JP2014170813A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device having higher light extraction efficiency compared with the conventional art.SOLUTION: A semiconductor laser device 1 comprises: a semiconductor substrate 10; a first reflector 11 formed on an upper layer at a first surface side of the semiconductor substrate 10; a light emission part 13 formed on an upper layer of the first reflector 11; a second reflector 15 formed on an upper layer of the light emission part 13; a contact layer 17 formed on an upper layer of the second reflector 15; a first electrode 19 formed on an upper layer at a second surface side opposite to the first surface, of the semiconductor substrate 10; and a second electrode 21 formed on an upper layer of the contact layer 17. In the first reflector 11, on a surface opposite to the side where the light emission part 13 is formed, a first region located at an outer edge contacts with the semiconductor substrate 10 (10a). The second region located inside the first region contacts with a region (10b) having a carrier concentration lower than that of the semiconductor substrate 10 (10a) provided at a position contacting with the first region, or contacts with a cavity.

Description

  The present invention relates to a semiconductor laser device.

  In recent years, vertical external cavity surface emitting lasers (hereinafter, abbreviated as “VECSEL”) having a configuration for extracting light in a direction perpendicular to the substrate surface have been developed as semiconductor laser devices. (For example, see Patent Document 1 and Non-Patent Document 1 below).

  FIG. 11 is a schematic cross-sectional view of a conventional laser device having a VECSEL structure disclosed in Patent Document 1 and Non-Patent Document 1. The conventional laser device 90 includes an n-side multilayer reflector 11, a light emitting unit 13, and a p-side multilayer reflector 15 on the upper surface of the semiconductor substrate 40, and the pair of reflecting mirrors 11 and 15 is a semiconductor. The structure is sandwiched in a direction perpendicular to the surface of the substrate 40.

  A p-side electrode 21 is formed on the p-side multilayer mirror 15 via a high-concentration contact layer 17. On the other hand, an n-side electrode 19 is formed on the surface of the semiconductor substrate 40 on the side where the light emitting unit 13 and the pair of reflecting mirrors 11 and 15 are not formed.

  An insulating layer 25 is formed outside the multilayer structure of the n-side multilayer mirror 11, the light emitting unit 13, the p-side multilayer reflector 15 and the contact layer 17. When a bias voltage is applied between the p-side electrode 21 and the n-side electrode 19, the insulating layer 25 concentrates a current in the region of the multilayer structure including the light-emitting portion 13 in order to increase the light emission efficiency, and A high resistance layer (current confinement layer) for preventing current from flowing in the region is configured. A passivation layer 27 covers the periphery of the insulating layer 25.

  An external output mirror 3 is provided at a position separated from the semiconductor substrate 40 in the light extraction direction d1.

  By applying a bias voltage between the p-side electrode 21 and the n-side electrode 19, a current flows through the light emitting unit 13 and the region emits light. This light is resonated by a resonator formed by the external output mirror 3, the n-side multilayer reflector 11, and the p-side multilayer reflector 15, and the excited light is emitted from the external output mirror 3 as laser light 5. Is done.

  In the laser device 90 shown in FIG. 11, since the formation side of the n-side electrode 19 is the extraction surface of the laser beam 5 (extraction direction d1), the n-side electrode 19 has a shape that does not block the light path. It has become. In the laser device 90 of FIG. 11, the n-side electrode 19 has a donut shape, and the dielectric layer 29 is formed on the surface of the semiconductor substrate 40 on the side where the n-side electrode 19 is formed. Is formed. The dielectric layer 29 is provided to suppress light loss during resonance.

The contact layer 17 is doped with high-concentration (for example, 1 × 10 ¹⁸ / cm ³ or more) carriers, and plays a role of reducing the contact resistance value with the p-side electrode 21.

  Here, similarly, in order to lower the resistance value between the n-side electrode 19 and the semiconductor substrate 40, for example, a method of doping the semiconductor substrate 40 at a high concentration is conceivable.

  However, it is generally known that highly doped semiconductor layers absorb a lot of light. According to the configuration of FIG. 11, the light generated by the light emitting unit 13 is repeatedly reflected while passing through the semiconductor substrate 40 with the external output mirror 3 and then extracted to the outside. Therefore, when the semiconductor substrate 40 is doped at a high concentration, the light generated by the light emitting unit 13 is absorbed in the semiconductor substrate 40, and there is a problem that the extraction efficiency is lowered.

In view of such a point, in the configurations of Patent Document 1 and Non-Patent Document 1, as the semiconductor substrate 40, low concentration carriers (for example, about 5 × 10 ¹⁶ / cm ³ or more and about 5 × 10 ¹⁷ / cm ³ or less) are used. A GaAs substrate is used.

JP-T 2006-511966

Gregory T. Niven, et.al. "Laser lighting revolution-Coming soon to a theater near you-", December 2010, Optik & Photonik No.4, p34-p37

  However, when such a low concentration GaAs substrate is used as the semiconductor substrate 40, the contact resistance between the semiconductor substrate 40 and the n-side electrode 19 and the resistance in the semiconductor substrate 40 increase. For this reason, when a bias voltage is applied between the p-side electrode 21 and the n-side electrode 19 during driving, high Joule heat is generated, and the laser apparatus 90 is greatly heated due to this. When the temperature rises, the wavelength of the laser beam 5 shifts to the longer wavelength side, so that the light extraction efficiency of a desired emission wavelength is lowered.

  A method of forming a high-concentration contact layer between the n-side electrode 19 and the semiconductor substrate 40 is also conceivable in order to reduce the resistance value between the n-side electrode 19 and the semiconductor substrate 40. However, when this method is employed, the contact resistance value between the n-side electrode 19 and the semiconductor substrate 40 can be reduced, but there is no change in the current passing through the low-concentration semiconductor substrate 40. The overall resistance cannot be reduced. Therefore, it has the same problem as the conventional configuration in that high Joule heat is generated and the wavelength of the laser light 5 is shifted to the long wavelength side.

  In view of the above points, an object of the present invention is to provide a semiconductor laser device having higher light extraction efficiency than conventional ones.

The semiconductor laser device of the present invention is
A semiconductor substrate;
A first reflecting mirror formed in an upper layer on the first surface side of the semiconductor substrate;
A light emitting part formed in an upper layer of the first reflecting mirror;
A second reflecting mirror formed on an upper layer of the light emitting unit;
A contact layer formed on an upper layer of the second reflecting mirror;
A first electrode formed in an upper layer on the second surface side opposite to the first surface of the semiconductor substrate;
A second electrode formed on the contact layer;
In the first reflecting mirror, a first region located on the outer edge of the surface opposite to the light-emitting portion forming side is in contact with the semiconductor substrate, and a second region located on the inner side of the first region is the It is characterized in that it is in contact with a region or a gap where the carrier concentration is lower than that of the semiconductor substrate at a location in contact with the first region.

  According to the above configuration, in the first reflecting mirror, the first region located at the outer edge is in contact with the semiconductor substrate on the surface opposite to the light-emitting portion forming side, and the second region located inside the first region. Are in contact with regions or voids where the carrier concentration is lower than that of the semiconductor substrate in contact with the first region. That is, when the light emitted from the light emitting part is emitted to the outside through the first reflecting mirror, it passes through the region or the gap where the carrier concentration is lower than that of the semiconductor substrate in contact with the first region. can do. The “region where the carrier concentration is lower than that of the semiconductor substrate in contact with the first region” includes an undoped region.

  That is, when the carrier concentration of the semiconductor substrate is set to a high concentration, the first reflector has a configuration in which only the outer edge portion is in contact with the high concentration region and the inner region is in contact with the low concentration region or the gap. Therefore, for example, by making the thickness of the outer edge portion as thin as possible compared to the inside, most of the light emitted from the first reflecting mirror is emitted to the outside through the low concentration region or the gap. It can be. Therefore, the amount of light passing through the high density region is greatly reduced as compared with the conventional configuration, and the amount of light absorbed is greatly suppressed.

  Since the outer edge portion of the first reflecting mirror is in contact with the semiconductor substrate, a low value of the contact resistance between the first electrode and the semiconductor substrate is realized by keeping the carrier concentration of the semiconductor substrate high. The Further, when a bias voltage is applied between the first electrode and the second electrode, a current path including the second electrode, the contact layer, the second reflecting mirror, the light emitting unit, the first reflecting mirror, the semiconductor substrate, and the first electrode However, since the low-concentration region is not interposed during this period, the resistance of the entire element does not increase. As a result, the problem that the extraction efficiency of light having a desired emission wavelength is reduced due to the generation of high Joule heat and the emission wavelength shifting is also solved.

  That is, according to the above configuration, it is possible to simultaneously realize both the reduction of the resistance of the element and the improvement of the light extraction efficiency.

As a more specific first configuration, the semiconductor substrate has a first substrate region and a second substrate region having a carrier concentration lower than that of the first substrate region,
The first reflecting mirror has a configuration in which the first region is in contact with the first substrate region and the second region is in contact with the second substrate region on a surface opposite to the formation side of the light emitting unit. be able to.

  In this configuration, the semiconductor substrate is divided into two carrier concentration regions, the first substrate region constituting the high concentration region is brought into contact with the outer edge portion of the first reflecting mirror, and the low concentration region is formed on the inner portion of the first reflecting mirror. It is in contact. Thereby, the above effect is realized.

  Further, at this time, an insulating layer for preventing carrier diffusion may be embedded in a boundary portion between the first substrate region and the second substrate region.

  In addition, a configuration may be adopted in which a first groove portion penetrating in a direction orthogonal to the substrate surface is formed at a boundary portion between the first substrate region and the second substrate region.

  According to these configurations, carriers are prevented from diffusing from the high concentration first substrate region toward the low concentration second substrate region. Therefore, the contact location of the 1st reflective mirror located in the light passage path | route can be maintained in a low concentration state, and the high light extraction efficiency is implement | achieved stably.

As a more specific second configuration, the semiconductor substrate has a second groove portion penetrating in a direction perpendicular to the substrate surface in a part of the semiconductor substrate,
In the first reflecting mirror, the first region is in contact with the surface of the semiconductor substrate located outside the second groove portion on the surface opposite to the light emitting portion formation side, and the second region is in the first region. It can be set as the structure which contacts the space | gap located inside two groove parts.

  In this configuration, a second groove portion penetrating in a direction orthogonal to the substrate surface is provided in a part of the semiconductor substrate. The semiconductor substrate is brought into contact with the outer edge portion of the first reflecting mirror, and the inner side of the second groove, that is, the gap is brought into contact with the inner portion of the first reflecting mirror. Thereby, the above effect is realized.

  As a modification of the above configuration, a dielectric layer having a carrier concentration lower than that of the semiconductor substrate is formed on the bottom surface of the second groove, and this dielectric layer is brought into contact with the inner portion of the first reflecting mirror. It doesn't matter. This dielectric layer may be realized by an undoped layer.

  In the second configuration, an insulating layer for protecting the semiconductor substrate may be formed so as to cover the inner surface of the second groove portion.

  Thereby, it is possible to simultaneously realize both the reduction of the resistance of the element and the improvement of the light extraction efficiency without exposing the semiconductor substrate to the inside of the second groove portion.

  According to the semiconductor laser device of the present invention, since the contact resistance and the element resistance can be made low, it is possible to have a configuration having little or no high-concentration region on the light passage path. High light extraction efficiency can be realized.

It is a typical sectional view of the laser apparatus of a 1st embodiment. It is a typical top view when the semiconductor substrate with which the laser apparatus of 1st Embodiment is mounted is seen from the light extraction direction side. 1 schematically illustrates a surface of an n-side multilayer reflector that contacts a semiconductor substrate on which the laser device of the first embodiment is mounted. It is another typical sectional view of the laser apparatus of a 1st embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is a part of process sectional drawing of the laser apparatus of 1st Embodiment. It is typical sectional drawing of the laser apparatus of 2nd Embodiment. It is a typical top view when the semiconductor substrate with which the laser apparatus of 2nd Embodiment is mounted is seen from the light extraction direction side. The surface of the n side multilayer film reflective mirror which contacts the semiconductor substrate with which the laser apparatus of 2nd Embodiment is mounted is shown typically. It is another schematic sectional drawing of the laser apparatus of 2nd Embodiment. It is a part of process sectional drawing of the laser apparatus of 2nd Embodiment. It is a part of process sectional drawing of the laser apparatus of 2nd Embodiment. It is a part of process sectional drawing of the laser apparatus of 2nd Embodiment. It is typical sectional drawing of the conventional laser apparatus.

  A semiconductor laser device of the present invention (hereinafter abbreviated as “laser device” as appropriate) will be described with reference to the drawings. In each figure, the dimensional ratio in the drawing does not necessarily match the actual dimensional ratio.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view of the laser apparatus of the first embodiment. In addition, the same code | symbol is attached | subjected to the element same as FIG.

(Constitution)
The laser apparatus 1 according to the first embodiment includes a semiconductor substrate 10, an n-side multilayer reflector 11 (corresponding to a “first reflector”), a light emitting unit 13, and a p-side multilayer reflector 15 (“second reflector”). ), A contact layer 17, an n-side electrode 19 (corresponding to “first electrode”), and a p-side electrode 21 (corresponding to “second electrode”).

  An n-side multilayer reflector 11 is formed on the upper layer of one surface (corresponding to the “first surface”) of the semiconductor substrate 10, and a light emitting unit 13 is formed on the upper layer of the n-side multilayer reflector 11. A p-side multilayer mirror 15 is formed in the upper layer of the light emitting unit 13. A contact layer 17 is formed above the p-side multilayer reflector 15, and a p-side electrode 21 is formed above the contact layer 17.

  An n-side electrode 19 is formed on the other surface (corresponding to the “second surface”) of the semiconductor substrate 10.

  In FIG. 1, the light extraction direction d1 is opposite to the side of the semiconductor substrate 10 on which the light emitting portion 13 and the pair of reflecting mirrors 11 and 15 are formed, and the position separated from the semiconductor substrate 10 in this direction d1 is external. An output mirror 3 is formed. Similar to the laser device 90 shown in FIG. 11, the laser device 1 shown in FIG. 1 also includes an insulating layer 25 for current confinement, a passivation layer 27, and a dielectric layer 29.

The semiconductor substrate 10 is composed of, for example, a GaAs substrate. Here, in the present embodiment, the semiconductor substrate 10 has two concentration regions, a high concentration region 10a (corresponding to “first substrate region”) and a low concentration region 10b (corresponding to “second substrate region”). ing. The high concentration region 10a is doped with a high concentration of carrier concentration of 1 × 10 ¹⁸ / cm ³ or more. On the other hand, the low concentration region 10b is doped at a low concentration of carrier concentration of less than 1 × 10 ¹⁸ / cm ³ , more preferably 5 × 10 ¹⁷ / cm ³ or less. In the present embodiment, the low concentration region 10b may be undoped.

  In the semiconductor substrate 10, an insulating layer 23 is embedded at the boundary between these two regions. The insulating layer 23 is formed for the purpose of preventing carriers from diffusing from the high concentration region 10a toward the low concentration region 10b. For example, an insulating layer such as SiN is used.

  The light emitting unit 13 is made of a material corresponding to the wavelength of the laser beam 5 to be extracted. For example, when the emission wavelength is 0.8 μm to 1 μm, GaInAs or AlGaAs is used.

  The n-side multilayer mirror 11 and the p-side multilayer reflector 15 are formed by laminating two kinds of materials having low absorption with respect to a desired wavelength and different refractive indexes, for example, GaAs / AlGaAs or GaAs / AlAs or the like is used. Further, the thickness of each layer constituting each reflecting mirror 11 and 15 is set to a thickness according to the material and the wavelength. It is preferable that the reflectance of the p-side multilayer reflector 15 is 99% or more and the reflectance of the n-side multilayer reflector 11 is 20% or more and 90% or less. The reason why the reflectance of the n-side multilayer reflector 11 is lower than that of the p-side multilayer reflector 15 is that the light from the light emitting unit 13 is reflected by the n-side multilayer reflector 11 and the p-side multilayer reflector 15. This is because it is necessary to pass through the n-side multilayer mirror 11 and take out to the outside after being excited by repeating reflection between the two.

  The n-side multilayer mirror 11 is formed in contact with the semiconductor substrate 10, of which the portion located at the outer edge contacts the high concentration region 10 a and the inner portion thereof contacts the low concentration region 10 b. This is the configuration. This point will be described in detail later.

The contact layer 17 is formed in the upper layer of the p-side multilayer mirror 15. The contact layer 17 is made of GaAs, for example, and is doped with a p-type impurity such as C at a high concentration of 1 × 10 ¹⁸ / cm ³ or more in order to reduce the contact resistance.

  As described above, the n-side electrode 19 is in contact with the surface of the semiconductor substrate 10 opposite to the side on which the light emitting unit 13 and the pair of reflecting mirrors 11 and 15 are formed, that is, the surface on the light extraction direction d1 side. Is formed. More specifically, the n-side electrode 19 is in contact with the high concentration region 10 a of the semiconductor substrate 10. As a material of the n-side electrode 19, for example, Ni / Ge / Au / Ni / Au, Au / Ge / Ni / Au, or the like can be used.

  The p-side electrode 21 is formed in the upper layer of the contact layer 17. The p-side electrode 21 may be formed of the same material as the n-side electrode 19.

  FIG. 2 is a schematic plan view of the semiconductor substrate 10 when viewed from the light extraction direction side, that is, the n-side electrode 19 side. For convenience of explanation, the illustration of the n-side electrode 19 and the dielectric layer 29 is omitted, and the bottom surface of the n-side multilayer reflector 11 formed on the surface of the semiconductor substrate 10 on the light emitting portion 13 side is indicated by a broken line. . 2 shows a state in which a plurality of laser devices 1 are arranged on the semiconductor substrate 10, and the light extraction direction from the laser device 1 is the front side of the sheet.

  As described above, the semiconductor substrate 10 includes the high concentration region 10a and the low concentration region 10b. In the example of FIG. 2, a circular low concentration region 10b is formed in a part of the high concentration region 10a. The high concentration region 10 a and the low concentration region 10 b are separated by the insulating layer 23.

  The n-side multilayer mirror 11 has a circular bottom shape, its outer edge portion (corresponding to “first region”) is in contact with the high concentration region 10a, and its inner portion (corresponding to “second region”) is low. It is formed so as to be in contact with the concentration region 10b. That is, the central portion of the n-side multilayer mirror 11 is in contact with the low concentration region 10b.

  FIG. 3 schematically shows the surface of the n-side multilayer film reflecting mirror 11 in contact with the semiconductor substrate 10. The outer edge portion (first region) 11a is in contact with the high concentration region 10a, and the inner portion (second region) 11b is in contact with the low concentration region 10b (see also FIG. 2). The outer edge portion 11a of FIG. 3 and the high concentration region 10a of FIG. 2 are indicated by the same hatching, and the inner portion 11b of FIG. 3 and the low concentration region 10b of FIG. expressing.

  Under such a configuration, when a bias voltage is applied between the p-side electrode 21 and the n-side electrode 19, the p-side electrode 21, the contact layer 17, the p-side multilayer reflector 15, the light emitting unit 13, and the n-side multilayer film. A current path including the reflecting mirror 11, the high concentration region 10a of the semiconductor substrate 10, and the n-side electrode 19 is formed. Thereby, an electric current flows into the light emission part 13, and the said area | region emits light. This light is excited while resonating inside the resonator composed of the p-side multilayer mirror 15, the n-side multilayer mirror 11, and the external output mirror 3, and is extracted outside as laser light 5.

  Further, since there is no low concentration region on the current path, the resistance of the entire element does not increase. Moreover, since the p-side electrode 21 is in contact with the high-concentration contact layer 17 and the n-side electrode 19 is in contact with the high-concentration region 10a of the semiconductor substrate 10, the contact resistance can be kept low in both cases. As a result, the problem that the extraction efficiency of light having a desired emission wavelength is reduced due to the generation of high Joule heat and the shift of the emission wavelength is solved.

  The light from the light emitting unit 13 is extracted to the outside through the n-side multilayer mirror 11, but the central portion of the n-side multilayer mirror 11 is in contact with the low concentration region 10 b of the semiconductor substrate 10. . For this reason, most of the light passes through the low concentration region 10b. Thereby, the amount of light absorbed in the semiconductor substrate 10 is greatly suppressed as compared with the conventional configuration.

  Note that the area of the outer edge portion region 11 a where the n-side multilayer film reflecting mirror 11 is in contact with the high concentration region 10 a of the semiconductor substrate 10 is larger than the area of the inner portion region 11 b of the semiconductor substrate 10 in contact with the low concentration region 10 b. By keeping it sufficiently small, almost all light can pass through the low concentration region 10b. Thereby, the amount of light absorbed in the semiconductor substrate 10 can be suppressed to the maximum.

  In the configuration of the present embodiment, an insulating layer 23 for preventing carrier diffusion is embedded at the boundary between the high concentration region 10 a and the low concentration region 10 b of the semiconductor substrate 10. Accordingly, since carrier diffusion from the high concentration region 10a toward the low concentration region 10b can be prevented, the low concentration region 10a is maintained in a low concentration state, and high light extraction efficiency is realized stably.

  As shown in FIG. 4, instead of embedding the insulating layer 23, a groove portion 31 (“first groove portion” penetrating in the direction perpendicular to the substrate surface at the boundary between the high concentration region 10 a and the low concentration region 10 b of the semiconductor substrate 10. ”) May be formed. Even in this configuration, carrier diffusion from the high concentration region 10a toward the low concentration region 10b can be prevented.

  The laser device 1 shown in FIG. 4 is configured not to include the dielectric layer 29, but may include the dielectric layer 29 as in the configuration of FIG. At this time, the dielectric layer 29 may be embedded in the groove 31. In this case, the dielectric layer 29 also functions as a carrier diffusion preventing function from the high concentration region 10a to the low concentration region 10b. In the configuration shown in FIG. 1, the dielectric layer 29 may not be provided.

  In the above embodiment, the light extraction direction d1 side of the semiconductor substrate 10 is described as the n side, and the opposite side is the p side. However, the positions of the p side and the n side may be reversed. The same applies to the following embodiments.

(Production method)
Hereinafter, an example of the manufacturing method of the laser apparatus 1 shown in FIG. 1 will be described with reference to the process cross-sectional views of FIGS. 5A to 5I.

(Step S1)
As shown in FIG. 5A, an n-side multilayer mirror 11, a light emitting portion 13, a p-side multilayer reflector 15 and a contact layer 17 are grown on the semiconductor substrate 10 in this order from the bottom.

Here, as the semiconductor substrate 10, for example, a low concentration GaAs substrate having a carrier concentration of 5 × 10 ¹⁷ / cm ³ or less is employed. An undoped substrate may be used.

  As the n-side multilayer mirror 11, GaAs / AlGaAs or GaAs / AlAs is used, and the number of layers is set so that the reflectance is 20% or more and 90% or less. As the light emitting portion 13, GaInAs, AlGaAs, or the like is used, and materials and composition ratios to be employed are set according to the emission wavelength. As the p-side multilayer mirror 15, GaAs / AlGaAs or GaAs / AlAs is used, and the number of layers is set so that the reflectance is 99% or more. As an example of the film thickness to be laminated, the n-side multilayer reflector 11 is about 100 nm to 2000 nm, the light emitting portion 13 is about 50 nm to 2000 nm, and the p-side multilayer reflector 15 is about 1000 nm to 5000 nm.

As the contact layer 17, for example, GaAs doped with a p-type impurity such as C at a high concentration of 1 × 10 ¹⁸ / cm ³ or more is formed with a film thickness of about 10 nm to 1000 nm.

(Step S2)
The multilayer structure formed in step S1 is processed into a mesa shape by wet etching or dry etching (see FIG. 5B).

(Step S3)
Of the multilayer structure, for example, a region near the center is masked to perform ion implantation, thereby forming an insulating layer 25 (high resistance layer) as a current confinement layer (see FIG. 5C). Note that the insulating layer 25 may be formed by oxidizing the portion.

(Step S4)
As shown in FIG. 5D, a passivation layer 27 is formed by depositing an insulating material such as SiN or SiO ₂ with a film thickness of about 10 nm to 2000 nm by sputtering or PVD (Physical Vapor Deposition). To do.

(Step S5)
For example, the passivation layer 27 formed in the non-mask region is removed by a wet etching method or a dry etching method while masking other than the position above the contact layer 17. Thereafter, an electrode material such as Au / Zn / Au or Ti / Pt / Au is formed in a thickness of about 100 nm to 3000 nm in the region by sputtering or vacuum evaporation to form the p-side electrode 21 (FIG. 5E). reference).

(Step S6)
A first groove 31 penetrating in a direction perpendicular to the substrate surface is formed by wet etching or dry etching on the surface of the semiconductor substrate 10 opposite to the side on which the light emitting layer 13 is formed (see FIG. 5F). ). The first groove portion 31 has an annular shape (such as an annular shape or a rectangular shape) when viewed from the surface opposite to the side on which the light emitting layer 13 of the semiconductor substrate 10 is formed, and the n-side multilayer reflector 11 is formed on the bottom surface thereof. Is exposed.

(Step S7)
An insulating material such as SiN or SiO ₂ is formed to a thickness of about 10 nm to 2000 nm from the direction opposite to the side where the light emitting layer 13 of the semiconductor substrate 10 is formed by sputtering or PVD. The inside of the groove 31 is filled. Thereby, the insulating layer 23 for preventing carrier diffusion is formed (see FIG. 5G).

(Step S8)
As shown in FIG. 5H, in a state where the insulating layer 23 and its inner region are covered with a mask 35, the dopant 43 is implanted from the direction opposite to the side where the light emitting layer 13 of the semiconductor substrate 10 is formed. As a result, the semiconductor substrate 10 in the outer region of the insulating layer 23 becomes a high concentration region 10a having a carrier concentration of 1 × 10 ¹⁸ / cm ³ or more. In addition, the semiconductor substrate 10 in the inner region remains a low concentration (or undoped) region. Therefore, by this step, the high concentration region 10 a and the low concentration region 10 b are formed in the semiconductor substrate 10, and the boundary thereof is separated by the insulating layer 23.

(Step S9)
After removing the mask 35, for example, Ni / Ge / Au / Ni is formed on the surface of the high concentration region 10a of the semiconductor substrate 10 by sputtering or vacuum deposition from the direction opposite to the side where the light emitting layer 13 is formed. An electrode material such as / Au or Au / Ge / Ni / Au is formed to a thickness of about 100 nm to 3000 nm to form the n-side electrode 19 (see FIG. 5I).

(Step S10)
Thereafter, a predetermined region is masked, and an optical thin film made of SiO ₂ , Ta ₂ O ₅ , SiNO or the like is opposite to the side where the light emitting layer 13 is formed on the exposed surface of the semiconductor substrate 10. From this direction, a film thickness of about 10 nm to 1000 nm is formed by sputtering or vacuum vapor deposition to form a dielectric layer 29 (see FIG. 1).

  In manufacturing the laser device 1 shown in FIG. 4, steps S8 and S9 may be executed after step S6 without performing step S7.

  The method of manufacturing the laser device 1 through the above steps S1 to S10 is merely an example, and is not limited to this method. Moreover, the conditions of the film thickness to form and the material used are examples, and are not limited to the above-mentioned content.

[Second Embodiment]
With respect to the second embodiment of the laser apparatus, only portions different from the first embodiment will be described.

(Constitution)
FIG. 6 is a schematic cross-sectional view of the laser apparatus of the second embodiment. In the laser device 1a of the second embodiment, a second groove portion 37 penetrating in a direction orthogonal to the substrate surface is formed in a part of the semiconductor substrate 10. A dielectric layer 29 is formed on the bottom surface of the second groove portion 37, and a passivation layer 33 is formed on the inner surface. The passivation layer 33 functions as a protective layer that prevents the semiconductor substrate 10 from being exposed inside the second groove portion 37.

In the present embodiment, the semiconductor substrate 10 has a carrier concentration equivalent to that of the high concentration region 10a in the first embodiment, that is, a carrier concentration of 1 × 10 ¹⁸ / cm ³ or more.

  FIG. 7 is a schematic plan view of the semiconductor substrate 10 on which the laser device 1a according to the present embodiment is mounted as viewed from the light extraction direction side, that is, the n-side electrode 19 side, following FIG. The semiconductor substrate 10 forms the high concentration region 10a in the region where the second groove portion 37 is not formed. In the configuration of FIG. 6, since the dielectric layer 29 is formed on the bottom surface of the second groove portion 37, the dielectric layer 29 is also displayed in FIG. 7.

  The n-side multilayer mirror 11 has a circular bottom shape, and its outer edge portion (corresponding to the “first region”) is in contact with the semiconductor substrate 10 (forming the high concentration region 10a), and the inner portion (“second region”). Is formed so as to be in contact with the dielectric layer 29. This dielectric layer 29 has an extremely low carrier concentration or constitutes an undoped layer.

  FIG. 8 schematically shows the surface of the n-side multilayer mirror 11 in contact with the semiconductor substrate 10 on which the laser device 1a of this embodiment is mounted, following FIG. The outer edge portion (first region) 11a is in contact with the semiconductor substrate 10 (forming the high concentration region 10a), and the inner portion (second region) 11b is in contact with the dielectric layer 29 (see also FIG. 7). . The outer edge portion 11a in FIG. 8 and the high-concentration region 10a in FIG. 7 are indicated by the same hatching, and the inner portion 11b in FIG. 8 and the dielectric layer 29 in FIG. doing.

  Even in such a configuration, as in the first embodiment, since there is no low concentration region on the current path when a bias voltage is applied between the p-side electrode 21 and the n-side electrode 19, the resistance of the entire element Will not grow. Moreover, since the p-side electrode 21 is in contact with the high-concentration contact layer 17 and the n-side electrode 19 is in contact with the high-concentration region 10a of the semiconductor substrate 10, the contact resistance can be kept low in both cases. As a result, the problem that the extraction efficiency of light having a desired emission wavelength is reduced due to the generation of high Joule heat and the shift of the emission wavelength is solved.

  The light from the light emitting unit 13 is extracted outside through the n-side multilayer mirror 11, and the central portion of the n-side multilayer reflector 11 is in contact with the dielectric layer 29. For this reason, most of the light passes through the dielectric layer 29. Thereby, the amount of light absorbed in the semiconductor substrate 10 is greatly suppressed as compared with the conventional configuration.

  As in the first embodiment, the area of the outer edge portion region 11 a where the n-side multilayer mirror 11 contacts the semiconductor substrate 10 is sufficiently smaller than the area of the inner portion region 11 b which contacts the dielectric layer 29. By doing so, almost all light can pass through the dielectric layer 29. Thereby, the amount of light absorbed in the semiconductor substrate 10 can be suppressed to the maximum.

  Further, the dielectric layer 29 formed on the bottom surface of the second groove 37 and the passivation layer 33 formed on the inner surface may be omitted (see FIG. 9). In this case, the outer edge portion (first region) 11a of the surface of the n-side multilayer mirror 11 is in contact with the semiconductor substrate 10 (forming the high concentration region 10a), and the inner portion (second region) 11b is the second groove portion. 37 is in contact with the air gap inside. Even in this configuration, the problem that the light is absorbed by passing through the high concentration region is greatly solved.

(Production method)
Hereinafter, only the differences from the first embodiment will be described for the method of manufacturing the laser device 1a shown in FIG.

  As in the first embodiment, steps S1 to S5 are sequentially executed (see FIGS. 5A to 5E).

(Step S6A)
From the direction opposite to the side where the light emitting layer 13 is formed, an electrode such as Ni / Ge / Au / Ni / Au or Au / Ge / Ni / Au is formed on the upper surface of the semiconductor substrate 10 by sputtering or vacuum deposition. The material is deposited to a thickness of about 100 nm to 3000 nm to form the n-side electrode 19 (see FIG. 10A).

(Step S6B)
Next, in a state where the portion to be left as the n-side electrode 19 is masked, the surface of the semiconductor substrate 10 opposite to the side where the light emitting layer 13 is formed is wet etched or dry etched to form the substrate surface. The 2nd groove part 37 penetrated in the orthogonal direction is formed (refer FIG. 10B). The second groove portion 37 has an annular shape (such as an annular shape or a rectangular shape) when viewed from the surface of the semiconductor substrate 10 opposite to the side on which the light emitting layer 13 is formed, and the n-side multilayer mirror 11 is formed on the bottom surface thereof. Is exposed. Note that the second groove portion 37 may have a truncated cone shape having a tapered shape such that the area becomes smaller toward the bottom surface (n-side multilayer reflector 11) side.

(Step S6C)
An optical thin film composed of SiO ₂ , Ta ₂ O ₅ , SiNO or the like is sputtered or vacuum deposited from the direction opposite to the side where the light emitting layer 13 is formed on the bottom surface of the exposed second groove 37. A film thickness of about 10 nm to 1000 nm is formed by a method to form a dielectric layer 29 (see FIG. 10C).

(Step S6D)
Thereafter, an insulating material such as SiN or SiO ₂ is formed on the inner surface of the second groove portion 37 on the inner surface of the second groove portion 37 from the side opposite to the side where the light emitting layer 13 is formed by a sputtering method or a PVD method. The passivation layer 33 is formed by forming a film (see FIG. 6).

  When manufacturing the laser device 1a shown in FIG. 9, steps S1 to S5, S6A and S6B may be executed in this order, and steps S6C and S6D may not be executed.

  The method of manufacturing the laser apparatus 1a through the above steps S1 to S5 and S6A to S6D is merely an example, and is not limited to this method. Moreover, the conditions of the film thickness to form and the material used are examples, and are not limited to the above-mentioned content.

1: Semiconductor laser device 3: External output mirror 5: Laser beam 10: Semiconductor substrate 10a: High concentration substrate region (first substrate region)
10b: Low concentration substrate region (second substrate region)
11: n-side multilayer mirror (first reflector)
11a: outer edge portion (first region) of n-side multilayer mirror
11b: Inner part of the n-side multilayer reflector (second region)
13: Light-emitting part 15: P-side multilayer reflector (second reflector)
17: contact layer 19: n-side electrode (first electrode)
21: p-side electrode (second electrode)
23: Insulating layer for preventing carrier diffusion 25: Insulating layer as current confinement layer 27: Passivation layer 29: Dielectric layer 31: Groove (first groove)
33: Passivation layer 35: Mask 37: Groove (second groove)
40: Semiconductor substrate 43: Dopant 90: Conventional laser device with VECSEL structure d1: Extraction direction of laser light

Claims (7)

A semiconductor substrate;
A first reflecting mirror formed in an upper layer on the first surface side of the semiconductor substrate;
A light emitting part formed in an upper layer of the first reflecting mirror;
A second reflecting mirror formed on an upper layer of the light emitting unit;
A contact layer formed on an upper layer of the second reflecting mirror;
A first electrode formed in an upper layer on the second surface side opposite to the first surface of the semiconductor substrate;
A second electrode formed on the contact layer;
In the first reflecting mirror, a first region located on the outer edge of the surface opposite to the light-emitting portion forming side is in contact with the semiconductor substrate, and a second region located on the inner side of the first region is the A semiconductor laser device, wherein the semiconductor laser device is in contact with a region or gap having a carrier concentration lower than that of the semiconductor substrate at a location in contact with the first region. The semiconductor substrate has a first substrate region and a second substrate region having a carrier concentration lower than that of the first substrate region,
The first reflecting mirror has a configuration in which the first region is in contact with the first substrate region and the second region is in contact with the second substrate region on a surface opposite to the light emitting unit formation side. The semiconductor laser device according to claim 1.   3. The semiconductor laser device according to claim 2, wherein an insulating layer for preventing carrier diffusion is embedded in a boundary portion between the first substrate region and the second substrate region in the semiconductor substrate.   3. The semiconductor laser device according to claim 2, wherein the semiconductor substrate has a first groove portion penetrating in a direction orthogonal to the substrate surface at a boundary portion between the first substrate region and the second substrate region. The semiconductor substrate has a second groove portion penetrating in a direction perpendicular to the substrate surface in a part of the semiconductor substrate,
In the first reflecting mirror, the first region is in contact with the surface of the semiconductor substrate located outside the second groove portion on the surface opposite to the light emitting portion formation side, and the second region is in the first region. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is in contact with a gap located inside the two groove portions. The semiconductor substrate has a second groove portion penetrating in a direction perpendicular to the substrate surface in a part of the semiconductor substrate,
A dielectric layer having a carrier concentration lower than that of the semiconductor substrate is formed on the bottom surface of the second groove portion,
In the first reflecting mirror, the first region is in contact with the outer region of the second groove portion of the semiconductor substrate on the surface opposite to the light emitting portion forming side, and the second region is in contact with the dielectric layer. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is in contact with the semiconductor laser device.   7. The semiconductor laser device according to claim 5, wherein an insulating layer for protecting the semiconductor substrate is formed so as to cover an inner surface of the second groove portion.

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