JP6098820B2 - Semiconductor laser device - Google Patents

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. 10 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 p-type 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 mirror 15 and the p-type 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. 10, since the n-side electrode 19 is formed on the laser beam 5 extraction surface (extraction direction d1), the n-side electrode 19 does not block the light path. It has become. In the laser device 90 of FIG. 10, 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 p-type contact layer 17 is doped with a high concentration (for example, 1 × 10 ¹⁸ / cm ³ or more) of impurities (carriers), and serves to lower 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. 10, the light generated by the light emitting unit 13 is extracted after being repeatedly reflected while passing through the semiconductor substrate 40 with the external output mirror 3. 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 points, in the configurations of Patent Document 1 and Non-Patent Document 1, the semiconductor substrate 40 is a GaAs substrate having a low impurity concentration (for example, 5 × 10 ¹⁶ / cm ³ or more and 5 × 10 ¹⁷ / cm ³ or less. Degree).

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 n-type 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 present invention is a semiconductor laser device in which a first reflecting mirror, a light emitting unit, and a second reflecting mirror are sequentially laminated on a semiconductor substrate,
A first contact layer formed so as to be in contact with a first region located on an outer edge of a surface of the first reflecting mirror opposite to a side on which the light emitting unit is formed;
Impurities than the first contact layer formed on the surface of the first reflecting mirror opposite to the light emitting portion forming side so as to be in contact with a second region located inside the first region. A first impurity diffusion region having a low concentration;
An impurity diffusion prevention layer formed of an insulating layer or a semiconductor layer formed at a boundary portion between the first contact layer and the first impurity diffusion region; and a bottom surface of the first contact layer at a position outside the first reflector. A first electrode formed in contact with the upper surface;
A second contact layer formed on an upper layer of the second reflecting mirror;
A second electrode formed on an upper layer of the second contact layer is provided.

  According to the above configuration, in the first reflecting mirror, the first region located on the outer edge is in contact with the first contact layer on the surface opposite to the light-emitting portion forming side, and the first reflecting mirror is located on the inner side of the first region. The two regions are in contact with the first impurity diffusion region having an impurity concentration lower than that of the first contact layer. That is, when the light emitted from the light emitting part is emitted to the outside through the first reflecting mirror, it can pass through the first impurity diffusion region having an impurity concentration lower than that of the first contact layer.

  That is, the first reflecting mirror is configured such that only the outer edge portion is in contact with the high concentration first contact layer, and the inner region is in contact with the low concentration first impurity diffusion region. Therefore, for example, by making the thickness of the outer edge portion as thin as possible compared to the inner side, most of the light emitted from the first reflecting mirror radiates to the outside through the first impurity diffusion region having a low concentration. Can be configured. 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 high-concentration first contact layer, the first electrode is formed by forming the first electrode so that the bottom surface is in contact with the upper surface of the first contact layer. A low value of the contact resistance between the first contact layer and the first contact layer is realized. Further, when a bias voltage is applied between the first electrode and the second electrode, the second electrode, the second contact layer, the second reflecting mirror, the light emitting unit, the first reflecting mirror, the first contact layer, and the first electrode However, since the low-concentration region can be omitted 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.

  In the above configuration, the first contact layer and the first reflecting mirror may be n-type semiconductor layers, and the second contact layer and the second reflecting mirror may be p-type semiconductor layers. The first reflecting mirror may be a p-type semiconductor layer, and the second contact layer and the second reflecting mirror may be an n-type semiconductor layer.

As a specific configuration example, the first impurity diffusion region is configured by a part of the semiconductor substrate having an impurity concentration lower than that of the first contact layer,
The impurity diffusion preventing layer may be formed at a boundary portion between the first contact layer and the semiconductor substrate.

As another specific configuration example, the semiconductor substrate is formed with an impurity concentration lower than that of the first contact layer,
The impurity diffusion preventing layer may be formed at a boundary portion between the first contact layer and the first impurity diffusion region and at a boundary portion between the first contact layer and the semiconductor substrate.

  In addition to the above-described configuration, the light emitting unit and the second reflecting mirror include a high resistance layer formed in contact with the side surface, and the bottom surface of the high resistance layer is the upper surface of the first reflecting mirror. It does not matter even if it is the composition which touches.

  By providing this high resistance layer, the current can be supplied only to the portion that contributes to light emission, so that the light emission efficiency can be increased. Further, by forming the high resistance layer as described above, the first reflecting mirror is formed to be larger than the diameter of the light emitting portion, so that the current path cross-sectional area increases and the electrical resistance decreases. This further reduces the resistance of the element.

  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.

1 is a schematic cross-sectional view of a semiconductor laser device according to a first embodiment. 1 schematically illustrates a surface of an n-side multilayer mirror that contacts a semiconductor substrate on which the semiconductor laser device of the first embodiment is mounted. It is another typical sectional view of the semiconductor laser device 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 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 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 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 another typical sectional drawing of the laser apparatus of 3rd Embodiment. It is a part of process sectional drawing of the laser apparatus of 3rd Embodiment. It is a typical sectional view of the conventional semiconductor laser device.

  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.

<Construction>
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”). N-type contact layer 9 (corresponding to “first contact layer”), p-type contact layer 17 (corresponding to “second contact layer”), n-side electrode 19 (corresponding to “first electrode”), A p-side electrode 21 (corresponding to “second electrode”) is included.

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

  An impurity diffusion prevention layer 7 made of an insulating layer or a semiconductor layer is formed on another part of the upper layer of the first surface of the semiconductor substrate 10, and an n-type contact layer 9 is formed on the impurity diffusion prevention layer 7. Has been.

The n-type contact layer 9 is made of GaAs, for example, and is doped with an n-type impurity such as Si at a high concentration of 1 × 10 ¹⁸ / cm ³ or more in order to reduce the contact resistance.

  When the impurity diffusion preventing layer 7 is formed of a semiconductor layer, it is formed of an undoped layer or an extremely low concentration impurity diffusion layer. Specifically, it can be formed of undoped AlGaAs or InGaP. The impurity diffusion preventing layer 7 prevents impurities (carriers) in the n-type contact layer 9 configured at a high concentration from diffusing to the semiconductor substrate 10 configured at a lower concentration than the n-type contact layer 9. It is provided for the purpose.

  Further, in the laser device 1 shown in FIG. 1, a light flux is applied to the surface of the semiconductor substrate 10 opposite to the surface on which the light emitting unit 13 is formed (hereinafter referred to as “second surface”). A light beam diffusion preventing member 16 for suppressing the diffusion of light is formed. The light beam diffusion preventing member 16 is formed of an insulating layer or a metal layer. When the light beam diffusion preventing member 16 is formed of a metal layer, the laser device 1 can be used for fixing the laser device 1 on another device surface by soldering the metal layer.

  In FIG. 1, the light extraction direction d1 is opposite to the side where the light emitting portion 13 and the pair of reflecting mirrors 11 and 15 of the semiconductor substrate 10 are formed (that is, the second surface side). An external output mirror 3 is formed at a position separated from d1. Similar to the laser device 90 shown in FIG. 10, the laser device 1 shown in FIG. 1 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 this embodiment, the semiconductor substrate 10 is doped at a low concentration of an impurity concentration of less than 1 × 10 ¹⁸ / cm ³ , more preferably 5 × 10 ¹⁷ / cm ³ or less.

  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 mirror 15 are formed by laminating two kinds of materials having little 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. The reflectance of the p-side multilayer mirror 15 is preferably 99% or more, and the reflectance of the n-side multilayer mirror 11 is preferably 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.

  As shown in FIG. 1, the n-side multilayer mirror 11 is formed so that the outer edge portion of the bottom surface is in contact with the n-type contact layer 9 and the inner portion is in contact with the semiconductor substrate 10. This point will be described in detail later.

The p-type contact layer 17 is formed in the upper layer of the p-side multilayer mirror 15. The contact layer 17 is made of, for example, GaAs, 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 shown in FIG. 1, in the laser device 1 of the present embodiment, the n-side electrode 19 is formed on the first surface side of the semiconductor substrate 10, similarly to the p-side electrode 21. 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 on the p-type contact layer 17. The p-side electrode 21 can be composed of, for example, Au / Zn / Au or Ti / Pt / Au. Further, the same material as that of the n-side electrode 19 may be used.

  FIG. 2 schematically shows the surface (bottom surface) of the n-side multilayer mirror 11 in contact with the semiconductor substrate 10. The outer edge portion (corresponding to the “first region”) 11 a contacts the n-type contact layer 9 having a higher concentration than the semiconductor substrate 10, and the inner portion (corresponding to the “second region”) 11 b from the n-type contact layer 9. Is also in contact with the semiconductor substrate 10 having a low concentration.

  In FIG. 2, the hatching of the bottom surface of the n-side multilayer mirror 11 is the same as the hatching of the layer in contact with the portion (see FIG. 1). That is, the first region 11 a is hatched in the same manner as the n-type contact layer 9, and the second region 11 b is hatched in the same manner as the semiconductor substrate 10. Of the bottom surface of the n-side multilayer reflector 11, the boundary between the first region 11a and the second region 11b is in contact with the impurity diffusion preventing layer 7, so that the portion is in contact with the impurity diffusion preventing layer 7. Similarly, no hatching is applied.

  In the present embodiment, the region of the semiconductor substrate 10 at the position in contact with the bottom surface of the n-type multilayer mirror 11 corresponds to the “first impurity diffusion region”.

  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 p-type contact layer 17, the p-side multilayer reflector 15, the light emitting unit 13, and the n-side A current path including the multilayer reflector 11, the n-type contact layer 9, 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.

  Since the n-side electrode 19 is in contact with the n-type contact layer 9 having a high impurity concentration, the contact resistivity is reduced, so that the contact resistance can be reduced. Further, since the current passes through the n-side contact layer 9 having a high impurity concentration, the voltage drop can be reduced. Furthermore, since the p-side electrode 21 is in contact with the high-concentration p-type contact layer 17, the contact resistance can be kept low. As a result, the resistance of the entire element can be kept low. This eliminates the problem that high Joule heat is generated, the emission wavelength is shifted, and the light extraction efficiency of the desired emission wavelength is reduced.

  The light from the light emitting unit 13 is extracted to the outside through the n-side multilayer reflector 11, but the central portion of the n-side multilayer reflector 11 has a low impurity concentration in the semiconductor substrate 10 (first impurity diffusion region). ). For this reason, most of the light passes through the low-concentration semiconductor substrate 10. 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 (first region) 11 a where the n-side multilayer mirror 11 is in contact with the high-concentration n-type contact layer 19 is the area of the inner portion (second region) where it is in contact with the semiconductor substrate 10. By making it sufficiently smaller than the area 11b, almost all light can pass through the low concentration region, that is, the semiconductor substrate 10. Thereby, the amount of light absorbed in the semiconductor substrate 10 can be suppressed to the maximum.

  Further, in the configuration of the present embodiment, the impurity diffusion preventing layer 7 is buried at the boundary between the low concentration semiconductor substrate 10 and the high concentration n-type contact layer 9. As a result, diffusion of impurities from the n-type contact layer 9 toward the low-concentration semiconductor substrate 10 can be prevented, so that the first impurity diffusion located directly below the bottom surface of the semiconductor substrate 10, more specifically the n-side multilayer reflector 11. The region is maintained in a low concentration state, and high light extraction efficiency is realized stably.

  In the configuration shown in FIG. 1, the dielectric layer 29 may not be provided (see FIG. 3).

  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.

(Step S1)
As shown in FIG. 4A, a semiconductor substrate 10 is prepared. As described above, a GaAs substrate having an impurity concentration of less than 1 × 10 ¹⁸ / cm ³ , more preferably 5 × 10 ¹⁷ / cm ³ or less can be employed as the semiconductor substrate 10.

(Step S2)
As shown in FIG. 4B, a portion of the first surface side of the semiconductor substrate 10 that is located on the outer peripheral portion of the portion that becomes a path through which the laser beam passes is etched by a wet etching method or a dry etching method to form the groove portion 31. Form.

(Step S3)
As shown in FIG. 4C, the impurity diffusion prevention layer 7 formed of AlGaAs or InGaP or the like is crystal-grown at a thickness of, for example, about 1000 nm to 10000 nm at the location where the groove 31 is formed.

(Step S4)
As shown in FIG. 4D, a part of the impurity diffusion prevention layer 7 formed in step S3 is etched by a wet etching method or a dry etching method to form a groove 32.

(Step S5)
As shown in FIG. 4E, an n-type contact layer 9 made of GaAs or the like is crystal-grown at a thickness of, for example, about 10 nm to 1000 nm at a location where the groove 32 is formed. The n-type contact layer 9 is doped with an n-type impurity such as Si at a high concentration of 1 × 10 ¹⁸ / cm ³ or more.

(Step S6)
On the upper layer of the semiconductor substrate 10 on which the impurity diffusion preventing layer 7 and the n-type contact layer 9 are formed on a part of the upper surface, the n-side multilayer mirror 11, the light emitting part 13, the p-side multilayer reflector 15 and the p-type contact are formed. The layer 17 is crystal-grown in this order from the bottom.

  As the n-side multilayer reflector 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 unit 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 p-type 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 S7)
Of the multilayer structure formed in step S6 and including the n-side multilayer mirror 11, the light emitting portion 13, the p-side multilayer mirror 15 and the p-type contact layer 17, for example, a region near the center is masked to form ions. By performing the implantation, an insulating layer 25 (high resistance layer) as a current confinement layer is formed (see FIG. 4G). Note that the insulating layer 25 may be formed by oxidizing the portion.

(Step S8)
The insulating layer 25 as a current confinement layer formed in step S7 is processed into a mesa shape by wet etching or dry etching (see FIG. 4H). By this step S8, a part of the n-type contact layer 9 is exposed.

(Step S9)
As shown in FIG. 4I, an insulating material such as SiN or SiO ₂ is formed to a thickness of about 10 nm to 2000 nm by sputtering or PVD (Physical Vapor Deposition), and a passivation layer 27 is formed. To do.

(Step S10)
Next, the passivation layer 27 formed in the non-mask region is removed by a wet etching method or a dry etching method, for example, by masking other than the position above the p-type 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 vapor deposition to form the p-side electrode 21. Further, for example, Ni / Ge / Au / Ni / Au or Au / Ge / Ni / is formed on the exposed surface of the n-side contact layer 9 by the sputtering method or the vacuum evaporation method from the same direction as the side where the light emitting portion 13 is formed. An electrode material such as Au is formed to a thickness of about 100 nm to 3000 nm to form the n-side electrode 19 (see FIG. 4J).

(Step S11)
An optical thin film made of SiO ₂ , Ta ₂ O ₅ , SiNO or the like is sputtered from the second surface side on the second surface (surface on which the light emitting unit 2 is not formed) of the semiconductor substrate 10. Alternatively, the dielectric layer 29 is formed by forming a film thickness of about 10 nm to 1000 nm by a vacuum deposition method. Thereafter, the dielectric layer 29 formed in the non-mask region is removed by a wet etching method or a dry etching method while masking other than the position related to the laser optical path.

(Step S12)
By sputtering or PVD, for example, an insulating material such as SiN or SiO ₂ is formed to a thickness of about 10 nm to 2000 nm to form a light beam diffusion preventing member 16 (see FIG. 1). In step S12, the light beam diffusion preventing member 16 may be formed by depositing a bonding metal such as Au with a film thickness of about 100 nm to 5000 nm by an evaporation method instead of the insulating material.

  The method of manufacturing the laser device 1 through the above steps S1 to S12 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. The same applies to the following embodiments.

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

<Construction>
FIG. 5 is a schematic cross-sectional view of the laser apparatus of the second embodiment. The laser device 1 according to the second embodiment is different in that an impurity diffusion region 8 having an impurity concentration lower than that of the n-type contact layer 9 is formed on the upper surface of the semiconductor substrate 10 on the first surface side on the laser optical path. In the present embodiment, the impurity diffusion region 8 corresponds to a “first impurity diffusion region”.

  Also in this configuration, as with the laser device 1 of the first embodiment, when a bias voltage is applied between the p-side electrode 21 and the n-side electrode 19, the p-side electrode 21, the p-type contact layer 17, and the p-side multilayer film are reflected. A current path including the mirror 15, the light emitting unit 13, the n-side multilayer reflector 11, the n-type contact layer 9, 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.

  Since the n-side electrode 19 is in contact with the high impurity concentration n-type contact layer 9 and the p-side electrode 21 is in contact with the high-concentration p-type contact layer 21, both the n-side electrode 19 and the p-side electrode 21 are in contact with each other. Resistance is kept low. As a result, the resistance of the entire element can be kept low. This eliminates the problem that high Joule heat is generated, the emission wavelength is shifted, and the light extraction efficiency of the desired emission wavelength is reduced.

  In addition, light from the light emitting unit 13 is extracted to the outside through the n-side multilayer reflector 11, but the central portion of the n-side multilayer reflector 11 has a low impurity concentration in the impurity diffusion region 8 (first impurity diffusion). Area). For this reason, most of the light passes through the low-concentration impurity diffusion region 8 and the semiconductor substrate 10. Thereby, the amount of light absorbed in the semiconductor substrate 10 is greatly suppressed as compared with the conventional configuration.

  As shown in FIG. 6, a part of the impurity diffusion region 8 may be further formed at a position in contact with the bottom surface of the impurity diffusion prevention layer 7.

<Production method>
Hereinafter, only the differences from the first embodiment will be described for the method of manufacturing the laser apparatus 1 shown in FIG.

  Similar to the first embodiment, the semiconductor substrate 10 is prepared (step S1).

(Step S2A)
Crystal growth of an impurity diffusion region 8 with a low impurity concentration is performed on the semiconductor substrate 10 at a position serving as a laser optical path, and an impurity diffusion prevention layer 7 is formed at a peripheral position of the semiconductor substrate 10 with a film thickness of, for example, about 1000 nm to 10000 nm. . The impurity diffusion region 8 is made of AlGaAs or InGaP having an impurity concentration of less than 1 × 10 ¹⁸ / cm ³ , more preferably 5 × 10 ¹⁷ / cm ³ or less, and the impurity diffusion prevention layer 7 is made of undoped AlGaAs or It can be formed of InGaP (see FIG. 7A).

  Thereafter, as in step S4 of the first embodiment, a part of the impurity diffusion preventing layer 7 is etched by wet etching or dry etching to form the groove 32 (see FIG. 7B). Then, similarly to step S5 of the first embodiment, the n-type contact layer 9 formed of GaAs or the like is crystal-grown at a thickness of, for example, about 10 nm to 1000 nm at the location where the groove 32 is formed (see FIG. 7C). ).

  Thereafter, the laser device 1 shown in FIG. 5 is formed through the same processes as steps S6 to S12 of the first embodiment.

  Next, regarding the method for manufacturing the laser apparatus 1 shown in FIG. 6, only the points different from the first embodiment will be described.

  Similar to the first embodiment, the semiconductor substrate 10 is prepared (step S1).

(Step S2B)
An impurity diffusion region 8 having a low impurity concentration is grown on the semiconductor substrate 10. At this time, the growth film thickness at the position that becomes the laser optical path is set to be thicker than the outer peripheral position (see FIG. 7D).

(Step S3B)
In step S2B, on the upper surface of the impurity diffusion region 8 formed of a thin film, the impurity diffusion prevention layer 7 is grown with a film thickness of, for example, about 1000 nm to 10000 nm.

  Thereafter, as in step S4 of the first embodiment, a part of the impurity diffusion prevention layer 7 is etched by a wet etching method or a dry etching method to form the groove 32 (see FIG. 7E). Then, similarly to step S5 of the first embodiment, the n-type contact layer 9 made of GaAs or the like is crystal-grown at a thickness of, for example, about 10 nm to 1000 nm at the location where the groove 32 is formed (see FIG. 7F). ).

  Thereafter, the laser device 1 shown in FIG. 6 is formed through the same processes as steps S6 to S12 of the first embodiment.

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

<Construction>
FIG. 8 is a schematic cross-sectional view of the laser device of the third embodiment. In the laser device 1 of the third embodiment, the n-side multilayer mirror 11 is formed with a larger area than the light emitting unit 13, the p-side multilayer reflector 15 and the p-type contact layer 17. The upper surface of the n-side multilayer mirror 11 is in contact with an insulating layer 25 (corresponding to a “high resistance layer”) as a current confinement layer, and a part of the bottom surface is in contact with the n-type contact layer 9. That is, the insulating layer 25 as a current confinement layer is formed at a position outside the light emitting unit 13 and the p-type multilayer mirror 15. The side surface of the insulating layer 25 is in contact with the light emitting portion 13 and the outer surface of the p-type multilayer reflector 15, and the bottom surface of the insulating layer 25 is in contact with the top surface of the n-side multilayer reflector 11.

  Even in such a configuration, it is possible to achieve both reduction in element resistance and improvement in light extraction efficiency for the same reason as in the laser device 1 of the first embodiment. Since the n-side multilayer mirror 11 is formed larger than the diameter of the light emitting portion 13 by adopting the configuration as shown in FIG. 8, the current path is cut off as compared with the laser device 1 of the first embodiment. The area increases and the electrical resistance decreases. This further reduces the resistance of the element.

  5 or 6 described above in the second embodiment, the n-side multilayer mirror 11 is replaced by a light emitting unit 13, a p-side multilayer reflector 15 and a p-type contact layer 17. Alternatively, the formation area may be increased.

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

  As in the first embodiment, steps S1 to S6 are sequentially executed.

(Step S7A)
As in step S7, among the multilayer structure formed by step S6 and including the n-side multilayer mirror 11, the light emitting unit 13, the p-side multilayer reflector 15 and the p-type contact layer 17, for example, near the center. By performing ion implantation while masking the region, an insulating layer 25 (high resistance layer) as a current confinement layer is formed. At this time, by adjusting the ion implantation energy, the ion-implantation is not performed on the formation site of the n-side multilayer mirror 11, and the formation site of the light emitting unit 13, the p-side multilayer mirror 15 and the p-type contact layer 17 is formed. (See FIG. 9). Note that the insulating layer 25 may be formed by oxidizing the portion.

  Thereafter, the laser device 1 shown in FIG. 8 is formed through the same processes as steps S8 to S12 of the first embodiment.

1: Semiconductor laser device 3: External output mirror 5: Laser beam 7: Impurity diffusion prevention layer 9: n-type contact layer (first contact layer)
10: Semiconductor substrate 11: n-side multilayer film reflecting mirror (first reflecting mirror)
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)
16: Light beam diffusion preventing member 17: p-type contact layer (second contact layer)
19: n-side electrode (first electrode)
21: p-side electrode (second electrode)
25: Insulating layer as a current confinement layer 27: Passivation layer 29: Dielectric layer 31: Groove portion 32: Groove portion 40: Semiconductor substrate 90: Conventional laser device with VECSEL structure d1: Laser light extraction direction

Claims (4)

A semiconductor laser device in which a first reflecting mirror, a light emitting unit, and a second reflecting mirror are sequentially laminated on a semiconductor substrate,
A first contact layer formed so as to be in contact with a first region located on an outer edge of a surface of the first reflecting mirror opposite to a side on which the light emitting unit is formed;
Impurities than the first contact layer formed on the surface of the first reflecting mirror opposite to the light emitting portion forming side so as to be in contact with a second region located inside the first region. A first impurity diffusion region having a low concentration;
An impurity diffusion prevention layer formed of an insulating layer or a semiconductor layer formed at a boundary portion between the first contact layer and the first impurity diffusion region; and a bottom surface of the first contact layer at a position outside the first reflector. A first electrode formed in contact with the upper surface;
A second contact layer formed on an upper layer of the second reflecting mirror;
A semiconductor laser device comprising a second electrode formed on an upper layer of the second contact layer. The first impurity diffusion region is configured by a part of the semiconductor substrate having an impurity concentration lower than that of the first contact layer,
2. The semiconductor laser device according to claim 1, wherein the impurity diffusion preventing layer is formed at a boundary portion between the first contact layer and the semiconductor substrate. The semiconductor substrate has a lower impurity concentration than the first contact layer,
2. The impurity diffusion preventing layer is formed at a boundary portion between the first contact layer and the first impurity diffusion region and at a boundary portion between the first contact layer and the semiconductor substrate. Semiconductor laser device.   A high resistance layer formed by contacting a side surface with the outer surface of the light emitting unit and the second reflecting mirror, and a bottom surface of the high resistance layer being in contact with an upper surface of the first reflecting mirror; The semiconductor laser device according to claim 1.

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