JP2016021484A - Compound semiconductor device and surface emitting laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound semiconductor device capable of achieving improvement in an output of a surface emitting laser.SOLUTION: Provided is a compound semiconductor device which has: a first electrode which is formed on one surface of a substrate and has an opening; an active layer laminated on the other surface of the substrate; an upper mirror laminated on the active layer; and a second electrode formed on the upper mirror. Thermal conductivity in a peripheral part of the second electrode is lower than thermal conductivity at a center part of the second electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compound semiconductor device and a surface emitting laser.

  A surface-emitting laser is a semiconductor laser that emits light in a direction perpendicular to the substrate surface. Compared with an edge-emitting semiconductor laser, the surface-emitting laser is characterized by low cost, low power consumption, small size, and high performance. Have.

  Conventionally, in a surface emitting laser, the current injection area into the active layer is limited by the current confinement structure formed between the electrode and the active layer, thereby further reducing the power consumption of the surface emitting laser. (For example, refer nonpatent literature 1).

  However, in the conventional technique described above, since the current injection area is limited, the current that can be injected is small, and it is difficult to increase the output of the surface emitting laser.

  Accordingly, an object of the present invention is to provide a compound semiconductor device capable of improving the output of a surface emitting laser.

  In one plan, a first electrode formed on one surface of the substrate and having an opening, an active layer stacked on the other surface of the substrate, an upper reflecting mirror stacked on the active layer, and There is provided a compound semiconductor device having a second electrode formed on the upper reflecting mirror, wherein the thermal conductivity in the peripheral portion of the second electrode is smaller than the thermal conductivity in the central portion of the second electrode. .

  According to one embodiment, a compound semiconductor device capable of improving the output of a surface emitting laser can be provided.

1 is a cross-sectional view illustrating a schematic configuration of a compound semiconductor device according to a first embodiment. 1 is a plan view illustrating a schematic configuration of a compound semiconductor device according to a first embodiment. The figure for demonstrating the effect | action and effect of the compound semiconductor device which concerns on 1st Embodiment. The figure which illustrates schematic structure of the surface emitting laser which concerns on 1st Embodiment. Sectional drawing which illustrates schematic structure of the compound semiconductor device which concerns on 2nd Embodiment. Sectional drawing which illustrates schematic structure of the compound semiconductor device which concerns on 3rd Embodiment. Sectional drawing which illustrates schematic structure of the compound semiconductor device which concerns on 4th Embodiment. Sectional drawing which illustrates schematic structure of the compound semiconductor device which concerns on 5th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[First Embodiment]
(Configuration of compound semiconductor device)
First, an example of a schematic configuration of the compound semiconductor device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view illustrating a schematic configuration of the compound semiconductor device according to the first embodiment. FIG. 2 is a plan view illustrating a schematic configuration of the compound semiconductor device according to the first embodiment.

  The compound semiconductor device 100a includes a substrate 101, a lower spacer layer 102, an active layer 103, an upper spacer layer 104, an upper reflecting mirror 105, a contact layer 106, an insulating layer 107, a first electrode 108, a second electrode 109a, and the like.

The substrate 101 is a GaAs substrate doped with Si (silicon) at a concentration of 1 × 10 ⁸ / cm ³ and having n-type conductivity. Further, the substrate 101 has a crystal orientation (100) plane inclined by 15 ° with respect to the crystal orientation (111) direction.

  The lower spacer layer 102 is laminated on the surface in the −Z direction of the substrate 101 and is a layer made of GaInP.

  The active layer 103 is stacked on the surface of the lower spacer layer 102 in the −Z direction, and is an active layer having a triple quantum well structure made of GaInPAs / GaInP. The GaInPAs layer, which is an example of the quantum well layer, is adjusted so that the emission wavelength is 700 nm, the lattice distortion is + 1.0%, and the film thickness is 5 nm. A GaInP layer, which is an example of a barrier layer, is adjusted to have a lattice strain of −0.3% and a film thickness of 8 nm.

  The upper spacer layer 104 is laminated on the surface in the −Z direction of the active layer 103 and is a layer made of GaInP. A portion composed of the lower spacer layer 102, the active layer 103, and the upper spacer layer 104 is also called a resonator, and is adjusted by each spacer layer so that its optical thickness is 710 nm. Each spacer layer is lattice-matched with the active layer 103.

The upper reflecting mirror 105 is laminated on the surface of the upper spacer layer 104 in the −Z direction, and has 25 pairs of a low refractive index layer made of AlAs and a high refractive index layer made of Al _0.3 Ga _0.7 As. ing. Each refractive index layer is doped with C (carbon) at a concentration of 5 × 10 ¹⁶ / cm ³ .

The contact layer 106 is laminated on the surface of the upper reflecting mirror 105 in the −Z direction, is a layer made of GaAs having p-type conductivity, doped with Zn (zinc) at a concentration of 1 × 10 ¹⁹ / cm ^3. .

The insulating layer 107 is laminated on the surface of the contact layer 106 in the −Z direction, and is a layer made of SiN, SiON, SiO ₂ or the like.

  The first electrode 108 is formed on a surface in the + Z direction of the substrate 101 and is an electrode made of a multilayer film (metal film) in which AuGe, Ni (nickel), and Au (gold) are sequentially stacked. In addition, the first electrode 108 has an opening A that serves as a laser beam exit. The shape of the first electrode 108 is not particularly limited as long as it is an annular shape having the opening A, and examples thereof include a rectangle and a circle.

  The second electrode 109a is formed on the surface in the −Z direction of the contact layer 106, and has, for example, a circular shape as shown in FIG. Further, the thermal conductivity in the peripheral portion S2 of the second electrode 109a is smaller than the thermal conductivity in the central portion S1 of the second electrode 109a. That is, the electrode material in the peripheral portion S2 of the second electrode 109a is made of a material having a lower thermal conductivity than the electrode material in the central portion S1 of the second electrode 109a. Specifically, as the electrode material in the central portion S1 of the second electrode 109a, for example, a material in which Cr (chrome), AuZn, and Au are sequentially stacked is preferably used. Moreover, as an electrode material in the peripheral portion S2 of the second electrode 109a, for example, a material in which Ti (titanium), Pt (platinum), and Au are sequentially stacked is preferably used. The shape of the second electrode 109a is not limited to the circular shape described above, and may be, for example, a rectangular shape.

(Method of manufacturing compound semiconductor device)
Next, an example of a method for manufacturing the compound semiconductor device according to the first embodiment will be described.

  First, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, and the contact layer 106 are formed on the surface of the substrate 101 in the −Z direction by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxial growth. It is formed by crystal growth by (MBE method).

Subsequently, an insulating layer 107 made of SiN, SiON, or SiO ₂ is formed on the surface in the −Z direction of the contact layer 106 by using a chemical vapor deposition method (CVD method).

  Subsequently, a second electrode contact window is opened in the insulating layer 107. Specifically, for example, after masking with a photoresist, the portion of the insulating layer 107 where the second electrode is to be formed is exposed to remove the photoresist, and the insulating layer 107 is formed with, for example, BHF (buffered hydrofluoric acid). Open by etching.

  Subsequently, the first electrode 108 is formed on the surface of the substrate 101 in the + Z direction. Specifically, after forming a resist pattern in a region other than the region to be the first electrode 108, the electrode material is deposited. Then, the resist pattern and the electrode material are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, the first electrode 108 is formed at a desired position on the substrate 101.

  Subsequently, the second electrode 109a is formed in the central portion S1 of the surface of the contact layer 106 in the −Z direction. Specifically, after forming a resist pattern other than the central portion S1, the electrode material is deposited. Then, the resist pattern and the electrode material are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, the second electrode 109a is formed in the central portion S1.

  Subsequently, the second electrode 109a is formed in the peripheral portion S2 of the surface of the contact layer 106 in the −Z direction. Specifically, after forming a resist pattern other than the peripheral portion S2, the electrode material is deposited. Then, the resist pattern and the electrode material are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, the second electrode 109a is formed in the peripheral portion S2.

  As an example, the first electrode 108, the second electrode 109a in the central portion S1, and the second electrode 109a in the peripheral portion S2 have been described in this order. However, the present invention is not limited in this respect. . For example, the order of forming the first electrode 108 and the second electrode 109a can be changed, such as forming the first electrode 108 after forming the second electrode 109b.

  Subsequently, ohmic conduction is established between the substrate 101 and the first electrode 108 and between the contact layer 106 and the second electrode 109a by heat treatment.

  The compound semiconductor device 100a shown in FIGS. 1 and 2 can be manufactured by the above method.

(Action / Effect)
Next, functions and effects of the compound semiconductor device according to the first embodiment will be described with reference to FIG. FIG. 3 is a diagram for explaining the operation and effect of the compound semiconductor device according to the first embodiment.

  In the compound semiconductor device 100a according to the first embodiment, the upper reflecting mirror 105 has p-type conductivity, and the substrate 101 has n-type conductivity. Further, since p-type carriers (hereinafter referred to as “holes”) have lower mobility than n-type carriers (hereinafter referred to as “electrons”), holes injected from the second electrode 109a (white arrows in FIG. 3). ) Is injected into the active layer 103 without diffusing as much as electrons injected from the first electrode 108 (see the black arrow in FIG. 3). Therefore, a region where holes and electrons are injected (hereinafter referred to as “current injection region I”) is formed in the active layer 103. As a result, since a current can be uniformly injected into the current injection region I, high-output light emission can be obtained.

  The size of the current injection region I can be adjusted by the shape of the second electrode 109a and the impurity concentration inside the upper reflecting mirror 105.

  Here, when a current is injected into the active layer 103 by applying a voltage to the first electrode 108 and the second electrode 109a from an external power source (not shown), the thermal conductivity in the peripheral portion S2 of the second electrode 109a is the second electrode. Since it is smaller than the thermal conductivity in the central portion S1 of 109a, the peripheral portion S2 has a higher temperature than the central portion S1. For this reason, the emission wavelength in the peripheral portion S2 is longer than the emission wavelength in the central portion S1. That is, the refractive index of the peripheral portion S2 is smaller than the refractive index of the central portion S1. As a result, a non-uniform refractive index distribution is formed inside the current injection region I, and a region having a high light confinement effect can be formed in the central portion S1 of the current injection region I.

  Further, the electrons injected from the first electrode 108 and the holes injected from the second electrode 109a are combined in the active layer 103 and emit light at a desired wavelength. The light emitted from the active layer 103 is emitted from the opening A of the first electrode 108. Here, as described above, since the compound semiconductor device 100a has a region having a high light confinement effect in the central portion S1 of the current injection region I, the compound semiconductor device 100a emits high-power light.

(Surface emitting laser)
Next, a surface emitting laser using the compound semiconductor device 100a according to the first embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating a schematic configuration of the surface emitting laser according to the first embodiment.

  As shown in FIG. 4, the surface emitting laser 200a includes a compound semiconductor device 100a, an external reflecting mirror 201, and a nonlinear optical crystal 202. That is, the surface emitting laser 200a is configured as a so-called external cavity type vertical surface emitting laser (VECSEL).

  The external reflecting mirror 201 is disposed on the optical path of the light emitted from the compound semiconductor device 100a, and forms a resonator (hereinafter referred to as “external resonator”) with the compound semiconductor device 100a. That is, the light emitted from the active layer 103 of the compound semiconductor device 100a is repeatedly reflected in the external resonator and laser oscillation occurs. The surface emitting laser 200a of the first embodiment can oscillate laser light having a wavelength of about 710 nm.

  The nonlinear optical crystal 202 is disposed between the compound semiconductor device 100a and the external reflecting mirror 201, and a second harmonic (SHG: Second Harmonic Generation) that makes the wavelength of the resonating fundamental wave 1/2 (frequency doubled). ) Is generated. Then, by adjusting the reflectance of the external reflector so that the reflectance is high for the fundamental wave and low for the second harmonic, only the second harmonic is emitted to the outside as the oscillation light. be able to. The surface emitting laser 200a of the first embodiment can oscillate laser light having a wavelength of about 355 nm, which is a half wavelength of the fundamental wave, that is, ultraviolet laser light.

  Further, since the surface emitting laser 200a includes the compound semiconductor device 100a capable of obtaining the above-described high-output light emission, the laser light can be emitted at a high output. That is, the surface emitting laser 200a can emit a laser beam having a wavelength half that of the oscillation wavelength of the active layer 103 at a high output.

  As described above, according to the compound semiconductor device according to the first embodiment, the first electrode formed on one surface of the substrate and having an opening, and the active layer stacked on the other surface of the substrate, And a reflecting mirror laminated on the active layer and a second electrode formed on the reflecting mirror. Further, the thermal conductivity in the peripheral part of the second electrode is smaller than the thermal conductivity in the central part of the second electrode. Therefore, a compound semiconductor device capable of improving the output of the surface emitting laser can be provided.

[Second Embodiment]
(Configuration of compound semiconductor device)
Next, a compound semiconductor device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view illustrating a schematic configuration of the compound semiconductor device according to the second embodiment.

  In the compound semiconductor device 100b according to the second embodiment, as shown in FIG. 5, the second electrode 109b has a low thermal conductivity layer having a smaller thermal conductivity than the electrode material of the second electrode 109b in a part of the peripheral portion S2. 121 is different from the compound semiconductor device 100a according to the first embodiment.

  The compound semiconductor device 100b according to the second embodiment has the same configuration as that of the compound semiconductor device 100a according to the first embodiment except for the above differences. For this reason, in the following description, it demonstrates focusing on the point which is different from 1st Embodiment.

  As shown in FIG. 5, the compound semiconductor device 100b includes a substrate 101, a lower spacer layer 102, an active layer 103, an upper spacer layer 104, an upper reflecting mirror 105, a contact layer 106, an insulating layer 107, a first electrode 108, a second electrode. The electrode 109b and the like are included.

  Since the substrate 101, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, the contact layer 106, the insulating layer 107, and the first electrode 108 are the same as those in the first embodiment, description thereof is omitted. To do.

  The second electrode 109b is formed on a part of the contact layer 106 in the −Z direction. The second electrode 109b includes a low thermal conductivity layer 121 having a lower thermal conductivity than the electrode material of the second electrode 109b in a part of the peripheral portion S2. That is, the thermal conductivity in the peripheral portion S2 of the second electrode 109b is smaller than the thermal conductivity in the central portion S1 of the second electrode 109b.

  As an electrode material of the second electrode 109b, a metal film or the like in which Cr, AuZn, and Au are sequentially stacked can be used.

  The material of the low thermal conductivity layer 121 of the second electrode 109b is not particularly limited as long as it has a lower thermal conductivity than the electrode material of the second electrode 109b, but it is preferable to use an insulator such as SiN. In the case where an insulator is used as the material of the low thermal conductivity layer 121 of the second electrode 109b, the low thermal conductivity layer 121 is preferably sandwiched between the electrode materials of the second electrode 109b. Thereby, the contact property between the contact layer 106 and the second electrode 109b and between the second electrode 109b and an external terminal (not shown) can be maintained.

  Further, the low thermal conductivity layer 121 can be formed at the same time as the insulating layer 107 as described later.

  Note that the thermal conductivity of Au, which is an example of the electrode material of the second electrode 109b, is about 300 W / m · K. Further, the thermal conductivity of SiN, which is an example of the material of the low thermal conductivity layer 121 of the second electrode 109b, is about 30 W / m · K.

(Method of manufacturing compound semiconductor device)
Next, a method for manufacturing a compound semiconductor device according to the second embodiment will be described.

  First, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, and the contact layer 106 are formed on the surface in the −Z direction of the substrate 101 by the same method as in the first embodiment. In addition, the first electrode 108 is formed on the surface in the + Z direction of the substrate 101.

  Subsequently, the second electrode 109b is formed on the surface of the contact layer 106 in the −Z direction.

  Specifically, first, after forming a resist pattern other than the central portion S1 and the peripheral portion S2, the electrode material is deposited. Then, the resist pattern and the electrode material are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, the layer which consists of electrode materials is formed in center part S1 and peripheral part S2.

  Next, after forming a resist pattern in the central portion S1, an insulating layer is formed. Then, the resist pattern and the insulating layer are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, the insulating layer 107 is formed on the surface in the −Z direction of the contact layer 106 excluding the central portion S1 and the peripheral portion S2, and the low heat composed of the insulating layer on the surface in the −Z direction of the layer made of the electrode material of the peripheral portion S2. A conductivity layer 121 is formed.

  Next, after forming a resist pattern other than the central portion S1 and the peripheral portion S2, the electrode material is evaporated. Then, the resist pattern and the electrode material are lifted off by ultrasonic treatment in an organic solvent such as acetone. Thereby, a layer made of the electrode material is formed on the surface in the −Z direction of the layer made of the electrode material in the central portion S1 and the low thermal conductivity layer 121 in the peripheral portion S2.

  By these steps, the second electrode 109b including the low thermal conductivity layer 121 having a lower thermal conductivity than the electrode material of the second electrode 109b is formed on a part of the peripheral portion S2 on the surface in the −Z direction of the contact layer 106. To do.

  Subsequently, ohmic conduction is established between the substrate 101 and the first electrode 108 and between the contact layer 106 and the second electrode 109b by heat treatment by the same method as in the first embodiment.

  By the above method, the compound semiconductor device 100b having the second electrode 109b including the low thermal conductivity layer 121 having a lower thermal conductivity than the electrode material of the second electrode 109b in a part of the peripheral portion S2 can be manufactured.

(Action / Effect)
Next, functions and effects of the compound semiconductor device according to the second embodiment will be described.

  Since the compound semiconductor device 100b according to the second embodiment includes the same configuration as that of the compound semiconductor device 100a according to the first embodiment, the same operations and effects as the compound semiconductor device 100a according to the first embodiment may be achieved. it can.

  In the compound semiconductor device 100b according to the second embodiment, the second electrode 109b includes the low thermal conductivity layer 121 having a lower thermal conductivity than the electrode material of the second electrode 109b in a part of the peripheral portion S2. . For this reason, the thermal conductivity in the peripheral portion S2 of the second electrode 109b is smaller than the thermal conductivity in the central portion S1 of the second electrode 109b. As a result, higher power emission is possible.

  In addition, the compound semiconductor device 100b according to the second embodiment has the second electrode 109b in which a difference in thermal conductivity is structurally provided between the central portion S1 and the peripheral portion S2. For this reason, even when the electrode material used for the central portion S1 and the electrode material used for the peripheral portion S2 are the same, the thermal conductivity in the peripheral portion S2 of the second electrode 109b is the center of the second electrode 109b. It can be made smaller than the thermal conductivity in the part S1. As a result, options of electrode materials that can be used as the second electrode 109b are expanded.

(Surface emitting laser)
Since the surface emitting laser according to the second embodiment has the same configuration as that of the first embodiment, the description thereof is omitted.

  As described above, according to the compound semiconductor device according to the second embodiment, it is possible to provide a compound semiconductor device capable of improving the output of the surface emitting laser. Moreover, according to the surface emitting laser according to the second embodiment, since the compound semiconductor device capable of emitting high output is used, the laser light can be emitted with high output.

  In particular, in the second embodiment, since the second electrode includes a low thermal conductivity layer having a lower thermal conductivity than the electrode material of the second electrode in a part of the peripheral portion, it is possible to emit light with higher output.

[Third Embodiment]
(Configuration of compound semiconductor device)
Next, a compound semiconductor device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view illustrating a schematic configuration of the compound semiconductor device according to the third embodiment.

  In the compound semiconductor device 100c according to the third embodiment, as shown in FIG. 6, at least a part of the substrate 101 immediately below the opening A of the first electrode 108 is removed, and an injection hole B is formed. This is different from the compound semiconductor device 100b according to the second embodiment.

  The compound semiconductor device 100c according to the third embodiment has the same configuration as that of the compound semiconductor device 100b according to the second embodiment except for the above differences. For this reason, in the following description, it demonstrates focusing on the point which is different from 2nd Embodiment.

  As shown in FIG. 6, the compound semiconductor device 100c includes a substrate 101, a lower spacer layer 102, an active layer 103, an upper spacer layer 104, an upper reflecting mirror 105, a contact layer 106, an insulating layer 107, a first electrode 108, a second electrode. The electrode 109b and the like are included. Further, in the compound semiconductor device 100c, at least a part of the substrate 101 immediately below the opening A of the first electrode 108 is removed, and an injection hole B is formed.

  Since the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, the contact layer 106, the insulating layer 107, the first electrode 108, and the second electrode 109b are the same as those in the second embodiment, description is made. Is omitted.

(Method of manufacturing compound semiconductor device)
Next, a method for manufacturing a compound semiconductor device according to the third embodiment will be described.

  First, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, and the contact layer 106 are formed on the surface in the −Z direction of the substrate 101 by the same method as in the second embodiment.

  Subsequently, the injection hole B is formed by removing a part of the substrate 101 by etching or the like.

  At this time, since the thickness of the substrate 101 is several tens of μm or more, the lower spacer layer 102, the active layer 103, and the upper spacer formed on the surface in the −Z direction of the substrate 101 unless strict film thickness control is performed. There is a risk of etching the layer 104 or the like.

Therefore, when the substrate 101 is GaAs and the resonator is Al _x Ga _1-x As (x ≠ 0), only the substrate 101 is selectively selected by wet etching using a mixed solution of ammonia and hydrogen peroxide. The injection hole B can be easily formed.

In addition, when the substrate 101 is GaAs and the resonator is AlGaInP _y As _1-y (y ≠ 0), dry etching such as ICP (Inductively Coupled Plasma) etching, or a mixed solution of sulfuric acid and hydrogen peroxide water is used. The injection hole B can be easily formed by selectively removing only the substrate 101 by wet etching or the like.

  Subsequently, the insulating layer 107, the first electrode 108, and the second electrode 109b are formed by the same method as in the second embodiment.

  Subsequently, ohmic conduction is established between the substrate 101 and the first electrode 108 and between the contact layer 106 and the second electrode 109b by heat treatment in the same manner as in the second embodiment.

  By the above method, the compound semiconductor device 100c having the substrate 101 including the injection hole B formed by removing at least part of the first electrode 108 immediately below the opening A can be manufactured.

(Action / Effect)
Next, functions and effects of the compound semiconductor device according to the third embodiment will be described.

  Since the compound semiconductor device 100c according to the third embodiment includes the same configuration as that of the compound semiconductor device 100b according to the second embodiment, the same operation and effect as the compound semiconductor device 100b according to the second embodiment can be obtained. it can.

  Here, in the compound semiconductor device 100b according to the second embodiment, since the light emitted from the active layer 103 is extracted to the outside through the substrate 101, the energy of the oscillation wavelength in the active layer 103 is the band gap of the substrate 101. If this is the case, it is absorbed by the substrate 101. For this reason, in the compound semiconductor device 100b according to the second embodiment, the energy of the emission wavelength in the active layer 103 needs to be less than the band gap of the substrate 101.

  In contrast, in the compound semiconductor device 100c according to the third embodiment, at least a part of the substrate 101 immediately below the opening A of the first electrode 108 is removed, and the injection hole B is formed. For this reason, in the compound semiconductor device 100c according to the third embodiment, even if the energy of the emission wavelength in the active layer 103 is equal to or greater than the band gap of the substrate 101, the light generated in the active layer 103 is absorbed by the substrate 101. Never happen. As a result, light having energy higher than the band gap of the substrate 101 can be emitted with high output.

(Surface emitting laser)
Since the surface emitting laser according to the third embodiment has the same configuration as the first embodiment and the second embodiment, the description thereof is omitted.

  As described above, the compound semiconductor device according to the third embodiment can improve the output of the compound semiconductor device. Moreover, according to the surface emitting laser according to the third embodiment, a compound semiconductor device capable of improving the output of the surface emitting laser can be provided.

  In particular, in the third embodiment, since at least a part of the substrate immediately below the opening of the first electrode is removed and an emission hole is formed, light having energy higher than the band gap of the substrate is emitted with high output. be able to.

[Fourth Embodiment]
(Configuration of compound semiconductor device)
Next, a compound semiconductor device according to a fourth embodiment of the invention will be described with reference to FIG. FIG. 7 is a cross-sectional view illustrating a schematic configuration of the compound semiconductor device according to the fourth embodiment.

  As shown in FIG. 7, the compound semiconductor device 100 d according to the fourth embodiment includes a current diffusion layer 141 between the substrate 101 and the active layer 103, more specifically, between the substrate 101 and the lower spacer layer 102. This is different from the compound semiconductor device 100c according to the third embodiment.

  The compound semiconductor device 100d according to the fourth embodiment has the same configuration as that of the compound semiconductor device 100c according to the third embodiment except for the above differences. For this reason, in the following description, it demonstrates focusing on the point which is different from 3rd Embodiment.

  As shown in FIG. 7, the compound semiconductor device 100 d includes a substrate 101, a current diffusion layer 141, a lower spacer layer 102, an active layer 103, an upper spacer layer 104, an upper reflecting mirror 105, a contact layer 106, an insulating layer 107, a first layer. The electrode 108, the second electrode 109b, and the like are included. In the compound semiconductor device 100d, at least a part of the substrate 101 immediately below the opening A of the first electrode 108 is removed, and an injection hole B is formed.

  The current diffusion layer 141 is a layer that diffuses electrons injected from the first electrode 108. The current spreading layer 141 is preferably made of a material having a high electron mobility so that electrons can diffuse efficiently in the layer. The current spreading layer 141 is preferably a material having a band gap equal to or larger than the band gap of the substrate 101 because absorption of light emitted from the active layer 103 can be suppressed. Specifically, as the current diffusion layer 141, AlGaAs or the like can be suitably used.

  Since other configurations are the same as those in the third embodiment, description thereof will be omitted.

(Method of manufacturing compound semiconductor device)
Next, a method for manufacturing a compound semiconductor device according to the fourth embodiment will be described.

  First, the current diffusion layer 141 is formed on the surface in the −Z direction of the substrate 101.

  Subsequently, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, and the contact layer 106 are formed on the surface in the −Z direction of the current diffusion layer 141 by the same method as in the third embodiment. .

  Subsequently, the injection hole B is formed in the substrate 101 by the same method as in the third embodiment.

  Subsequently, the insulating layer 107, the first electrode 108, and the second electrode 109b are formed by the same method as in the third embodiment.

  Subsequently, ohmic conduction is established between the substrate 101 and the first electrode 108 and between the contact layer 106 and the second electrode 109b by heat treatment in the same manner as in the third embodiment.

  With the above method, the compound semiconductor device 100d having the current diffusion layer 141 between the substrate 101 and the active layer 103 can be manufactured.

(Action / Effect)
Next, functions and effects of the compound semiconductor device according to the fourth embodiment will be described.

  Since the compound semiconductor device 100d according to the fourth embodiment includes the same configuration as that of the compound semiconductor device 100c according to the third embodiment, the same operations and effects as the compound semiconductor device 100c according to the third embodiment may be achieved. it can.

  In addition, according to the compound semiconductor device 100d according to the fourth embodiment, since the current diffusion layer 141 is inserted between the substrate 101 and the active layer 103, a path for realizing uniform current injection is ensured. And an increase in electrical resistance can be suppressed.

(Surface emitting laser)
Since the surface emitting laser according to the fourth embodiment has the same configuration as that of the first to third embodiments, the description thereof is omitted.

  As described above, the compound semiconductor device according to the fourth embodiment can provide a compound semiconductor device capable of improving the output of the surface emitting laser. Moreover, according to the surface emitting laser according to the fourth embodiment, since the compound semiconductor device capable of emitting high output is used, the laser beam can be emitted with high output.

  In particular, in the fourth embodiment, since the current diffusion layer is provided between the substrate and the active layer, an increase in electrical resistance of the compound semiconductor device can be suppressed.

[Fifth Embodiment]
(Configuration of compound semiconductor device)
Next, a compound semiconductor device according to a fifth embodiment of the invention will be described with reference to FIG. FIG. 8 is a cross-sectional view illustrating a schematic configuration of the compound semiconductor device according to the fifth embodiment.

  As shown in FIG. 8, the compound semiconductor device 100e according to the fifth embodiment includes a lower reflecting mirror 151 between the substrate 101 and the active layer 103, more specifically, between the current diffusion layer 141 and the lower spacer layer 102. This is different from the compound semiconductor device 100d according to the fourth embodiment.

  The compound semiconductor device 100e according to the fifth embodiment has the same configuration as the compound semiconductor device 100d according to the fourth embodiment except for the above differences. For this reason, in the following description, it demonstrates focusing on the point which is different from 4th Embodiment.

  As shown in FIG. 8, the compound semiconductor device 100e includes a substrate 101, a current diffusion layer 141, a lower reflecting mirror 151, a lower spacer layer 102, an active layer 103, an upper spacer layer 104, an upper reflecting mirror 105, a contact layer 106, an insulating layer. The layer 107, the first electrode 108, the second electrode 109b, and the like are included. Further, in the compound semiconductor device 100e, at least a part of the substrate 101 immediately below the opening A of the first electrode 108 is removed, and an injection hole B is formed.

The lower reflecting mirror 151 is laminated on the surface in the −Z direction of the current diffusion layer 141 and has, for example, 20 pairs of a low refractive index layer made of AlAs and a high refractive index layer made of Al _0.3 GaAs.

  By providing the lower reflecting mirror 151, a cavity mode is defined as a surface emitting laser, and a resonance wavelength when laser oscillation is performed is fixed. In addition, by appropriately setting the reflectance of the lower reflecting mirror 151, the compound semiconductor device 100e operates as a so-called vertical cavity surface emitting laser (VCSEL).

  The reflectances of the lower reflecting mirror 151 and the upper reflecting mirror 105 are preferably 99% or more. Further, since the oscillation light is extracted in the direction in which the opening A of the first electrode 108 and the emission hole B of the substrate 101 are formed, the reflectance of the lower reflecting mirror 151 is made smaller than the reflectance of the upper reflecting mirror 105. Adjusted to

  Since other configurations are the same as those in the fourth embodiment, description thereof is omitted.

(Method of manufacturing compound semiconductor device)
Next, a method for manufacturing a compound semiconductor device according to the fifth embodiment will be described.

  First, the current diffusion layer 141 is formed on the surface in the −Z direction of the substrate 101 by the same method as in the fourth embodiment.

  Subsequently, the lower reflecting mirror 151 is formed on the surface in the −Z direction of the current diffusion layer 141.

  Subsequently, the lower spacer layer 102, the active layer 103, the upper spacer layer 104, the upper reflecting mirror 105, and the contact layer 106 are formed on the surface in the −Z direction of the lower reflecting mirror 151 by the same method as in the fourth embodiment.

  Subsequently, the injection hole B is formed in the substrate 101 by the same method as in the fourth embodiment.

  Subsequently, the insulating layer 107, the first electrode 108, and the second electrode 109b are formed by the same method as in the fourth embodiment.

  Subsequently, ohmic conduction is established between the substrate 101 and the first electrode 108 and between the contact layer 106 and the second electrode 109b by heat treatment in the same manner as in the fourth embodiment.

  By the above method, the compound semiconductor device 100e having the lower reflecting mirror 151 between the substrate 101 and the active layer 103 can be manufactured.

(Action / Effect)
Next, functions and effects of the compound semiconductor device according to the fifth embodiment will be described.

  Since the compound semiconductor device 100e according to the fifth embodiment includes the same configuration as that of the compound semiconductor device 100d according to the fourth embodiment, the same operations and effects as the compound semiconductor device 100d according to the fourth embodiment can be achieved. it can.

  In addition, according to the compound semiconductor device 100e according to the fifth embodiment, since the lower reflecting mirror 151 is provided between the substrate 101 and the active layer 103, the wavelength controllability during laser oscillation can be improved.

(Surface emitting laser)
Next, a surface emitting laser according to the fifth embodiment will be described.

  The surface emitting laser according to the fifth embodiment includes a compound semiconductor device 100e, an external reflecting mirror 201, and a nonlinear optical crystal 202, as in the first to fourth embodiments.

  In the surface emitting laser according to the fifth embodiment, as described above, the compound semiconductor device 100e includes the lower reflecting mirror 151. Therefore, the reflectance of the lower reflecting mirror 151 and the outer reflecting mirror 201 is adjusted so that the total reflectance of the lower reflecting mirror 151 and the outer reflecting mirror 201 is 99% or more and smaller than the reflectance of the upper reflecting mirror 105. . As a result, laser light with excellent wavelength controllability can be emitted from the external reflecting mirror side.

  As described above, according to the compound semiconductor device according to the fifth embodiment, a compound semiconductor device capable of improving the output of the surface emitting laser can be provided. Further, according to the surface emitting laser according to the fifth embodiment, since the compound semiconductor device capable of emitting high output is used, the laser beam can be emitted with high output.

  In particular, in the fifth embodiment, since the lower reflecting mirror is provided between the substrate and the active layer, the wavelength controllability during laser oscillation can be improved.

  The compound semiconductor device and the surface emitting laser have been described above by way of the embodiment. However, the present invention is not limited to the above embodiment, and various modifications and improvements can be made within the scope of the present invention.

100a, 100b, 100c, 100d, 100e Compound semiconductor device 101 Substrate 103 Active layer 105 Upper reflection mirror 108 First electrode 109 Second electrode 121 Low thermal conductivity layer 141 Current diffusion layer 151 Lower reflection mirror 200a Surface emitting laser 201 External reflection mirror A opening B injection hole S1 center part S2 peripheral part

IEEE, Photonic Technology Letters, Vol. 11, no. 12 (1999), p. 1539-1541

Claims (6)

A first electrode formed on one surface of the substrate and having an opening;
An active layer laminated on the other surface of the substrate;
An upper reflector laminated on the active layer;
A second electrode formed on the upper reflecting mirror;
The thermal conductivity at the periphery of the second electrode is smaller than the thermal conductivity at the center of the second electrode,
Compound semiconductor device. The second electrode includes a low thermal conductivity layer having a thermal conductivity smaller than that of the material of the second electrode in a part of the peripheral portion.
The compound semiconductor device according to claim 1. At least a part of the substrate immediately below the opening of the first electrode is removed, and an injection hole is formed.
The compound semiconductor device according to claim 1 or 2. Having a current spreading layer between the substrate and the active layer;
The compound semiconductor device according to any one of claims 1 to 3. Having a lower reflector between the substrate and the active layer;
The compound semiconductor device according to any one of claims 1 to 4. A compound semiconductor device according to any one of claims 1 to 5,
An external reflecting mirror disposed on an optical path of light emitted from the compound semiconductor device,
Surface emitting laser.

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