JP5803167B2 - Manufacturing method of nitride semiconductor laser device - Google Patents

Description

  The present invention relates to a method for manufacturing a nitride semiconductor laser device having a light absorption layer on a resonator surface.

In the semiconductor laser element, light leaking from the waveguide region is emitted in addition to the desired laser light. Such leakage light deteriorates the beam quality, and causes erroneous recognition and image degradation in an apparatus incorporating a semiconductor laser element. In particular, since a nitride semiconductor laser element uses a material that does not absorb light emitted from an active layer as a substrate, leakage light is guided through the substrate and emitted to the outside. Patent Document 1 proposes forming an opaque film on the end face.
Patent Document 2 discloses a light emitting element including a wavefront conversion unit having a pinhole in a light emitting unit.
Further, in the nitride semiconductor laser element, when a gas containing Si as a constituent element exists in the surrounding atmosphere, this gas reacts with the emitted laser beam, and Si oxide is formed on the emission end face. When such Si oxide is formed, the reflectance of the emission end face changes, and the drive current and drive voltage may fluctuate. Therefore, the nitride semiconductor laser element is normally hermetically sealed and used as a nitride semiconductor device. Patent Document 3 discloses a semiconductor laser device that prevents an organic substance from adhering to an end face by using an inert gas having a predetermined humidity as an atmosphere in a package.

JP 2002-280663 A JP 2000-022277 JP JP 2007-227587

However, the opaque film as disclosed in Patent Document 1 is not formed as a countermeasure against the leakage light because it is not formed corresponding to the laser beam emitting portion. Further, in the method of providing a pinhole as in Patent Document 2, it is conceivable that the emission end face or the reflection mirror is damaged and the laser characteristics are deteriorated due to the damage.
Accordingly, an object of the present invention is to manufacture a light absorption layer corresponding to a laser beam emitting portion on a resonator surface of a nitride semiconductor laser element while reducing damage caused by processing.

  The method of manufacturing a semiconductor laser device according to the embodiment includes a step of forming a nitride semiconductor layer having a resonator surface at an end of a waveguide region, a reflection mirror, a protective film, and light absorption on the resonator surface. And a step of forming an opening corresponding to the waveguide region in the light absorption layer.

  According to the method for manufacturing a nitride semiconductor laser device of the present invention, it is possible to obtain a nitride semiconductor laser device in which damage to the resonator surface is reduced and a light absorption layer corresponding to the laser beam emitting portion is formed.

It is a schematic sectional drawing for demonstrating the structure of the nitride semiconductor laser element of embodiment. It is a schematic sectional drawing for demonstrating the structure of the nitride semiconductor laser element of embodiment. It is a schematic perspective view for demonstrating the structure of the nitride semiconductor laser apparatus using the nitride semiconductor laser element of embodiment. It is a graph which shows the relationship between the drive current and drive time of the nitride semiconductor laser element of embodiment. It is a graph which shows the relationship between the drive current of the nitride semiconductor laser element of a comparative example, and drive time.

  Embodiments will be described below with reference to the drawings. However, the embodiments described below exemplify a method of manufacturing a nitride semiconductor laser device for embodying the technical idea of the present invention, and the present invention is not limited to the following. In addition, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the embodiments are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation.

FIG. 1 is a cross-sectional view in the resonator direction in the waveguide region of the nitride semiconductor laser device of the embodiment, and FIG. 2 is a cross-sectional view in the direction perpendicular to the resonator direction of the nitride semiconductor laser device of the embodiment.
In the nitride semiconductor laser device 1 according to the embodiment, the nitride semiconductor layer 3 is formed on the substrate 2, and the light emitting side (emitting surface) 3 a of the pair of resonator surfaces 3 a and 3 b of the nitride semiconductor layer is not provided. The reflection mirror 4a, the protective film 5, and the light absorption layer 6 are sequentially formed. An opening 6a is formed in the light absorption layer 6, and laser light is emitted from the light emitting portion 5a on the surface of the protective film. A reflection mirror 4b is formed on the light reflection side (reflection surface) 3b.
The nitride semiconductor layer 3 includes an n-side semiconductor layer 31, an active layer 32, and a p-side semiconductor layer 33 provided on the substrate 2. A ridge 3c is provided on the surface of the p-side semiconductor layer 3, and an active layer 32 corresponding to the ridge and a waveguide region 3d are formed in the vicinity thereof. A first insulating film 9 is formed on the side surface of the ridge and the surface of the nitride semiconductor layer continuous from the side surface of the ridge. A second insulating film 10 is formed on the side surface of the nitride semiconductor layer. A p-side electrode 7a is provided on the surface of the nitride semiconductor layer, and an n-side electrode 7b is formed on the back surface of the substrate.

Such a nitride semiconductor laser device can be manufactured by the following steps.
(A) Step of forming a nitride semiconductor layer having a resonator surface at the end of the waveguide region (b) Step of sequentially forming a reflection mirror, a protective film, and a light absorption layer on the resonator surface ( c) Step of forming an opening corresponding to the waveguide region in the light absorption layer

According to such a manufacturing method, damage to the resonator surface can be reduced, and a light absorption layer having an opening corresponding to the laser light emitting portion can be formed. The details are as follows. The light absorption layer formed of a material that absorbs light of the oscillation wavelength of the nitride semiconductor laser element is irradiated to the light emitting portion from the waveguide region by the laser oscillation, so that the light emitting portion is irradiated to the waveguide region. The light absorption layer in the corresponding region is removed, and a light absorption layer having an opening can be formed. Further, as in the step (b), the opening can be formed in a state where the reflection mirror is protected by forming a protective film on the reflection mirror. In other words, when the opening is formed in the light absorption layer formed on the protective film in the step (c), the light absorption layer is removed by the high-density laser light because the protective film is provided. However, it is possible to manufacture a nitride semiconductor laser element in which an opening is formed without suppressing damage to the reflecting mirror and without changing the reflectance of the reflecting mirror.
Further, in a semiconductor laser that emits light having a relatively short wavelength, such as a nitride semiconductor, a gas containing Si as a constituent element in the surrounding atmosphere reacts by the laser light, and a Si oxide is formed on the surface of the laser light emitting portion. Form. However, since the light absorption layer formed on the resonator surface has an opening, Si oxide is formed not on the surface of the light emitting part in the opening but on the surface of the light absorption layer around the opening. Si oxide can be made difficult to be formed on the surface of the emitted light exit portion. The reason for this is that the density of the gas containing Si as a constituent element is lower in the opening than in the periphery of the opening, so that the gas reaction is less likely to occur in the opening and the Si oxide is not formed. Guessed. As a result, Si oxide is preferentially formed on the surface of the light absorption layer around the opening, and the formation of deposits on the light emitting portion can be suppressed.
Furthermore, since there is a light absorption layer in a region other than the laser light emitting part, the beam quality can be improved by absorbing light leaking from the waveguide region including spontaneous emission light.

Hereinafter, a method for manufacturing the nitride semiconductor laser device of the embodiment will be described.
(A) Step of forming a nitride semiconductor layer having a resonator surface at the end of the waveguide region For example, on the substrate 2, the nitride semiconductor layer 3, the electrodes (7a and 7b), the first insulating film 9, and the first The resonator surface can be obtained by sequentially forming the two insulating films 10 and the like and cleaving the substrate.

As the nitride semiconductor layer 3, a layer containing the general formula In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) can be used. In addition to this, an element in which B is partially substituted as a group III element or an element in which N is partially substituted with P or As as a group V element may be used. The n-side semiconductor layer 31 may contain any one or more of group IV elements such as Si, Ge, and Sn or group VI elements as n-type impurities. The p-side semiconductor layer 33 may contain Mg or the like as a p-type impurity. Impurities can be contained in a concentration range of, for example, about 5 × 10 ¹⁶ / cm ³ to 1 × 10 ²¹ / cm ³ .

The active layer 32 may have either a multiple quantum well structure or a single quantum well structure. When using an active layer corresponding to a short wavelength whose oscillation wavelength is about 550 nm or less,
Since it easily reacts with Si in the surrounding atmosphere, it is effective to apply the present invention.
The nitride semiconductor layer 3 includes a light guide layer that constitutes an optical waveguide in the n-side semiconductor layer and the p-side semiconductor layer, so that an SCH (Separate Confinement Heterostructure) that has a separated light confinement structure with an active layer interposed therebetween. A structure is preferable.

  The growth method of the nitride semiconductor layer 3 is not particularly limited, but a nitride semiconductor growth method such as MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam epitaxy), etc. Can be used.

A ridge 3 c is formed on the surface of the p-side semiconductor layer 33. The ridge functions as a waveguide region, and the width thereof can be formed in the range of about 1.0 μm to 30.0 μm. The height of the ridge (etching depth) can be appropriately adjusted in consideration of the material of the layer constituting the p-side semiconductor layer, the film thickness, the degree of light confinement, etc. Can be mentioned. The ridge is preferably set so that the length in the resonator direction is about 100 to 1000 μm.
The ridge can be formed by a method usually used in this field. For example, photolithography and an etching process are mentioned.

The resonator surface can be formed by any surface other than the M surface, C surface, A surface, and R surface. Moreover, the surface which has an off-angle in these surfaces may be sufficient.
The resonator surface can be formed by cleavage, etching, or the like.

  The substrate 2 may be an insulating substrate or a conductive substrate. Examples thereof include nitride semiconductors such as GaN and AlN, sapphire, spinel, silicon carbide, silicon, ZnO, and GaAs. Specifically, any one of the C-plane, M-plane, A-plane, and R-plane is used as the main surface, and the off-angle of greater than 0 ° and 10 ° or less is formed on the surface on which the nitride semiconductor layer is formed and / or the back surface thereof. A GaN substrate having the same is preferable. As for the film thickness, 50 micrometers or more and 10 mm or less are mentioned, for example.

  The p-side electrode 7a and the n-side electrode 7b are, for example, a single layer of metal or alloy such as Pd, Pt, Ni, Au, Ti, W, Cu, Ag, Zn, Sn, In, Al, Ir, Rh, and ITO. It can be formed of a film or a laminated film. Specifically, the p-side electrode can be formed of Ni / Au / Pt, ITO, or the like. The n-side electrode can be formed of Ti / Pt / Au or the like. The film thickness of the electrode can be appropriately adjusted depending on the material used, and for example, about 500 to 5000 mm is appropriate. Further, one or a plurality of conductive layers such as the pad electrode 8 may be formed on these electrodes.

The first insulating film 9 is provided in a region other than the region connected to the electrode on the upper surface of the nitride semiconductor in order to confine the current supplied to the nitride semiconductor layer to a predetermined region. For example, in the case of the ridge structure as shown in FIG. 2, the ridge structure is provided on the side surface of the ridge and the upper surface of the nitride semiconductor layer on both sides thereof.
The first insulating film is preferably made of an insulating material and has a refractive index smaller than that of the nitride semiconductor in order to confine light in the waveguide region. _{Specifically, ZrO 2, HfO 2, SiO} 2, Ta 2 O 5, SiN, SiON, BN, SiC, SiOC , and the like. Of these, ZrO ₂ or SiO ₂ is particularly preferable. The film thickness is preferably about 0.1 to 0.5 μm.

  The second insulating film 10 may be formed so as to cover the side surface of the nitride semiconductor layer and / or the side surface or surface of the substrate. On the surface of the nitride semiconductor layer, the first insulating film may be provided, or the second insulating film may be provided directly. The second insulating film can be formed of an oxide such as Si, Zr, V, Nb, Hf, Ta, Al, Ce, In, Sb, Zn, nitride, oxynitride, or the like. The film thickness is about 0.1 to 1 μm.

(B) Step of sequentially forming a reflection mirror, a protective film, and a light absorption layer on the resonator surface Next, a reflection mirror, a protection film, and a light absorption layer are formed on the resonator surface obtained in the previous step. Sequentially formed.

The reflection mirror is provided on the resonator surface of the nitride semiconductor laser element and plays a role of suitably emitting the laser light by reflecting and amplifying the laser light.
The reflection mirror can be formed of a single layer or a multilayer film composed of a pair of a low refractive index layer and a high refractive index layer. It is preferable that reflection mirrors are provided on the resonator surfaces on both the emission side and the reflection side. A single layer film may be formed on the emission-side resonator surface, and a multilayer film may be formed on the reflection-side resonator surface.
The reflection mirror can be appropriately adjusted in material, film thickness, number of pairs of multilayer films, etc. in order to obtain a desired reflectance. The thickness of each layer can be adjusted as appropriate depending on the material used, and is determined by the desired oscillation wavelength (λ) and the refractive index (n) at λ of the material used. Specifically, it is preferably an integer multiple of λ / (4n), and is preferably adjusted as appropriate in consideration of the reflectance.
For example, in a laser element having an oscillation wavelength of 405 nm, when formed with Ta ₂ O ₅ / SiO ₂ , about 40 to 70 nm is exemplified. In the case of such a multilayer film, the number of pairs is 2 pairs or more, preferably about 5 to 15 pairs. The film thickness as a whole of the reflection mirror is, for example, about 50 to 900 nm.
It is preferable to adjust the material, film thickness, and number of pairs so that the reflectance is about 11% on the emission side and about 95% on the reflection side.
In addition, the reflection mirror may be formed over the entire width direction of the nitride semiconductor laser element or may be formed partially. It may be formed at least in the waveguide region and its periphery.

The reflection mirror is made of an insulating material, and is made of a nitride semiconductor, particularly a material having a refractive index smaller than that of the active layer. For example, it can be formed of an oxide film, a nitride film, an oxynitride film, a combination thereof, or the like. _{Specifically, SiO 2, Al 2 O 3} , Ta 2 O 5, HfO 2, ZrO 2, TiO 2, Nb 2 O 5, SiN, SiON, AlN, AlON , and the like.
Further, in order to protect the resonator surface, a single crystal is formed of a nitride film such as Al _x Ga _1-x N (0 <x ≦ 1) or a hexagonal material so as to be in contact with the resonator surface. A containing film may be formed.

The reflection mirror can be formed by a method known in the art. For example, a vapor deposition method, a sputtering method (reactive sputtering method, ECR plasma sputtering method, magnetron sputtering method, etc.), a CVD method, a method combining two or more of these methods, or a combination of these methods and an oxidation treatment (heat treatment). Various methods such as a combination method can be used. Of these, the ECR plasma sputtering method is preferable.
In addition, a reflection mirror is formed on the resonator surface after using pretreatment, irradiation with plasma containing noble gas (Ar, He, Xe, etc.), nitrogen, oxygen, ozone gas, oxidation treatment, heat treatment, exposure treatment, etc. Also good.

The protective film is provided on the reflection mirror on the resonator surface. In the nitride semiconductor laser device of the embodiment, the protective film is provided on the reflection mirror, so that the surface of the reflection mirror can be protected, the deterioration of the reflection mirror can be suppressed, and the laser light can be appropriately reflected and amplified. . Further, since the laser light is emitted through the protective film, the laser light is diffused corresponding to the film thickness of the protective film, and light on the surface of the emission part at the time of emission (the surface of the protective film in the case of FIG. 1). Since the density can be relaxed, the formation of Si oxide can be more effectively suppressed.
The material for the protective film can be selected in consideration of adhesion to the reflection mirror and stability in the atmosphere. _{Specifically, SiO 2, Al 2 O 3} , Ta 2 O 5, HfO 2, ZrO 2, TiO 2, Nb 2 O 5, SiN, SiON, AlN, AlON , and the like. In particular, it is preferable to form with SiO ₂ or AlN. As a film thickness, about 30-8000 nm is mentioned.
In addition, the protective film preferably has an attenuation coefficient with respect to the oscillation wavelength of the laser light that is smaller than 0.01. The attenuation coefficient of the protective film is a spectroscopic ellipsometer using ellipsometry. A. It can be measured using HS-190 manufactured by WOOLLAM.

The light absorption layer is provided on the protective film on the resonator surface. The light absorption layer is formed of a material that absorbs light having a laser oscillation wavelength. Although details will be described later, this is because it is possible to easily form an opening by using such a material. In addition, since the spontaneous emission light or the like leaking from the waveguide region can be absorbed, a nitride semiconductor laser device having a good beam quality can be obtained.
The material of the light absorption layer is preferably made of metal or semiconductor, for example, metal such as Au, Pt, Ag, Cu, Sn, Ni, Fe, Zn, Al, Si, Ge, GaAs, InAs, SiC, etc. The semiconductor is mentioned. Moreover, it is preferable that the attenuation coefficient with respect to the oscillation wavelength of a laser beam is 0.01 or more. Preferably, it is Si or SiC. The light absorption layer is preferably provided with a thickness of about 20 to 500 nm.

(C) Step of forming an opening corresponding to the waveguide region in the light absorption layer Next, an opening corresponding to the waveguide region is formed in the previously formed light absorption layer. The opening provided in the light absorption layer is provided so as to correspond to the laser light emitting portion. That is, the light emitting portion is a portion where the light absorption layer provided on the protective film is opened and the protective film is exposed from the light absorption layer. Specifically, when the resonator surface is viewed from the front, it opens in a horizontally long elliptical shape at a position corresponding to the waveguide region.

  As a method of forming the opening, a current is applied to the electrode of the nitride semiconductor laser element, a constant driving current is supplied to cause laser oscillation, and the laser light is absorbed by the light absorption layer, whereby a position corresponding to the light emitting portion is obtained. The light absorption layer is removed. As described above, since the light absorption layer is formed of a material that absorbs light having the oscillation wavelength of the nitride semiconductor laser element, the light emitting portion is irradiated with high-density laser light by laser oscillation. The light absorption layer in the region is evaporated, and a light absorption layer having an opening can be formed.

The opening can be formed by adjusting the laser output according to the light density of the waveguide region, the thickness of the light absorption layer, and the wavelength of the nitride semiconductor laser element. The output of the laser necessary for forming the opening is determined according to the light density of the emitted laser light. For example, a single-mode laser element has a high light density of the emitted laser light, so an opening can be formed with a relatively low output, but a multi-mode laser element has a high light output because the light density of the laser light is small. The laser beam is emitted to form an opening. Further, as the thickness of the light absorption layer is larger, the output of the laser beam necessary for forming the opening is increased. Further, the longer the wavelength of the nitride semiconductor laser element, the larger the output of the laser beam necessary for forming the opening. This is because the energy of the laser beam (the reciprocal of the wavelength) is converted into the kinetic energy of the elements constituting the light absorption layer, thereby evaporating the light absorption layer.
In addition, in order to take out a desired laser beam, the size of the opening of the light absorption layer is formed to be equal to or larger than the near field size when the nitride semiconductor laser element is driven at the rated light output. Is preferred. For this reason, it is suitable for the laser beam output when forming the opening to oscillate at or above the rated light output, and preferably at least twice the rated light output.
As the driving condition, the opening can be provided by pulse driving, continuous driving, or a combination thereof.
Specifically, in a 405 nm band nitride semiconductor laser device in which the transverse mode is a single mode, when the light absorption layer is Si having a thickness of 30 nm, Si begins to evaporate with a light output of about 10 mW. Alternatively, in a 445 nm band nitride semiconductor laser device in which the transverse mode is a single mode, when the light absorption layer is Si with a thickness of 30 nm, Si begins to evaporate with a light output of about 20 mW.

  Further, as shown in FIG. 3, the nitride semiconductor laser device thus obtained can be placed on the stem 20 via the submount 30 to obtain a nitride semiconductor laser device. A nitride semiconductor laser device will be described with reference to the drawings. FIG. 3 is a perspective view of the nitride semiconductor laser device. The stem is provided with leads 40a, 40b and 40c so as to penetrate the stem. The nitride semiconductor laser element is electrically connected to the lead by wires 50a and 50b and can be electrically connected to the outside.

  If the nitride semiconductor laser device manufactured by the manufacturing method of this embodiment is used, a nitride semiconductor laser that does not require hermetic sealing and does not cause the formation of deposits due to the surrounding atmosphere even in an open state. A device can be obtained.

  In the nitride semiconductor laser device of this embodiment, the nitride semiconductor laser element is placed on the stem. The stem is preferably formed of a material having a relatively high thermal conductivity, for example, a material having a thermal conductivity of about 20 W / mK or more in order to efficiently release the heat generated in the nitride semiconductor laser element to the outside. Specific materials include metals such as Cu, Al, Fe, Ni, Mo, CuW, and CuMo, and ceramics such as AlN, SiC, and alumina. These metals or ceramics may be used as a base material, and the whole or part of the surface thereof may be plated with Au, Ag, Al, or the like. Especially, what is formed with the copper or copper alloy by which the surface was gold-plated is preferable.

  The shape and size of the stem are not particularly limited, and can be appropriately adjusted according to the final desired shape and size of the nitride semiconductor laser device. As the planar shape, a circular shape, an elliptical shape, a polygonal shape including a rectangular shape, or a shape similar to these can be used. For example, a circular plate having a diameter of about 3 to 10 mm can be used. The thickness is preferably about 0.5 to 5 mm. Further, the stem is not limited to a flat plate shape, and a concave portion and / or a convex portion may be provided on the surface thereof. Specifically, as shown in FIG. 3, there may be mentioned one in which a convex portion is provided in a region where a flat plate-shaped semiconductor laser element is placed.

  The nitride semiconductor laser element may be disposed on the stem via the submount. For the submount, a member having high thermal conductivity is preferably used for heat dissipation, and specific examples include AlN, CuW, diamond, SiC, ceramics, and the like. A thin film such as Ti / Pt / Au or Ni / Au may be formed on the surface.

The method for assembling the nitride semiconductor laser device of the present invention is not particularly limited. First, the nitride semiconductor laser element is mounted on the submount and bonded, and then the lower surface of the submount is bonded to the stem. For example, there is a method in which a submount is mounted on the stem and bonded, and then a nitride semiconductor laser element is bonded to the submount.
Furthermore, any structure such as face-down mounting in which the semiconductor layer side of the nitride semiconductor laser element is mounted on the stem and face-up mounting in which the substrate side of the nitride semiconductor laser element is mounted on the stem may be employed.

In the nitride semiconductor laser device, a cap may be attached to the stem so as to cover the nitride semiconductor laser element 1. Providing a cap can improve waterproofness and dustproofness.
Examples of the shape of the cap include a bottomed cylindrical shape (such as a cylinder or a polygonal column), a truncated cone shape (such as a truncated cone or a polygonal truncated cone), a dome shape, and a deformed shape thereof. The cap is preferably formed of a material having high thermal conductivity. For example, a material such as Ni, Co, Fe, Ni—Fe alloy, Kovar, or brass can be used.
The portion corresponding to the laser light emission part on the upper surface or side surface of the cap has an opening for allowing the laser light to pass therethrough, and a transparent member for taking out the laser light is supported in the opening. Can be used. The translucent member can be formed of, for example, glass, sapphire, ceramics, resin, or the like. Further, a light transmissive film may be provided on the surface so that the laser light can be suitably transmitted. Moreover, the translucent member may contain the wavelength conversion member, the light-diffusion material, etc.

  A photodiode may be arranged on the stem in order to monitor the output of the nitride semiconductor laser element. In addition, a protective element may be arranged to protect the nitride semiconductor laser element from element destruction and performance deterioration due to excessive voltage application.

  Examples of the method for manufacturing a nitride semiconductor laser device of the present invention will be described below. In addition, this invention is not limited to a following example.

(Example 1)
The nitride semiconductor laser device as shown in FIGS. 1 to 3 can be manufactured as follows.
First, a nitride semiconductor substrate containing an n-type impurity is set in a MOVPE reaction vessel, and nitride semiconductor layers are grown in order as follows.
(N-side semiconductor layer 31)
Si-doped AlGaN 2.4 μm
Undoped GaN 0.17μm
(Active layer 32)
Si-doped In _0.02 Ga _0.98 N barrier layer 140 Å undoped In _0.07 Ga _0.93 N well layer 80 Å Si-doped In _0.02 Ga _0.98 N barrier layer 140 Å undoped In _0.07 Ga _0.93 N well layer 80 Å Si-doped In _0.02 Ga _0.98 N barrier layer 140 Å (p-side semiconductor layer 33)
Mg-doped AlGaN 100 angstrom undoped GaN 0.15 μm
Super lattice layer Mg-doped GaN 150 Å with a total film thickness of 0.6 μm, which is a repetitively grown undoped AlGaN 25 Å and Mg-doped AlGaN 25 Å

The wafer on which the nitride semiconductor layer has been grown is taken out of the reaction vessel, and a mask pattern having a predetermined shape for defining the shape of the nitride semiconductor laser element is formed on the upper surface of the uppermost p-side semiconductor layer, and RIE is performed. Etching is performed to expose the n-side semiconductor layer.
Subsequently, a stripe-shaped mask pattern having a width of 1.5 μm is formed on the upper surface of the uppermost p-side semiconductor layer, and etching is performed halfway through the p-side semiconductor layer by RIE to form a stripe-shaped ridge having a width of 1.5 μm. 3c is formed.
Subsequently, a first insulating film 9 having a thickness of 2000 ZrO ₂ film is formed on the upper surface of the nitride semiconductor layer by photolithography and a lift-off method using an ECR sputtering apparatus.
Next, a p-side electrode 7a formed by sequentially forming Ni, Au, and Pt is formed on the outermost surface of the ridge.
A second insulating film 10 made of SiO ₂ is formed from the insulating film to the side surface of the nitride semiconductor layer and the exposed surface of the n-side semiconductor layer.
Subsequently, the p-side pad electrode 8 electrically connected to the p-side electrode 7a is formed.
Thereafter, the substrate is polished to a thickness of about 80 μm, and the n-side electrode 7 b is formed on the back surface of the substrate 2.

(Formation of resonator surfaces 3a and 3b)
Thereafter, the nitride semiconductor layer and the substrate are cleaved to form a bar shape. Cleavage is performed so that the cleavage plane of the bar becomes the (1-100) plane, and a resonator plane is produced.

(Formation of reflection mirrors 4a and 4b)
A reflection mirror is formed on the resonance surface. First, a 32 nm-thickness AlN film is formed as a first film on the emission-side resonator surface from the resonator surface to the top surface of the nitride semiconductor layer and the surface of the insulating film using an Al target with an ECR plasma sputtering apparatus. Form. Furthermore, SiO ₂ having a film thickness of 260 nm is formed as a second film by an ECR plasma sputtering apparatus.
Subsequently, AlN having a film thickness of 32 nm is formed as a first film on the resonator surface on the reflection surface side, as in the emission surface side. On top of that, SiO _{2 is formed} to a thickness of 69 nm using a Si target with a sputtering apparatus, and Ta ₂ O _{5 is formed} to a thickness of 46 nm. SiO ₂ and Ta ₂ O ₅ are repeatedly formed, and (SiO ₂ / Ta ₂ O ₅ ) is formed for six periods to form a second film on the reflection side.

(Formation of protective film 5)
A protective film is formed on the reflection mirror on the emission side. A sputtering apparatus forms SiO ₂ with a thickness of 1100 nm using a Si target.

(Formation of the light absorption layer 6)
A light absorption layer is formed on the protective film. A SiC film having a film thickness of 200 nm is formed using a SiC target by a sputtering apparatus.

(Formation of opening 6a)
An opening corresponding to the waveguide region (light emitting portion) is formed in the light absorption layer of the obtained nitride semiconductor laser element.
The electrode of the nitride semiconductor laser element is energized and driven by a pulse drive at an output of 70 mW to cause laser oscillation. When the emission-side resonator surface is observed after driving, it is observed that the light absorption layer at the position corresponding to the light emission part is removed.

  Finally, a semiconductor laser element is obtained by chip-forming bars in a direction perpendicular to the cavity end face.

The obtained nitride semiconductor laser device was placed on the stem 20 via the submount 30 and attempted to oscillate at an optical output of 20 mW at Tc = 75 ° C. in an open state. The relationship between the drive current and drive time of this nitride semiconductor laser device is shown in FIG. The number of tests is eight. The nitride semiconductor laser device of the embodiment did not fluctuate drive current due to deposits even after 1000 hours and operated stably. Further, when the light emission state of the obtained nitride semiconductor laser device was observed, the leakage light emitted from the region other than the waveguide region was greatly reduced.
Further, FIG. 5 shows the relationship between the drive current and drive time obtained by driving a nitride semiconductor laser element formed in the same manner except that the light absorption layer is not formed. In the nitride semiconductor laser element of the comparative example, fluctuations in driving current were observed with the lapse of driving time.

(Example 2)
This example is the same as Example 1 except that the structures of the protective film and the light absorption layer are changed. As a protective film, AlN is formed with a film thickness of 110 nm on the output-side reflecting mirror using an Al target with a sputtering apparatus. On the protective film, Si is formed in a film thickness of 30 nm in the same manner as in Example 1 by using a Si target with a sputtering apparatus.
In the present embodiment, the same effect as in the first embodiment can be obtained.

  The nitride semiconductor laser element and the nitride semiconductor laser device of the present invention can be used for all devices such as an optical disk, an optical communication system, a projector, a printer, and a measuring instrument.

1: Nitride semiconductor laser element 2: Substrate 3: Nitride semiconductor layer 3a: Light emitting side resonator surface (emitting surface)
3b: Light reflection side resonator surface (reflection surface)
4a, 4b: reflection mirror 5: protective film 5a: light emitting part 6: light absorption layer 6a: opening 100: nitride semiconductor laser device 20: stem 30: submount

Claims (4)

Forming a nitride semiconductor layer having a resonator surface at an end of the waveguide region;
A step of sequentially forming a reflection mirror, a protective film, and a light absorption layer on the resonator surface;
A method of manufacturing a nitride semiconductor laser device comprising: an opening forming step of forming an opening by removing the light absorbing layer in the entire region corresponding to the waveguide region in the light absorbing layer;
The method for manufacturing a nitride semiconductor laser device, wherein, in the opening forming step, the opening is provided with a size equal to or larger than a near field size by oscillating the nitride semiconductor laser device.   The method for manufacturing a nitride semiconductor laser element according to claim 1, wherein the protective film, the light absorption layer, and the opening are provided on the resonator surface on a light emitting side. The protective film manufacturing method of the nitride semiconductor laser device according to claim 1 or 2 made of SiO ₂ or AlN. Manufacturing method of the nitride semiconductor laser device according to any one of claims 1 to 3 wherein the light absorbing layer is made of Si or SiC.