JP4497859B2 - Surface emitting semiconductor laser device, optical transmission module, and optical transmission system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface emitting semiconductor laser device, an optical transmission module, and an optical transmission system.
[0002]
[Prior art]
Japanese Laid-Open Patent Publication No. 11-354881 discloses a surface emitting semiconductor laser that reduces the series resistance of an element by forming a p-side electrode on a resonator and preventing current from flowing through a p-DBR mirror. . However, in this surface emitting semiconductor laser, since current is injected into the active region from the lateral side, it is difficult to uniformly inject current into the active region, and the threshold current becomes high.
[0003]
On the other hand, Japanese Patent Laid-Open No. 2000-196189 discloses a surface emitting semiconductor laser in which a transparent electrode is provided between a resonator and a DBR mirror, and this structure makes current injection into the active region uniform. However, it is difficult to actually produce a transparent electrode having a small light absorption coefficient and a small contact resistance.
[0004]
On the other hand, U.I. S. P. 08 / 997,712 shows a surface emitting semiconductor laser that reduces series resistance by providing a highly doped layer at the position of a standing wave node in a resonator. When the doping concentration is increased, the resistance of the device can be lowered, but free carrier absorption is increased and high output operation cannot be obtained. Therefore, in this surface emitting semiconductor laser, the highly doped layer is provided at the node position where the light intensity is low.
[0005]
However, since the highly doped layer has a certain thickness, light absorption occurs at a portion shifted from the node of the standing wave. On the other hand, if the highly doped layer is made too thin, the effect of reducing the series resistance is reduced.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a surface-emitting semiconductor laser device, an optical transmission module, and an optical transmission system that have a low element resistance, can uniformly inject current into an active region, and have a small optical absorption loss.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the invention described in claim 1 includes a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, an active layer disposed in the resonator,A spacer layer adjacent to the active layer;A first electrode is formed on the resonator, and a second electrode is formed on the back surface of the substrate.And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRukoIt is characterized by.
[0008]
  According to a second aspect of the present invention, there is provided a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, an active layer disposed in the resonator,A spacer layer adjacent to the active layer;And a first electrode and a second electrode for injecting current into the active layer are formed in the resonator.And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRukoIt is characterized by.
[0009]
  According to a third aspect of the present invention, there is provided a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, an active layer disposed in the resonator,A spacer layer adjacent to the active layer;And at least one of the first electrode and the second electrode is formed in the middle of the multilayer film reflecting mirror,And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRukoIt is characterized by.
[0010]
According to a fourth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to third aspects, the carrier diffusion layer has a compressive strain. .
[0011]
According to a fifth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to fourth aspects, the carrier diffusion layer is provided in a p-type region of the resonator. It is characterized by.
[0012]
According to a sixth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to fifth aspects, a plurality of the carrier diffusion layers are provided.
[0013]
According to a seventh aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to sixth aspects, the carrier diffusion layer includes a layer having a compressive strain and a layer having a tensile strain. It is characterized in that a plurality of layers are alternately stacked.
[0014]
According to an eighth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to seventh aspects, the layer thickness of the p-type region of the resonator is greater than the layer thickness of the n-type region. It is characterized by being formed thick.
[0015]
According to a ninth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects of the present invention, a high level by ion implantation is provided between the active layer and the carrier diffusion layer in the resonator. A current confinement structure including a resistance region is provided.
[0016]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects, the active layer and the carrier diffusion layer in the resonator are selectively disposed between the active layer and the carrier diffusion layer. A current confinement structure including an oxidized insulating region and a conductive region which is a non-oxidized region is provided.
[0017]
According to an eleventh aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects, the etching is selectively performed between the active layer and the carrier diffusion layer in the resonator. The present invention is characterized in that a current confinement structure including a formed air gap region and a conductive region which is a non-etched region is provided.
[0019]
  Also,Claim 12In the surface emitting semiconductor laser device according to any one of claims 9 to 11, high-concentration doping is provided between the current confinement region provided in the resonator and the first electrode. It is characterized by providing an area.
[0020]
  Also,Claim 13The invention described in claims 1 toClaim 12In the surface emitting semiconductor laser device according to any one of the above, the active layer is made of a mixed crystal semiconductor containing nitrogen and another group V element.
[0021]
  Also,Claim 14The invention described in claims 1 toClaim 13An optical transmission module comprising the surface-emitting semiconductor laser device according to any one of the above.
[0022]
  Also,Claim 15The described inventionClaim 14An optical transmission system comprising the described optical transmission module.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0024]
(First embodiment)
The surface-emitting semiconductor laser device according to the first embodiment of the present invention includes a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, and an active layer disposed in the resonator. The first electrode is formed on the resonator, the second electrode is formed on the back surface of the substrate, and the resonator is made of a material that is larger than the band gap of the active layer and that constitutes the resonator. A carrier diffusion layer having a band gap smaller than the band gap is provided.
[0025]
The multilayer mirror (DBR) is formed by alternately stacking a high refractive index layer and a low refractive index layer with a thickness of ¼ of the wavelength in the medium. When the multilayer mirror is formed of a semiconductor, layers having different refractive indexes are alternately stacked for 20 cycles or more. Since a hetero barrier is formed at the interface between the high refractive index semiconductor layer and the low refractive index semiconductor layer, the semiconductor multilayer mirror has a high resistance. In particular, the increase in resistance becomes a problem in a p-type semiconductor multilayer mirror.
[0026]
In order to reduce the resistance of the semiconductor multilayer reflector, a method of increasing the carrier concentration of the semiconductor layer is effective. However, in a semiconductor layer doped at a high concentration, light absorption due to free carriers increases, which causes a problem that absorption loss in the reflecting mirror increases.
[0027]
In the first embodiment of the present invention, the first electrode is formed on the resonator, and the current is injected into the active layer without flowing through the upper multilayer reflector. Therefore, an increase in series resistance due to current passing through the upper multilayer mirror is avoided.
[0028]
On the other hand, when the first electrode is formed on the resonator, the current is injected from the lateral side with respect to the oscillation region of the active layer. This causes a problem that it is difficult to uniformly inject current into the active layer.
[0029]
Therefore, in the first embodiment of the present invention, a carrier diffusion layer is provided in the resonator. The band gap of the carrier diffusion layer is smaller than the band gap of the spacer layer constituting the resonator. For this reason, in the carrier diffusion layer, carriers are confined in a hetero barrier with the spacer layer, so that carrier diffusion in the lateral direction (in-plane direction) is promoted. Thereby, the uniformity of the current flowing from the first electrode into the active layer can be improved.
[0030]
Since the band gap of the carrier diffusion layer is smaller than the band gap of the spacer layer constituting the resonator, the effect of increasing the series resistance due to the hetero barrier between the carrier diffusion layer and the spacer layer is reduced. .
[0031]
Moreover, since the band gap of the carrier diffusion layer is larger than the band gap of the active layer, interband light absorption does not occur in the carrier diffusion layer. This is a conventional example. U. S. P. Unlike 08/997 and 712, it is not necessary to highly dope the carrier diffusion layer. Therefore, light absorption by free carriers can be suppressed in the carrier diffusion layer.
[0032]
Further, since the current does not pass through the upper multilayer reflector, it is not necessary to lower the resistance of the upper multilayer reflector. Therefore, as the upper multilayer mirror, a low carrier concentration or undoped semiconductor multilayer mirror can be used. Alternatively, the upper multilayer reflector can be made of a dielectric material having a very small absorption coefficient. Therefore, the light absorption loss of the upper multilayer mirror can be reduced.
[0033]
From the above, according to the first embodiment of the present invention, it is possible to realize a surface emitting semiconductor laser with reduced element resistance, improved current injection uniformity with respect to the active layer, and a small light absorption loss.
[0034]
(Second Embodiment)
The surface-emitting semiconductor laser device according to the second embodiment of the present invention has a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, and an active layer disposed in the resonator. Then, a first electrode and a second electrode for injecting current into the active layer are formed in the resonator, and within the resonator, the band gap of the material constituting the resonator is larger than that of the active layer. In addition, a carrier diffusion layer having a small band gap is provided.
[0035]
In the second embodiment of the present invention, both the first electrode and the second electrode are formed in the resonator. Accordingly, current can be injected into the active layer without passing through the upper multilayer mirror and the lower multilayer mirror. Therefore, the series resistance can be further reduced as compared with the first embodiment.
[0036]
Further, by providing a carrier diffusion layer in the resonator, lateral carrier diffusion is promoted so that current can be uniformly injected into the oscillation region of the active layer.
[0037]
Note that the lower multilayer mirror is made of a semiconductor material. For example, Al as a high refractive index material_aGa_1-aAs (0 ≦ a <b) is used, and Al is used as the low refractive index material._bGa_1-bAs (a <b ≦ 1) is used. In the second embodiment of the present invention, since it is not necessary to pass a current through the lower multilayer reflector, it is not necessary to lower the resistance of the lower multilayer reflector. Therefore, although the hetero barrier becomes large, it can be composed of a GaAs high refractive index layer and an AlAs low refractive index layer that can have the largest refractive index difference. Therefore, in order to obtain a high reflectance of 99.9% or more, it can be formed with a smaller number of layers. Moreover, since it is a combination of binary compound semiconductor materials, thermal resistance is lowered. Therefore, the heat dissipation of the element can be improved.
[0038]
Further, since the lower multilayer reflector can be formed at a low concentration or non-doped, free carrier light absorption in the lower multilayer reflector can be suppressed.
[0039]
(Third embodiment)
The surface-emitting semiconductor laser device according to the third embodiment of the present invention has a lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, and an active layer disposed in the resonator. In addition, at least one of the first electrode and the second electrode is formed in the middle of the multilayer reflector, and has a resonator larger than the band gap of the active layer in the resonator. A carrier diffusion layer having a band gap smaller than the band gap of the constituent material is provided.
[0040]
In the third embodiment of the present invention, the first electrode or the second electrode is provided not in the resonator but in the middle of the multilayer reflector. In this structure, the current is injected into the active layer through a part of the multilayer reflector. Therefore, the series resistance increases as compared with the first or second embodiment. However, an increase in series resistance can be relatively suppressed by reducing the period of the reflecting mirror through which the current passes to a few periods.
[0041]
The carrier concentration of the reflector through which the current passes is, for example, 1 × 10 so that free carrier absorption is reduced.¹⁸cm^-3It needs to be lowered below. In addition, in order to reduce the series resistance of the reflecting mirror, a composition gradient layer is provided between the high refractive index layer and the low refractive index layer, or the band gap difference between the high refractive index layer and the low refractive index layer is reduced. A means such as increasing the doping concentration is used in the section of the standing wave distribution of light.
[0042]
In addition, a carrier diffusion layer is provided in the resonator, which promotes carrier diffusion in the lateral direction so that current can be uniformly injected into the oscillation region of the active layer.
[0043]
Furthermore, in the third embodiment of the present invention, the distance between the electrode and the active layer can be increased by providing the first electrode or the second electrode in the middle of the multilayer reflector. In addition, since the current flows through the heterointerface, the current is more easily diffused in the lateral direction and uniformly injected.
[0044]
In general, the electrode has a 1 × 10 in order to reduce the contact resistance.¹⁸cm^-3It is formed on the contact layer doped with the above high concentration. In order to suppress light absorption by the heavily doped contact layer, the contact layer is provided at the node of the standing wave of light. However, since the contact layer has a certain thickness, light absorption occurs at a portion shifted from the node of the standing wave.
[0045]
In the third embodiment of the present invention, since the electrode is provided in the middle of the multilayer reflector, reflection occurs by the multilayer reflector between the contact layer and the resonator, and the envelope of the light intensity distribution is Reduced to reach contact layer. Therefore, when the contact layer is provided in the middle of the multilayer reflector, the light intensity distribution in the vicinity of the contact layer is lowered at the antinode position as compared with the case where the contact layer is provided in the resonator. Therefore, it is possible to reduce the light absorption that occurs in the contact layer in the portion that deviates from the standing wave node.
[0046]
(Fourth embodiment)
The fourth embodiment of the present invention is characterized in that, in the surface emitting semiconductor laser device of any one of the first to third embodiments, the carrier diffusion layer has a compressive strain.
[0047]
By having compressive strain, the band structure of the valence band is deformed and the effective mass of holes is reduced. Accordingly, since the hole mobility in the carrier diffusion layer is increased, the lateral diffusion of the holes is further promoted.
[0048]
It is also known that InAs, which has a large lattice constant relative to a GaAs substrate or InP substrate, is a material having particularly high mobility. Therefore, by using InGaAs or InAsP, which has a compressive strain with respect to the GaAs substrate or InP substrate, for the carrier diffusion layer, it is possible to promote carrier diffusion for electrons.
[0049]
(Fifth embodiment)
The fifth embodiment of the present invention is characterized in that, in the surface emitting semiconductor laser device of any one of the first to fourth embodiments, the carrier diffusion layer is provided in the p-type region of the resonator. .
[0050]
The effective mass of holes in the semiconductor layer is larger than the effective mass of electrons. Therefore, the resistance of the p-type semiconductor multilayer film reflecting mirror is higher than the resistance of the n-type semiconductor multilayer film reflecting mirror. Therefore, it is more necessary to inject the current without passing through the p-type semiconductor multilayer mirror in order to reduce the series resistance.
[0051]
Moreover, since the mobility of holes in the semiconductor layer is smaller than the mobility of electrons, holes are less likely to diffuse. Therefore, in the fifth embodiment of the present invention, the carrier diffusion layer is provided particularly in the p-type region of the resonator, thereby promoting the diffusion of holes and making the current injection into the active layer uniform.
[0052]
At this time, when a material having a compressive strain is used for the carrier diffusion layer as shown in the fourth embodiment, the hole mobility is further increased, which is highly effective.
[0053]
(Sixth embodiment)
The sixth embodiment of the present invention is characterized in that a plurality of carrier diffusion layers are provided in the surface emitting semiconductor laser device of any one of the first to fifth embodiments.
[0054]
By overlapping a plurality of carrier diffusion layers, carrier diffusion can be further promoted as compared with the case where only one layer is provided.
[0055]
The carrier diffusion layer can be configured with a multi-quantum well structure in which a semiconductor layer having a band gap smaller than that of the spacer layer constituting the resonator is used as a well layer and the spacer layer material is used as a barrier layer.
[0056]
In particular, in the carrier diffusion layer having compressive strain, the layer thickness needs to be smaller than the critical thickness in order to prevent dislocation. Thus, carriers can be diffused more by forming a multi-quantum well structure in which a carrier diffusion layer having a thin compressive strain is laminated with an unstrained barrier layer.
[0057]
It is also possible to provide a plurality of carrier diffusion layers at different locations in the resonator.
[0058]
It can also be provided in both the p-side spacer layer and the n-side spacer layer of the resonator. In this case, the injection into the active layer can be made uniform for both electrons and holes.
[0059]
Since the carrier diffusion layer does not need to be highly doped, light absorption by free carriers can be suppressed. Therefore, it is not always necessary to provide the carrier diffusion layer at the node of the standing wave of light. Therefore, the degree of freedom in designing the position where the carrier diffusion layer is arranged is higher than in the case where a highly doped layer is provided. Therefore, it is possible to easily provide a plurality of carrier diffusion layers.
[0060]
(Seventh embodiment)
In a layer having compressive strain, the effective mass of holes is reduced by deformation of the valence band structure due to strain. Therefore, the hole mobility in the carrier diffusion layer is increased, and lateral carrier diffusion is promoted.
[0061]
By stacking a plurality of layers having this compressive strain, carrier diffusion can be further promoted as compared with the case where only one layer is provided. However, when layers having compressive strain are stacked in multiple layers, internal strain energy is accumulated, and dislocation occurs when the limit value is exceeded.
[0062]
Therefore, in the seventh embodiment, the carrier diffusion layer is configured by alternately laminating a plurality of layers having compressive strain and layers having tensile strain. Thereby, the number of lamination | stacking of the carrier diffusion layer which has a compressive strain can be increased without a dislocation by compensating a compressive strain layer with a tensile strain layer and making a net amount of strains near zero. Thereby, lateral carrier diffusion can be promoted.
[0063]
(Eighth embodiment)
According to an eighth embodiment of the present invention, in the surface-emitting type semiconductor laser device according to any one of the first to seventh embodiments, the layer thickness of the p-type region of the resonator is thicker than the layer thickness of the n-type region. It is characterized by.
[0064]
Since the mobility of holes in the semiconductor layer is smaller than the mobility of electrons, the current in the p-type layer is less likely to spread than in the n-type layer. Thus, in the seventh embodiment, the distance between the p-side electrode and the active layer is increased by shifting the position of the active layer from the center of the resonator and making the p-type region thicker than the n-type region. In addition, lateral current spreading is further promoted.
[0065]
Further, by thickening the p-side region of the resonator, it becomes easy to provide a plurality of carrier diffusion layers on the p-side of the resonator.
[0066]
The active layer needs to be provided in the cavity of the standing wave of light in the resonator. In order to shift the active layer position from the center of the resonator, the resonator length is 0.5λ × m (m = 3, 4, 5,...) With respect to the wavelength (λ) of the light in the medium. It is trying to become.
[0067]
(Ninth embodiment)
According to a ninth embodiment of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth embodiments, a high resistance region by ion implantation is provided between the active layer and the carrier diffusion layer in the resonator. A current confinement structure is provided.
[0068]
As ions implanted to form the high resistance region, for example, proton ions or oxygen ions can be used.
[0069]
By providing a current confinement structure consisting of a high resistance region between the active layer and the carrier diffusion layer in the resonator, current can be concentrated in the active layer region located below the upper multilayer reflector. . Thereby, the current injection uniformity with respect to the active layer in the oscillation region can be further improved.
[0070]
(Tenth embodiment)
The tenth embodiment of the present invention is selectively oxidized between the active layer and the carrier diffusion layer in the resonator in the surface emitting semiconductor laser device according to any one of the first to eighth embodiments. In addition, a current confinement structure including an insulating region and a conductive region which is a non-oxidized region is provided.
[0071]
As the current confinement structure of the active layer, high resistance by ion implantation is also used. However, when the high resistance region increases in the resonator, there is a problem that the resistance increases when a current flows in the lateral direction.
[0072]
On the other hand, when the current confinement structure is formed using the selectively oxidized insulating region, a sufficient insulating region can be formed only by providing the oxide layer as thin as 50 nm or less. Therefore, even if the oxide layer is provided in the resonator, a path through which a current flows in the lateral direction can be increased, so that an increase in resistance can be suppressed.
[0073]
Moreover, by providing the carrier diffusion layer between the selectively oxidized insulating region and the electrode, lateral carrier diffusion can be further promoted to make current injection more uniform.
[0074]
(Eleventh embodiment)
According to an eleventh embodiment of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth embodiments, air selectively etched between an active layer and a carrier diffusion layer in a resonator is used. A current confinement structure including a gap region and a conductive region which is a non-etched region is provided.
[0075]
In the case where the current confinement structure is formed using the selectively etched air gap region, a sufficient insulating region can be formed only by providing the etching layer as thin as 50 nm or less. Therefore, even if the air gap region is provided in the resonator, it is possible to increase a path through which a current flows in the lateral direction, thereby suppressing an increase in resistance.
[0076]
In addition, in the selectively oxidized insulating region, stress is applied to the element due to volume shrinkage due to oxidation, but when the insulating region is formed in the air gap region as in this embodiment, stress may be generated. Absent. Accordingly, it is possible to suppress a decrease in reliability of the element.
[0077]
(Twelfth embodiment)
The twelfth embodiment of the present invention is the surface emitting semiconductor laser device according to any one of the ninth to eleventh embodiments, wherein the band gap of the carrier diffusion layer above the insulating region is the band of the carrier diffusion layer above the conductive region. It is characterized by being smaller than the gap.
[0078]
In the carrier diffusion layer, the band gap at the upper part of the insulating region is smaller than the band gap at the upper part of the conductive region, so that carriers are likely to concentrate on the conductive region side having a smaller band gap in the carrier diffusion layer. Thereby, the current injection into the conductive region can be made more uniform.
[0079]
As a method for changing the band gap of the carrier diffusion layer, for example, the carrier diffusion layer can be formed with a (multiple) quantum well structure and the (multiple) quantum well structure above the insulating region can be mixed. In the mixed crystal part, the band gap becomes larger than that of the (multiple) quantum well structure which is not mixed crystal.
[0080]
As a means for making a (multiple) quantum well structure a mixed crystal, a method of diffusing a dopant such as Zn or Si, a method of performing a heat treatment after ion implantation of an element such as Ga, Al, As, Zn, or Si, A method of diffusing holes can be used.
[0081]
(13th Embodiment)
In the surface emitting semiconductor laser device according to any one of the ninth to eleventh embodiments of the present invention, a high concentration doping region is provided between the current confinement region provided in the resonator and the first electrode. It is characterized by.
[0082]
By providing a high-concentration doping region between the current confinement region provided in the resonator and the first electrode, the electrical resistance from the first electrode to the conductive region of the current confinement structure is greatly reduced. can do.
[0083]
In addition, since no current is injected into the active layer located under the current confinement region, no light emission recombination occurs. Further, in the current confinement structure by selective oxidation or selective etching, a difference in refractive index is generated in the lateral direction, so that light is confined in the conductive region. Therefore, in the resonator, the light intensity rapidly attenuates outside the conductive region. Therefore, the free carrier absorption loss of light in the high concentration doping region can be sufficiently reduced.
[0084]
That is, the doping concentration is reduced in the laser oscillation region to suppress free carrier absorption, and the electrical resistance is reduced by doping at a high concentration outside the laser oscillation region.
[0085]
As a doping concentration of the high concentration doping region, for example, 1 × 10¹⁸cm^{− 3}The above is desirable. It is also possible to increase the doping concentration toward the outside from the oscillation region.
[0086]
The high concentration doping region can be formed by diffusing a dopant such as Zn, Be, Mg, C, Si, or Se, or annealing after ion implantation.
[0087]
(Fourteenth embodiment)
A fourteenth embodiment of the present invention is the surface emitting semiconductor laser device according to any one of the first to thirteenth embodiments, wherein the active layer is made of a mixed crystal semiconductor containing nitrogen and another group V element. It is said.
[0088]
Examples of mixed crystal semiconductors containing nitrogen and other group V elements include GaNAs, GaInNAs, GaNAsSb, GaInNAsSb, GaNAsP, GaInNAsP, and GaInNAsPSb. A mixed crystal semiconductor containing nitrogen and another group V element has a characteristic that the band gap is reduced to a certain extent when nitrogen is added. This characteristic makes it possible to form an active layer having a long wavelength band of 1.3 to 1.6 μm suitable for transmission of a quartz optical fiber on a GaAs substrate.
[0089]
Further, the use of a GaAs substrate has an advantage that a multilayer film reflecting mirror can be formed of an AlGaAs material system having a large difference in refractive index and a low thermal resistance. A current confinement structure in which AlAs is selectively oxidized can also be used.
[0090]
Since the fourteenth embodiment has the characteristics shown in the first to ninth embodiments in the surface emitting semiconductor laser having a long wavelength band of 1.3 to 1.6 μm, the element resistance is reduced, The uniformity of current injection into the active layer can be improved and the light absorption loss can be reduced. Therefore, a long wavelength band-emitting semiconductor laser with a low operating voltage and high output can be formed.
[0091]
(Fifteenth embodiment)
The fifteenth embodiment of the present invention is an optical transmission module comprising the surface-emitting semiconductor laser device of any one of the first to fourteenth embodiments.
[0092]
In the surface emitting semiconductor laser devices shown in the first to fourteenth embodiments, the element resistance can be reduced and the current injection into the active layer can be made uniform, so that the operating voltage can be reduced. Further, by reducing the light absorption loss, laser light can be obtained with high efficiency. Therefore, when this is applied to an optical transmission module, the power consumption of the optical transmission module can be reduced.
[0093]
(Sixteenth embodiment)
The sixteenth embodiment of the present invention is an optical transmission system comprising the optical transmission module of the fifteenth embodiment.
[0094]
In the optical transmission module of the fifteenth embodiment, since the power consumption of the surface emitting semiconductor laser that is the light source is reduced, an optical transmission system with low power consumption can be constructed.
[0095]
【Example】
Examples of the present invention will be described below.
[0096]
[Example 1]
FIG. 1 is a diagram showing a surface emitting semiconductor laser according to Example 1 of the present invention. Referring to FIG. 1, an n-type GaAs / AlGaAs DBR 102 is stacked on an n-type GaAs substrate 101. Here, the n-type GaAs / AlGaAs DBR 102 includes an n-type GaAs high refractive index layer and an n-type Al._0.8Ga_0.2As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0097]
On the n-type GaAs / AlGaAs DBR 102, Al_0.3Ga_0.7As lower spacer layer 103, InGaAs / GaAs multiple quantum well active layer 104, Al_0.3Ga_0.7An As upper spacer layer 106 is laminated. And Al_0.3Ga_0.7A GaAs carrier diffusion layer 105 is provided in the middle of the As upper spacer layer 106.
[0098]
Al_0.3Ga_0.7As lower spacer layer 103 is n-type, Al_0.3Ga_0.7The As upper spacer layer 106 is p-type.
[0099]
In FIG. 1, a mesa structure is formed by etching in a cylindrical shape from the surface of the laminated structure until reaching the n-type GaAs / AlGaAs DBR 102. A ring-shaped p-side electrode 108 is formed on the surface of the mesa structure except for the light extraction region. The p-side electrode 108 has a p-type carrier concentration of 1 × 10.¹⁸cm^-3It is formed on the contact layer (not shown).
[0100]
And Al at the top of the mesa_0.3Ga_0.7A dielectric multilayer film reflecting mirror 107 is laminated on the As upper spacer layer 106. The dielectric multilayer film reflecting mirror 107 is formed by alternately laminating dielectric materials having different refractive indexes with a layer thickness of ¼ of the wavelength in the medium. Here, as the high refractive index layer, TiO₂, ZrO₂, MgO, Al₂O₃, ZnSe, etc., and the low refractive index layer can be made of SiO.₂, MgF₂, CaF₂Etc. can be used.
[0101]
In FIG. 1, an n-side electrode 109 is formed on the back surface of the n-type GaAs substrate 101.
[0102]
In the surface emitting semiconductor laser of FIG. 1, by applying a forward bias to the p-side electrode 108 and the n-side electrode 109, current is injected into the InGaAs / GaAs multiple quantum well active layer 104, and a wavelength of 0.98 μm band is obtained. Flashes on. At this time, a region sandwiched between the dielectric multilayer film reflecting mirror 107 and the n-type GaAs / AlGaAs DBR 102 has a resonator structure, and has a structure in which laser light is extracted vertically upward with respect to the substrate 101. .
[0103]
In the surface emitting semiconductor laser of FIG. 1, the p-side electrode 108 is formed on the resonator, and the current is injected into the active layer without flowing through the upper multilayer reflector. Therefore, an increase in series resistance due to current passing through the upper multilayer mirror is avoided.
[0104]
In particular, since the effective mass of holes in the semiconductor layer is larger than the effective mass of electrons, the resistance of the p-type semiconductor multilayer reflector is higher than the resistance of the n-type semiconductor multilayer reflector. . In the structure of FIG. 1, since the current is injected without passing through the p-side multilayer reflector, the effect of reducing the series resistance is great.
[0105]
On the other hand, the n-type GaAs / AlGaAs DBR 102 having a relatively low resistance has a structure through which a current passes.
[0106]
In the surface emitting semiconductor laser shown in FIG._0.3Ga_0.7A GaAs carrier diffusion layer 105 is provided in the As upper spacer layer 106. The band gap of the GaAs carrier diffusion layer 105 is Al._0.3Ga_0.7It is smaller than the band gap of the As upper spacer layer 106, and in the GaAs carrier diffusion layer 105, carriers (holes) are Al._0.3Ga_0.7Since it is confined to the hetero barrier with the As upper spacer layer 106, carrier diffusion in the lateral direction (in-plane direction) is promoted. This improves the uniformity of the current flowing from the p-side electrode 108 into the active layer 104 in the mesa structure.
[0107]
Since the GaAs carrier diffusion layer 105 does not need to be doped at a high concentration, the GaAs carrier diffusion layer 105 is not necessarily provided at the node position in the standing wave distribution of light in the resonator.
[0108]
The upper multilayer reflector 107 is made of a dielectric material having a very small absorption coefficient. Therefore, the light absorption loss of the upper multilayer film reflecting mirror 107 can be reduced. Al_0.3Ga_0.7As lower spacer layer 103 and Al_0.3Ga_0.7The carrier concentration of the As upper spacer layer 106 is 1 × 10¹⁸cm^-3By making it lower as follows, free carrier absorption in the resonator is suppressed.
[0109]
From the above, in the surface emitting semiconductor laser of FIG. 1, the element resistance can be reduced, the current injection uniformity with respect to the active layer can be improved, and the light absorption loss can be reduced.
[0110]
[Example 2]
FIG. 2 is a diagram showing a surface emitting semiconductor laser according to Example 2 of the present invention. Referring to FIG. 2, an n-type GaAs / AlGaAs DBR 102 is stacked on an n-type GaAs substrate 101. Here, the n-type GaAs / AlGaAs DBR 102 includes an n-type GaAs high refractive index layer and an n-type Al._0.8Ga_0.2As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0111]
On the n-type GaAs / AlGaAs DBR 102, a GaAs lower spacer layer 201, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 204 are stacked. An AlAs layer 203 is provided in the middle of the GaAs upper spacer layer 204, and two InGaAs carrier diffusion layers 205 are provided above the AlAs layer 203 in the GaAs upper spacer layer 204. ing. Here, the GaAs lower spacer layer 201 is n-type, and the GaAs upper spacer layer 204 is p-type.
[0112]
A GaAs / AlGaAs DBR 206 is stacked on the GaAs upper spacer layer 204. The GaAs / AlGaAs DBR 206 includes a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0113]
In the surface emitting semiconductor laser shown in FIG. 2, a first-stage mesa structure is formed by etching in a cylindrical shape from the surface of the laminated structure to the outermost surface of the GaAs upper spacer layer 204. Further, the second stage mesa structure is formed by etching in a cylindrical shape with a size larger than the above size until reaching the n-type GaAs / AlGaAs DBR 102.
[0114]
The AlAs layer 203 is selectively oxidized from the mesa side surface to form an insulating region 207.
[0115]
A ring-shaped p-side electrode 108 is formed on the bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). The p-side electrode 108 has a p-type carrier concentration of 1 × 10.¹⁸cm^-3It is formed on the contact layer (not shown).
[0116]
An n-side electrode 109 is formed on the back surface of the n-type GaAs substrate 101.
[0117]
In the surface emitting semiconductor laser of FIG. 2, by applying a forward bias to the p-side electrode 108 and the n-side electrode 109, current is injected into the GaInNAs / GaAs multiple quantum well active layer 202, and a wavelength of 1.3 μm band is obtained. Flashes on. At this time, the current flows through the non-oxidized conductive region in the AlAs layer 203 formed on the GaInNAs / GaAs multiple quantum well active layer 202. Thereby, the threshold current is reduced by concentrating the current in a region narrower than the second mesa size. Further, since the oxidized insulating region 207 has a refractive index much lower than that of the non-oxidized AlAs layer 203, it plays the role of a lens that collects light and reduces diffraction loss.
[0118]
In the surface emitting semiconductor laser of FIG. 2, a region sandwiched between GaAs / AlGaAs DBR 206 and n-type GaAs / AlGaAs DBR 102 has a resonator structure, and laser light is extracted vertically upward with respect to substrate 101.
[0119]
In the surface emitting semiconductor laser of FIG. 2, the p-side electrode 108 is formed on the resonator as in the structure of FIG. 1, and current is injected into the active layer 202 without flowing through the upper multilayer reflector 206. It has a structure. Therefore, an increase in series resistance due to current passing through the p-type semiconductor multilayer mirror having high resistance is avoided.
[0120]
On the other hand, when the p-side electrode 108 is formed on the resonator, the current is injected from the lateral side with respect to the oscillation region of the active layer. This causes a problem that it is difficult to uniformly inject current into the active layer.
[0121]
Therefore, in the surface emitting semiconductor laser of FIG. 2, two InGaAs carrier diffusion layers 205 are provided between the AlAs layer 203 and the p-side electrode 108. In the InGaAs carrier diffusion layer 205 having a band gap smaller than that of the upper GaAs spacer layer 204, carriers (holes) are confined in a hetero barrier with the spacer layer, so that carrier diffusion in the lateral direction (in-plane direction) is promoted. The Thereby, the uniformity of the current flowing from the p-side electrode 108 into the active layer 202 can be improved.
[0122]
InGaAs is known to be a material with high mobility. And since it has a larger lattice constant than the GaAs substrate, it has compressive strain. By having compressive strain, the band structure of the valence band is deformed and the effective mass of holes is reduced. Therefore, in the InGaAs carrier diffusion layer 205, the mobility of holes is high and the holes are easily diffused.
[0123]
Further, by providing two InGaAs carrier diffusion layers 205, carrier diffusion can be further promoted compared to the case where only one layer is provided.
[0124]
Since the InGaAs carrier diffusion layer 205 does not need to be highly doped, light absorption by free carriers can be suppressed. Therefore, it is not always necessary to provide the InGaAs carrier diffusion layer 205 at the node of the standing wave of light. Therefore, the InGaAs carrier diffusion layer 205 can be disposed in any position between the AlAs layer 203 and the p-side electrode 108 in the upper GaAs spacer layer 204.
[0125]
It should be noted that the effective insulating region 207 can be formed by selective oxidation only by providing the AlAs oxide layer 203 as thin as 20 to 50 nm. Therefore, there is no restriction on the path through which current flows in the lateral direction in the upper GaAs spacer layer 204.
[0126]
Further, since the current does not pass through the upper GaAs / AlGaAs DBR 206, there is no need to lower the resistance of the GaAs / AlGaAs DBR 206. Therefore, the GaAs / AlGaAs DBR 206 can be composed of a low carrier concentration non-doped layer, and the light absorption loss of the GaAs / AlGaAs DBR 206 can be greatly reduced.
[0127]
[Example 3]
FIG. 3 is a diagram showing a surface emitting semiconductor laser according to Example 3 of the present invention. Referring to FIG. 3, a GaAs / AlAs DBR 301 is stacked on an n-type GaAs substrate 101. Here, the GaAs / AlAs DBR 301 is formed by alternately stacking non-doped GaAs high refractive index layers and non-doped AlAs low refractive index layers with a layer thickness of ¼ of the wavelength in the medium.
[0128]
On the GaAs / AlAs DBR 301, a GaAs lower spacer layer 302, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 303 are stacked. An AlAs layer 203 is provided in the middle of the GaAs upper spacer layer 303, and two InGaAs carrier diffusion layers 205 are provided above the AlAs layer 203 in the GaAs upper spacer layer 303. . Here, the GaAs lower spacer layer 302 is n-type, and the GaAs upper spacer layer 303 is p-type.
[0129]
A GaAs / AlGaAs DBR 206 is stacked on the GaAs upper spacer layer 303. Here, the GaAs / AlGaAs DBR 206 is composed of a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0130]
In the surface emitting semiconductor laser of FIG. 3, the first-stage mesa structure is formed by etching in a cylindrical shape from the surface of the laminated structure to the outermost surface of the GaAs upper spacer layer 303. Further, the second-stage mesa structure is formed by etching in a cylindrical shape up to the middle of the GaAs lower spacer layer 302 with a size larger than the above size.
[0131]
Further, the AlAs layer 203 is selectively oxidized from the mesa side surface to form an insulating region 207.
[0132]
A ring-shaped p-side electrode 108 is formed on the bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). An n-side electrode 109 is formed on the etching bottom surface of the second-stage mesa structure. Note that the p-side electrode 108 and the n-side electrode 109 have a carrier concentration of 1 × 10 6.¹⁸cm^-3It is formed on the contact layer (not shown). The contact layer is disposed so as to be located at a node in the standing wave distribution of light.
[0133]
In the surface emitting semiconductor laser of FIG. 3, by applying a forward bias to the p-side electrode 108 and the n-side electrode 109, current is injected into the GaInNAs / GaAs multiple quantum well active layer 202, and the wavelength of 1.3 μm band is obtained. Flashes on. At this time, the current flows through the non-oxidized conductive region in the AlAs layer 203 formed on the GaInNAs / GaAs multiple quantum well active layer 202. As a result, the threshold current can be reduced by concentrating the current in a region narrower than the second mesa size. Further, since the oxidized insulating region 207 has a refractive index much lower than that of the non-oxidized AlAs layer 203, it can serve as a lens for collecting light and reduce diffraction loss.
[0134]
In the surface emitting semiconductor laser of FIG. 3, a region sandwiched between GaAs / AlAs DBR 301 and GaAs / AlGaAs DBR 206 has a resonator structure, and laser light is extracted vertically upward with respect to substrate 101.
[0135]
In the surface emitting semiconductor laser of FIG. 3, both the p-side electrode 108 and the n-side electrode 109 are formed in the resonator. Therefore, current can be injected into the active layer 202 without passing through the upper multilayer mirror and the lower multilayer mirror. Therefore, the series resistance can be further reduced as compared with the structures of FIGS.
[0136]
In the structure of FIG. 3, the resonator length of the resonator structure sandwiched between the GaAs / AlAs DBR 301 and the GaAs / AlGaAs DBR 206 is 0.5λ × m 2 (m) with respect to the wavelength (λ) of light in the medium. = 3, 4, 5,... For example, when m = 6, the resonator length is 3λ.
[0137]
The active layer 202 is provided on the antinode of the standing wave of light in the resonator. The active layer position is shifted from the center of the resonator, and the layer thickness of the p-type GaAs spacer layer 303 is changed to n-type GaAs. The spacer layer 302 can be thicker than the layer thickness. When the resonator length is 3λ, the p-side region can be thickened by providing the active layer at a position of 0.5λ or 1λ from the bottom.
[0138]
Thereby, the distance between the p-side electrode 108 and the active layer 202 can be increased, and the current diffusion in the lateral direction in the p-side region having high resistance in the mesa structure can be promoted.
[0139]
Further, in the surface emitting semiconductor laser of FIG. 3, two InGaAs carrier diffusion layers 205 are provided between the AlAs layer 203 and the p-side electrode 108 in the p-type GaAs spacer layer 303. Also in the third embodiment, as in the second embodiment, by providing an InGaAs layer with high mobility, current diffusion in the lateral direction is promoted, and the current flowing from the p-side electrode 108 into the active layer 202 is increased. The uniformity can be further improved.
[0140]
In the surface emitting semiconductor laser of FIG. 3, it is not necessary to pass a current through the lower multilayer reflector 301, so that it is not necessary to lower the resistance of the lower multilayer reflector 301. Therefore, although the hetero barrier becomes large, the lower multilayer reflector 301 can be composed of a GaAs high refractive index layer and an AlAs low refractive index layer that can have the largest refractive index difference. Accordingly, the lower multilayer reflector 301 can be formed with a smaller number of layers in order to obtain a high reflectance of 99.9% or more. Moreover, since GaAs and AlAs are materials having lower thermal resistance than AlGaAs mixed crystals, the heat dissipation of the element can be improved.
[0141]
The lower multilayer reflector 301 and the upper multilayer reflector 206 are both formed of a low carrier concentration non-doped layer, thereby significantly reducing free carrier light absorption in the multilayer reflector. Can do.
[0142]
[Example 4]
FIG. 4 is a diagram showing a surface emitting semiconductor laser according to Example 4 of the present invention. Referring to FIG. 4, GaAs / AlAs DBR 401 is stacked on an n-type GaAs substrate 101. Here, the GaAs / AlAs DBR 401 is formed by alternately laminating non-doped GaAs high refractive index layers and non-doped AlAs low refractive index layers with a layer thickness of ¼ of the wavelength in the medium.
[0143]
An n-type GaAs / AlGaAs DBR 402 is stacked on the GaAs / AlAs DBR 401. Here, the n-type GaAs / AlGaAs DBR 402 includes an n-type GaAs high refractive index layer and an n-type Al._0.8Ga_0.2As low refractive index layers are formed by alternately laminating two periods with a layer thickness of ¼ of the wavelength in the medium.
[0144]
On the n-type GaAs / AlGaAs DBR 402, a GaAs lower spacer layer 302, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 303 are stacked. An AlAs layer 203 is provided in the middle of the GaAs upper spacer layer 303, and an InGaAs carrier diffusion layer 205 is provided above the AlAs layer 203 in the GaAs upper spacer layer 303. Here, the GaAs lower spacer layer 302 is n-type, and the GaAs upper spacer layer 303 is p-type.
[0145]
A p-type GaAs / AlGaAs DBR 403 is stacked on the GaAs upper spacer layer 303. Here, the p-type GaAs / AlGaAs DBR 403 includes a p-type GaAs high refractive index layer and a p-type Al._0.7Ga_0.3As low refractive index layers are formed by alternately laminating two periods with a layer thickness of ¼ of the wavelength in the medium.
[0146]
In the surface emitting semiconductor laser shown in FIG. 4, a mesa structure is formed by etching from the surface of the stacked structure to the outermost surface of the GaAs / AlAs DBR 401 to form a mesa structure, and the AlAs layer 203 is selectively oxidized from the mesa side surface. Thus, an insulating region 207 is formed. A ring-shaped p-side electrode 108 is formed on the top of the mesa structure except for the light extraction region.
[0147]
A dielectric multilayer reflector 107 is laminated on the p-type GaAs / AlGaAs DBR 403 at the top of the mesa.
[0148]
An n-side electrode 109 is formed on the etching bottom surface of the mesa structure. Note that the p-side electrode 108 and the n-side electrode 109 have a carrier concentration of 1 × 10 6.¹⁸cm^-3It is formed on the contact layer (not shown).
[0149]
In the surface emitting semiconductor laser shown in FIG. 4, the p-side electrode 108 and the n-side electrode 109 are provided not in the resonator but in the middle of the multilayer reflector. That is, the p-side electrode 108 is provided in the middle of the p-type GaAs / AlGaAs DBR 403 and the dielectric multilayer reflector 107, and the n-side electrode 109 is provided between the GaAs / AlAs DBR 401 and the n-type GaAs / AlGaAs DBR 402. Is provided.
[0150]
In this structure, current is injected into the active layer through the multilayer reflectors 403 and 402. Therefore, compared with the structure of FIG. 3, the series resistance increases. However, the increase in series resistance is relatively suppressed by thinning the cycle of the multilayer-film reflective mirror through which the current passes to 2 cycles.
[0151]
With respect to the dielectric multilayer film reflecting mirror 107 and the GaAs / AlAs DBR 401 which are most of the reflecting mirrors, the light absorption loss is reduced.
[0152]
In the structure of FIG. 4, the multilayer reflectors 403 and 402 are provided between the p-side electrode 108 and the n-side electrode 109 and the resonator, so that the current can easily spread in the lateral direction.
[0153]
Further, by providing the InGaAs carrier diffusion layer 205 in the GaAs upper spacer layer 303, the carrier (hole) diffusion is promoted in the lateral direction so that current can be uniformly injected into the oscillation region of the active layer. Yes.
[0154]
In addition, since the contact layer on which the p-side electrode 108 and the n-side electrode 109 are formed is highly doped, free carrier absorption occurs. In order to suppress this, the contact layer is provided at a node position in the standing wave distribution of light. However, since the contact layer has a certain thickness, light absorption occurs at a portion shifted from the node of the standing wave.
[0155]
In the structure of FIG. 4, the multilayer reflection mirror is provided between the p-side electrode 108, the n-side electrode 109, and the resonator, so that the envelope of the light intensity distribution decreases before reaching the contact layer. Therefore, compared with the case where the contact layer is provided in the resonator, the light intensity distribution in the vicinity of the contact layer also decreases at the antinode position. Therefore, the light absorption that occurs in the contact layer at a portion deviated from the node of the standing wave can be further reduced.
[0156]
[Example 5]
FIG. 5 is a view showing a surface emitting semiconductor laser according to Example 5 of the present invention. Referring to FIG. 5, a GaAs / AlAs DBR 301 is stacked on an n-type GaAs substrate 101. Here, the GaAs / AlAs DBR 301 is formed by alternately stacking non-doped GaAs high refractive index layers and non-doped AlAs low refractive index layers with a layer thickness of ¼ of the wavelength in the medium.
[0157]
And on GaAs / AlAs DBR301, Al_0.3Ga_0.7As lower spacer layer 103, GaInNAs / GaAs multiple quantum well active layer 202, Al_0.3Ga_0.7An As upper spacer layer 106 is laminated.
[0158]
And Al_0.3Ga_0.7An AlAs layer 203 is provided in the middle of the As upper spacer layer 106. Al_0.3Ga_0.7An InGaAs carrier diffusion layer 501 is provided in the As lower spacer layer 103, and Al_0.3Ga_0.7In the As upper spacer layer 106, the AlGaAs layer 203 is disposed above the GaAs / Al._0.3Ga_0.7An As multiple quantum well carrier diffusion layer 502 is provided.
[0159]
Al_0.3Ga_0.7As lower spacer layer 103 is n-type, Al_0.3Ga_0.7The As upper spacer layer 106 is p-type.
[0160]
Al_0.3Ga_0.7A GaAs / AlGaAs DBR 206 is stacked on the As upper spacer layer 106. Here, the GaAs / AlGaAs DBR 206 is composed of a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0161]
In the surface-emitting semiconductor laser shown in FIG. 5, the first-stage mesa structure is formed by etching in a cylindrical shape from the surface of the laminated structure to the outermost surface of the upper spacer layer 106. Furthermore, it is larger than the above size, Al_0.3Ga_0.7A portion of the As lower spacer layer 103 is etched into a cylindrical shape to form a second-stage mesa structure.
[0162]
The AlAs layer 203 is selectively oxidized from the mesa side surface to form an insulating region 207.
[0163]
In addition, a ring-shaped p-side electrode 108 is formed on the etching bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). An n-side electrode 109 is formed on the etching bottom surface of the second-stage mesa structure. Note that the p-side electrode 108 and the n-side electrode 109 have a carrier concentration of 1 × 10 6.¹⁸cm^-3It is formed on the GaAs contact layer (not shown). The contact layer is disposed so as to be located at a node in the standing wave distribution of light.
[0164]
The structure of FIG. 5 differs from the structure of FIG. 3 in that the carrier diffusion layer is made of Al in the resonator._0.3Ga_0.7As lower spacer layer 103 and Al_0.3Ga_0.7This is a point provided on both of the As upper spacer layers 106. This promotes lateral diffusion for both electrons and holes.
[0165]
GaAs / Al_0.3Ga_0.7In the As multi-quantum well carrier diffusion layer 502, in the region above the insulating region 207 where the AlAs layer 203 is selectively oxidized, GaAs / Al_0.3Ga_0.7The As multiple quantum well structure is mixed. The mixed crystal region 503 is formed by performing heat treatment after ion implantation of elements such as Ga, Al, As, and Zn from the etching bottom surface of the first-stage mesa structure. The band gap of the mixed AlGaAs layer 503 is Al._0.3Ga_0.7It is smaller than the As lower spacer layer 103 and functions as a carrier diffusion layer.
[0166]
Furthermore, the band gap of the mixed crystal region 503 is larger than the band gap of the multiple quantum well structure 502 which is not mixed crystal. Therefore, in the carrier diffusion layer, the band gap above the insulating region 207 is smaller than the band gap above the conductive region 203. This makes it easier for carriers in the carrier diffusion layer to concentrate in the multiple quantum well structure 502 on the conductive region side having a smaller band gap. Thereby, the current injection into the conductive region 203 can be made more uniform.
[0167]
The region in which Zn ions are implanted from the bottom surface of the first-stage mesa structure is activated by the Zn after the heat treatment and becomes a high-concentration p-type doping region 504. By providing the high-concentration doping region 504 between the insulating region 207 and the p-side electrode 108, the electrical resistance from the p-side electrode 108 to the conductive region of the AlAs layer 203 can be significantly reduced.
[0168]
On the other hand, since carriers and light are confined by the selectively oxidized insulating region 207, the light intensity rapidly attenuates outside the conductive region of the AlAs layer 203. In the structure of FIG. 5, the diameter of the region where Zn ions are not implanted is substantially the same as or larger than the diameter of the region 203 where AlAs is not selectively oxidized. Therefore, the high-concentration doping region 504 can reduce the influence of light on free carrier absorption loss.
[0169]
[Example 6]
FIG. 6 is a diagram illustrating an optical transmission system according to a sixth embodiment of the present invention. In the optical transmission system of FIG. 6, the optical signal generated by the optical transmitter 601 is transmitted to the optical receiver 602 through the quartz optical fiber 604. In FIG. 6, two series of optical transmitters 601, optical fibers 604, and optical receivers 602 are provided so that bidirectional communication is possible. Here, the optical transmission unit 601 and the optical reception unit 602 are integrated in one package, and constitute an optical transmission / reception module 603.
[0170]
The sixth embodiment is characterized in that the surface emitting semiconductor laser device according to any one of the first to fifth embodiments is used as the light source of the optical transmitter 601. In the surface emitting semiconductor lasers according to the first to fifth embodiments, the device resistance can be reduced and the current injection into the active layer can be made uniform, so that the operating voltage can be reduced. Further, by reducing the light absorption loss, laser light can be obtained with high efficiency. Therefore, by using the surface emitting semiconductor laser device according to any one of the first to fifth embodiments as the light source of the optical transmission unit 601, the power consumption of the optical transmission unit 601 can be reduced, and light with low power consumption can be obtained. A transmission system can be constructed.
[0171]
In the above example, only one surface emitting semiconductor laser element is shown, but it can also be used as a one-dimensional or two-dimensional array light source. Since the surface emitting semiconductor laser element of the present invention can suppress heat generation by reducing element resistance, it can suppress thermal crosstalk when used as an array light source.
[0172]
[Example 7]
FIG. 7 is a sectional view of a surface emitting semiconductor laser according to Example 7 of the present invention. An n-type GaAs / AlGaAs DBR 102 is stacked on an n-type GaAs substrate 101. The n-type GaAs / AlGaAs DBR 102 includes an n-type GaAs high refractive index layer and an n-type Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium. On the n-type GaAs / AlGaAs DBR 102, a GaAs lower spacer layer 201, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 204 are stacked. An InGaAs carrier diffusion layer 205 is provided in the middle of the GaAs upper spacer layer 204. The GaAs lower spacer layer 103 is n-type, and the GaAs upper spacer layer 106 is p-type.
[0173]
A GaAs / AlGaAs DBR 206 is stacked on the GaAs upper spacer layer 204. The GaAs / AlGaAs DBR 206 includes a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0174]
From the surface of the laminated structure to the outermost surface of the GaAs upper spacer layer 204, the first stage mesa structure is formed in a cylindrical shape. Further, the second stage mesa structure is formed by etching in a cylindrical shape with a size larger than the above size until reaching the n-type GaAs / AlGaAs DBR 102.
[0175]
Proton ions are implanted from the surface of the second-stage mesa structure, and a high resistance region 701 is formed in the vicinity of the active layer except for the active layer located under the GaAs / AlGaAsDBR 206.
[0176]
A ring-shaped p-side electrode 108 is formed on the etching bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). The p-side electrode 108 has a p-type carrier concentration of 1 × 10.¹⁸cm^-3It is formed on the contact layer described above. (Not shown)
[0177]
An n-side electrode 109 is formed on the back surface of the n-type GaAs substrate 101.
[0178]
In the surface emitting semiconductor laser of FIG. 7, by applying a forward bias to the p-side electrode 108 and the n-side electrode 109, current is injected into the GaInNAs / GaAs multiple quantum well active layer 202, and the wavelength is 1.3 μm. Emits light. At this time, the current is confined in the high resistance region 701 and flows into the GaInNAs / GaAs multiple quantum well active layer 202 where proton ions are not implanted. Thereby, the threshold current is reduced by concentrating the current in a region narrower than the second mesa size.
[0179]
A region sandwiched between the GaAs / AlGaAs DBR 206 and the n-type GaAs / AlGaAs DBR 102 has a resonator structure, and laser light is extracted vertically upward with respect to the substrate.
[0180]
In the surface emitting semiconductor laser of FIG. 7, an InGaAs carrier diffusion layer 205 is provided between the active layer 202 and the p-side electrode 108. In the InGaAs carrier diffusion layer 205 having a band gap smaller than that of the upper GaAs spacer layer 204, carriers (holes) are confined in a hetero barrier with the spacer layer, so that carrier diffusion in the lateral direction (in-plane direction) is promoted. The Thereby, the uniformity of the current flowing from the p-side electrode 108 into the active layer 202 is improved.
[0181]
Further, since the high resistance region 701 provided in the vicinity of the active layer 202 can flow a current concentratedly in the active layer region located under the GaAs / AlGaAs DBR 206, the current injection uniformity with respect to the active layer in the oscillation region Can be further improved.
[0182]
[Example 8]
FIG. 8 is a sectional view of a surface emitting semiconductor laser according to Example 8 of the present invention. An n-type GaAs / AlGaAs DBR 102 is stacked on an n-type GaAs substrate 101. The n-type GaAs / AlGaAs DBR 102 includes an n-type GaAs high refractive index layer and an n-type Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium. On the n-type GaAs / AlGaAs DBR 102, a GaAs lower spacer layer 201, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 204 are stacked. An AlAs layer 203 is provided in the middle of the GaAs upper spacer layer 204, and a strain compensation superlattice carrier diffusion layer 801 is provided above the AlAs layer 203 in the GaAs upper spacer layer 204.
[0183]
The strain compensation superlattice carrier diffusion layer 801 is formed by alternately stacking 5.5 periods of GaAsP layers having a tensile strain of 0.5% and InGaAs layers having a compression strain of 1.4%. The thickness of the GaAsP layer was 14 nm, and the thickness of the InGaAs layer was 6 nm.
[0184]
A GaAs / AlGaAs DBR 206 is stacked on the GaAs upper spacer layer 106. The GaAs / AlGaAs DBR 206 includes a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0185]
From the surface of the laminated structure to the outermost surface of the GaAs upper spacer layer 204, the first stage mesa structure is formed in a cylindrical shape. Further, the second stage mesa structure is formed by etching in a cylindrical shape with a size larger than the above size until reaching the n-type GaAs / AlGaAs DBR 102.
[0186]
The AlAs layer 203 is selectively oxidized from the mesa side surface to form an insulating region 207.
[0187]
A ring-shaped p-side electrode 108 is formed on the etching bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). An n-side electrode 109 is formed on the back surface of the n-type GaAs substrate 101.
[0188]
A feature of the surface emitting semiconductor laser of FIG. 8 is that a strain compensation superlattice carrier diffusion layer 801 is provided between the AlAs layer 203 and the p-side electrode 108. Since the InGaAs layer in the strain-compensated superlattice carrier diffusion layer 801 has a band gap smaller than that of the upper GaAs spacer layer 204, carriers (holes) are confined in a hetero barrier with the spacer layer, and the lateral direction (in-plane direction) Carrier diffusion is promoted. Furthermore, in the InGaAs layer having compressive strain, the band structure of the valence band is deformed and the effective mass of holes is reduced, so that the mobility of holes is increased. Thereby, the uniformity of the current flowing from the p-side electrode 108 into the active layer 202 is improved.
[0189]
In addition, in the strain compensation superlattice carrier diffusion layer 801, by laminating multiple InGaAs layers, carrier diffusion can be further promoted as compared with the case where only one layer is provided. However, when an InGaAs layer having compressive strain is laminated in multiple layers, internal strain energy is accumulated, and dislocation occurs when the limit value is exceeded. Therefore, in this embodiment, the InGaAs layer having compressive strain and the GaAsP layer having tensile strain are alternately laminated. As a result, the compressive strain layer is compensated by the tensile strain layer, and the net strain amount is made substantially zero, and the formation of dislocations in the strain compensation superlattice carrier diffusion layer 801 is suppressed.
[0190]
[Example 9]
FIG. 9 is a sectional view of a surface emitting semiconductor laser according to Example 9 of the present invention. A GaAs / AlAs DBR 301 is stacked on the n-type GaAs substrate 101. The GaAs / AlAs DBR 301 is formed by alternately stacking non-doped GaAs high refractive index layers and non-doped AlAs low refractive index layers with a layer thickness of ¼ of the wavelength in the medium. On the GaAs / AlAs DBR 301, a GaAs lower spacer layer 302, a GaInNAs / GaAs multiple quantum well active layer 202, and a GaAs upper spacer layer 303 are stacked. An AlAs etching layer 901 is provided in the middle of the GaAs upper spacer layer 303, and two InGaAs carrier diffusion layers 205 are provided above the AlAs etching layer 901 in the GaAs upper spacer layer 303. . The GaAs lower spacer layer 302 is n-type, and the GaAs upper spacer layer 303 is p-type.
[0191]
A GaAs / AlGaAs DBR 206 is stacked on the GaAs upper spacer layer 303. The GaAs / AlGaAs DBR 206 includes a non-doped GaAs high refractive index layer and a non-doped Al._0.9Ga_0.1As low refractive index layers are alternately stacked with a layer thickness of ¼ of the wavelength in the medium.
[0192]
A first-stage mesa structure is formed by cylindrical etching from the surface of the laminated structure to the outermost surface of the GaAs upper spacer layer 303. Further, the second-stage mesa structure is formed by etching in a cylindrical shape up to the middle of the GaAs lower spacer layer 302 with a size larger than the above size.
[0193]
The AlAs etching layer 901 is selectively side-etched from the mesa side surface to form an air gap region 902.
[0194]
A ring-shaped p-side electrode 108 is formed on the etching bottom surface of the first-stage mesa structure (the top of the second-stage mesa structure). In addition, an n-side electrode 109 is formed on the etching bottom surface of the second-stage mesa structure.
[0195]
In the surface emitting semiconductor laser of FIG. 9, by applying a forward bias to the p-side electrode 108 and the n-side electrode 109, current is injected into the GaInNAs / GaAs multiple quantum well active layer 202, and the wavelength is 1.3 μm. Emits light. At this time, the current flows through the AlAs etching layer 901 that is not side-etched and formed on the GaInNAs / GaAs multiple quantum well active layer 202. Thereby, the threshold current is reduced by concentrating the current in a region narrower than the second mesa size. Further, since the refractive index of the air gap region 902 is significantly lower than that of the unetched AlAs layer 901, the air gap region 902 serves as a lens that collects light and reduces diffraction loss.
[0196]
A region sandwiched between GaAs / AlAs DBR 301 and GaAs / AlGaAs DBR 206 has a resonator structure, and laser light is extracted vertically upward with respect to the substrate.
[0197]
Two InGaAs carrier diffusion layers 205 are provided between the AlAs etching layer 901 and the p-side electrode 108 in the p-type GaAs spacer layer 303. Similar to the second embodiment, by providing an InGaAs layer having high mobility, the current diffusion in the lateral direction is promoted, and the uniformity of the current flowing from the p-side electrode 108 into the active layer 202 is improved.
[0198]
In the case of forming a current confinement structure using the selectively etched air gap region 902, the AlAs etching layer 901 can be sufficiently electrically insulated simply by providing the AlAs etching layer 901 as thin as 50 nm or less, for example, 20 nm. . Therefore, even if the air gap region 902 is provided, an increase in resistance can be suppressed because a path through which current flows in the lateral direction in the resonator can be increased.
[0199]
In addition, in the insulating region in which the AlAs layer is selectively oxidized, stress is applied to the element due to volume contraction due to oxidation. However, when the insulating region is formed in the air gap region 902 as in this embodiment, stress is generated. do not do. Accordingly, it is possible to suppress a decrease in reliability of the element.
[0200]
【The invention's effect】
  As described above, according to the first aspect of the present invention, the lower multilayer reflector and the upper multilayer reflector that form the resonator perpendicular to the substrate, the active layer disposed in the resonator,A spacer layer adjacent to the active layer;A first electrode is formed on the resonator, and a second electrode is formed on the back surface of the substrate.And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRuThus, it is possible to provide a surface emitting semiconductor laser device that reduces the element resistance, improves the uniformity of current injection into the active layer, and has a small light absorption loss.
[0201]
  According to the second aspect of the invention, the lower multilayer reflector and the upper multilayer reflector that form a resonator perpendicular to the substrate, the active layer disposed in the resonator,A spacer layer adjacent to the active layer;And a first electrode and a second electrode for injecting current into the active layer are formed in the resonator.And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRuThus, the series resistance can be further reduced as compared with the first aspect of the invention. Further, the lower multilayer mirror can be composed of a GaAs high refractive index layer and an AlAs low refractive index layer. In this case, the thermal resistance is lowered and the heat dissipation of the element can be improved.
[0202]
  According to the invention described in claim 3, the lower multilayer reflector and the upper multilayer reflector that form a resonator perpendicular to the substrate, an active layer disposed in the resonator,A spacer layer adjacent to the active layer;And at least one of the first electrode and the second electrode is formed in the middle of the multilayer film reflecting mirror,And a carrier diffusion layer is provided between the spacer layers, and the carrier diffusion layer isLarger than the band gap of the active layer, andThe spacer layerHave a smaller band gap thanRuTherefore, it is possible to relatively suppress an increase in series resistance and to easily inject current more uniformly. In addition, the influence of light absorption by the contact layer can be reduced.
[0203]
According to a fourth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to third aspects, the carrier diffusion layer has a compressive strain. The mobility in the diffusion layer is increased, and the lateral diffusion of carriers can be further promoted.
[0204]
According to a fifth aspect of the present invention, in the surface-emitting semiconductor laser device according to any one of the first to fourth aspects, the carrier diffusion layer is provided in the p-type region of the p-type resonator. As a result, lateral diffusion of holes can be promoted, and current injection into the active layer can be made uniform.
[0205]
According to a sixth aspect of the invention, in the surface emitting semiconductor laser device according to any one of the first to fifth aspects, since a plurality of the carrier diffusion layers are provided, carrier diffusion is further improved. Can be promoted.
[0206]
According to a seventh aspect of the present invention, in the surface-emitting semiconductor laser device according to any one of the first to sixth aspects, the carrier diffusion layer has a compressive strain layer and a tensile strain. Since a plurality of layers are alternately stacked, the number of stacked carrier diffusion layers having compressive strain can be increased without introducing dislocations, and lateral carrier diffusion can be promoted.
[0207]
According to an eighth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to seventh aspects, the layer thickness of the p-type region of the resonator is the layer thickness of the n-type region. Therefore, the holes can be easily diffused in the lateral direction, and the holes can be more uniformly injected into the active layer.
[0208]
According to the ninth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects, ion implantation is performed between the active layer and the carrier diffusion layer in the resonator. Since the current confinement structure comprising the high resistance region is provided, the current injection uniformity with respect to the active layer in the oscillation region can be improved.
[0209]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects, a selection is made between the active layer and the carrier diffusion layer in the resonator. Since the current confinement structure including the electrically oxidized insulating region and the conductive region which is a non-oxidized region is provided, the current can be concentrated in a narrow region of the active layer to reduce the threshold current. Since the insulating region can be formed thin, even if an oxide layer is provided in the resonator, a large path for current flow in the lateral direction can be taken, and an increase in resistance can be suppressed.
[0210]
According to an eleventh aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the first to eighth aspects, the selective operation is performed between the active layer and the carrier diffusion layer in the resonator. Since a current confinement structure consisting of an air gap region etched into a conductive region and a non-etched region is provided, a large current path can be taken in the lateral direction to suppress an increase in resistance. Can do. In addition, in the air gap region formed by selective etching, stress due to volume change does not occur, so that deterioration in device reliability can be suppressed.
[0212]
  Also,Claim 12According to the described invention, in the surface-emitting semiconductor laser device according to any one of claims 9 to 11, a high current is provided between the current confinement region provided in the resonator and the first electrode. By providing the concentration doping region, the electric resistance can be reduced without increasing free carrier absorption.
[0213]
  Also,Claim 13According to the described invention, claims 1 toClaim 12In the surface emitting semiconductor laser device according to any one of the above, since the active layer is made of a mixed crystal semiconductor containing nitrogen and another group V element, the operating voltage is low and the long wavelength band emitting semiconductor laser with high output is provided. An apparatus can be provided.
[0214]
  Also,Claim 14According to the described invention, claims 1 toClaim 13Since the optical transmission module includes the surface-emitting semiconductor laser device according to any one of the above, power consumption of the optical transmission module can be reduced.
[0215]
  Also,Claim 15According to the described invention,Claim 14Since the optical transmission system includes the described optical transmission module, an optical transmission system with low power consumption can be constructed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a surface emitting semiconductor laser according to Example 1 of the present invention.
FIG. 2 is a view showing a surface emitting semiconductor laser according to Example 2 of the present invention.
FIG. 3 is a diagram showing a surface emitting semiconductor laser according to Example 3 of the present invention.
FIG. 4 is a diagram showing a surface emitting semiconductor laser according to Example 4 of the present invention.
FIG. 5 is a diagram showing a surface emitting semiconductor laser according to Example 5 of the present invention.
FIG. 6 is a diagram illustrating an optical transmission system according to a sixth embodiment of the present invention.
FIG. 7 is a view showing a surface emitting semiconductor laser according to Example 7 of the present invention.
FIG. 8 is a diagram showing a surface emitting semiconductor laser according to Example 8 of the present invention.
FIG. 9 is a diagram showing a surface emitting semiconductor laser according to Example 9 of the present invention.
[Explanation of symbols]
101 n-type GaAs substrate
102 n-type GaAs / AlGaAs DBR
103 AlGaAs lower spacer layer
104 InGaAs / GaAs multiple quantum well active layer
105 GaAs carrier diffusion layer
106 AlGaAs upper spacer layer
107 dielectric multilayer reflector
108 p-side electrode
109 n-side electrode
201 GaAs lower spacer layer
202 GaInNAs / GaAs multiple quantum well active layer
203 AlAs layer
204 GaAs upper spacer layer
205 InGaAs carrier diffusion layer
206 GaAs / AlGaAs DBR
207 Selective oxidation region
301 GaAs / AlAs DBR
302 GaAs lower spacer layer
303 GaAs upper spacer layer
401 GaAs / AlAs DBR
402 n-type GaAs / AlGaAs DBR
403 p-type GaAs / AlGaAs DBR
501 InGaAs carrier diffusion layer
502 GaAs / AlGaAs multiple quantum well carrier diffusion layer
503 Mixed crystallization region
601 Optical transmitter
602 Optical receiver
603 Optical transceiver module
604 quartz optical fiber
504 Highly doped region
701 High resistance region
801 Strain compensated superlattice carrier diffusion layer
901 AlAs etching layer
902 Air gap area

Claims (15)

A lower multilayer mirror and an upper multilayer mirror that form a resonator perpendicular to the substrate; an active layer disposed in the resonator; and a spacer layer adjacent to the active layer . 1 is formed, a second electrode is formed on the back surface of the substrate, a carrier diffusion layer is provided in the resonator and sandwiched between the spacer layers, and the carrier diffusion layer is active the surface emitting semiconductor laser device according to claim and larger than the band gap of the layer, and having a smaller band gap than the band gap of the spacer layer Turkey. A lower multilayer reflector and an upper multilayer reflector that form a resonator perpendicular to the substrate, an active layer disposed in the resonator, and a spacer layer adjacent to the active layer, and a current to the active layer A first electrode and a second electrode to be injected are formed in a resonator, and a carrier diffusion layer is provided in the resonator and sandwiched between the spacer layers. The carrier diffusion layer is a band of an active layer. the surface emitting semiconductor laser device according to claim and Turkey that having a smaller band gap than the band gap of greater than the gap, and the spacer layer. A lower multilayer mirror and an upper multilayer mirror that form a resonator perpendicular to the substrate, an active layer disposed in the resonator, and a spacer layer adjacent to the active layer , the first electrode; At least one of the second electrodes is formed in the middle of the multilayer reflector , and a carrier diffusion layer is provided in the resonator and sandwiched between the spacer layers. layer, the surface emitting semiconductor laser device comprising the larger than the band gap of the active layer, and having a smaller band gap than the band gap of the spacer layer Turkey.   4. The surface emitting semiconductor laser device according to claim 1, wherein the carrier diffusion layer has a compressive strain. 5.   5. The surface emitting semiconductor laser device according to claim 1, wherein the carrier diffusion layer is provided in a p-type region of the resonator. 6.   6. The surface emitting semiconductor laser device according to claim 1, wherein a plurality of the carrier diffusion layers are provided.   7. The surface emitting semiconductor laser device according to claim 1, wherein the carrier diffusion layer is formed by alternately stacking a plurality of layers having compressive strain and layers having tensile strain. A surface-emitting semiconductor laser device.   8. The surface-emitting semiconductor laser device according to claim 1, wherein the layer thickness of the p-type region of the resonator is greater than the layer thickness of the n-type region. Surface emitting semiconductor laser device.   9. The surface emitting semiconductor laser device according to claim 1, wherein a current confinement structure including a high resistance region by ion implantation is provided between the active layer and the carrier diffusion layer in the resonator. A surface-emitting semiconductor laser device comprising:   9. The surface emitting semiconductor laser device according to claim 1, wherein an insulating region and a non-oxidized region that are selectively oxidized are provided between the active layer and the carrier diffusion layer in the resonator. A surface emitting semiconductor laser device comprising a current confinement structure including a conductive region.   9. The surface emitting semiconductor laser device according to claim 1, wherein an air gap region selectively etched between the active layer and the carrier diffusion layer in the resonator, and a non-etching region. A surface emitting semiconductor laser device comprising a current confinement structure including a conductive region.   12. The surface emitting semiconductor laser device according to claim 9, wherein a high concentration doping region is provided between the current confinement region provided in the resonator and the first electrode. A surface emitting semiconductor laser device. 13. The surface emitting semiconductor laser device according to claim 1, wherein the active layer is made of a mixed crystal semiconductor containing nitrogen and another group V element. apparatus. An optical transmission module comprising the surface-emitting semiconductor laser device according to any one of claims 1 to 13 . An optical transmission system comprising the optical transmission module according to claim 14 .

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