelength band of 0.6 μm, an active region including an active layer can be formed of an AlGaInP-based material that can grow on a GaAs substrate without misfit dislocations. The second semiconductor distributed Bragg reflector can be formed on the GaAs substrate by using an AlGaAs-based material continuously with the active region. By bonding these, the above-mentioned surface-emitting type semiconductor laser can be manufactured.
[0136]
According to the eighth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth or sixth aspect, the active region made of a material lattice-matched to GaAs and the semiconductor distributed Bragg made of a material lattice-matched to GaP are provided. A part of a semiconductor distributed Bragg reflector made of a material lattice-matched to GaAs is formed between the reflector and the semiconductor distributed Bragg reflector made of a material lattice-matched to the GaP and lattice-matched to the GaAs. Since a part of the semiconductor distributed Bragg reflector made of the material is adhered, it is possible to prevent a decrease in reliability. That is, when the wafer bonding interface is near the active layer, heat generated in the active layer and confined light act to cause crystal defects due to a difference in lattice constant between GaP-based and GaAs-based materials. In some cases, the influence may be exerted on the active layer to lower the reliability. However, by providing an AlGaAs-based DBR lattice-matched to the GaAs substrate between the wafer bonding interface and the active layer as described in claim 8, the above-mentioned effect is obtained. Can be prevented.
[0137]
According to the ninth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth or eighth aspect, the semiconductor substrate is a GaP substrate, and light is extracted from the GaP substrate side. Therefore, junction down mounting is possible, heat radiation can be extremely improved, and temperature characteristics can be improved. That is, the GaP substrate is transparent to light having a wavelength longer than about 0.55 μm, and can extract light. Therefore, a so-called junction-down mounting in which a heat sink or the like can be attached to a side where heat is mainly generated becomes possible, so that heat radiation can be extremely improved and temperature characteristics can be improved. Further, by preparing wirings and the like on the mounting substrate, wire bonding becomes unnecessary, which is particularly effective in the case of an array element.
[0138]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth, eighth or ninth aspect, AlAs containing Al and As as main components is selectively used. Since the oxidized current narrowing layer is provided, both low power consumption and thinning of the surface emitting semiconductor laser can be achieved. That is, Al_xGa_1-xOxidation experiments have shown that the addition of P to As decreases the refractive index and lowers the oxidation rate even though the group III is only Al. Therefore, it is not necessary to use AlGaAs having a smaller Al composition than the oxide layer as in the case of the AlGaAs-based reflector, and it is possible to use AlGaP having a large Al composition. Therefore, since the oxidation of the semiconductor distributed Bragg reflector can be suppressed without reducing the refractive index difference of the semiconductor distributed Bragg reflector, the current narrowing structure by the selective oxidation layer can be achieved without increasing the number of layers of the semiconductor distributed Bragg reflector. It is possible to achieve both low power consumption and thinning of the surface emitting semiconductor laser.
[0139]
According to the eleventh aspect of the present invention, in the surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth or tenth aspect, the active region has at least Ga, In, P And the wavelength is shorter than 0.78 μm, so that it is possible to provide a surface emitting semiconductor laser having a good temperature characteristic and a wavelength shorter than 0.78 μm. That is, since the AlGaP-based material has a larger band gap energy than the AlGaAs-based material, the AlGaP-based material transmits light in a wavelength band longer than about 0.55 μm, and particularly, transmits the AlGaAs-based material in a shorter wavelength band than 0.78 μm. High reflectivity of 99% or more can be obtained more easily than when used, the number of stacked layers can be reduced to about half, and a distributed Bragg reflector with low resistance can be formed. Further, since the thermal conductivity of the AlGaP-based material is higher than that of the AlGaAs-based material, the heat radiation is improved, the temperature rise during operation can be suppressed, and the temperature characteristics are improved. Therefore, it is possible to provide a surface emitting semiconductor laser having a good temperature characteristic and a wavelength shorter than 0.78 μm using an active region made of an AlGaInP-based material.
[0140]
According to a twelfth aspect of the present invention, there is provided a surface emitting semiconductor laser array comprising the surface emitting semiconductor laser according to the eleventh aspect. Since heat generation and heat dissipation are improved, when this is used as an array, characteristic deterioration (threshold rise, output decrease, etc.) due to heat generated by other elements is reduced, and a high performance surface emitting semiconductor laser Array can be realized. Further, since the influence of heat on other elements can be reduced, there is an advantage that the interval between the elements can be reduced.
[0141]
According to a thirteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or the surface described in the twelfth aspect. An optical transmission module, wherein a light-emitting type semiconductor laser array is used as a light source, wherein the surface according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11 is provided. The light emitting type semiconductor laser or the surface emitting type semiconductor laser array according to the twelfth aspect is particularly improved in heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, has a high output, and uses an acrylic POF. Optical transmission becomes possible, and an economical optical transmission module using a surface emitting semiconductor laser, which is a cheap light source, and POF, which is a cheap optical fiber, can be realized.
[0142]
According to a fourteenth aspect of the present invention, there is provided a surface emitting semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a twelfth aspect. 12. A light transmitting / receiving module, wherein a light emitting type semiconductor laser array is used as a light source, wherein the surface according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11. The light emitting type semiconductor laser or the surface emitting type semiconductor laser array according to the twelfth aspect is particularly improved in heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, has a high output, and uses an acrylic POF. Optical transmission becomes possible, and an economical optical transmitting and receiving module using a surface emitting semiconductor laser, which is a cheap light source, and POF, which is a cheap optical fiber, can be realized.
[0143]
According to a fifteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspect, or a surface according to the twelfth aspect. An optical communication system, wherein a light-emitting type semiconductor laser array is used as a light source, and the surface according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11. The light emitting type semiconductor laser or the surface emitting type semiconductor laser array according to the twelfth aspect is particularly improved in heat generation and heat radiation, so that it has a low threshold value, can operate at a high temperature, has a high output, and uses an acrylic POF. Optical transmission becomes possible, and an economical optical communication system using a surface emitting semiconductor laser, which is a cheap light source, and POF, which is a cheap optical fiber, can be realized. Since a surface emitting semiconductor laser is used, high-speed transmission is possible and extremely economical, and it is particularly effective to use it for a short-distance optical communication system such as a general home or office room.
[0144]
According to a sixteenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a twelfth aspect. An optical writing system (specifically, for example, a laser printer) characterized in that a light emitting semiconductor laser array is used as a light source, and a surface emitting semiconductor laser is advantageous for low power consumption operation. The temperature rise in a box such as a printer can be reduced. In addition, since a surface emitting laser is used, arraying is easy, and it can be formed by a normal semiconductor process, so that the position accuracy of the elements is high, writing with a multi-beam is easy, and the writing speed is high. The printing is remarkably improved, and printing can be performed without decreasing the printing speed even when the writing dot density increases. In the case of the same writing dot density, the printing speed can be increased.
[0145]
According to a seventeenth aspect of the present invention, there is provided a surface-emitting type semiconductor laser according to the fourth, sixth, eighth, ninth, tenth, or eleventh aspects, or a surface emitting semiconductor laser according to the twelfth aspect. An optical pickup system characterized in that a light emitting semiconductor laser array is used as a light source. A surface emitting semiconductor laser consumes about one digit less power than an edge emitting semiconductor laser and has a long lasting power. The present invention is particularly effective not only for a normal optical pickup system but also for a handy type optical pickup system using a 0.65 μm surface emitting semiconductor laser as a reproduction light source.
[Brief description of the drawings]
FIG. 1 is a view showing a semiconductor distributed Bragg reflector according to a first embodiment of the present invention.
FIG. 2 is a view showing a surface emitting semiconductor laser device according to a second embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a manufacturing process of a wafer of a surface emitting semiconductor laser according to a second embodiment.
FIG. 4 is a diagram showing a surface emitting semiconductor laser device according to a third embodiment of the present invention.
FIG. 5 is a diagram showing a surface emitting semiconductor laser device according to a fourth embodiment of the present invention.
FIG. 6 is a diagram showing a surface emitting semiconductor laser device according to a fifth embodiment of the present invention.
FIG. 7 is a view showing a surface emitting semiconductor laser device according to a sixth embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of a manufacturing process of a wafer of a surface emitting semiconductor laser according to a sixth embodiment.
FIG. 9 is a diagram (top view) showing a surface-emitting type semiconductor laser array (surface-emitting type semiconductor laser array chip) according to a seventh embodiment of the present invention.
FIG. 10 is a diagram illustrating an optical transmission module according to an eighth embodiment.
FIG. 11 is a diagram showing an optical transceiver module according to a ninth embodiment of the present invention.
FIG. 12 is a diagram showing a tenth embodiment of the present invention.
13 is a diagram (top view) showing a schematic configuration of the surface-emitting type semiconductor laser array chip in FIG. 12;

Claims (17)

Refractive index periodically changes in a semiconductor distributed Bragg reflector that reflects the optical interference of incident light, the layer in which the refractive index is small consists _{Al x Ga 1-x P (} 0 <x ≦ 1), the refractive index There semiconductor distributed Bragg reflector is larger. layers, characterized in that it consists of _{Al y Ga 1-y P (} 0 ≦ y <x ≦ 1). In a semiconductor distributed Bragg reflector formed by laminating two kinds of semiconductor layers having different refractive indexes, two kinds of semiconductor layers having different refractive indexes are a layer having a small refractive index and a layer having a large refractive index, layers in which the refractive index is small consists _{Al x Ga 1-x P (} 0 <x ≦ 1), a layer in which the refractive index is large is made of _{Al y Ga 1-y P (} 0 ≦ y <x ≦ 1), A semiconductor distributed Bragg reflector, wherein a semiconductor layer having a refractive index between the two semiconductor layers having different refractive indexes is provided between the two semiconductor layers having different refractive indexes. A resonance including, on a semiconductor substrate, an active region including at least one active layer for generating laser light, and an upper reflecting mirror and a lower reflecting mirror provided above and below the active region for obtaining laser light 3. A surface-emitting type semiconductor laser having a reflector structure, wherein the semiconductor distributed Bragg reflector according to claim 1 or 2 is used as an upper reflecting mirror and / or a lower reflecting mirror. A resonator including, on a semiconductor substrate, an active region including at least one active layer for generating a laser beam, and an upper reflector and a lower reflector provided at an upper portion and a lower portion of the active region for obtaining the laser beam In a surface emitting semiconductor laser having a structure, the active region is made of a material lattice-matched to GaAs, and the upper mirror and / or the lower reflector is a semiconductor distributed Bragg reflector made of a material lattice-matched to GaP. A surface-emitting type semiconductor laser characterized by being a mirror. Crystal growing a first semiconductor distributed Bragg reflector on a first GaP substrate; crystal growing an active region on a GaAs substrate; and crystal growing a second semiconductor distributed Bragg reflector on a second GaP substrate. Bonding the active region to the first semiconductor distributed Bragg reflector and removing the GaAs substrate; and bonding the active region to the second semiconductor distributed Bragg reflector. A method for manufacturing a surface emitting semiconductor laser. A first semiconductor distributed Bragg reflector made of a material lattice-matched to GaP, an active region made of a material lattice-matched to GaAs, and a second semiconductor distributed Bragg reflector made of a material lattice-matched to GaAs on a semiconductor substrate; A surface-emitting type semiconductor laser comprising: Crystal growing a first semiconductor distributed Bragg reflector on a GaP substrate; crystal growing a second semiconductor distributed Bragg reflector and an active region on a GaAs substrate; Bonding a surface emitting semiconductor laser. 7. The surface emitting semiconductor laser according to claim 4, wherein the GaAs is lattice-matched between an active region made of a material lattice-matched to GaAs and a semiconductor distributed Bragg reflector made of a material lattice-matched to GaP. A part of a semiconductor distributed Bragg reflector made of a material is formed, and a semiconductor distributed Bragg reflector made of a material lattice-matched to the GaP and a part of a semiconductor distributed Bragg reflector made of a material lattice-matched to the GaAs are formed. A surface-emitting type semiconductor laser characterized by being bonded. 9. The surface emitting semiconductor laser according to claim 4, wherein the semiconductor substrate is a GaP substrate, and light is extracted from the GaP substrate side. Surface emitting semiconductor laser. The surface-emitting type semiconductor laser according to any one of claims 4, 6, 8 and 9, further comprising a current narrowing layer selectively oxidized from AlAs containing Al and As as main components. Characteristic surface emitting semiconductor laser. The surface emitting semiconductor laser according to any one of claims 4, 6, 8, 9 and 10, wherein the active region contains at least Ga, In, and P, and the wavelength is shorter than 0.78 μm. A surface-emitting type semiconductor laser characterized by the above-mentioned. A surface emitting semiconductor laser array comprising the surface emitting semiconductor laser according to claim 11. The surface emitting semiconductor laser according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11, or the surface emitting semiconductor laser array according to claim 12 is used as a light source. An optical transmission module, comprising: The surface emitting semiconductor laser according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11, or the surface emitting semiconductor laser array according to claim 12 is used as a light source. An optical transceiver module, comprising: The surface emitting semiconductor laser according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11, or the surface emitting semiconductor laser array according to claim 12 is used as a light source. An optical communication system, comprising: The surface emitting semiconductor laser according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11, or the surface emitting semiconductor laser array according to claim 12 is used as a light source. An optical writing system, comprising: The surface emitting semiconductor laser according to claim 4, claim 6, claim 8, claim 9, claim 10, or claim 11, or the surface emitting semiconductor laser array according to claim 12 is used as a light source. An optical pickup system.

Images