JP2009054815A - Semiconductor laser, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser and a manufacturing method thereof, in which the semiconductor laser can have an end face film for preventing generation of COD simply by a general semiconductor laser element manufacturing process. <P>SOLUTION: This bluish purple semiconductor laser element 100 (semiconductor laser) includes a semiconductor substrate 10 having a cut-out face 10a on which a first region 11a constituted by a GaN layer 11 and a second region 12a constituted by an Al<SB>x</SB>Ga<SB>(1-x)</SB>N layer 12 made of a material different from that of the GaN layer 11 and joined with the GaN layer 11 are disposed in stripes and a semiconductor laser device layer 20 having a device center part formed on the first region 11a on the cut-out face 10a and a device end face part having a resonator surface 20a formed on the second region 12a on the cut-out face 10a. A band gap E<SB>2</SB>in a region 20d (a region 22b of an active layer 22) having the resonator surface 20a is larger than a band gap E<SB>1</SB>in a region 20e (a region 22a of the active layer 22). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser and a manufacturing method thereof.

  Conventionally, a semiconductor light emitting element made of a nitride material such as gallium nitride (GaN) has been put into practical use as a blue-violet semiconductor laser mounted on an optical recording device such as a DVD (Digital Versatile Disc) device. The optical recording apparatus was originally put into practical use as a read-only apparatus, but in recent years, development has been continued as an apparatus capable of reading and writing at a high speed with respect to a recording medium. For high-speed reading and writing, high output of the semiconductor laser is required.

  However, when the semiconductor laser is driven at a limit output or more, optical damage destruction (COD) occurs due to heat generation due to light absorption at the resonator end face (particularly the light emitting face), and thus the semiconductor laser element is destroyed.

  Thus, conventionally, a nitride semiconductor laser device and a method for manufacturing the same have been proposed for the purpose of suppressing COD (see, for example, Patent Document 1).

The aforementioned Patent Document 1, with laminating the nitride semiconductor layers including an active layer on a sapphire substrate, the cavity end face which is exposed by etching, the single crystal _{Al X Ga (1-X)} N (0 <X ≦ A nitride semiconductor laser device in which an end face film made of 1) is separately formed and a method for manufacturing the same are disclosed. In the nitride semiconductor laser device described in Patent Document 1, an end face film made of single crystal Al _X Ga _(1-X) N (0 <X ≦ 1) is formed at a low temperature that does not affect the active layer. At the same time, the mixed crystal ratio is such that the band gap energy is larger than that of the active layer, so that the generation of COD at the resonator end face can be suppressed.

WO2003 / 036771

However, in the nitride semiconductor laser element proposed in Patent Document 1 and the manufacturing method thereof, after forming a semiconductor laser element having a resonator surface, a single crystal Al _X Ga ₍₁₎ is separately provided so as to cover the resonator surface. _{-X) Since the} end face film made of N (0 <X ≦ 1) is formed, there is a problem that the manufacturing process becomes complicated.

  The present invention has been made to solve the above-described problems, and one object of the present invention is a semiconductor laser capable of suppressing the generation of COD without complicating the manufacturing process, and the semiconductor laser. It is to provide a manufacturing method.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, a semiconductor laser according to a first aspect of the present invention includes a first region composed of a first semiconductor layer and a second semiconductor made of a material different from that of the first semiconductor layer and bonded to the first semiconductor layer. A semiconductor substrate having a main surface in which a second region composed of layers is arranged in a stripe pattern, an element central portion formed on the first region of the main surface, and a resonance formed on the second region of the main surface A semiconductor element layer including an element end face portion having a cavity surface, and the band gap of the semiconductor element layer at the element end face portion having the resonator face is larger than the band gap of the semiconductor element layer at the element center portion.

  In the semiconductor laser according to the first aspect of the present invention, as described above, the band gap of the semiconductor element layer is formed on the semiconductor substrate including the first region and the second region, and the element end surface portion having the resonator surface has a band gap. By providing a semiconductor element layer larger than the band gap of the semiconductor element layer at the element center, the laser light in the light emitting layer near the element center of the semiconductor element layer has a larger band gap than near the element center. As a result, light is emitted from the element end face part (resonator face) in a state of being relatively transparent with respect to the light emitting layer in the vicinity of the center part of the element, so that light absorption on the resonator face is suppressed. Thereby, it can suppress that COD generate | occur | produces on the resonator surface (end surface film) resulting from the heat_generation | fever by light absorption of a laser beam. Further, by configuring as described above, a resonator surface that suppresses the generation of COD is formed only by dividing after the formation of the semiconductor element layer. For example, on a semiconductor substrate made of a single material. COD is formed by forming a semiconductor element layer and then separately forming an end face film that covers the resonator surface of the semiconductor element layer exposed by cleaving or etching, using AlGaN having a band gap larger than that of the active layer. Unlike the case of forming a semiconductor laser in which the generation of COD is suppressed, it is possible to form a semiconductor laser in which the generation of COD is suppressed without complicating the manufacturing process of the semiconductor laser element.

  In the semiconductor laser according to the first aspect, preferably, the lattice constant of the first region of the first semiconductor layer in the semiconductor substrate is larger than the lattice constant of the second region of the second semiconductor layer. If comprised in this way, while the stress resulting from the difference of the lattice constant of a 1st area | region and the lattice constant of a 2nd area | region will generate | occur | produce in the semiconductor element layer formed on a semiconductor substrate, respectively, The compressive strain in the light emitting layer of the semiconductor element layer (resonator surface) formed on the second region is larger than the compressive strain in the light emitting layer of the formed semiconductor element layer (near the center of the element). Thereby, in the GaN-based semiconductor element layer, the band gap on the resonator surface can be easily made larger than the band gap in the vicinity of the center of the element.

In the semiconductor laser according to the first aspect, preferably, the first semiconductor layer includes GaN, and the second semiconductor layer includes Al _X Ga _(1-X) N (0 <X ≦ 1). With this configuration, the lattice constant of Al _X Ga _(1-X) N (approximately 3.112 or more and 3.189 in the a-axis direction) is greater than the lattice constant of GaN (having approximately 3.189 in the a-axis direction). Therefore, stress caused by the difference between the lattice constant of the first region and the lattice constant of the second region can be easily generated in the semiconductor element layer formed on the semiconductor substrate. .

  In the semiconductor laser manufacturing method according to the second aspect of the present invention, the first region composed of the first semiconductor layer and the second region composed of the second semiconductor layer made of a material different from the first semiconductor layer are arranged in stripes. And forming a semiconductor element layer on the semiconductor substrate such that the band gap of the region corresponding to the second region is larger than the band gap of the region corresponding to the first region. Forming a semiconductor element layer in a region corresponding to the second region of the semiconductor substrate, and forming a device end surface portion having a resonator surface.

  In the method of manufacturing a semiconductor laser according to the second aspect of the present invention, as described above, the semiconductor device is configured such that the band gap of the region corresponding to the second region is larger than the band gap of the region corresponding to the first region. Providing a step of forming a semiconductor element layer on the substrate and a step of forming an element end face portion having a resonator surface by dividing the semiconductor element layer in a region corresponding to the second region of the semiconductor substrate; For example, a semiconductor laser element is formed by forming a semiconductor element layer on a semiconductor substrate made of a single material, and then exposed by cleavage or etching using AlGaN having a band gap larger than that of the active layer. A manufacturing process for forming a semiconductor laser in which generation of COD is suppressed by separately forming an end face film covering the resonator surface of the semiconductor element layer. Unlike the process, after the formation of the semiconductor element layer, the semiconductor element layer is divided by the second region of the semiconductor substrate to thereby have an element end face part (resonator face) having a larger band gap than the semiconductor element layer (near the element central part). Therefore, it is possible to form a semiconductor laser having a resonator surface that can suppress the generation of COD without complicating the manufacturing process.

  In the method of manufacturing a semiconductor laser according to the second aspect, preferably, the step of forming a semiconductor substrate includes a semiconductor growth layer in which first semiconductor layers and second semiconductor layers are alternately stacked on a growth substrate. And dividing the growth surface of the semiconductor growth layer along the direction intersecting the growth surface, so that the first semiconductor region and the second semiconductor region are adjacent to each other along the main surface. Forming a provided semiconductor substrate. If comprised in this way, the semiconductor substrate in which the 1st area | region and the 2nd area | region of the material different from a 1st area | region were adjacently provided in the direction along the main surface can be formed easily.

In the semiconductor laser manufacturing method according to the second aspect, preferably, when the lattice constants of the first semiconductor layer and the second semiconductor layer are a ₁ and a ₂ , respectively, the first semiconductor layer and the second semiconductor layer Has a relationship of a ₁ > a ₂ . If comprised in this way, the semiconductor substrate which has a lattice constant difference can be obtained easily.

In the method of manufacturing a semiconductor laser according to the second aspect, preferably, the first semiconductor layer includes GaN, and the second semiconductor layer includes Al _X Ga _(1-X) N (0 <X ≦ 1). . According to this structure, about a lattice constant _a 2 (a-axis direction of the _{Al X Ga (1-X)} N than GaN lattice constant _a 1 (having about 3.189 in the a-axis direction) 3.112 ≦ a2 <3.189), the semiconductor element layer formed on the semiconductor substrate is easily subjected to stress caused by the difference between the lattice constant of the first region and the lattice constant of the second region. A semiconductor substrate that can be generated can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view for explaining the structure of a blue-violet semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a view for explaining the structure of the blue-violet semiconductor laser device according to the embodiment shown in FIG. With reference to FIGS. 1 and 2, the configuration of the blue-violet semiconductor laser device 100 according to the present embodiment will be described. In the present embodiment, a case where the present invention is applied to a blue-violet semiconductor laser element which is an example of a semiconductor laser will be described.

  As shown in FIG. 1, a blue-violet semiconductor laser device 100 (oscillation wavelength: about 400 nm) according to an embodiment of the present invention includes a semiconductor substrate 10, a semiconductor laser device layer 20, a p-side electrode 30, and an n-side electrode. 31. The semiconductor laser element layer 20 is an example of the “semiconductor element layer” in the present invention.

Here, in this embodiment, as shown in FIG. 1 and FIG. 2, the semiconductor substrate 10 has a GaN layer 11 at the center and Al _X Ga _(1-X) N (0 ₎ at both ends of the GaN layer 11. <X ≦ 1) It is configured as a substrate arranged so that the layers 12 are adjacent to each other. In the following description, the Al _X Ga _(1-X) N (0 <X ≦ 1) layer 12 is described as the Al _X Ga _(1-X) N layer 12.

In the present embodiment, as shown in FIG. 2, a predetermined region 20d (element end face) including the resonator face 20a (including both the light emitting face 20b and the light reflecting face 20c) of the semiconductor laser element layer 20 is provided. Part) is formed in a region corresponding to the upper surface of the Al _X Ga _(1-X) N layer 12 (second region 12a), and the region 20e (resonator direction (arrow A direction) of the semiconductor laser element layer 20 ) In the vicinity of the central portion of the element) is formed in a region corresponding to the upper surface of the GaN layer 11 (first region 11a). The GaN layer 11 and the Al _X Ga _(1-X) N layer 12 are examples of the “first semiconductor layer” and the “second semiconductor layer” of the present invention, respectively, and the region 20 d and the region 20 e are respectively These are examples of the “element end face portion” and the “element central portion” of the present invention.

  In the present invention, the light emitting surface 20b and the light reflecting surface 20c are distinguished by the magnitude relation of the intensity of the laser light emitted from each resonator surface 20a. That is, the side with relatively high laser beam emission intensity is the light emission surface 20b, and the side with relatively low laser beam emission intensity is the light reflection surface 20c.

  Further, as shown in FIG. 1, the semiconductor laser element layer 20 is composed of semiconductor layers such as an n-type AlGaN cladding layer 21, an active layer 22, and a p-type AlGaN cladding layer 23.

Here, in this embodiment, as shown in FIG. 2, the lattice constant a ₁ (having about 3.189 in the a-axis direction) of the GaN layer 11 of the semiconductor substrate 10 is arranged in the region of the resonator surface 20a. Al _X Ga _(1-X) N layer 12 having a lattice constant a ₂ (having approximately 3.112 ≦ a ₂ <3.189 in the a-axis direction) (a ₁ > a ₂ ). Has been. Thereby, as shown in FIG. 2, the band gap E ₂ of the active layer 22 (region 22 b) in the region 20 d including the resonator surface 20 a disposed on the upper surface of the Al _X Ga _(1-X) N layer 12 is In a state (E ₂ > E ₁ ) larger than the band gap E ₁ of the active layer 22 (region 22a) in the region 20e of the semiconductor laser element layer 20 disposed on the upper surface of the GaN layer 11 (first region 11a). It is configured to be.

  The n-type AlGaN cladding layer 21 has a larger band gap than the active layer 22 (regions 22a and 22b), and the p-type AlGaN cladding layer 23 has a larger band gap than the active layer 22 (regions 22a and 22b). As the material of the n-type AlGaN cladding layer 21 and the p-type AlGaN cladding layer 23, a nitride compound or the like is used as described above. Further, the semiconductor laser element layer 20 having the above-described configuration may be formed of a nitride-based semiconductor layer having a wurtz structure made of GaN, AlN, InN, BN, TlN, and mixed crystals thereof.

  In addition, an optical guide layer having an intermediate band gap between the n-type AlGaN cladding layer 21 and the active layer 22 is formed between the n-type AlGaN cladding layer 21 and the active layer 22 (regions 22a and 22b). A light guide layer having a band gap intermediate between the active layer 22 and the p-type AlGaN cladding layer 23 is formed between the active layer 22 (regions 22a and 22b) and the p-type AlGaN cladding layer 23. May be.

  As shown in FIG. 1, the active layer 22 (regions 22 a and 22 b) may be undoped or may be doped with impurities such as Si. In particular, InGaN or the like is used as the material of the active layer 22. The active layer 22 is formed by a multiple quantum well (MQW) structure in which, for example, four barrier layers made of GaN and three well layers made of InGaN are alternately stacked. The active layer 22 may be formed of a single layer or a single quantum well (SQW) structure.

  Further, as shown in FIG. 1, a ridge portion 23a is formed on the upper surface side of the p-type AlGaN cladding layer 23. The ridge portion 23a is a convex portion extending in a ridge shape in the direction in which the resonator extends (in the direction of arrow A). ing. The ridge portion 23a forms a waveguide structure. The method for forming the waveguide structure is not limited to the method for forming the ridge portion 23a, and the waveguide structure may be formed by a buried heterostructure or the like.

  Further, as shown in FIG. 1, on the upper surface of the ridge portion 23a of the p-type AlGaN cladding layer 23, a p-side electrode 30 is provided along the direction in which the ridge portion 23a extends (arrow A direction) (see FIG. 1). Is formed. Note that a contact layer (not shown) having a smaller band gap than that of the p-type AlGaN cladding layer 23 may be formed between the p-type AlGaN cladding layer 23 and the p-side electrode 30. Further, as shown in FIG. 1, an n-side electrode 31 is formed on the lower surface of the semiconductor substrate 10 adjusted to a predetermined thickness by polishing or etching.

  3 to 10 are views for explaining a manufacturing process of the blue-violet semiconductor laser device according to the embodiment shown in FIG. Next, with reference to FIGS. 1-10, the manufacturing process of the blue-violet semiconductor laser device 100 by one Embodiment of this invention is demonstrated.

  In the manufacturing process of the blue-violet semiconductor laser device 100 according to an embodiment of the present invention, first, a semiconductor substrate forming process as a crystal growth source substrate and a semiconductor laser device layer and electrode forming process on the semiconductor substrate are performed. Do. Then, a blue-violet semiconductor laser device 100 as shown in FIGS. 1 and 2 is formed by performing a dividing step on the semiconductor laser device formed in a wafer shape. Hereinafter, it demonstrates concretely in order of each process.

  First, in the step of forming a semiconductor substrate, as shown in FIG. 3, a sapphire substrate 60 serving as a growth substrate for forming a semiconductor growth layer 50 is prepared, and an organometallic chemistry is formed on the upper surface of the sapphire substrate 60. The GaN layer 11 is epitaxially grown to a predetermined thickness (about several hundreds μm to about 1 mm) by a chemical vapor deposition method (MOCVD method). At that time, in order to grow the growth surface of the GaN layer 11 as a polar surface (c-plane), a sapphire substrate 60 having a substantially (0001) plane as a main surface is used.

The growth substrate on which the GaN layer 11 is grown is not limited to the sapphire substrate 60, but a nitride semiconductor substrate or a heterogeneous substrate that is not a nitride semiconductor (for example, an α-SiC substrate, a ZnO substrate, a spinel substrate, and LiAlO). ₃ substrates) may be used. Alternatively, a GaAs substrate having a main surface made of a substantially (111) plane may be used.

  Further, since the GaN layer 11 is formed by a thin film growth method utilizing a reaction from a gas phase to a solid layer, in addition to the MOCVD method, a hydride vapor phase growth method (HVPE method) or an organometallic chloride is used. A vapor phase growth method (MOC method) or the like may be applied.

As shown in FIG. 3, when the GaN layer 11 is formed on the sapphire substrate 60, the sapphire substrate 60 and the GaN layer are usually stacked in order to stack a buffer layer (not shown) immediately before the GaN layer 11. Warpage due to the difference in lattice constant with the layer 11 is unlikely to occur. Further, in the film formation on the GaAs substrate, when the lateral growth method is used, the warpage due to the difference in lattice constant between the GaAs substrate and the GaN layer hardly occurs. However, the coefficient of thermal expansion α _sub of the sapphire substrate 60 (having about 7.5 × 10 ⁻⁶ / K for the a-axis and about 8.5 × 10 ⁻⁶ / K for the c-axis) Coefficient of thermal expansion α ₁ (having about 5.59 × 10 ⁻⁶ / K for the a-axis and about 3.17 × 10 ⁻⁶ / K for the c-axis) (α _sub > α ₁ ) Therefore, when a single layer of only the GaN layer 11 is directly laminated on the sapphire substrate 60, the GaN is caused by thermal stress in the cooling process after growth (corresponding to the tensile stress in the direction of arrow P in FIG. 3). Some convex warpage deformation occurs on the layer 11 side (in the direction of arrow C in FIG. 3).

Therefore, in the present embodiment, after the GaN layer 11 is grown, as shown in FIG. 3, an Al _X Ga _(1-X) N layer 12 having a lattice constant different from that of the GaN layer 11 is formed to a predetermined thickness ( Epitaxial growth to several μm to 10 μm). The growth of the _{Al X Ga (1-X)} N layer _12, the Al _{X Ga (1-X)} lattice constant _a 2 of _the N layer 12 (a-axis direction with about 3.112 ≦ _a 2 <3.189 ) Is smaller than the lattice constant a ₁ (having about 3.189 in the a-axis direction) of the GaN layer 11 (a ₁ > a ₂ ), the Al _X Ga _(1-X) N layer 12 includes As shown in FIG. 3, a compressive stress is generated in the direction toward the inside of the semiconductor layer (the direction of arrow Q). For this reason, the internal stress (compressive stress) generated in the Al _X Ga _(1-X) N layer 12 is deformed so as to protrude toward the GaN layer 11 in the direction of arrow D (see FIG. 3). Works.

Further, as shown in FIG. 3, after the Al _X Ga _(1-X) N layer 12 is grown, the GaN layer 11 is again epitaxially grown to a predetermined thickness (several hundreds μm to about 1 mm). Further, after the growth of the GaN layer 11, the Al _X Ga _(1-X) N layer 12 is again epitaxially grown to a predetermined thickness (several μm to about 10 μm). In this case, the lattice constant _{a 1} of GaN layer _11, in order to have Al _{X Ga (1-X)} similar magnitude relation as described above to a lattice constant _{a 2} of N layer 12, generated within one another of the semiconductor layer The action of canceling out the stress is generated. That is, as shown in FIG. 3, by repeatedly laminating the GaN layer 11 and the Al _X Ga _(1-X) N layer 12, the semiconductor growth layer 50 is in a state in which no warpage occurs on the sapphire substrate 60, Or it forms so that it may have big thickness in the state where curvature was relieved. _{Incidentally, Al X Ga (1-X} ) N layer 12 formed on both sides of the GaN layer 11 is formed in a substantially distance corresponding to the length of the resonator of the blue-violet semiconductor laser device 100.

  Further, in the above process, the semiconductor growth layer 50 may be slightly warped, but the degree of warping is the growth for the semiconductor substrate 10 to form the semiconductor laser element layer 20 after the formation of the semiconductor substrate 10 described later. This is not to the point of causing trouble when used as an industrial substrate or a support substrate.

In this manner, the semiconductor growth layer 50 (see FIG. 3) is formed by repeatedly stacking the GaN layer 11 and the Al _X Ga _(1-X) N layer 12 on the sapphire substrate 60 a predetermined number of times. Is done.

  Then, as shown in FIG. 4, the sapphire substrate 60 is separated and removed from the semiconductor growth layer 50. At that time, the sapphire substrate 60 may be physically removed by a slicer (not shown) or the like. If the growth substrate is a GaAs substrate or the like, it may be removed by chemical etching.

Thereafter, as shown in FIG. 4, with respect to the growth surface (surface perpendicular to the arrow C direction) of the semiconductor growth layer 50 in which the GaN layer 11 and the Al _X Ga _(1-X) N layer 12 are repeatedly stacked. Slicing along a dividing line 600 (broken line) using a slicer (not shown) or the like in a substantially vertical direction (stacking direction of the semiconductor growth layer 50 (arrow C direction in FIG. 3)) Thus, the semiconductor substrate 10 is cut out from the semiconductor growth layer 50 into a thin plate shape. Thereby, as shown in FIG. 5, the first regions 11 a of the GaN layer 11 and the second regions 12 a of the Al _X Ga _(1-X) N layer 12 are alternately arranged in the lateral direction (arrow B direction). As a result, the semiconductor substrate 10 having a large area formed in a stripe shape is obtained.

  In this embodiment, as shown in FIG. 5, the cut surface 10a of the semiconductor substrate 10 (the surface in which the first regions 11a and the second regions 12a are alternately arranged) is an m-plane ((1-100). The semiconductor substrate 10 having a nonpolar surface (non-c surface) is obtained by cutting out to be a surface) or a surface ((11-20) surface). Here, the nonpolar plane (non-c plane) is a plane (m plane or a plane) in the normal direction to a polar plane called c plane ((0001) plane) in crystal growth of the GaN layer 11. Show. Thus, the striped semiconductor substrate 10 is formed (manufactured). The cut surface 10a is an example of the “main surface” in the present invention.

  Next, in the step of forming the semiconductor laser element layer and the electrode layer on the semiconductor substrate, as shown in FIG. 6, the n-type AlGaN cladding layer 21 is formed on the upper surface (cut surface 10a) of the semiconductor substrate 10 by MOCVD. Then, semiconductor layers such as the active layer 22 and the p-type AlGaN cladding layer 23 are sequentially stacked. Then, as shown in FIG. 7, patterning by lithography and dry etching are performed on the upper surface side of the p-type AlGaN cladding layer 23 to extend in a ridge shape in the direction in which the resonator extends (direction of arrow A in FIG. 1). A ridge portion 23a is formed.

  Further, as shown in FIG. 7, a p-side electrode 30 is formed on the upper surface of the ridge portion 23a of the p-type AlGaN cladding layer 23 by vacuum deposition. Also, as shown in FIG. 6, an n-side electrode 31 is formed by vacuum deposition on the lower surface of the semiconductor substrate 10 adjusted to a predetermined thickness by polishing or etching. In this manner, the semiconductor laser element layer 20 and the electrodes (p-side electrode 30 and n-side electrode 31) on the semiconductor substrate 10 are formed.

Here, in the present embodiment, the band gap E ₁ in the region 22 a in the vicinity of the central portion (region 20 e) of the active layer 22 is caused by the internal stress as shown in FIG. 9 acting inside the semiconductor laser element layer 20. The semiconductor laser element layer 20 is formed such that the band gap E ₂ in the region 22b in the vicinity (region 20d) of the resonator surface 20a (see FIG. 2), which will be described later, becomes larger (E ₂ > E ₁ ).

Specifically, as shown in FIG. 9, the lattice constant b ₁ of the region 21 a of the n-type AlGaN cladding layer 21 formed on the GaN layer 11 (first region 11 a) is the lattice constant a of the GaN layer 11. _Since it is smaller than ₁ (a ₁ > b ₁ ), a tensile stress R ₁ is generated inside the region 21 a of the n-type AlGaN cladding layer 21 in an attempt to match the lattice constant a ₁ of the GaN layer 11. The lattice constant b ₂ of the region 21b of the n-type AlGaN cladding layer 21 formed on the Al _X Ga _(1-X) N layer 12 (second region 12a) is Al _X Ga _(1-X) N. Since the lattice constant is smaller than the lattice constant a ₂ of the layer 12 (a ₂ > b ₂ ), the region 21 b of the n-type AlGaN cladding layer 21 tries to match the lattice constant a ₂ of the Al _X Ga _(1-X) N layer 12. stress _{R 2} tensile internal occurs. In this case, the lattice constant _{a 2} of the lattice constants _{a 1} and _{Al X Ga (1-X)} N layer 12 of GaN layer _11, a 1> in order to have a relation of _{a 2,} a tensile internal region 21a stress R ₁ and the tensile stress R ₂ inside the region 21b are in a state of R ₁ > R ₂ . The magnitudes of the tensile stresses R ₁ and R ₂ are indicated by the size of the arrows shown in FIG. As a result, the lattice constants b ₁ and b ₂ of the regions 21 a and 21 b of the n-type AlGaN cladding layer 21 change so as to have a relationship of b ₁ > b ₂ .

Further, as shown in FIG. 9, in the region 22 a of the active layer 22 formed on the n-type AlGaN cladding layer 21 in the above state, the lattice constant c ₁ of the region 22 a is the same as that of the n-type AlGaN cladding layer 21. Since it is larger than the lattice constant b ₁ (c ₁ > b ₁ ), a compressive stress S ₁ is generated inside the region 22a in an attempt to match the lattice constant b ₁ of the region 21a of the n-type AlGaN cladding layer 21. Further, in the region 22b of the active layer 22, the lattice constant _{c 2} with the region 22b is larger than the lattice constant _{b 2} of n-type AlGaN cladding layer 21 _(c 2> _{b 2)} for, n-type AlGaN cladding layer 21 internal compressive stress _{S 2} occurs as a response to the lattice constant _{b 2} region 21b in the region 22b. At this time, since the lattice constants b ₁ and b ₂ of the regions 21a and 21b of the n-type AlGaN cladding layer 21 are b ₁ > b ₂ , the compressive stress S ₁ inside the region 22a of the active layer 22 and the region 22b inside the compressive stress _{S 2,} a state of _S 1 <S _2. Incidentally, the size of the arrows shown in FIG. 9, the magnitude of the compressive stress S ₁ and S ₂ are shown.

From the above, in the active layer 22, the compressive stress S ₂ inside the region 22 b acts more than the compressive stress S ₁ inside the region 22 a, so that the region 22 b is distorted more than the region 22 a. In the semiconductor laser element layer 20 of GaN-based, when compressive stress _{S 1} and _{S 2} in the inner active layer 22 is the _S 1 _{<S 2} is in the vicinity of the central portion of the active layer 22 (a region 20e in FIG. 2) than the band gap _{E 1} in the corresponding region (region 22a), the cavity surface 20a near the band gap _{E 2} in the region (the region 22b) that corresponds to (see FIG. 2) is increased properties _(E 2> _{E 1)} Show.

In the present embodiment, a cleavage process (bar-shaped cleavage) is performed on the wafer-shaped semiconductor laser device by the following method. Specifically, as shown in FIG. 8, the direction in which the resonator extends by the diamond cutter or the like on the upper surface of the semiconductor laser element layer 20 corresponding to the Al _X Ga _(1-X) N layer 12 of the semiconductor substrate 10. A scribing line 700 (one-dot chain line) is put in a direction (arrow B direction) substantially perpendicular to (arrow A direction), and then cleaving is performed along the scribing line 700. Thereby, as shown in FIG. 2, the resonator surface 20a (light emitting surface 20b and light reflecting surface 20c) is formed.

If the resonator surface 20a is formed as described above, the semiconductor laser element layer 20 is cleaved with the Al _X Ga _(1-X) N layer 12 of the semiconductor substrate 10 after the semiconductor laser element layer 20 is formed, thereby forming the semiconductor forming a cavity surface 20a (light emitting surface 20b and the light reflecting surface 20c) than the band gap _{E 1} of the active layer 22 in the central portion near the laser device layer 20 (a region 20e in FIG. 2) having a large band gap _{E 2} Is possible. That is, the active layer in the vicinity of the central portion of the semiconductor laser element layer 20 is formed only by a normal manufacturing process of the semiconductor laser element without separately performing a process for forming a resonator surface (end face film or the like) having a larger band gap than the active layer. Since the resonator surface 20a that is relatively transparent than 22 is obtained, the semiconductor laser element layer 20 that can suppress light absorption on the resonator surface 20a can be obtained. Thereby, the blue-violet semiconductor laser device 100 in which the generation of COD on the resonator surface 20a is suppressed can be formed without complicating the manufacturing process.

  Then, after the cleavage plane forming step (bar-shaped cleavage), as shown in FIG. 10, the direction in which the resonator extends from the back surface side (the lower surface side of the n-side electrode 31) of the semiconductor substrate 10 toward the semiconductor laser element layer 20. After forming a plurality of marking lines (not shown) with a diamond cutter or the like in a direction substantially parallel to the direction (arrow A direction), division is sequentially performed along each marking line. That is, the blue-violet semiconductor laser device 100 is divided into chips along a one-dot chain line 800 shown in FIG. Thereby, as shown in FIG. 1, a blue-violet semiconductor laser device 100 formed into a chip is formed. Thus, the blue-violet semiconductor laser device 100 according to the present embodiment is formed.

In the present embodiment, as described above, the active layer 22 (region 22b) in the region 20d (see FIG. 2) formed on the semiconductor substrate 10 including the first region 11a and the second region 12a and having the resonator surface 20a. ) band gap _{E 2} is, by providing the region 20e (semiconductor laser element layer 20 larger than the band gap _{E 1} of the active layer 22 in FIG. 2) (region 22a), the region 20e of the semiconductor laser element layer 20 The resonator surface 20a (formed in the region 20d as a state in which the laser light in the adjacent active layer 22 has a larger band gap than the region 20e and thus is relatively transparent than the active layer 22 in the region 20e. Since the light is emitted from the light emitting surface 20b), light absorption at the resonator surface 20a is suppressed. Thereby, it can suppress that COD generate | occur | produces on the resonator surface 20a (the light-projection surface 20b and the light reflection surface 20c) resulting from the heat_generation | fever by light absorption of a laser beam.

  Further, by configuring as described above, the resonator surface 20a that suppresses the generation of COD is formed only by dividing after the formation of the semiconductor laser element layer 20, so that, for example, a semiconductor made of a single material A semiconductor laser element layer is formed on the substrate, and then an end face film that covers the resonator surface of the semiconductor laser element layer exposed by cleaving, etching, or the like using AlGaN having a band gap larger than that of the active layer is separately provided. Unlike the case of forming a semiconductor laser in which the generation of COD is suppressed by forming, the blue-violet semiconductor laser element 100 in which the generation of COD is suppressed without complicating the manufacturing process of the semiconductor laser element is formed. Can do.

In the present embodiment, the lattice constant a ₁ (about 3.189: a-axis direction) of the GaN layer 11 (first region 11a) in the semiconductor substrate 10 is changed to the Al _X Ga _(1-X) N layer 12 (first 2 region 12a) by making it larger than the lattice constant a ₂ (about 3.112 ≦ a ₂ <3.189: a-axis direction), in the semiconductor laser element layer 20 formed on the semiconductor substrate 10, compressing the GaN layer lattice constant _{a 1} of 11 and _{Al X Ga (1-X)} tensile due to the difference between the lattice constant _{a 2} of N layer 12 stress _{R 1} and _{R 2} (see FIG. 9) stress _{S 1} and S ₂ (see FIG. 9) respectively, and Al _X Ga ₍ 1−2) is larger than the compressive strain in the active layer 22 (region 22a) of the semiconductor laser element layer 20 (near the center) formed on the GaN layer 11. _X) formed on the N layer 12 Compressive strain in the active layer 22 (region 22b) of the conductive laser element layer 20 (the cavity surface 20a near) increases. Thus, the semiconductor laser element layer 20 of GaN-based, easily, the band gap _{E 2} in the active layer 22 of the cavity surface 20a, is larger than the band gap _{E 1} in the vicinity of the central portion of the active layer 22 _{(E 2} > E ₁ state).

(Modification)
FIG. 11 is a perspective view for explaining the structure of a green semiconductor laser device according to a modification of one embodiment of the present invention. In this modification, as shown in FIG. 11, unlike the above embodiment (see FIG. 1), the green semiconductor laser device 200 is formed by changing the material (composition) of the active layer 122 of the semiconductor laser device layer 120. Is configured to do.

  Specifically, as shown in FIG. 11, the semiconductor laser element layer 120 is composed of semiconductor layers such as an n-type AlGaN cladding layer 21, an active layer 122, and a p-type AlGaN cladding layer 23. In particular, InGaN or the like is used as the material of the active layer 122. For example, the active layer 122 is formed by a multiple quantum well (MQW) structure in which four barrier layers made of InGaN and three well layers made of InGaN are alternately stacked. ing. Thereby, the green semiconductor laser element 200 having an oscillation wavelength of about 530 nm is formed.

  The remaining structure, manufacturing process, and effect of the invention of the green semiconductor laser device 200 according to this modification are the same as those of the above embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

In the above embodiment, the GaN layer 11 (first semiconductor layer region) and the Al _X Ga _(1-X) N layer 12 (second semiconductor layer region) are repeatedly stacked on the sapphire substrate 60 to form a semiconductor growth layer. However, the present invention is not limited to this, and Al _X Ga _(1-X) N (0 <X ≦ 1) and In _Y Ga _(1-Y ) are applied to the sapphire substrate 60. _{) A} semiconductor growth layer forming step may be performed by repeatedly stacking different kinds of semiconductor layers made of N (0 <Y ≦ 1) or the like.

  In the above-described embodiment, an example in which the sapphire substrate 60 is used as a growth substrate for the striped semiconductor substrate 10 has been described. However, the present invention is not limited to this, and examples other than the sapphire substrate such as GaAs, SiC, and Si. A substrate made of a material may be used.

In the above embodiment, thereby forming respectively the _{Al X Ga (1-X)} N layer 12 on both sides of the GaN layer 11 of the semiconductor substrate _10, corresponding to the upper surface of the _{Al X Ga (1-X)} N layer 12 Although an example in which the resonator surface 20a (the light emitting surface 20b and the light reflecting surface 20c) is formed in the region to be formed has been shown, the present invention is not limited thereto, and Al _X Ga is formed only on one side of the GaN layer 11. _(1-X) with a semiconductor substrate of the N layer 12 formed by _adjacent, may be formed only the light emitting surface on the top surface of the _{Al X Ga (1-X)} N layer 12.

It is a perspective view for demonstrating the structure of the blue-violet semiconductor laser element by one Embodiment of this invention. It is a figure for demonstrating the structure of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a figure for demonstrating the manufacturing process of the blue-violet semiconductor laser element by one Embodiment shown in FIG. It is a perspective view for demonstrating the structure of the green semiconductor laser element by the modification of one Embodiment of this invention.

Explanation of symbols

10 Semiconductor substrate 10a Cut-out surface (main surface)
11 GaN layer (first semiconductor layer)
11a first region _{12 Al X Ga (1-X} ) N layer (second semiconductor layer)
12a Second region 20, 120 Semiconductor laser element layer (semiconductor element layer)
20a Resonator surface 20d region (element end face part)
20e area (element center)

Claims (7)

A first surface made of a first semiconductor layer and a second surface made of a material different from that of the first semiconductor layer and made of a second semiconductor layer joined to the first semiconductor layer have a main surface arranged in a stripe pattern. A semiconductor substrate;
A semiconductor element layer including an element center portion formed on the first region of the main surface and an element end surface portion having a resonator surface formed on the second region of the main surface;
A semiconductor laser, wherein a band gap of the semiconductor element layer at the element end face portion having the resonator surface is larger than a band gap of the semiconductor element layer at the element central portion.   2. The semiconductor laser according to claim 1, wherein a lattice constant of the first region of the first semiconductor layer in the semiconductor substrate is larger than a lattice constant of the second region of the second semiconductor layer. 3. The semiconductor laser according to claim 1, wherein the first semiconductor layer includes GaN, and the second semiconductor layer includes Al _X Ga _(1-X) N (0 <X ≦ 1). Forming a semiconductor substrate having a main surface in which a first region made of a first semiconductor layer and a second region made of a second semiconductor layer made of a material different from the first semiconductor layer are arranged in a stripe pattern;
Forming a semiconductor element layer on the semiconductor substrate such that a band gap of a region corresponding to the second region is larger than a band gap of a region corresponding to the first region;
Forming a device end surface portion having a resonator surface by dividing the semiconductor device layer in a region corresponding to the second region of the semiconductor substrate.   The step of forming the semiconductor substrate includes a step of forming a semiconductor growth layer in which the first semiconductor layer and the second semiconductor layer are alternately stacked on a growth substrate, and a growth surface of the semiconductor growth layer. 5. The method of manufacturing a semiconductor laser according to claim 4, comprising: dividing the semiconductor laser along a direction intersecting with the growth surface. If the lattice constant of the first semiconductor layer and the second semiconductor layer, respectively, was a ₁ and a _2,
6. The method of manufacturing a semiconductor laser according to claim 4, wherein the first semiconductor layer and the second semiconductor layer have a relationship of a ₁ > a ₂ . 7. The device according to claim 4, wherein the first semiconductor layer includes GaN, and the second semiconductor layer includes Al _X Ga _(1-X) N (0 <X ≦ 1). Semiconductor laser manufacturing method.

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