JP2012124274A - Semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element capable of increasing the selection flexibility of laser resonance surfaces, capable of increasing the design flexibility by the increased selection flexibility, and capable of contributing to characteristic improvement, and to provide a method of manufacturing the same.SOLUTION: A semiconductor laser element 70 has a semiconductor stacked structure including a substrate 1 and a group III nitride semiconductor stacked structure 2. The group III nitride semiconductor stacked structure 2 has a light-emitting layer 10, a p-type guide layer 17 disposed on one side of the light-emitting layer 10, an n-type guide layer 15 disposed on the other side of the light-emitting layer 10, a p-type cladding layer 18 disposed on the surface of the p-type guide layer 17 opposite to the surface on which the light-emitting layer 10 is provided, and an n-type cladding layer 14 disposed on the surface of the n-type guide layer 15 opposite to the surface on which the light-emitting layer 10 is provided. The semiconductor stacked structure includes a linear ridge 20 formed on a first surface, a pair of laser resonance surfaces 21 and 22 formed on the longitudinal edges of the ridge 20, and edge-face processing marks 8 formed in the lower edge portions of the laser resonance surfaces 21 and 22 continuing to a second surface of the semiconductor stacked structure.

Description

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

  A semiconductor laser element has a semiconductor laminated structure including a light emitting layer, a p-type guide layer and an n-type guide layer disposed with the light emitting layer interposed therebetween, and a p-type cladding layer and an n-type cladding layer disposed with the light emitting layer interposed therebetween. Have. This semiconductor multilayer structure has, for example, a ridge extending linearly, and a waveguide is formed along this ridge. The semiconductor multilayer structure has a pair of end faces orthogonal to the ridge at both ends of the ridge. The pair of end surfaces are mirror surfaces formed by cleavage, and form a laser resonance surface that reflects light propagating through the waveguide.

  The semiconductor laser element is manufactured by cutting out a plurality of individual element regions from an original substrate arranged in a matrix. On the original substrate, a plurality of ridges are formed in stripes. When the original substrate is cut, as described in Patent Document 1, first, division guide grooves are formed by laser processing on the surface corresponding to the surface of the semiconductor laser element (the surface on the ridge side). Thereafter, the original substrate is divided by applying an external force by applying a blade from the back side of the original substrate. A laser resonance surface is formed by dividing (cleaving) the original substrate along a direction intersecting a plurality of ridges formed in a stripe shape. In order not to damage the laser resonance surface in the vicinity of the ridge (waveguide), the division guide groove is formed in a perforated discontinuous pattern that is discontinuous in the vicinity of the ridge.

JP 2009-81428 A (paragraphs 0043 and 0051)

  The split guide groove of the discontinuous pattern is effective for dividing along a crystal plane with good cleaving property. I can't get it. Therefore, if it is assumed that the prior art of Patent Document 1 is applied, the degree of freedom in selecting the laser resonance surface becomes narrow. Therefore, even if an attempt is made to select the crystal growth surface and ridge direction of the semiconductor according to the required specifications, the laser resonant surface cannot be formed with a good cleavage plane, so that a semiconductor laser element with the required specifications is eventually realized. It becomes difficult.

  Accordingly, an object of the present invention is to provide a semiconductor laser device that can increase the degree of freedom of selection of the laser resonance surface, thereby increasing the degree of freedom of design, and contribute to improving the characteristics, and a method of manufacturing the same. is there.

  The invention according to claim 1 for achieving the above object includes a light emitting layer, a p-type guide layer disposed on one side of the light emitting layer, and an n-type guide layer disposed on the other side of the light emitting layer. A p-type cladding layer disposed on the p-type guide layer opposite to the light-emitting layer, and an n-type cladding layer disposed on the n-type guide layer opposite to the light-emitting layer. The semiconductor multilayer structure includes a linear ridge formed on the surface side, a pair of laser resonance surfaces formed at both ends in the longitudinal direction of the ridge so as to be orthogonal to the ridge, and the pair A semiconductor laser element including an end face processing mark formed in a lower edge region continuous with the back surface of the semiconductor multilayer structure on a laser resonance surface.

  According to this configuration, the laser resonance surface has the end face processing mark in the lower edge region continuous with the back surface (surface opposite to the ridge) of the semiconductor multilayer structure. That is, this semiconductor laser element is processed from the back surface side of the semiconductor multilayer structure to form end surface processing traces, and an external force is applied by applying a blade from the front surface side (side on which the ridge is formed) of the semiconductor multilayer structure. The original substrate can be cleaved, and a laser resonance surface can be formed by the cleaved surface. Since the end face processing trace is formed on the back side where the ridge is not formed, it is not necessary to form a discontinuous pattern having a discontinuous portion in the vicinity of the ridge, and therefore, it can be formed in a continuous pattern. Therefore, since the cleavage by the external force applied from the surface side can be performed stably, a good cleavage surface can be obtained. More specifically, even if the crystal plane perpendicular to the ridge is a crystal plane with insufficient cleavage, the semiconductor multilayer structure can be cleaved well along such a crystal plane. As a result, the crystal growth surface for forming the semiconductor multilayer structure and the degree of freedom in selecting the ridge direction are increased, so that the degree of freedom in designing the semiconductor laser element is increased. Therefore, it becomes easy to realize a semiconductor laser element having a required specification. In addition, since the laser resonance surface can be formed with a good cleavage surface, the characteristics of the semiconductor laser device can be improved. More specifically, the threshold current can be reduced, the slope efficiency can be increased, and the operating current can be reduced.

  The invention according to claim 2 is the semiconductor laser device according to claim 1, wherein the end face processing trace is continuous over the entire width direction of the semiconductor multilayer structure. The “width direction” refers to a direction (resonator width direction) perpendicular to the longitudinal direction of the ridge (resonator length direction) and parallel to the crystal growth surface of the semiconductor multilayer structure. According to this configuration, processing is performed from the rear surface side over the entire width direction of the semiconductor multilayer structure, and then the original substrate is divided (cleaved) by applying an external force by applying a blade from the front surface side of the semiconductor multilayer structure. )it can. As a result, even if the crystal plane perpendicular to the ridge is a crystal plane with poor cleaving property, a laser resonance surface composed of a good cleavage plane can be provided.

  A third aspect of the present invention is the semiconductor laser device according to the first or second aspect, wherein the thickness of the end face processing trace is 10% or more of the thickness of the semiconductor multilayer structure. According to this configuration, since the end face processing trace has a sufficient thickness, the laser resonance surface can be formed with a better cleaved surface. Thereby, the characteristics of the semiconductor laser device can be improved. The “thickness of the end face processing trace” is a length along the stacking direction (direction perpendicular to the crystal growth surface) of the semiconductor stacked structure.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the semiconductor multilayer structure is made of a group III nitride semiconductor having an m plane as a crystal growth plane, and the laser resonance plane is a c plane. The semiconductor laser device according to one item. In this configuration, the semiconductor multilayer structure is made of a group III nitride semiconductor having an m-plane as a crystal growth surface. In this case, TE mode laser oscillation can be efficiently generated by taking the longitudinal direction of the ridge (waveguide direction, resonator length direction) in the c-axis direction. Since the longitudinal direction of the ridge is the c-axis direction, the laser resonance surface is the c-plane. By forming the end face processing trace of the continuous pattern from the back surface side of the semiconductor multilayer structure, cleavage of the group III nitride semiconductor crystal (semiconductor multilayer structure) along the c-plane can be performed stably. Therefore, it is possible to provide a laser resonance surface composed of a good cleavage plane.

The group III nitride semiconductor is a semiconductor using nitrogen as a group V element in a group III-V semiconductor. Aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN) are typical examples. In general, it can be expressed as Al _X In _Y Ga _1-XY N (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1).
According to a fifth aspect of the present invention, the surface electrode formed on the surface of the semiconductor multilayer structure is disposed at a position separated in the width direction perpendicular to the longitudinal direction of the ridge on the surface of the semiconductor multilayer structure, And a receiving portion that has a height equal to or greater than the width of the ridge and is longer than the width of the ridge and spaced from the surface electrode. 4. The semiconductor laser device according to claim 4.

  According to this configuration, when an external force is applied by applying a blade to the surface side of the semiconductor multilayer structure, the external force can be applied to the receiving portion. As a result, it is possible to divide (cleave) the original substrate while protecting the ridge, thereby forming a laser resonance surface having a good cleavage surface. In addition, since the length of the receiving portion in the width direction of the semiconductor multilayer structure (the direction parallel to the cleavage plane and the crystal growth surface, the resonator width direction) is larger than the width of the ridge, it is possible to reliably receive an external force. Moreover, since the receiving part is formed with a space from the surface electrode, the surface electrode is not damaged when receiving external force. Therefore, problems such as current leakage can be avoided.

  6. The semiconductor device according to claim 5, further comprising a back surface electrode formed on the back surface of the semiconductor multilayer structure and having an end surface retreating portion retreated inwardly from the pair of laser resonance surfaces. It is a laser element. According to this configuration, the peripheral edge of the back surface electrode has the end surface receding portion that recedes inward from the laser resonance surface, so that processing from the back surface side of the semiconductor multilayer structure is performed using the end surface receding portion as a mark. be able to.

  According to a seventh aspect of the present invention, the semiconductor multilayer structure has a pair of side surfaces parallel to the longitudinal direction of the ridge, and side processing traces formed in a lower edge region that is continuous with the back surface of the semiconductor multilayer structure on the pair of side surfaces. The semiconductor laser device according to claim 1, further comprising: According to this configuration, the division on the side surface parallel to the ridge is performed by processing the original substrate from the back surface side of the semiconductor multilayer structure, and then applying an external force to the original substrate by applying the blade from the front surface side of the semiconductor multilayer structure. It can be carried out. Processing from the back side can be performed in a continuous pattern, and since there is no fear of damaging the waveguide, deep processing can be performed as necessary. Thereby, the division | segmentation of the original board | substrate along the side surface of a semiconductor laminated structure can be performed stably.

  The invention according to claim 8 is the semiconductor according to claim 7, wherein the back electrode formed on the back surface of the semiconductor multilayer structure has a side receding portion that recedes inwardly from the pair of side surfaces. It is a laser element. According to this configuration, since the back surface electrode has the side surface receding portion that recedes inward from the side surface, it is possible to perform processing from the back surface side of the semiconductor multilayer structure using the side surface receding portion as a mark. .

  The invention according to claim 9 is characterized in that the semiconductor multilayer structure has a pair of side surfaces parallel to the longitudinal direction of the ridge and side processing marks formed in an upper edge region that is continuous with the surface of the semiconductor multilayer structure on the pair of side surfaces. The semiconductor laser device according to claim 1, further comprising: According to this configuration, the division on the side surface parallel to the ridge is performed by processing the original substrate from the front surface side of the semiconductor multilayer structure, and then applying an external force by applying a blade to the original substrate from the rear surface side of the semiconductor multilayer structure. It can be carried out. As for the side surface, since it is not necessary to avoid the ridge, a continuous pattern can be processed even from the surface side, and since there is no possibility of damaging the waveguide, deep processing can be performed as necessary. Thereby, the division | segmentation of the original board | substrate along the side surface of a semiconductor laminated structure can be performed stably.

  A tenth aspect of the present invention is the semiconductor laser device according to any one of the seventh to ninth aspects, wherein the side surface processing trace is continuous over the entire lengthwise direction of the semiconductor multilayer structure. According to this configuration, the original substrate can be divided along the direction parallel to the ridge after being processed over the entire region in the longitudinal direction of the semiconductor multilayer structure (the direction parallel to the longitudinal direction of the ridge). Thereby, the division | segmentation regarding the side surface of a semiconductor laminated structure can be performed more stably.

  The invention according to claim 11 is the semiconductor laser device according to any one of claims 7 to 10, wherein the thickness of the side surface processing trace is 80% or more of the semiconductor multilayer structure. According to this configuration, since the thickness of the side processing trace is sufficiently thick, the original substrate can be reliably divided along the side processing trace. Thereby, the division | segmentation regarding the side surface of a semiconductor laminated structure can be performed more stably. “Thickness of side surface processing trace” is the length in a direction perpendicular to the crystal growth surface of the semiconductor multilayer structure.

  According to a twelfth aspect of the present invention, an original substrate having a plurality of ridges formed in stripes so that a plurality of semiconductor laser element regions are arranged in a matrix and pass through the plurality of semiconductor laser element regions aligned in one direction, respectively. And scribing the original substrate with a scribing process along a cutting line set along a boundary line of the plurality of semiconductor laser element regions from the back surface opposite to the surface on which the ridge is formed. A method of manufacturing a semiconductor laser device, comprising: a step; and a dividing step of applying a blade to the original substrate along the cutting line from the surface of the original substrate, and dividing the original substrate along the cutting line.

  According to this method, scribing is performed from the back surface of the original substrate, and then an external force in a direction intersecting the surface of the original substrate (more specifically, a perpendicular direction) is applied from the surface of the original substrate. To divide (cleave) the original substrate. If such scribing and division (cleavage) is performed along a cutting line perpendicular to the ridge, a laser resonance surface composed of a cleavage plane perpendicular to the ridge can be obtained. Since the scribe processing is performed from the back side where the ridge is not formed, it is not necessary to form a discontinuous pattern having a discontinuous portion in the vicinity of the ridge, and the continuous pattern scribing can be performed. Therefore, since the cleavage performed by applying the blade from the surface side can be performed stably, a good cleavage surface can be obtained. More specifically, even if the crystal plane perpendicular to the ridge is a crystal plane that is not sufficiently cleaved, the original substrate can be cleaved well along such a crystal plane. As a result, the degree of freedom in design of the semiconductor laser device is increased because the crystal growth surface for forming the semiconductor multilayer structure forming the semiconductor laser diode structure and the degree of freedom of selection in the ridge direction are increased. Therefore, it becomes easy to realize a semiconductor laser element having a required specification. In addition, since a laser resonance surface composed of a good cleavage surface can be provided, it is possible to contribute to improving the characteristics of the semiconductor laser element.

  A thirteenth aspect of the present invention is the method for manufacturing a semiconductor laser device according to the twelfth aspect, wherein the scribing process includes a step of scribing the original substrate so as to be continuous along the cutting line. In this method, continuous pattern scribing is performed, so that the original substrate can be stably divided (cleaved), and accordingly, a laser resonant surface having a good cleaved surface can be formed.

According to a fourteenth aspect of the present invention, the cutting line includes an end surface cutting line set along a direction orthogonal to the ridge, and the dividing step is performed along the end surface cutting line, thereby orthogonal to the ridge. 14. The method of manufacturing a semiconductor laser device according to claim 12, wherein a laser resonance surface comprising a cleavage plane is formed.
By this method, with respect to the end face cutting line orthogonal to the ridge, scribing from the back side and division of the original substrate by external force applied from the front side are performed. Thereby, the laser resonance surface which consists of a stable cleavage surface can be formed. The depth of the scribing process along the end face cutting line is preferably 10% or more of the thickness of the original substrate.

The invention according to claim 15 is characterized in that the cutting line includes a side cutting line set along a longitudinal direction of the ridge, and the dividing step is performed along the side cutting line so as to be parallel to the ridge. It is a manufacturing method of the semiconductor laser element as described in any one of Claims 12-14 in which a side surface is formed.
By this method, with respect to the side surface cutting line parallel to the ridge, scribing from the back surface side and division of the original substrate by external force applied from the front surface side are performed. Thereby, the division | segmentation of the original board | substrate regarding the side surface of a semiconductor laser element can be performed stably. In order to perform this division more stably, it is preferable that the depth of the scribing process related to the side surface cutting line is 80% or more of the thickness of the original substrate.

  According to a sixteenth aspect of the present invention, a side scribing process is performed on the original substrate along a side cutting line set parallel to the longitudinal direction of the ridge along the boundary between the plurality of semiconductor laser elements from the surface of the original substrate. The method of claim 14, further comprising: applying a blade to the original substrate along the side surface cutting line from the back surface of the original substrate, and dividing the original substrate along the side surface cutting line. This is a method for manufacturing the semiconductor laser device.

  In this method, with respect to the end face cutting line orthogonal to the ridge, scribing from the back side and division of the original substrate by external force applied from the front side are performed. Thereby, the laser resonance surface which consists of a stable cleavage surface can be formed. On the other hand, with respect to the side cutting line parallel to the ridge, scribing from the front side and division of the original substrate by external force applied from the back side are performed. With respect to the side cutting line, since it is not necessary to avoid the ridge, processing in a continuous pattern is possible even from the surface side. Therefore, the original substrate can be stably divided with respect to the side surface of the semiconductor laser element.

  The invention according to claim 17 is the method of manufacturing a semiconductor laser device according to claim 16, wherein the side scribing step includes a step of scribing the original substrate so as to continue along the side cutting line. is there. By this method, the original substrate can be divided more stably with respect to the side cutting line. In order to perform this division more stably, it is preferable that the depth of the scribing process related to the side surface cutting line is 80% or more of the thickness of the original substrate.

FIG. 1 is a perspective view for explaining the configuration of a semiconductor laser device according to an embodiment of the present invention. 2 is a longitudinal sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. It is an illustrative perspective view showing a wafer which is a base substrate for manufacturing a semiconductor laser diode. FIG. 5A is an illustrative perspective view for explaining an outline of a procedure for dividing a wafer into individual elements (semiconductor laser elements). FIG. 5B is an illustrative perspective view for explaining an outline of a procedure for dividing the wafer into individual elements (semiconductor laser elements). FIG. 5C is an illustrative perspective view for explaining an outline of a procedure for dividing the wafer into individual elements (semiconductor laser elements). FIG. 6 is a partially enlarged plan view for explaining the arrangement of the p-side electrode and the receiving part on the surface of the wafer. FIG. 7A is a bottom view showing a first formation pattern example of the n-side electrode. FIG. 7B is a bottom view showing a second formation pattern example of the n-side electrode. FIG. 7C is a bottom view illustrating a third formation pattern example of the n-side electrode. 8A and 8B are explanatory diagrams for explaining a specific example of primary cleavage. 9A and 9B are explanatory diagrams for describing a specific example of secondary cleavage. 10A and 10B are explanatory diagrams for explaining another specific example of the secondary cleavage. FIG. 11A shows the result of measuring the threshold current for a plurality of samples (semiconductor laser elements) according to a comparative example in which primary cleaving was performed in the scribing process from the front side of the wafer and the braking process from the back side. It is a histogram. FIG. 11B shows the result of measuring the threshold current for a plurality of samples (semiconductor laser elements) according to an example in which primary cleaving was performed in the scribing process from the back side of the wafer and the braking process from the front side. It is a histogram. FIG. 12A is a histogram showing the results of measuring the slope efficiency of a plurality of samples according to the comparative example, and FIG. 12B is a histogram showing the results of measuring the slope efficiency of a plurality of samples according to the example. FIG. 13A is a histogram showing the result of measuring the operating current for a plurality of samples according to the comparative example, and FIG. 13B is a histogram showing the result of measuring the operating current for a plurality of samples according to the example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 is a perspective view for explaining a configuration of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view taken along a line II-II in FIG. 1, and FIG. It is a cross-sectional view which follows the III-III line of FIG.
The semiconductor laser device 70 includes a substrate 1, a group III nitride semiconductor multilayer structure 2 formed by crystal growth on the substrate 1, and a back surface of the substrate 1 (a surface opposite to the group III nitride semiconductor multilayer structure 2). Fabry-Perot comprising an n-side electrode 3 as a back electrode formed so as to be in contact with the p-type electrode and a p-side electrode 4 as a surface electrode formed so as to be in contact with the surface of the group III nitride semiconductor multilayer structure 2 Of the type. The p-side electrode 4 includes a p-side ohmic electrode 4A and a p-side pad electrode 4B. In this embodiment, the substrate 1 and the group III nitride semiconductor multilayer structure 2 form a semiconductor multilayer structure that constitutes a semiconductor laser diode structure.

  In this embodiment, the substrate 1 is composed of a GaN single crystal substrate. In this embodiment, the substrate 1 has an m-plane which is one of nonpolar surfaces as a main surface, and a group III nitride semiconductor multilayer structure 2 is formed by crystal growth on the main surface. Yes. Therefore, the group III nitride semiconductor multilayer structure 2 is made of a group III nitride semiconductor having the m-plane as a crystal growth surface (main surface).

Each layer forming the group III nitride semiconductor multilayer structure 2 is coherently grown with respect to the substrate 1. Coherent growth refers to crystal growth in a state where the continuity of the lattice from the underlayer is maintained. The lattice mismatch with the base layer is absorbed by the lattice distortion of the layer on which the crystal is grown, and the continuity of the lattice at the interface with the base layer is maintained.
The a-axis lattice constant of GaN is 3.189 、, and the c-axis lattice constant is 5.185 Å. On the other hand, the a-axis lattice constant of AlN in a strain-free state is 3.112 、, and the c-axis lattice constant is 4.982 Å. Therefore, the a-axis lattice constant and c-axis lattice constant of AlGaN are smaller as the Al composition is larger. The increase rate with respect to the increase in Al composition is larger for the c-axis lattice constant than the a-axis lattice constant. Therefore, when an AlGaN crystal is coherently grown on a GaN substrate, tensile strain (internal stress) is generated in the c-axis direction and the a-axis direction in the AlGaN crystal, and the magnitude is larger in the c-axis direction.

  The group III nitride semiconductor multilayer structure 2 includes a light emitting layer 10, an n-type semiconductor layer 11, and a p-type semiconductor layer 12. The n-type semiconductor layer 11 is disposed on the substrate 1 side with respect to the light emitting layer 10, and the p-type semiconductor layer 12 is disposed on the p-side ohmic electrode 4 </ b> A side with respect to the light emitting layer 10. Thus, the light emitting layer 10 is sandwiched between the n-type semiconductor layer 11 and the p-type semiconductor layer 12, and a double heterojunction is formed. In the light emitting layer 10, electrons are injected from the n-type semiconductor layer 11 and holes are injected from the p-type semiconductor layer 12. When these are recombined in the light emitting layer 10, light is generated.

  The n-type semiconductor layer 11 includes, in order from the substrate 1 side, an n-type GaN contact layer 13 (for example, 2 μm thickness), an n-type AlInGaN cladding layer 14 (for a thickness of 1.5 μm or less, for example, 1.0 μm thickness), and an n-type InGaN guide layer. 15 (for example, 0.1 μm thickness) is laminated. On the other hand, the p-type semiconductor layer 12 has a p-type AlGaN electron blocking layer 16 (for example, 20 nm thickness), a p-type InGaN guide layer 17 (for example, 0.1 μm thickness), and a p-type AlInGaN cladding layer on the light emitting layer 10 in order. 18 (1.5 μm thickness or less, for example, 0.4 μm thickness) and a p-type GaN contact layer 19 (for example, 0.3 μm thickness) are laminated.

The n-type GaN contact layer 13 and the p-type GaN contact layer 19 are low resistance layers. The p-type GaN contact layer 19 is in ohmic contact with the p-side ohmic electrode 4A. The n-type GaN contact layer 13 is made an n-type semiconductor by doping GaN with, for example, Si as an n-type dopant at a high concentration (doping concentration is, for example, 3 × 10 ¹⁸ cm ⁻³ ). The p-type GaN contact layer 19 is made a p-type semiconductor layer by doping Mg as a p-type dopant at a high concentration (doping concentration is, for example, 3 × 10 ¹⁹ cm ⁻³ ).

The n-type AlInGaN cladding layer 14 and the p-type AlInGaN cladding layer 18 produce a light confinement effect that confines light from the light emitting layer 10 therebetween. The n-type AlInGaN cladding layer 14 is made an n-type semiconductor by doping AlInGaN with, for example, Si as an n-type dopant (doping concentration is, for example, 1 × 10 ¹⁸ cm ⁻³ ). The p-type AlInGaN cladding layer 18 is made a p-type semiconductor layer by doping Mg as a p-type dopant (doping concentration is, for example, 1 × 10 ¹⁹ cm ⁻³ ). The n-type AlInGaN cladding layer 14 has a wider band gap than the n-type InGaN guide layer 15, and the p-type AlInGaN cladding layer 18 has a wider band gap than the p-type InGaN guide layer 17. Thereby, good confinement can be performed, and a low threshold and high efficiency semiconductor laser diode can be realized.

The n-type InGaN guide layer 15 and the p-type InGaN guide layer 17 are semiconductor layers that generate a carrier confinement effect for confining carriers (electrons and holes) in the light-emitting layer 10, and emit light together with the cladding layers 14 and 18. An optical confinement structure is formed in the layer 10. Thereby, the efficiency of recombination of electrons and holes in the light emitting layer 10 is increased. The n-type InGaN guide layer 15 is an n-type semiconductor by doping InGaN with, for example, Si as an n-type dopant (doping concentration is, for example, 1 × 10 ¹⁸ cm ⁻³ ), and the p-type InGaN guide layer 17 is made a p-type semiconductor by doping InGaN with, for example, Mg as a p-type dopant (doping concentration is, for example, 5 × 10 ¹⁸ cm ⁻³ ).

The p-type AlGaN electron blocking layer 16 is a p-type semiconductor formed by doping AlGaN with, for example, Mg as a p-type dopant (doping concentration is, for example, 5 × 10 ¹⁸ cm ⁻³ ). This prevents the outflow of electrons and increases the recombination efficiency of electrons and holes.
The light emitting layer 10 has, for example, an MQW (multiple-quantum well) structure containing InGaN. Light is generated by recombination of electrons and holes, and the generated light is amplified. It is a layer for.

  The light emitting layer 10 is, for example, a multiple quantum well formed by alternately laminating a quantum well layer (for example, 3 nm thick) made of an InGaN layer and a barrier layer (barrier layer: for example 9 nm thick) made of an AlGaN layer alternately for a plurality of periods. (MQW: Multiple-Quantum Well) structure. In this case, the quantum well layer made of InGaN has a relatively small band gap by setting the In composition ratio to 5% or more, and the barrier layer made of AlGaN has a relatively large band gap. For example, the quantum well layers and the barrier layers are alternately stacked repeatedly for 2 to 7 periods, thereby forming a light emitting layer having a multiple quantum well structure. The emission wavelength corresponds to the band gap of the quantum well layer, and the band gap can be adjusted by adjusting the composition ratio of indium (In). As the composition ratio of indium increases, the band gap decreases and the emission wavelength increases. In this embodiment, the emission wavelength is adjusted to, for example, 450 nm to 550 nm (blue to green) by adjusting the composition of In in the quantum well layer (InGaN layer). In the multiple quantum well structure, the number of quantum well layers containing In is preferably 3 or less.

  As shown in FIG. 1 and the like, the p-type semiconductor layer 12 is partially removed to form a linear ridge 20. More specifically, the p-type contact layer 19, the p-type AlInGaN cladding layer 18, and the p-type InGaN guide layer 17 are partially removed by etching to form a ridge 20 having a substantially trapezoidal shape (mesa shape) in cross section. Yes. The ridge 20 is formed along the c-axis direction.

  Further, on the surface of the group III nitride semiconductor structure 2 (the main surface on the side where the ridge 20 is formed), four receiving portions are provided on both sides of the ridge 20 at positions separated in a direction perpendicular to the longitudinal direction of the ridge 20. 30 is formed. More specifically, a pair of receiving portions 30 are arranged on both sides of one end of the ridge 20, and another pair of receiving portions 30 are arranged on both sides of the other end of the ridge 20. Each receiving part 30 includes a base part 31 made of the p-type semiconductor layer 12 and a thin film part 32 formed on the base part 31. The base portion 31 is formed by removing a part of the p-type semiconductor layer 12, similarly to the ridge 20. That is, the p-type contact layer 19, the p-type AlInGaN cladding layer 18, and the p-type InGaN guide layer 17 are partially removed by etching to form a base portion 31 having a substantially trapezoidal shape (mesa shape) in cross-sectional view. The thin film portion 32 includes insulating films 33 and 34 (an insulating layer 6 described later) formed on the surface of the base portion 31.

  Each receiving portion 30 is formed in a rectangular shape in plan view in this embodiment. Each receiving portion 30 has a length in the width direction (resonator width direction; a-axis direction in this embodiment) perpendicular to the longitudinal direction of the ridge 20 (resonator length direction; c-axis direction in this embodiment). It is formed larger than the width of 20. For example, the width of the ridge 20 is about 2.5 μm, whereas the length of the receiving portion 30 in the width direction may be several tens μm to several hundreds μm. Each receiving portion 30 is formed so that the length in the direction parallel to the ridge 20 is sufficiently shorter than the length of the ridge 20 (resonator length). For example, the length of the ridge 20 may be about 600 μm, while the length of the receiving portion 30 in the resonator length direction may be about several tens of μm. Further, each receiving portion 30 is arranged at a predetermined distance from the ridge 20 along the width direction. The distance between the center of the ridge 20 in the width direction and the edge of the receiving portion 30 on the ridge 20 side may be about several μm to several tens of μm.

  The group III nitride semiconductor multilayer structure 2 has a pair of end surfaces 21 and 22 (cleavage surfaces) formed of mirror surfaces formed by cleavage at both longitudinal ends of the ridge 20. The pair of end faces 21 and 22 are parallel to each other, and in this embodiment, both are perpendicular to the c-axis (that is, c-plane). Thus, the n-type InGaN guide layer 15, the light emitting layer 10 and the p-type InGaN guide layer 17 form a Fabry-Perot resonator having the end faces 21 and 22 as laser resonance surfaces. That is, the light generated in the light emitting layer 10 is amplified by stimulated emission while reciprocating between the laser resonance surfaces 21 and 22. A part of the amplified light is extracted from the laser resonance surfaces 21 and 22 as laser light to the outside of the device.

  In the laser resonance surfaces 21 and 22, end face processing marks 8 resulting from scribing when the laser resonance surfaces 21 and 22 are formed by cleaving are formed over the entire width direction in the lower edge region on the back surface side. The lower edge region is a region connected to the back surface of the semiconductor multilayer structure including the substrate 1 and the group III nitride semiconductor multilayer structure 2. The width direction is a direction parallel to the crystal growth surface of the group III nitride semiconductor multilayer structure 2 and perpendicular to the longitudinal direction of the ridge 20 (resonator width direction).

  The semiconductor multilayer structure including the substrate 1 and the group III nitride semiconductor multilayer structure 2 has a pair of side surfaces 25 parallel to the ridge 20. On these pair of side surfaces 25, side surface processing traces 28 resulting from scribing when the semiconductor laminated structure is cleaved and divided from the wafer as the original substrate are formed over the entire length direction. The longitudinal direction is a direction (resonator length direction) parallel to the longitudinal direction of the ridge 20. When the scribe processing is performed from the back side, a side processing mark 28 is formed in the lower edge region of the side surface 25 as shown in FIG. Further, when the scribing process is performed from the surface side, as shown in FIG. 10B, a side surface processing mark 38 is formed in the upper edge region of the side surface 25. The upper edge region is a region continuous with the surface of the semiconductor multilayer structure (the surface on the ridge 20 side).

The n-side electrode 3 is made of, for example, Al and is ohmically connected to the substrate 1. The p-side ohmic electrode 4A is made of, for example, Pt and is ohmic-connected to the p-type contact layer 19. Insulation covering the exposed surfaces of the p-type InGaN guide layer 17 and the p-type AlInGaN cladding layer 18 so that the p-side ohmic electrode 4A contacts only the p-type GaN contact layer 19 on the top surface (band-like contact region) of the ridge 20 Layer 6 is provided. As a result, current can be concentrated on the ridge 20, so that efficient laser oscillation is possible. Further, since the surface of the ridge 20 is protected by covering the region except for the contact portion with the p-side ohmic electrode 4A with the insulating layer 6, the lateral light confinement can be moderated to facilitate the control. In addition, leakage current from the side surface can be prevented. The insulating layer 6 can be made of an insulating material having a refractive index larger than 1, for example, SiO ₂ or ZrO ₂ . The p-side pad electrode 4B is made of, for example, Ti / Au.

  The insulating layer 6 covers the surface and side surfaces of the receiving portion 30, and a part of the insulating layer 6 is an insulating film 34 that constitutes the thin film portion 32. On the other hand, the p-side ohmic electrode 4 </ b> A is formed in a pattern that exposes the receiving portion 30. More specifically, a predetermined interval is provided between the receiving portion 30 and the peripheral edge of the p-side ohmic electrode 4A. This interval may be about 10 μm, for example.

  The p-side ohmic electrode 4A is in contact with the top surface of the ridge 20, while the receiving portion 30 has a thin film portion 32 in which insulating films 33 and 34 are stacked on a base portion 31 that is almost the same height as the ridge 20. It has a structure. The thickness of the thin film portion 32 is equal to or greater than the thickness of the p-side ohmic electrode 4A. Therefore, the height of the surface of the receiving portion 30 (the distance from the surface of the group III nitride semiconductor multilayer structure 2) is equal to or higher than the surface of the p-side ohmic electrode 4A on the ridge 20. As a result, the ridge 20 can be protected because the ridge 20 does not receive a large external stress from the blade for cleavage in a dividing step (break step) described later.

The laser resonance surfaces 21 and 22 are covered with insulating films 23 and 24 (not shown in FIG. 1), respectively. The laser resonance surface 21 is a + c-axis side end surface, and the laser resonance surface 22 is a −c-axis side end surface. That is, the crystal plane of the laser resonance surface 21 is a + c plane, and the crystal plane of the laser resonance plane 22 is a −c plane. The insulating film 23 formed so as to cover the laser resonance surface 21 which is the + c plane is made of, for example, a single film of ZrO ₂ . On the other hand, the insulating film 24 formed on the laser resonance surface 22 that is the −c plane is composed of, for example, a multiple reflection film in which an SiO ₂ film and a ZrO ₂ film are alternately and repeatedly stacked a plurality of times. The ZrO ₂ single film constituting the insulating film 23 has a thickness of λ / 2n ₁ (where λ is the emission wavelength of the light emitting layer 10 and n ₁ is the refractive index of ZrO ₂ ). On the other hand, multiple reflection film constituting the insulating film 24, for example, a SiO ₂ film with a thickness of lambda / 4n ₂ (provided that _{n 2} is the refractive index of SiO _2), and a ZrO ₂ film with a thickness of lambda / 4n ₁ It has a laminated structure.

  With such a structure, the reflectance at the + c-axis side laser resonance surface 21 is small, and the reflectance at the −c-axis side laser resonance surface 22 is large. More specifically, for example, the reflectance of the + c-axis side laser resonance surface 21 is about 20%, and the reflectance of the −c-axis side laser resonance surface 22 is about 99.5% (almost 100%). Therefore, a larger laser output is emitted from the + c-axis side laser resonance surface 21. That is, in the semiconductor laser element 70, the + c-axis side laser resonance surface 21 is a laser emission end surface.

  With such a configuration, the n-side electrode 3 and the p-side electrode 4 are connected to a power source, and electrons and holes are injected from the n-type semiconductor layer 11 and the p-type semiconductor layer 12 into the light-emitting layer 10, thereby 10 can cause recombination of electrons and holes to generate light having a wavelength of 450 nm to 550 nm. This light is amplified by stimulated emission while reciprocating between the laser resonance surfaces 21 and 22 along the guide layers 15 and 16. And more laser output is taken out from the laser resonance surface 21 which is a laser emission end face.

Next, a method for manufacturing the semiconductor laser element 70 will be described.
In order to manufacture the semiconductor laser device 70, first, as schematically shown in FIG. 4, a semiconductor laser is formed on a wafer 5 which is a base substrate constituting a group III nitride semiconductor substrate 1 made of a GaN single crystal substrate. A plurality of individual elements 80 (semiconductor laser element regions) constituting the elements 70 are arranged in a matrix.

More specifically, the n-type semiconductor layer 11, the light emitting layer 10 and the p-type semiconductor layer 12 are epitaxially grown on the wafer 5 (in the state of a GaN single crystal substrate), thereby obtaining a group III nitride semiconductor multilayer structure 2 Is formed.
After the group III nitride semiconductor multilayer structure 2 is formed, the ridge 20 and the base portion 31 (a part of the receiving portion 30) are formed by dry etching, for example. Prior to this dry etching, an insulating film 33 (for example, a silicon oxide film) is selectively formed as a hard mask for dry etching in the formation region of the ridge 20 and the base portion 31. This insulating film 33 is selectively removed after dry etching. Specifically, the insulating film 33 is left on the base portion 31, and the insulating film 33 on the top surface of the ridge 20 is removed. Thus, the first insulating film 33 constituting the thin film portion 32 is formed on the base portion 31, while the top surface of the ridge 20 is exposed.

Next, after an insulating layer 6 made of, for example, silicon oxide is formed on the entire surface, the insulating layer 6 on the top surface of the ridge 20 is removed by etching. As a result, the second insulating film 34 (insulating layer 6) is formed on the insulating film 33 in the base portion 31.
Thereafter, the p-side ohmic electrode 4A, the p-side pad electrode 4B, and the n-side electrode 3 are formed. The p-side ohmic electrode 4A and the p-side pad electrode 4B are formed by patterning except for the receiving portion 30 and its peripheral region. As a result, the p-side ohmic electrode 4A and the p-side pad electrode 4B do not cover the receiving part 30 at all, and the periphery of the p-side electrode 4 is located at a distance from the receiving part 30. The p-side electrode 4 can be formed by, for example, resistance heating or a metal vapor deposition apparatus using an electron beam.

In this way, the wafer 5 in which a plurality of individual elements 80 are formed is obtained. If necessary, prior to the formation of the n-side electrode 3, a grinding / polishing process (for example, chemical mechanical polishing) is performed from the back side thereof in order to reduce the thickness of the wafer 5.
Each individual element 80 is formed in each rectangular area defined by a grid-like cutting line 7 (virtual line) virtually on the wafer 5. The cutting line 7 has an end surface cutting line 7a along the a axis (along the c surface) and a side surface cutting line 7b along the c axis (along the a surface).

Along the cutting line 7, the wafer 5 is divided into individual elements 80. That is, the individual element 80 is cut out by cleaving the wafer 5 along the cutting line 7.
Next, a method for dividing the wafer 5 into the individual elements 80 will be specifically described.
5A, 5B and 5C are schematic perspective views for explaining an outline of a procedure for dividing the wafer 5 into the individual elements 80. FIG. The wafer 5 is first cleaved along an end face cutting line 7a orthogonal to the resonator length direction (c-axis direction) (that is, parallel to the c-plane). This is hereinafter referred to as “primary cleavage”. By this primary cleavage, a plurality of bar-like bodies 90 shown in FIG. 5B are obtained. Both side surfaces 91 of each bar-shaped body 90 are crystal planes that become the laser resonance surfaces 21 and 22. On the side surface 91 of the bar-shaped body 90, the above-described insulating films 23 and 24 (end surface coating films for adjusting the reflectance, see FIG. 2) are formed.

Next, each bar-like body 90 is cut along a side cut line 7b parallel to the resonator length direction (c-axis direction). This is hereinafter referred to as “secondary cleavage”. By this secondary cleavage, as shown in FIG. 5C, the bar-like body 90 is divided for each individual element 80, and a plurality of chips are obtained.
FIG. 6 is a partially enlarged plan view for explaining the arrangement of the p-side electrode 4 and the receiving portion 30 on the surface of the wafer 5. A plurality of ridges 20 are formed in a stripe shape on the wafer 5. That is, the plurality of ridges 20 are formed in parallel to each other with a certain interval. Each ridge 20 is formed to pass through a plurality of individual elements 80 aligned in one direction. An end face cutting line 7 a is set along a direction orthogonal to each ridge 20. The end face cutting lines 7 a are set along the direction parallel to the ridge 20 (resonator length direction) at intervals equal to the resonator length.

  On both sides of each ridge stripe 20, a receiving portion 30 having a substantially rectangular shape in plan view is formed in a region in the vicinity of the end face cutting line 7a so as to straddle the end face cutting line 7a. On the other hand, the side surface cutting line 7 b is set in parallel with the ridge 20 at an intermediate position substantially equidistant from the adjacent ridges 20. The receiving part 30 is formed over the region straddling the side cutting line 7b. That is, on the surface of the wafer 5 before cutting, the four receiving portions 30 respectively belonging to the four individual elements 80 sharing the intersection of the end surface cutting line 7a and the side surface cutting line 7b are integrated.

  The p-side ohmic electrode 4 </ b> A is formed over the entire top surface of the ridge 20. In the region other than the top surface of the ridge 20, the p-side electrode 4 is formed in a band-like pattern in which the width direction peripheral edge is disposed at a position retracted by a predetermined distance from the side surface cutting line 7b. Further, the p-side electrode 4 is formed in a narrow strip pattern in a region corresponding to the receiving portion 30 in the longitudinal direction of the ridge 20, and avoids the receiving portion 30. More specifically, in this region, the p-side ohmic electrode 4A is formed only near the top surface of the ridge 20, and the p-side pad electrode 4B is not formed.

  FIG. 7A is a bottom view showing a first formation pattern example of the n-side electrode 3. In this example, the n-side electrode 3 is formed in a rectangular pattern in each of a plurality of rectangular areas defined by the cutting lines 7a and 7b. Each n-side electrode 3 has a peripheral edge that is set back by a predetermined distance from both the end face cutting line 7a and the side face cutting line 7b. More specifically, each n-side electrode 3 corresponds to the end surface receding portion 3 a that recedes from the end surface cutting line 7 a corresponding to the laser resonance surfaces 21 and 22 of the semiconductor laser element 70 and the side surface 25 of the semiconductor laser element 70. The side surface retreat part 3b which opposes the side surface cutting line 7b to be performed is provided in the periphery. The end face receding part 3a is formed in a straight line parallel to the end face cutting line 7a, and the side face receding part 3b is formed in a straight line parallel to the side face cutting line 7b. Therefore, the portion where the plurality of n-side electrodes 3 are not formed forms a thin linear region that matches the cutting lines 7a and 7b. Therefore, processing necessary when cutting the wafer 5 can be performed using the linear region as a mark.

  FIG. 7B is a bottom view illustrating a second formation pattern example of the n-side electrode 3. In this example, the n-side electrode 3 is formed in a strip pattern in each of a plurality of strip regions defined by the end face cutting lines 7a. The n-side electrode 3 in this example is not separated by the side surface cutting line 7b. Each n-side electrode 3 has an end face receding portion 3 c that is receded by a predetermined distance from the end face cutting line 7 a corresponding to the laser resonance surfaces 21 and 22 of the semiconductor laser element 70. The end surface receding portion 3c is formed in a straight line parallel to the end surface cutting line 7a. Therefore, the portion where the plurality of n-side electrodes 3 are not formed forms a thin linear region that matches the end face cutting line 7a. Therefore, processing necessary when cutting the wafer 5 can be performed using the linear region as a mark.

  FIG. 7C is a bottom view showing a third formation pattern example of the n-side electrode 3. In this example, the n-side electrode 3 has a pair of notches 37 at both ends of each end face cutting line 7a. The notch 37 has a shape that recedes inward of the n-side electrode 3. The n-side electrode 3 in this example is not separated by the cutting lines 7a and 7b. A straight line passing through a pair of notches 37 facing along the direction orthogonal to the ridge 20 is aligned with the end face cutting line 7a. Therefore, using the notch 37 as a mark, processing necessary for cutting the wafer 5 can be performed.

8A and 8B are explanatory diagrams for explaining a specific example of primary cleavage. The primary cleavage includes a back surface scribing process shown in FIG. 8A and a front surface breaking process shown in FIG. 8B.
As shown in FIG. 8A, the back surface scribing step is a step of performing a scribing process from the back surface of the wafer 5 along the end surface cutting line 7a. The front surface of the wafer 5 is a main surface on which the ridge 20 is formed, and the opposite main surface is the back surface of the wafer 5. The scribe processing may be performed by a laser processing machine (laser scriber) or may be performed by a diamond scriber. By the scribing process, a continuous end surface processing mark 8 is formed on the back surface side of the wafer 5 along the end surface cutting line 7a. This end face processing mark 8 is continuous over the entire width direction of the laser resonance surfaces 21 and 22 in each individual element 80 (semiconductor laser element 70). The end surface processing mark 8 may have a groove shape (divided guide groove). The depth of the scribing process is 10% or more of the thickness of the wafer 5 in the end face cutting line 7a (more precisely, the thickness of the semiconductor multilayer structure including the substrate 1 and the group III nitride semiconductor multilayer structure 2). preferable. Therefore, the end face processing mark 8 is formed in the lower edge region extending from the back surface of the wafer 5 (the substrate 1 and the group III nitride semiconductor multilayer structure 2) to a depth range of 10% or more of the thickness. Become.

  As shown in FIG. 8B, the surface breaking step is a step of applying an external force to the wafer 5 by applying a blade 9 (for example, a ceramic blade) along the end surface cutting line 7 a from the surface side of the wafer 5. As a result, the wafer 5 is cleaved along a crystal plane perpendicular to the main surface of the wafer 5 along the end face processing marks 8. In this way, the laser resonance surfaces 21 and 22 composed of cleavage planes perpendicular to the ridge 20 are obtained. These laser resonance surfaces 21 and 22 respectively have end face processing marks 8 in the lower edge region on the back surface side. The end surface processing mark 8 may have, for example, a shape (partial groove shape) obtained by halving a linear groove along the longitudinal direction.

  When the blade 9 is applied to the wafer 5, the edge of the blade 9 abuts on the receiving portion 30, and most of the external force from the plate 9 is received by the receiving portion 30. This is because the height of the receiving portion 30 is equal to or higher than the height of the ridge 20 (more precisely, the height of the p-side ohmic electrode 4A formed on the top surface), and in the direction along the blade 9 of the receiving portion 30. This is because the length is larger than the width of the ridge 20. Therefore, when an external force is applied to the wafer 5 by the blade 9, most (or all) of the external force is received by the receiving portion 30 and hardly (or not) acts on the ridge 20. Therefore, the braking process by the blade 9 can be performed while protecting the ridge 20 from external force. Therefore, since the primary cleavage can be performed without damaging the waveguide, the yield is improved.

9A and 9B are explanatory diagrams for describing a specific example of secondary cleavage. The secondary cleavage according to this specific example includes a back surface scribe process shown in FIG. 9A and a front surface breaking process shown in FIG. 9B.
As shown in FIG. 9A, the back surface scribing step is a step of performing a scribing process from the back surface of the wafer 5 along the side surface cutting line 7b. The scribing process is preferably performed before the primary cleavage braking process, but may be performed before or after the primary cleavage scribing process (scribing process along the end surface cutting line 7a). The scribe processing may be performed by a laser processing machine (laser scriber) or a diamond scriber, but the same processing method as the primary cleavage scribe processing is preferable. By the scribing process, a side surface processing mark 28 is formed on the back surface side of the wafer 5 along the side surface cutting line 7b. The side surface processing mark 28 may have a groove shape (divided guide groove). The depth of the scribing process is the thickness of the wafer 5 in the side surface cutting line 7b (more precisely, the total thickness of the substrate 1 and the group III nitride semiconductor multilayer structure 2 in a portion other than the ridge 20 and the receiving portion 30). It is preferable that it is 80% or more. Therefore, the side surface processing trace 28 is in the lower edge region extending from the back surface of the wafer 5 (the semiconductor multilayer structure including the substrate 1 and the group III nitride semiconductor multilayer structure 2) to a depth range of 80% or more of the thickness. Will be formed.

  As shown in FIG. 9B, the surface braking process is performed after the braking process in the primary cleavage. Therefore, in the surface breaking process in the secondary cleavage, the blade 29 (for example, a ceramic blade) is applied along the side surface cutting line 7b from the surface side of the bar-shaped body 80 obtained by the primary cleavage, and the wafer 5 (bar-shaped). This is a step of applying an external force to the body 80). As a result, the wafer 5 (bar-shaped body 80) is cleaved along a side surface processing mark 28 with a crystal plane perpendicular to the main surface of the wafer 5. Thus, the side surface 25 parallel to the ridge 20 is formed. Each of the side surfaces 25 has a side processing mark 28 in a lower edge region on the back surface side. The side surface processing mark 28 may have, for example, a shape (partial groove shape) obtained by halving a linear groove along the longitudinal direction.

  When the blade 29 is applied to the wafer 5 (bar-shaped body 80), the edge of the blade 29 comes into contact with the receiving portion 30. This is because the height of the receiving portion 30 is higher than the height of the p-side ohmic electrode 4A. Therefore, when an external force is applied to the wafer 5 (bar-shaped body 80) by the blade 29, the external force is first received by the receiving portion 30. Therefore, the cleavage starts from the receiving portion 30 and the cleavage range is extended to the entire resonator length direction of the bar-shaped body 80. Thereby, the cleavage regarding the side surface parallel to the ridge 20 can also be performed stably.

10A and 10B are explanatory diagrams for explaining another specific example of the secondary cleavage. The secondary cleavage according to this specific example includes a front surface scribing process shown in FIG. 10A and a back surface braking process shown in FIG. 10B.
The surface scribing step is a step of performing a scribing process from the surface of the wafer 5 along the side surface cutting line 7b as shown in FIG. 10A. The scribing process is preferably performed before the primary cleavage braking process, but may be performed before or after the primary cleavage scribing process (scribing process along the end surface cutting line 7a). The scribe processing may be performed by a laser processing machine (laser scriber) or may be performed by a diamond scriber. By the scribing process, side surface processing marks 38 are formed on the front surface side of the wafer 5 along the side surface cutting line 7b. The side surface processing mark 38 may have a groove shape (divided guide groove). The depth of the scribing process is the thickness of the wafer 5 in the side surface cutting line 7b (more precisely, the total thickness of the substrate 1 and the group III nitride semiconductor multilayer structure 2 in a portion other than the ridge 20 and the receiving portion 30). It is preferable that it is 80% or more. Therefore, the side surface processing trace 38 is in the upper edge region extending from the surface of the wafer 5 (the semiconductor laminated structure including the substrate 1 and the group III nitride semiconductor laminated structure 2) to a depth range of 80% or more of the thickness. Will be formed.

  As shown in FIG. 10B, the back surface braking process is performed after the braking process in the primary cleavage. Therefore, the back surface breaking process in the secondary cleavage is performed by applying the blade 39 (for example, a ceramic blade) along the side surface cutting line 7b from the back surface side of the bar-like body 80 obtained by the primary cleavage, and the wafer 5 (bar shape). This is a step of applying an external force to the body 80). As a result, the wafer 5 (bar-shaped body 80) is cleaved along a side surface processing mark 38 with a crystal plane perpendicular to the main surface of the wafer 5. Thus, the side surface 25 parallel to the ridge 20 is formed. These side surfaces 25 respectively have side surface processing marks 38 in the upper edge region on the back surface side. The side surface processing mark 38 may have, for example, a shape (partial groove shape) obtained by halving a linear groove along the longitudinal direction.

  FIG. 11A shows the result of measuring the threshold current Ith for a plurality of samples (semiconductor laser elements) according to a comparative example in which primary cleavage was performed in the scribing process from the front surface side and the braking process from the back surface side of the wafer 5. It is a histogram which shows. In this case, the scribing process was performed with a perforated discontinuous pattern cut along the edge cutting line 7 a along the ridge 20 so as not to damage the ridge 20. On the other hand, FIG. 11B shows the measurement of the threshold current Ith for a plurality of samples (semiconductor laser devices) according to an example in which primary cleaving was performed in the scribing process from the back surface side and the braking process from the front surface side of the wafer 5. It is a histogram which shows the result. As described above, the scribing process was performed in a continuous line along the end face cutting line 7a. From the comparison between FIG. 11A and FIG. 11B, it can be seen that the threshold current Ith was reduced by about 40% in the example compared to the comparative example.

FIG. 12A is a histogram showing the result of measuring the slope efficiency SE for a plurality of samples according to the above-described comparative example, and FIG. 12B is a histogram showing the result of measuring the slope efficiency SE for a plurality of samples according to the above-described example. is there. From these comparisons, it can be seen that the slope efficiency SE of the example increased by about 40% compared to the comparative example.
FIG. 13A is a histogram showing the result of measuring the operating current Iop for a plurality of samples according to the above-described comparative example, and FIG. 13B is a histogram showing the result of measuring the operating current Iop for a plurality of samples according to the above-described embodiment. is there. From these comparisons, it can be seen that the operating current Iop was reduced by about 40% in the example compared to the comparative example.

  As described above, in the semiconductor laser device 70 of this embodiment, the end surface processing in which the semiconductor multilayer structure including the substrate 1 and the group III nitride semiconductor multilayer structure 2 is formed in the lower edge region of the laser resonance surfaces 21 and 22 is performed. It has a mark 8. That is, in this semiconductor laser device 70, processing is performed from the back surface side of the semiconductor multilayer structure to form an end surface processing mark 8, and the original substrate is cleaved by applying an external force by applying the blade 9 from the front surface side of the semiconductor multilayer structure. The laser resonant surfaces 21 and 22 can be formed by the cleaved surfaces. Since the end surface processing mark 8 is formed on the back surface side where the ridge 20 is not formed, it is not necessary to form the discontinuous pattern having a discontinuous portion in the vicinity of the ridge 20, so that it can be formed in a continuous pattern. Therefore, since the cleavage by the external force applied from the surface side can be performed stably, a good cleavage surface can be obtained. Thereby, the semiconductor laser device 70 having excellent characteristics can be provided. Specifically, a reduction in threshold current, an increase in slope efficiency, and a reduction in operating current can be achieved.

  Further, in the semiconductor laser element 70, the receiving portion 30 is disposed at a position away from the surface of the group III nitride semiconductor multilayer structure 2 in the width direction perpendicular to the longitudinal direction of the ridge 20, It has a height equal to or greater than that of the ridge 20, has a length in the width direction larger than the width of the ridge 20, and is spaced from the p-side ohmic electrode 4A. Thereby, when the blade 9 is applied to the surface side of the wafer 5 and an external force is applied, most or all of the external force can be applied to the receiving portion 30. As a result, it is possible to divide (cleave) the wafer 5 which is the original substrate while protecting the ridge 20, and to form the laser resonance surfaces 21 and 22 each having a good cleavage surface. In addition, since the receiving portion 30 has a length in the width direction that is larger than the width of the ridge 20, it can reliably receive an external force. In addition, since the receiving portion 30 is formed at a distance from the p-side ohmic electrode 4A, the p-side ohmic electrode 4A is not damaged when receiving an external force. Thereby, it does not cause troubles such as current leakage.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the receiving portions 30 are provided on both sides of the ridge 20 so that the blade 9 hardly exerts an external force on the ridge 20 when the wafer 5 is divided along the end face cutting line 7a. . However, when the height of the ridge 20 is not so high and the possibility that the ridge 20 is damaged is low, the receiving portion 30 may be omitted. The composition of each layer constituting group III nitride semiconductor multilayer structure 2 is only an example, and may be changed according to the required specifications. Furthermore, in the above-described embodiment, the example using the group III nitride semiconductor multilayer structure 2 with the m-plane as the growth main surface has been described. However, the a-plane which is another nonpolar plane, the c-plane which is a polar plane, or The semiconductor laser diode structure may be constituted by a group III nitride semiconductor multilayer structure having a semipolar plane as a main surface (crystal growth surface). According to the present invention, it is possible to provide a semiconductor laser device having a laser resonance surface composed of a good cleavage plane, regardless of which crystal plane is the crystal growth surface.

  In addition, various design changes can be made within the scope of matters described in the claims.

1 Substrate (GaN single crystal substrate)
2 Group III nitride semiconductor laminated structure 3 n-side electrode 3a end face recess 3b side recess 3c end face recess 4 p side electrode 4A p side ohmic electrode 4B p side pad electrode 5 wafer 6 insulating layer 7 cutting line 7a end cutting line 7b Side cut line 8 End face processing mark 9 Blade 10 Light emitting layer 11 n-type semiconductor layer 12 p-type semiconductor layer 13 n-type GaN contact layer 14 n-type AlInGaN clad layer 15 n-type InGaN guide layer 16 p-type AlGaN electron block layer 17 p Type InGaN guide layer 18 p-type AlInGaN cladding layer 19 p-type GaN contact layer 20 ridge 21 laser resonance surface 22 laser resonance surface 23 insulating film 24 insulating film 25 side surface 28 side surface processing trace 29 blade 30 receiving portion 31 base portion 32 thin film portion 33 Insulating film 34 Insulating film 37 Notch 3 Side machining mark 39 blade 70 semiconductor laser element 80 discrete element (semiconductor laser element region)
90 Bar-shaped body 91 Side surface of the bar-shaped body

Claims (17)

A light-emitting layer, a p-type guide layer disposed on one side of the light-emitting layer, an n-type guide layer disposed on the other side of the light-emitting layer, and the p-type guide layer opposite to the light-emitting layer Including a semiconductor multilayer structure having a p-type cladding layer disposed and an n-type cladding layer disposed on a side opposite to the light emitting layer of the n-type guide layer,
The semiconductor laminated structure includes a linear ridge formed on the surface side, a pair of laser resonance surfaces formed at both ends in the longitudinal direction of the ridge so as to be orthogonal to the ridge, and the pair of laser resonance surfaces Including an end face processing mark formed in a lower edge region connected to the back surface of the semiconductor multilayer structure,
Semiconductor laser element.   The semiconductor laser device according to claim 1, wherein the end face processing trace is continuous over the entire width direction of the semiconductor multilayer structure.   3. The semiconductor laser device according to claim 1, wherein a thickness of the end face processing trace is 10% or more of a thickness of the semiconductor multilayer structure. The semiconductor stacked structure is made of a group III nitride semiconductor having an m-plane as a crystal growth surface,
The semiconductor laser device according to claim 1, wherein the laser resonance surface is a c-plane. A surface electrode formed on the surface of the semiconductor multilayer structure;
The semiconductor multilayer structure is disposed at a position spaced apart in the width direction perpendicular to the longitudinal direction of the ridge on the surface of the semiconductor multilayer structure, and has a height equal to or greater than the ridge, and the length in the width direction of the ridge The semiconductor laser device according to claim 1, further comprising a receiving portion that is larger than a width and is spaced from the surface electrode.   6. The semiconductor laser device according to claim 5, further comprising a back surface electrode formed on the back surface of the semiconductor multilayer structure and having an end surface receding portion that recedes inwardly from the pair of laser resonance surfaces.   The semiconductor stacked structure further includes a pair of side surfaces parallel to the longitudinal direction of the ridge, and a side surface processing mark formed in a lower edge region that is continuous with the back surface of the semiconductor stacked structure on the pair of side surfaces. The semiconductor laser element as described in any one of -6.   8. The semiconductor laser device according to claim 7, wherein a back surface electrode formed on the back surface of the semiconductor multilayer structure has a side surface receding portion that recedes inwardly from the pair of side surfaces.   2. The semiconductor stacked structure further includes a pair of side surfaces parallel to a longitudinal direction of the ridge, and a side surface processing mark formed in an upper edge region connected to the surface of the semiconductor stacked structure on the pair of side surfaces. The semiconductor laser element as described in any one of -6.   10. The semiconductor laser device according to claim 7, wherein the side surface processing trace is continuous over the entire region in the longitudinal direction of the semiconductor multilayer structure. 11.   The semiconductor laser device according to any one of claims 7 to 10, wherein a thickness of the side surface processing trace is 80% or more of the semiconductor multilayer structure. A step of preparing an original substrate having a plurality of ridges formed in stripes so that a plurality of semiconductor laser element regions are arranged in a matrix and pass through a plurality of semiconductor laser element regions aligned in one direction;
A scribing step for performing scribing on the original substrate along a cutting line set along a boundary line of the plurality of semiconductor laser element regions from the back surface opposite to the surface on which the ridge is formed;
And a dividing step of applying a blade to the original substrate along the cutting line from the surface of the original substrate, and dividing the original substrate along the cutting line.   The method of manufacturing a semiconductor laser device according to claim 12, wherein the scribing includes a step of scribing the original substrate so as to be continuous along the cutting line. The cutting line includes an end face cutting line set along a direction orthogonal to the ridge,
14. The method of manufacturing a semiconductor laser device according to claim 12, wherein a laser resonance surface comprising a cleavage plane orthogonal to the ridge is formed by performing the dividing step along the end face cutting line. The cutting line includes a side cutting line set along the longitudinal direction of the ridge;
The method of manufacturing a semiconductor laser device according to claim 12, wherein a side surface parallel to the ridge is formed by performing the dividing step along the side surface cutting line. From the surface of the original substrate, a step of subjecting the original substrate to side scribing along a side cutting line set parallel to the longitudinal direction of the ridge along the boundaries of the plurality of semiconductor laser elements;
The semiconductor laser device according to claim 14, further comprising: applying a blade to the original substrate along the side surface cutting line from the back surface of the original substrate, and dividing the original substrate along the side surface cutting line. Manufacturing method.   The method of manufacturing a semiconductor laser device according to claim 16, wherein the side scribing step includes a step of scribing the original substrate so as to continue along the side cutting line.

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