JP2010003806A - Nitride compound semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a far-field pattern (FFP) of which the Gaussian shape is good even in high output power operation of the class exceeding 200 mW, and to obtain long term reliability with good yield ratio. <P>SOLUTION: A nitride compound semiconductor device is formed on a substrate 1A, and is equipped with a laminated structure 40 including an n-type nitride compound semiconductor layer, a multiple quantum well active layer 13, and a p-type nitride compound semiconductor layer. The laminated structure 40 has a resonant plane constituted by a ridge stripe region 18 formed in the upper part of the laminated structure 40, and an end face formed perpendicular to the direction to which the ridge stripe region 18 extends, in the laminated structure 40, a level difference portion 19a in which the end face is engraved in the direction to which the ridge stripe region 18 extends is formed. The end portion of the ridge stripe region side in the level difference portion 19a contacts with the ridge stripe region 18. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nitride compound semiconductor device, and more particularly to a nitride compound semiconductor device having a ridge stripe region.

The band gap energy of a nitride compound semiconductor whose composition is represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). Can have a size corresponding to blue light or ultraviolet light by adjusting the composition ratio of each element. For this reason, gallium nitride (GaN) -based light emitting devices such as semiconductor laser devices having a nitride compound semiconductor in the active layer have been actively studied.

  A GaN-based semiconductor laser element is important as a light source for a next-generation DVD (Digital Versatile Disc) represented by a Blu-ray disc. In order to realize further high-speed recording operation for the next-generation DVD, it is essential to further increase the output of the GaN-based semiconductor laser element. However, it is difficult to stably operate and maintain a light output exceeding 200 mW in a stable light emission shape, that is, a far field pattern (FFP). In addition, in a DVD set, since a single GaN-based semiconductor laser element is used for both light sources for recording and reproduction, it is necessary to simultaneously realize high output and low noise.

  In general, in a GaN-based semiconductor laser element, the injection current constriction in the direction parallel to the substrate surface uses a ridge structure formed by etching the upper portion of the GaN-based semiconductor layer in a stripe shape. Therefore, the light confinement structure in the direction parallel to the substrate is an actual refractive index waveguide structure. For this reason, laser light propagating in the stripe-shaped optical waveguide region is likely to leak in a direction parallel to the substrate, and this leaked light (stray light) is multiple-reflected in the direction of the laser resonator and leaks from the exit end face. Interferes with light. As a result, the ripple is likely to be mixed in the far-field image of the GaN-based semiconductor laser element, and often deviates from the Gaussian shape.

  When such a laser element is used in a DVD set, a reduction in effective light usage causes a load on the laser element to further increase output, increase noise, and cause a reading error.

  As a method for obtaining a good FFP shape in a GaN-based semiconductor laser element, methods described in Patent Document 1 and Patent Document 2 are known.

  Patent Document 1 describes a method of suppressing ripples generated in an FFP by forming a plurality of recesses in the vicinity of an optical waveguide region on the output end face, and scattering and refracting stray light leaking outside the optical waveguide region. Yes.

  In Patent Document 2, a concave portion having a rough wall surface other than the bottom surface is formed in advance on the top of a substrate made of GaN, and the concave portion having the roughened wall surface is cleaved so as to be exposed on the end face of the resonator. Thus, there is described a method for suppressing ripples generated in the FFP by scattering and refracting stray light leaking out of the optical waveguide region in the recesses.

  Here, FIG. 10 shows a crystal structure of a nitride compound semiconductor. As shown in FIG. 10, the nitride compound semiconductor has a hexagonal crystal structure. For this reason, when fabricating a semiconductor laser device in which the plane orientation of the upper surface of the element is the (0001) plane and the plane orientation of the resonator end face is the (1-100) plane (= M plane), both are perpendicular to these planes. Cleavage is likely to occur along the crystal plane that is inclined by 30 ° from the A plane instead of the (11-20) plane (= A plane). As a result, not only when cleaving along the A-plane, but also when cleaving along the M-plane to form the resonator end faces, the cleavage shift (end-face cracks) in a direction inclined by 60 ° from the M-plane. ) Occurs.

  For this reason, conventionally, it is very difficult to manufacture a nitride compound semiconductor element having a smooth resonator end face.

  By the way, when cleaving a semiconductor laser device formed on a gallium nitride (GaN) substrate used in recent years, a scribe groove is formed along the M plane from the side of the nitride compound semiconductor layer grown on the GaN substrate. Attempts have been made to facilitate cleavage by the formed scribe grooves. Patent Document 1 and Patent Document 2 described above also describe a method in which a scribe groove is linearly formed in a nitride compound semiconductor layer and then cleaved by braking or the like.

In the present specification, the negative sign attached to the index representing the crystal plane orientation and the crystal axis represents the inversion of one index following the sign for convenience.
Japanese Patent Laying-Open No. 2005-311308 JP 2006-287137 A

  However, it is difficult to stably obtain a good FFP shape when the semiconductor laser device according to the conventional example is operated at a high output such that the output exceeds 200 mW (hereinafter referred to as “over 200 mW class”). . This is because the above-mentioned Patent Document 1 and Patent Document 2 are separated from the optical waveguide in order to avoid applying damage such as crystal defects to the inside of the GaN crystal included in the optical waveguide region when the recess is formed. A recess is formed at the position. For this reason, at the time of high output operation exceeding 200 mW, the light density in the optical waveguide region and the vicinity thereof becomes very high, so that the effects of stray light scattering and refraction in the concave portion are weakened. In addition, the damage which arises at the time of recessed part formation is an etching damage in said patent document 1, and in patent document 2, it is the abnormal growth at the time of crystal growth, etc.

  Further, in Patent Document 2, since crystal growth on a processed substrate having a recess is required, it is difficult to stably form a recess having a desired shape due to a change in crystal growth conditions or the like. is there. Therefore, in the above conventional example, it is difficult to stably obtain a good FFP shape at the time of high output operation exceeding 200 mW.

  The present invention solves the above-mentioned conventional problems, and its main object is to obtain a far field image (FFP) having a good Gaussian shape even during high output operation exceeding 200 mW, and to obtain long-term reliability. There is to be able to get well.

  In order to achieve the above object, according to the present invention, a nitride compound semiconductor device is provided with a stepped portion so as to be in contact with a ridge stripe region in a laminated structure composed of a plurality of nitride compound semiconductors or not in contact with a ridge stripe region. A groove portion in contact with the step portion and the ridge stripe region is provided.

  Specifically, a first nitride compound semiconductor device according to the present invention includes a multilayer structure formed on a substrate and including an n-type nitride compound semiconductor layer, an active layer, and a p-type nitride compound semiconductor layer. The body has a ridge stripe region formed in the upper part of the laminated structure and a resonance surface composed of an end face formed in a direction perpendicular to the direction in which the ridge stripe region extends. The step portion is formed by carving the end face in the direction in which the ridge stripe region extends, and the end portion of the step portion on the ridge stripe region side is in contact with the ridge stripe region.

  According to the first nitride compound semiconductor device, since the step portion in contact with the ridge stripe region and the end portion is provided in the laminated structure, an FFP shape having a good Gaussian shape can be obtained even during high output operation exceeding 200 mW. Can do. Furthermore, by providing the stepped portion, it is possible to suppress leakage light from the ridge stripe region from leaking from the emission end face, so that noise can be reduced at the same time.

  In the first nitride compound semiconductor element, it is preferable that an end of the step portion on the ridge stripe region side is in contact with the resonance surface.

  In the first nitride compound semiconductor element, the end surface is preferably composed of an emitting end surface that emits laser light and a reflecting end surface that reflects the laser light, and the stepped portion is preferably provided on the emitting end surface side.

  In the first nitride compound semiconductor element, the step portion is preferably formed such that the distance between the side surface of the step portion and the resonance surface is larger in the vicinity of the ridge stripe region than in the other portions.

  In the first nitride compound semiconductor element, the side surface of the stepped portion is preferably covered with the first insulating film.

  In the first nitride compound semiconductor element, the side surface of the step portion is preferably covered with a light absorption film.

  In the first nitride compound semiconductor element, the ridge stripe region is preferably covered with a second insulating film formed so that a part of its upper surface is in contact with the resonance surface.

  In the first nitride compound semiconductor element, the end of the step portion on the ridge stripe region side is away from the resonance surface, and the laminated structure is formed with a groove portion spaced from the step portion and along the step portion. The end of the groove on the ridge stripe region side is preferably in contact with the ridge stripe region.

  A second nitride compound semiconductor device according to the present invention includes a stacked structure formed on a substrate and including an n-type nitride compound semiconductor layer, an active layer, and a p-type nitride compound semiconductor layer. The laminated structure has a ridge stripe region formed on the upper portion and a resonance surface composed of an end face formed in a direction perpendicular to a direction in which the ridge stripe region extends. A stepped portion engraved in the direction in which the stripe region extends is formed, the end of the stepped portion on the ridge stripe region side is away from the ridge stripe region, and the stacked structure is spaced from the stepped portion and is A groove portion is formed along the ridge stripe region, and an end of the groove portion on the ridge stripe region side is in contact with the ridge stripe region.

  According to the second nitride compound semiconductor element, since the stepped portion where the ridge stripe region and the end portion are in contact is provided in the laminated structure, an FFP shape having a favorable Gaussian shape can be obtained even during high output operation exceeding 200 mW. Can do. Further, in the laminated structure, a groove portion is formed at a distance from the step portion and along the step portion, and the end portion on the ridge stripe region side of the groove portion is in contact with the ridge stripe region. Since leakage light can be suppressed from leaking from the exit end face by the groove (stray light suppression groove), noise can be reduced at the same time.

  In the second nitride compound semiconductor element, it is preferable that an end of the step portion on the ridge stripe region side is in contact with the resonance surface.

  In the second nitride compound semiconductor element, the end face is preferably composed of an emission end face that emits laser light and a reflection end face that reflects the laser light, and the stepped portion is preferably provided on the emission end face side.

  In the second nitride compound semiconductor element, the side surface of the stepped portion is preferably covered with the first insulating film.

  In the second nitride compound semiconductor element, the side surface of the step portion is preferably covered with a light absorption film.

  In the second nitride compound semiconductor element, the ridge stripe region is preferably covered with a second insulating film formed so that a part of the upper surface thereof is in contact with the resonance surface.

  According to the nitride compound semiconductor device of the present invention, stray light can be suppressed even during a high output operation, and a good FFP shape can be obtained with a high yield.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1A shows a nitride compound semiconductor device according to the first embodiment of the present invention, which shows a planar configuration on the emission end face side of the semiconductor laser device, and FIG. 1B shows a line Ib-Ib in FIG. A cross-sectional structure is shown, and (c) shows a cross-sectional structure taken along line Ic-Ic in (a).

As shown in FIGS. 1A to 1C, the semiconductor laser device according to the first embodiment includes, for example, a substrate made of n-type gallium nitride (GaN) whose principal plane has a (0001) plane orientation. It is made of a nitride compound semiconductor represented by In _x Ga _y Al _z N (x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) formed on the main surface of 1A. A laminated structure 40 is provided.

  A ridge stripe region 18 that is an optical waveguide region is formed in the upper part of the laminated structure 40 in parallel to the <1-100> direction of the crystal axis, and is a plane perpendicular to the <1-100> direction (1- The (00) plane (M plane) is exposed as a resonance plane by cleavage.

  As a feature of the present invention, a stepped portion 19a in which the resonance surface is carved in the direction in which the ridge stripe region 18 extends is formed on at least the emission end face side of the mutually opposing resonance faces (only the emission end face is shown). ing. Further, the end of the step portion 19a on the ridge stripe region 18 side is in contact with the ridge stripe region 18 and the resonance surface.

Further, the exposed surface including the step portion 19 a in the laminated structure 40 is covered with the insulating film 20 made of silicon oxide (SiO ₂ ) except for the upper surface of the ridge stripe region 18.

Here, an example of the structure of the laminated structure 40 is shown. On the main surface of the substrate 1A, an n-type GaN layer 10 having a thickness of about 0.2 μm, an n-type cladding layer 11 made of n-type Al _0.03 Ga _0.97 N having a thickness of about 2.0 μm, First optical guide layer 12 made of n-type GaN having a thickness of about 150 nm, In _0.01 Ga _0.99 N layer having a thickness of about 9 nm, and In _0.08 Ga _0.92 having a thickness of about 3 nm A multiple quantum well active layer 13 composed of a quantum well (three layers) made of N and a barrier layer (two layers) made of In _0.01 Ga _0.99 N having a thickness of about 9 nm; An active layer protective layer 14 made of 70 nm of In _0.01 Ga _0.99 N, a cap layer 15 made of p-type Al _0.20 Ga _0.80 N having a thickness of about 10 nm, and a thickness of about _{0.2 mm} . A p-type cladding layer 16 made of 4 μm p-type Al _0.03 Ga _0.97 N; A p-type contact layer 17 made of p-type GaN having a thickness of about 0.1 μm is sequentially formed.

  Hereinafter, a method of manufacturing the semiconductor laser device configured as described above will be described.

  First, the process of forming the laminated structure 40 on the main surface of the wafer 1 will be described with reference to FIGS. 2 (a) and 2 (b). 2A and 2B are partial cross-sectional views, and the illustrated portion is actually only a part of the wafer 1 having a diameter of about 50 mm.

  As shown in FIG. 2A, a wafer 1 made of n-type GaN whose main surface has a (0001) plane orientation is prepared. Here, the cross section of the wafer 1 appearing in FIG. 2A is the (1-100) plane and is exposed by the primary cleavage. The <11-20> direction is on the plane of the drawing and is parallel to the (0001) plane, which is the plane orientation of the main surface of the wafer 1.

  Next, as shown in FIG. 2B, a laminated structure 40 made of a nitride compound semiconductor is formed on the main surface of the wafer 1.

First, a wafer 1 made of GaN is held on a susceptor in a reaction furnace in a metal-organic vapor phase epitaxy (MOVPE) apparatus. Subsequently, the temperature of the reaction furnace is raised to about 1000 ° C., and trimethylgallium (TMG) and ammonia (NH ₃ ) gases as raw material gases and hydrogen and nitrogen as carrier gases are simultaneously supplied. At the same time, silane (SiH ₄ ) gas is supplied as an n-type dopant to grow the n-type GaN layer 10 having a thickness of about 0.2 μm and an Si impurity concentration of about 5 × 10 ¹⁷ cm ⁻³ .

Thereafter, while also supplying trimethylaluminum (TMA) onto the n-type GaN layer 10, the n-type Al _0.03 Ga having a thickness of about 2.0 μm and an Si impurity concentration of about 5 × 10 ¹⁷ cm ⁻³ is used. _An n-type cladding layer 11 made of _0.97 N is grown. Thereafter, a first optical guide layer 12 made of n-type GaN having a thickness of about 150 nm and an Si impurity concentration of about 5 × 10 ¹⁷ cm ⁻³ is grown on the n-type cladding layer 11, and then the growth temperature is increased. The temperature is lowered to about 800 ° C., the carrier gas is changed to only nitrogen, and trimethylindium (TMI) and TMG are supplied to grow an In _0.01 Ga _0.99 N layer having a thickness of about 9 nm. To do. Further, a quantum well layer (three layers) made of In _0.08 Ga _0.92 N having a thickness of about 3 nm and an In _0.01 Ga _0.99 N barrier layer (two layers) having a thickness of about 9 nm are alternately arranged. The multiple quantum well active layer 13 is formed. Thereafter, an active layer protective layer 14 made of In _0.01 Ga _0.99 N having a thickness of about 70 nm is grown on the multiple quantum well active layer 13 to protect the surface of the multiple quantum well active layer 13. .

Next, the temperature in the reactor is again raised to about 1000 ° C., hydrogen is mixed into the carrier gas, and p-type dopant biscyclopentadienyl magnesium (Cp ₂ Mg) gas is supplied, A cap layer 15 made of p-type Al _0.20 Ga _0.80 N having a thickness of about 10 nm and an Mg impurity concentration of about 1 × 10 ²⁰ cm ⁻³ is grown on the active layer protective layer 14.

Next, the p-type cladding layer 16 made of p-type Al _0.03 Ga _0.97 N having a thickness of about 0.4 μm and an Mg impurity concentration of about 1 × 10 ²⁰ cm ⁻³ is formed on the cap layer 15. To grow.

Next, a p-type contact layer 17 made of p-type GaN having a thickness of about 0.1 μm and an Mg impurity concentration of about 1 × 10 ²¹ cm ⁻³ is grown on the p-type cladding layer 16.

  In the present invention, the specific configuration of the stacked structure 40 and the growth method of each of the semiconductor layers 10 to 17 are arbitrary, and the above configuration and growth method are merely examples.

  Next, after the laminated structure 40 is formed, a step of forming a ridge stripe region 18 having a width of about 1.2 μm for current confinement on the upper portion of the laminated structure 40 by dry etching, and the wafer 1 by dry etching. A step of forming the cleavage guide groove 19 constituting the stepped portion 19a in the cleavage region to be cleaved, a step of forming the insulating film 20 on the laminated structure 40 excluding the ridge stripe region 18 by sputtering, and a ridge stripe region by vacuum evaporation A step of forming a p-side electrode (contact electrode) on 18, a step of polishing the back surface of the wafer 1 to a thickness of about 80 μm, a step of forming an n-side electrode, and the like are sequentially performed. Here, a laminated film of palladium (Pd) and platinum (Pt) is used for the p-side electrode, and a laminated film made of titanium (Ti), platinum (Pt), and gold (Au) is used for the n-side electrode. Further, a wiring electrode made of titanium (Ti) / platinum (Pt) / gold (Au) having the same configuration as that of the n-side electrode is formed on the p-side electrode.

  Hereinafter, an arrangement example of the cleavage guide groove 19 and a method for forming the cleavage guide groove 19 will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A shows a state before division (cleavage), and FIG. 3B shows one of the divided individual laser chips. In FIG. 3A and FIG. 3B, the detailed configuration of the laminated structure 40 is omitted for simplicity. A p-side electrode or the like is formed on the upper surface of the ridge stripe region 18 but is omitted here.

  As shown in FIG. 3A, the plurality of cleavage guide grooves 19 formed in the upper part of the laminated structure 40 are discretely arranged in the <11-20> direction of the crystal axis, that is, discontinuously arranged. In addition, they are also discretely arranged in the <1-100> direction. Further, like the cleaved laser chip shown in FIG. 3B, the cleavage guide groove 19, here, the stepped portion 19 a formed by cleaving the cleavage guide groove 19, is a ridge stripe region formed in the laminated structure 40. 18 does not cross.

  First, the arrangement of the cleavage guide grooves 19 in the <11-20> direction will be described in detail. In order to form the resonator end face in the ridge stripe region 18 smoothly and accurately, the cleavage guide groove 19 preferably extends to the side surface of the ridge stripe region 18 in the <11-20> direction. Furthermore, in order to avoid damage to the ridge stripe region 18 when the cleavage guide groove 19 is formed by etching, the cleavage guide groove 19 is formed such that its width decreases as the ridge stripe region 18 is approached. Is preferred. By setting the cleavage guide groove 19 in such a form, damage to the ridge stripe region 18 which is an optical waveguide is relieved, so that the influence on the characteristics and reliability of the laser element can be minimized.

  On the other hand, the arrangement pitch of the cleavage guide grooves 19 in the <1-100> direction is set to a value equal to the resonator length of each laser element. In the first embodiment, since the resonator length is about 300 μm to 900 μm, the arrangement pitch of the cleavage guide grooves 19 in the <1-100> direction is also set to 300 to 900 μm. The dimension of the resonator length in the laser element is not limited to the above value. Therefore, the arrangement interval of the cleavage guide grooves 19 is set to an appropriate value according to the design dimension of the laser element.

  Next, the shape of each cleavage guide groove 19 will be described in detail. In the first embodiment, the planar shape of the cleavage guide groove 19 typically has a hexagonal shape, but may have an elliptical shape with rounded corners. The extending direction of the cleavage guide groove 19 is the <11-20> direction, and the length dimension is set to 200 μm or less. The width direction of the cleavage guide groove 19 is the <1-100> direction, and the width dimension is set to, for example, about 2 μm to 6 μm. The depth of the cleavage guide groove 19 reaches at least the multiple quantum well active layer 13 in the depth direction from the p-type contact layer 17 which is the crystal growth surface of the stacked structure 40 shown in FIG. The n-type light guide layer 12 is formed, and the n-type clad layer 11 is more preferably formed. Furthermore, the depth of the cleavage guide groove 19 may extend to the wafer 1 in view of the ease of primary cleavage.

  A first cleavage line 21 shown in FIG. 3A regulates a plurality of cleavage guide grooves 19 arranged in the <11-20> direction, and the wafer 1 is primarily cleaved along the first cleavage line 21. Is done. In this way, by accurately arranging the cleavage guide grooves 19 along the first cleavage line 21 shown in FIG. 3A, the primary cleavage that forms the resonator end face of the laser element can be performed with high accuracy and high yield. It is possible to carry out at the exact position obtained. A second cleavage line 22 extending in the <1-100> direction shown in FIG. 3A is a line that divides adjacent laser elements.

  Hereinafter, the cleavage process will be described in detail with reference to FIGS. 3 (a) and 3 (b).

  After the cleavage guide groove 19 is formed by the method described above, primary cleavage is performed along the first cleavage line 21 shown in FIG. At this time, when stress is applied from the back surface of the wafer 1 using an apparatus not shown, cleavage is performed along the plurality of cleavage guide grooves 19 arranged on the first cleavage lines 21 parallel to the <11-20> direction. proceed. For this reason, since the occurrence of cleavage deviation in the 60 ° direction is suppressed, a laser bar having a smooth resonator end face of the M plane, that is, the (1-100) plane can be manufactured. The laser bar refers to a bar-shaped wafer in which laser chips are continuous in a lateral direction, which is obtained by performing only cleavage along each first cleavage line 21 on the wafer 1.

  In addition, in the first embodiment, the cleavage guide groove 19 is provided in the cleavage region, so that the laser bar is hardly divided due to the occurrence of cleavage displacement. For this reason, since it becomes possible to extend the length of the laser bar itself, the manufacturing cost can be reduced and the yield can be improved as the manufacturing efficiency is improved.

  FIG. 4A and FIG. 4B each show a planar configuration in the vicinity of the ridge stripe region 18 on the exit end face after the primary cleavage. In FIG. 4A and FIG. 4B, the insulating film 20 and the p-side electrode are omitted for simplicity.

  In the example shown in FIG. 4A, the stepped portion 19a formed by dividing the cleavage guide groove 19 by cleavage is formed so that the end on the ridge stripe region 18 side is in contact with the ridge stripe 18 region. In FIG. 4A, the cleavage guide groove 19 is shown to have a hexagonal planar shape in a plane parallel to the main surface of the wafer 1, but this is only an example, and dry etching is performed. By adjusting the mask shape, the cleavage guide grooves 19 having various planar shapes can be formed. In order to guide the primary cleavage in a predetermined direction, each cleavage guide groove 19 preferably has an anisotropic shape having a long axis in the cleavage direction.

  In addition, in another example shown in FIG. 4B, a case is shown in which the dimension in the width direction of the cleavage guide groove 19 is continuously changed in the <11-20> direction. The primary cleavage that forms the resonator end face of the laser element is regulated along the first cleavage line 21 in FIG. For this reason, in order to increase the accuracy of the resonator length, it is preferable to make the width dimension of the cleavage guide groove 19 as small as possible, for example, about 2 μm. However, in order to suppress the phenomenon that the stray light leaking to the side of the ridge stripe region 18 and multiple-reflected at the resonator end face except the ridge stripe area 18 is emitted from the exit end face and interferes with the laser light. It is preferable that the width dimension of the cleavage guide groove 19 adjacent to the ridge stripe region 18 is larger than a dimension that does not affect the primary cleavage, for example, about 6 μm.

  Therefore, in the example shown in FIG. 4B, since the degree of interference of the stray light with the laser light is greatly reduced, it is easy to obtain a good FFP with little ripple and a Gaussian shape.

  FIG. 5A shows a planar configuration in which the insulating film 20 is provided on the laminated structure 40 having the laser structure shown in FIG.

  As shown in FIG. 5A, by covering the entire surface including the side and bottom surfaces of the stepped portion 19a with the insulating film 20 except for the top surface of the ridge stripe region 18, the electrical insulation at the stepped portion 19a can be maintained. In particular, electrical leakage at the position where the step portion 19a is in contact with the ridge stripe region 18 can be avoided.

  5B shows a cross-sectional configuration along the line Vb-Vb in FIG. 5A, that is, a cross-sectional configuration along the stepped portion 19a in the vicinity of the emission end face, and FIG. 5C shows the cross-sectional configuration in FIG. The cross-sectional configuration along the line Vc-Vc, that is, the internal cross-sectional configuration of the laser structure (laminated structure 40) at a position away from the emission end face is shown. 5B and 5C schematically show only the position of the multiple quantum well active layer 13 in the stacked structure 40. FIG. FIG. 5C shows that the lower part of the ridge stripe region 18 is located on the upper side of the multiple quantum well active layer 13 in the stacked structure 40 away from the cleavage end face. On the other hand, from FIG. 5B, in the end face portion, the lower portion of the ridge stripe region 18 is located above the multiple quantum well active layer 13, but the bottom of the stepped portion 19a is the multiple quantum well active layer 13. You can see that they are crossing. Accordingly, as can be seen from FIGS. 5A to 5C, the width of the multi-quantum well active layer 13 in the direction parallel to the substrate is restricted at the emission end face, so that the ridge stripe from the ridge stripe region 18 is constrained. It is possible to prevent light (stray light) that leaks and propagates to the side of the region 18 from leaking from the exit end face.

Next, as a laser chip manufacturing process, aluminum oxide (Al _A dielectric protective film made of ₂ O ₃ ) or the like is formed, and a dielectric multilayer film made of silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ) or the like is formed on the other reflection end face.

  In a GaN-based semiconductor laser device, in order to achieve a high output of over 200 mW, it is necessary to prevent instantaneous optical damage (COD: Catastrophic Optical Damage) that occurs on the emission end face. Therefore, the dielectric film coating on the emission end face side will be described in detail.

  Since the emission end face formed by the primary cleavage on the laminated structure 40 is exposed to the atmosphere before the dielectric film coat is formed by the ECR apparatus, moisture, organic matter, etc. are easily attached. Contaminated. There is also a method of cleaving the wafer 1 in a vacuum, but considering the workability and cost at the time of manufacture, it lacks mass productivity. Compared with conventional infrared laser elements and red laser elements, GaN-based semiconductor laser elements generate laser light with a short wavelength and large optical energy, so the contaminants attached to the end face are decomposed by the laser light itself. Is done. The decomposed foreign matter induces end face oxidation, light absorption at the end face, and changes in end face reflectivity. For this reason, it is promoted that the laser element is killed due to a decrease in the light output value at the time when COD occurs and a decrease in the COD level during aging.

Therefore, particularly on the emission end face side, the end face treatment method immediately before the formation of the dielectric film coat is important. Specifically, the plasma processing in an atmosphere in which a rare gas and an inert gas in a high vacuum state in the ECR apparatus are mixed, and the subsequent Al ₂ O ₃ coating suppress the death due to COD generation during aging. As effective. According to this method, it is possible to suppress death due to the generation of COD without depending on the standing time in the atmosphere from the primary cleavage to the dielectric film coating.

  Next, a plurality of laser chips (individual semiconductor laser elements) are obtained from the laser bar by cleaving (secondary cleavage) along the second cleavage line with respect to the laser bar on which the end surface coating has been performed. Each semiconductor laser element includes a chip divided from the wafer 1 as a substrate 1A.

  Thus, after the secondary cleavage step is completed, the n-side portion of the semiconductor laser element, for example, the substrate 1A is fixed onto the submount made of aluminum nitride (AlN) or the like via the solder material, The p-side electrode is wired by wire bonding.

  At this time, utilizing the fact that the step portion 19a is formed at a specific position of the semiconductor laser element, the step portion 19a can also function as a positioning marker in the mounting process.

  The semiconductor laser device manufactured by the above method has a smooth resonator end face led to the cleavage guide groove 19, and a dielectric film coat that suppresses COD deterioration is applied to the emission end face side. Therefore, in the pulse measurement at room temperature, it was confirmed that the threshold current was 30 mA and the output current was 250 mW, and it oscillated with an operating current of 120 mA, indicating a lifetime of 1000 hours or more.

  Further, when a far field image (FFP) in a direction parallel to the substrate is evaluated, interference of the laser beam due to stray light is suppressed. Therefore, a good FFP shape with a small Gaussian distribution with a small ripple is 250 mW from a low output operation of about 5 mW. It has been obtained in a high range up to high power operation. Further, when evaluating a low output noise (RIN: Referential Intensity Noise) of about 5 mW by superimposing a high frequency of about 300 MHz, it becomes −125 dB / Hz or less, which is a low practical light source for the next generation DVD set. Noise can be achieved.

  In the first embodiment, the end portion of the step portion 19 a is in contact with the side surface of the ridge stripe region 18, but the end portion of the step portion 19 a is not necessarily in contact with the side surface of the ridge stripe region 18. For example, if the distance between the step portion 19 a and the side surface of the ridge stripe region 18 is smaller than 0.1 μm, the same effect as when the end portion of the step portion 19 a is in contact with the ridge stripe region 18 is obtained. That is, even when the distance between the step portion 19a and the ridge stripe region 18 is smaller than 0.1 μm, it can be considered that both are in contact. The reason for this is not clear, but the distance between the stepped portion 19a and the ridge stripe region 18 is caused by the diffusion length (about 0.1 μm) of carriers (especially holes) leaked from the ridge stripe region 18 to the outside. In the region smaller than 0.1 μm, the component contributing to the laser light is mainly, and it is estimated that it may be difficult to become stray light.

(One modification of the first embodiment)
This modification has a configuration in which the planar shape of the cleavage guide groove 19 is variously changed. FIG. 6A to FIG. 6E show a laser structure according to this modification. As shown in FIGS. 6A to 6E, the cleavage guide groove 19 (step 19a) according to this modification is divided into a plurality of portions in the <11-20> direction.

  FIG. 6 (a) and FIG. 6 (b), which is an enlarged view after cleavage, show a case where the lengths of the plurality of cleavage guide grooves 19 (steps 19a) along the first cleavage line 21 are equal to each other. FIG. 6C shows a case where the lengths of the plurality of cleavage guide grooves 19 (steps 19 a) along the first cleavage line 21 are different. From the viewpoint of cleavage accuracy, there is no significant difference between FIGS. 6 (b) and 6 (c).

  On the other hand, FIGS. 6D and 6E are characterized in that the planar shape of the cleavage guide groove 19 (step 19a) in the vicinity of the ridge stripe region 18 is changed. That is, in FIG. 6D, the distance between the emission end surface and the side surface of the step portion 19a is large only in the step portion 19a in contact with the ridge stripe region 18. For this reason, since the rate at which the stray light leaked from the ridge stripe region 18 interferes with the laser light can be reduced, a favorable FFP shape can be realized even during high output operation.

  In FIG. 6E, the side surface of the stepped portion 19a is not a linear shape but a wave shape only in the stepped portion 19a in contact with the ridge stripe region 18. For this reason, stray light can be scattered even during high output operation, and a good FFP shape can be realized.

  In FIG. 6D and FIG. 6E, the cleavage performed on the laminated structure 40 is restricted by the long cleavage guide groove 19 along the first cleavage line 21 away from the ridge stripe region 18. Therefore, the accuracy of cleavage itself is not hindered.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

  In the second embodiment, the configuration of the insulating film covering the stacked structure is changed so that the FFP shape obtained by the first embodiment can be further improved.

  FIG. 7A is a nitride compound semiconductor device according to the second embodiment of the present invention, and shows a planar configuration on the emission end face side of the semiconductor laser device, and FIG. 7B is a line VIIb-VIIb in FIG. A cross-sectional structure is shown, (c) has shown the cross-sectional structure in the VIIc-VIIc line of (a). In FIGS. 7A to 7C, the same components as those shown in FIGS. 1A to 1C are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 7A to 7C, the semiconductor laser device according to the second embodiment emits stray light on the end including the emission end face in the insulating film 20 covering the stacked structure 40. A light absorbing film 23 for absorbing is provided. Here, like the first embodiment, the insulating film 20 has an electrical passivation function and a light confinement function based on a difference in refractive index.

  Hereinafter, the wavelength of stray light leaking in the in-plane direction of the main surface of the substrate from the ridge stripe region 18 which is an optical waveguide region will be described in detail.

  The inventor of the present application investigated the wavelength component with a laser Raman microscope for the purpose of reliably suppressing stray light. As a result, long wavelength light over a wide area having a wavelength of 405 nm or more (and about 600 nm or less) was observed mixed with 405 nm which is the wavelength of the main laser light. The origin of this long wavelength light is not clear, but when a laser beam having a wavelength of 405 nm leaking through the ridge stripe region 18 leaks, the leaked laser beam has a band gap energy smaller than 405 nm. It is presumed that this is caused by exciting the region to emit light. Here, the excited region refers to a segregation region of indium (In) in the multi-quantum well active layer 13 whose wavelength is assumed to have an energy level (level) smaller than 405 nm, and a p-type semiconductor such as the cap layer 15. An impurity-added region (including a diffused region) made of Mg in the layer and an impurity-added region made of Si in the n-type semiconductor layer such as the first light guide layer 12.

  For this reason, in order to reliably suppress stray light, it is effective to suppress light having a wavelength longer than that of the main laser light. Therefore, in the second embodiment, amorphous silicon (α-Si) having light absorption in a wide area extending over a long wavelength region having a wavelength of 405 nm or more is used as the light absorption film 23 that absorbs stray light.

  Here, the light absorption film 23 made of α-Si is deposited by an ECR apparatus or the like, and may be formed only in the vicinity of the emission end face as shown in FIGS. 7A and 7C. You may form along the ridge stripe area | region 18 in the whole region of a resonator length direction.

  Furthermore, in the second embodiment, the light absorption film 23 is formed on the insulating film 20. On the contrary, the light absorption film is deposited on the stacked structure body 40 and then insulated. The film 20 may be formed.

  In the second embodiment, α-Si is used for the light absorption film 23, but the medium is not limited to a dielectric film as long as it is a medium that absorbs stray light. For example, metals such as palladium (Pd) and gold (Au) may be used.

  Also in the second embodiment, the end portion of the step portion 19 a is in contact with the side surface of the ridge stripe region 18, but even if the step portion 19 a is not in contact with the ridge stripe region 18, the step portion 19 a If the distance between the ridge stripe region 18 and the ridge stripe region 18 is smaller than 0.1 μm, the same effect as when the end portion of the step portion 19a is in contact with the ridge stripe region 19a can be obtained. That is, even when the distance between the stepped portion 19a and the ridge stripe region 18 is smaller than 0.1 μm, it can be regarded as being in contact.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

  In the third embodiment, the insulating film 20 covering the laminated structure is provided so that the COD level obtained by the first embodiment and the second embodiment can be further increased in output and the reliability exceeding 200 mW can be improved. The formation position is changed.

  FIG. 8A is a nitride compound semiconductor device according to the third embodiment of the present invention, and shows a planar configuration on the emission end face side of the semiconductor laser device, and FIG. 8B is a line VIIIb-VIIIb in FIG. A cross-sectional structure is shown, (c) has shown the cross-sectional structure in the VIIIc-VIIIc line | wire of (a). In FIG. 8A to FIG. 8C, the same components as those shown in FIG. 1A to FIG.

As shown in FIGS. 8A to 8C, the semiconductor laser device according to the third embodiment is made of SiO ₂ formed on the laminated structure 40 including the side surface of the ridge stripe region 18. The insulating film 20 is also formed on the ridge stripe region 18 at the end on the emission end face side so as not to contact the p-side electrode.

  Since the pn junction and the active layer (multiple quantum well active layer 13) constituting the laminated structure 40 are exposed at the resonator end face, there are non-radiative recombination centers such as interface states, and the output end face In particular, since the light density is high, an increase in reactive current, an increase in heat generation, and deterioration of COD through non-radiative recombination centers are accelerated.

  In the third embodiment, as shown in FIGS. 8A and 8B, a ridge is formed from the p-side electrode by the insulating film 20 formed at the end on the emission end face side on the ridge stripe region 18. Current injection into the stripe region 18 is prevented. Thereby, since light emission from the multiple quantum well active layer 13 is suppressed in the vicinity of the emission end face, the progress of COD deterioration is suppressed. Further, by adopting the end face non-injection structure as shown in FIG. 8A, the influence of the introduction of damage to the ridge stripe region 18 resulting from the contact of the step portion 19a with the ridge stripe region 18 is reduced. be able to.

Although only the insulating film 20 made of SiO ₂ is shown in FIGS. 8A to 8C, the light absorption film made of, for example, α-Si is formed as in the second embodiment. The stray light may be effectively suppressed.

In the third embodiment, both the insulating film 20 formed on the side of the ridge stripe region 18 in the stacked structure 40 and the insulating film 20 formed on the end face side on the ridge stripe region 18 are both used. Although formed of SiO _{2, the} insulating film 20 formed on the ridge stripe region 18 and the insulating film 20 formed on the side of the ridge stripe region 18 may be insulating films having different compositions. . For example, either one may be silicon nitride (SiN).

  Here, when the third embodiment is compared with the first embodiment and the second embodiment, the semiconductor laser device according to the third embodiment has a COD level before aging improved by about 100 mW and is aging. The decrease in COD level was also suppressed. For this reason, a stable operation of 1000 hours or more can be ensured with a high yield even at a high output aging of 200 mW.

  In the third embodiment, the configuration for preventing current injection to the emission end face is realized by the insulating film 20 provided on the ridge stripe region 18. However, the configuration is not limited to this configuration, and the current to the p-side semiconductor layer is not limited. The same effect can be obtained with other configurations as long as the configuration inhibits injection.

  Also in the third embodiment, the end portion of the stepped portion 19 a is in contact with the side surface of the ridge stripe region 18, but even if the stepped portion 19 a is not in contact with the ridge stripe region 18, the stepped portion 19 a If the distance between the ridge stripe region 18 and the ridge stripe region 18 is smaller than 0.1 μm, the same effect as when the end portion of the step portion 19a is in contact with the ridge stripe region 19a can be obtained. That is, even when the distance between the stepped portion 19a and the ridge stripe region 18 is smaller than 0.1 μm, it can be regarded as being in contact.

(One Modification of Third Embodiment)
The present modification adopts a configuration in which the cleavage guide function provided in the cleavage guide groove 19 (step 19a) and the stray light suppression function are separated from the configuration for achieving high output in the third embodiment. FIGS. 9A to 9D show a laser structure according to this modification.

  As shown in FIGS. 9A to 9C, the stepped portion 19 a is configured not to contact the side surface of the ridge stripe 18 at the emission end face of the laminated structure 40.

  Further, in the region inside the stepped portion 19a in the upper part of the laminated structure 40, a stray light suppressing groove 24 along the stepped portion 19a is formed with a gap of about 5 μm from the stepped portion 19a. Here, the width dimension of the stray light suppressing groove 24 is approximately 10 μm, and the depth dimension thereof is approximately the same as that of the cleavage guide groove 19. Thus, by providing the stray light suppression groove 24, leakage of stray light from the ridge stripe region 18 to the emission end face is suppressed. The stray light suppressing groove 24 is preferably different from the step portion 19 a in that the end portion on the ridge stripe region 18 side is in contact with the side surface of the ridge stripe region 18.

  The insulating film 20 is formed on the ridge stripe region 18 so as to reach the region beyond the stray light suppression groove 24 without contacting the p-side electrode at the end on the emission end face side.

  As described above, according to the present modification, the peripheral portion of the ridge stripe region 18 on the cleavage end surface is physically formed by separating the end portion of the cleavage guide groove 19 (stepped portion 19a) from the side surface of the ridge stripe region 18. Therefore, the stress load applied to the ridge stripe region 18 at the time of primary cleavage can be reduced.

  Further, in combination with the end face non-injection structure in which the insulating film 20 is also formed on the emission end face side on the ridge stripe region 18, it is possible to further improve the yield of the semiconductor laser device capable of realizing a high output stable operation.

  In the present modification, only the insulating film 20 is shown. However, as in the second embodiment, for example, a light absorbing film made of, for example, α-Si is formed to effectively suppress stray light. Also good.

  INDUSTRIAL APPLICABILITY The nitride compound semiconductor device according to the present invention can suppress stray light and obtain a good FFP shape at a high yield even during high output operation, and is particularly useful for a nitride compound semiconductor laser device having a ridge stripe region. .

(A)-(c) shows the nitride compound semiconductor element which concerns on the 1st Embodiment of this invention, (a) is a top view by the side of an output end surface, (b) is the Ib-Ib line | wire of (a). (C) is sectional drawing in the Ic-Ic line | wire of (a). (A) And (b) shows the manufacturing method of the nitride compound semiconductor element which concerns on the 1st Embodiment of this invention, and is sectional drawing which shows the process of forming the laminated structure which consists of a nitride compound semiconductor on a wafer. (A) is a top view which shows the state before the cleavage process in the nitride compound semiconductor element which concerns on the 1st Embodiment of this invention, (b) is a top view which shows the chip | tip after a cleavage. (A) And (b) is a top view which shows the radiation | emission end surface vicinity in the nitride compound semiconductor element which concerns on the 1st Embodiment of this invention. (A)-(c) shows the state after formation of the insulating film in the nitride compound semiconductor element which concerns on the 1st Embodiment of this invention, (a) is a top view by the side of an output end surface, (b) is It is sectional drawing in the Vb-Vb line | wire of (a), (c) is sectional drawing in the Vc-Vc line | wire of (a). (A)-(e) shows the state before the cleavage process in the nitride compound semiconductor element which concerns on the modification of the 1st Embodiment of this invention, (a) is a top view, (b)-(e ) Shows the emission end face side of the chip after cleavage, and is a plan view showing the planar shape of the stepped portion. (A)-(c) shows the nitride compound semiconductor element which concerns on the 2nd Embodiment of this invention, (a) is a top view by the side of an output end surface, (b) is the VIIb-VIIb line | wire of (a). (C) is sectional drawing in the VIIc-VIIc line | wire of (a). (A)-(c) shows the nitride compound semiconductor element which concerns on the 3rd Embodiment of this invention, (a) is a top view by the side of an output end surface, (b) is a VIIIb-VIIIb line | wire of (a). (C) is sectional drawing in the VIIIc-VIIIc line | wire of (a). (A)-(c) shows the nitride compound semiconductor element which concerns on the modification of the 3rd Embodiment of this invention, (a) is a top view by the side of an output end surface, (b) is (a). It is sectional drawing in the IXb-IXb line, (c) is sectional drawing in the IXc-IXc line of (a), (d) is sectional drawing in the IXd-IXd line of (a). It is a schematic diagram which shows the crystal structure of a nitride compound semiconductor.

Explanation of symbols

1 Wafer 1A Substrate 10 n-type GaN layer 11 n-type cladding layer 12 first light guide layer 13 multiple quantum well active layer 14 active layer protective layer 15 cap layer 16 p-type cladding layer 17 p-type contact layer 18 ridge stripe region 19 Cleavage guide groove 19a Step portion 20 Insulating film 21 First cleavage line (resonance surface formation)
22 Second cleavage line (chip division)
23 light absorption film 24 stray light suppression groove (groove)
40 Laminated structure

Claims (13)

A stacked structure formed on a substrate and including an n-type nitride compound semiconductor layer, an active layer, and a p-type nitride compound semiconductor layer;
The multilayer structure has a ridge stripe region formed on the top of the multilayer structure, and a resonance surface composed of an end surface formed in a direction perpendicular to a direction in which the ridge stripe region extends,
In the stacked structure, a stepped portion is formed by carving the end face in the direction in which the ridge stripe region extends,
An end of the step portion on the ridge stripe region side is in contact with the ridge stripe region.   2. The nitride compound semiconductor device according to claim 1, wherein an end of the step portion on the ridge stripe region side is in contact with the resonance surface. The end face includes an emission end face that emits laser light and a reflection end face that reflects the laser light,
3. The nitride compound semiconductor device according to claim 1, wherein the step portion is provided on the emission end face side. 4.   The step portion is formed such that a distance between a side surface of the step portion and the resonance surface is larger in the vicinity of the ridge stripe region than in other portions. The nitride compound semiconductor element of any one of Claims 1.   5. The nitride compound semiconductor element according to claim 1, wherein a side surface of the stepped portion is covered with a first insulating film.   6. The nitride compound semiconductor device according to claim 1, wherein a side surface of the stepped portion is covered with a light absorbing film.   The said ridge stripe area | region is covered with the 2nd insulating film formed so that a part of upper surface might contact | connect the said resonance surface, The one of Claims 1-6 characterized by the above-mentioned. Nitride compound semiconductor element. A stacked structure formed on a substrate and including an n-type nitride compound semiconductor layer, an active layer, and a p-type nitride compound semiconductor layer;
The multilayer structure has a ridge stripe region formed on the top of the multilayer structure, and a resonance surface composed of an end surface formed in a direction perpendicular to a direction in which the ridge stripe region extends,
In the stacked structure, a stepped portion is formed by carving the end face in the direction in which the ridge stripe region extends,
An end of the step portion on the ridge stripe region side is away from the ridge stripe region,
The laminated structure is formed with a groove portion spaced from the step portion and along the step portion,
An end of the groove portion on the ridge stripe region side is in contact with the ridge stripe region.   9. The nitride compound semiconductor device according to claim 8, wherein an end of the step portion on the ridge stripe region side is in contact with the resonance surface. The end face includes an emission end face that emits laser light and a reflection end face that reflects the laser light,
10. The nitride compound semiconductor device according to claim 8, wherein the step portion is provided on the emission end face side. 11.   11. The nitride compound semiconductor device according to claim 8, wherein a side surface of the step portion is covered with a first insulating film.   12. The nitride compound semiconductor device according to claim 8, wherein a side surface of the stepped portion is covered with a light absorbing film.   The said ridge stripe area | region is covered with the 2nd insulating film formed so that a part of upper surface might contact | connect the said resonance surface, The one of Claims 8-12 characterized by the above-mentioned. Nitride compound semiconductor element.

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