Laser diode, and manufacturing method of laser diode

Abstract

To provide a laser diode capable of suppressing the occurrence of characteristic defects at the ends.SOLUTION: A laser diode 40 obtained by cleaving a GaN substrate 1 has multiple emitters 30 arranged spaced apart from each other along a longitudinal-X direction, and each emitter 30 has a p-side electrode pattern 8. Defining the length of the laser diode 40 in the-X direction as W, and the distance between adjacent p-side electrode patterns 8 in the Y-direction perpendicular to the X-direction before cleavage as 2D, from the top view, the angle θ12 between a second imaginary line passing through the midpoint of the front end face of the multiple p-side electrode patterns 8 and a first imaginary line along the cleavage plane of the laser diode 40 satisfies the relationship represented in formula (1): |θ12|<tan-1(2(D-A) / W)(A is a positive constant and D≥A).SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to laser diode bars and methods of making laser diode bars, and more particularly to laser diode bars made of nitride semiconductor materials and methods of making same. [Background technology]

[0002] In recent years, expectations for laser processing of various materials such as copper, gold, and resin are increasing. To achieve highly productive processing, a laser light source that can generate a highly efficient and high-power laser light is required. A semiconductor laser element is known as a laser light source suitable for this requirement. To increase the output of the laser light, a laser diode bar having a plurality of emitters that each emit a laser light is useful. In addition, because of the high absorption rate in copper and the like, the use of nitride semiconductor (hereinafter sometimes referred to as GaN or GaN-based) laser elements that emit blue laser light is becoming more widespread.

[0003] Usually, when manufacturing a laser diode bar, a mask pattern is used to form a ridge portion constituting a current confinement portion, an electrode pattern, and the like, on a GaN substrate on which a GaN-based semiconductor layer is laminated. Then, the GaN substrate is cleaved along a predetermined direction to separate the laser diode bar from the GaN substrate. The cleavage planes become the resonator end faces of each emitter in the laser diode bar.

[0004] However, since GaN substrates have poor cleavage properties unlike GaAs substrates etc., various methods for stably cleaving have been proposed. For example, Patent Document 1 discloses a method for stabilizing the chip shape and improving the manufacturing yield by forming dashed scribe lines along the planned division lines of the laser diode bar and then cleaving the bar. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-117015 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, a GaN substrate usually has an orientation flat (hereinafter referred to as "orientation flat") formed as a pattern indicating the crystal orientation. When forming a ridge portion or an electrode pattern, a mask pattern is formed based on the crystal orientation indicated by the orientation flat.

[0007] However, compared to Si substrates, GaAs substrates, etc., the degree of agreement between the direction indicated by the orientation flat formed on a GaN substrate and the actual crystal orientation is low. In the conventional method disclosed in Patent Document 1, even in a state where the degree of agreement is low, scribes are formed along the planned division line and cleavage is forcibly performed. This may cause damage to the cleavage plane, which is the resonator end face of the emitter, and the emitter will not emit light at the damaged location.

[0008] In a laser diode bar, each of multiple emitters must emit laser light that meets specified requirements. Therefore, if any of the emitters fail to emit light, the entire laser diode bar becomes defective, resulting in a significant drop in yield.

[0009] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide a laser diode bar and a manufacturing method for a laser diode bar in which the occurrence of characteristic defects at the end portions is suppressed. [Means for solving the problem]

[0010] In order to achieve the above object, a laser diode bar according to the present disclosure is a laser diode bar having a plurality of emitters, the laser diode bar being obtained by cleaving a GaN substrate on which a plurality of the emitters are formed, each of the plurality of emitters having a p-side electrode pattern, and when an arrangement direction of the emitters in the laser diode bar is defined as an X direction, a direction parallel to a main surface of the GaN substrate and perpendicular to the X direction is defined as a Y direction, a length of the laser diode bar in the X direction is defined as W, and a distance between the p-side electrode patterns adjacent to each other in the Y direction before cleavage of the laser diode bar is defined as 2D, an angle θ between a second virtual line passing through a midpoint of a front end surface of the plurality of p-side electrode patterns and a first virtual line along a cleavage surface of the laser diode bar in a top view is defined as 12 But, |θ 12 | <tan -1 It is characterized by satisfying the relationship (2(DA) / W) (A is a positive constant, and D≧A).

[0011] A method for manufacturing a laser diode bar according to the present disclosure includes a first step of preparing a GaN substrate having an orientation flat; a second step of forming a GaN laminate having a plurality of nitride semiconductor layers on a surface of the GaN substrate; a third step of processing the GaN laminate using a mask pattern to form a plurality of emitter prototypes; a fourth step of forming a p-side electrode pattern on a surface of each of the plurality of emitter prototypes using another mask pattern after the third step is performed; a fifth step of dividing the GaN substrate into blocks of a predetermined size including a plurality of the emitters after the fourth step is performed; The method includes at least a sixth step of forming a plurality of cleavage grooves at predetermined intervals along an X direction perpendicular to one end face and in a Y direction parallel to the one end face, and a seventh step of cleaving the block from the cleavage grooves as starting points to obtain a laser diode bar, wherein in the fourth step, the p-side electrode patterns are provided at intervals along the Y direction, and when an interval between the p-side electrode patterns adjacent to each other in the Y direction in the block is 2D, in the seventh step, an angle θ between a second virtual line passing through midpoints of front end faces of the plurality of p-side electrode patterns and a first virtual line along the cleavage plane of the laser diode bar in a top view is set to 1 / 2D. 12 The block is cleaved so as to satisfy the relationship shown in formula (1), and formula (1) is expressed as |θ 12 | <tan -1 It is characterized by the fact that (2(DA) / W) (A is a positive constant and D≧A). Effect of the Invention

[0012] According to the present disclosure, it is possible to suppress the occurrence of characteristic defects at the ends of a laser diode bar, and also to suppress the occurrence of damage to the cleavage planes. [Brief description of the drawings]

[0013] [Figure 1] 4 is a flowchart showing a method for manufacturing the laser diode bar according to the first embodiment. [Figure 2A] FIG. 2 is a plan view of the GaN substrate after the formation of a GaN stack. [Figure 2B] FIG. 2B is a cross-sectional view taken along line IIB-IIB in FIG. 2A. [Figure 3A] FIG. 2 is a plan view of the GaN substrate after the emitter is formed. [Figure 3B] FIG. 3B is an enlarged plan view of a portion of FIG. 3A after the emitters are formed. [Figure 3C] FIG. 3C is a cross-sectional view taken along line IIIC-IIIC in FIG. 3B. [Figure 3D] FIG. 3D is a cross-sectional view taken along line IIID-IIID in FIG. 3B. [Figure 3E] FIG. 3D is an enlarged view of the area enclosed by the dashed line in FIG. 3C. [Figure 4] FIG. 2 is a plan view showing the GaN substrate after being divided into a plurality of blocks. [Diagram 5] 1A to 1C are schematic diagrams for explaining a step of forming a cleavage groove. [Figure 6A] FIG. 2 is a schematic diagram for explaining a cleavage step as viewed from one direction. [Figure 6B] FIG. 13 is a schematic view for explaining the cleavage step as viewed from another direction. [Figure 7] FIG. 2 is a perspective view of a laser diode bar. [Figure 8] 1 is a schematic diagram for explaining an angle deviation between a cleavage line and a pattern line of a laser diode bar. FIG. [Figure 9] 1 is a schematic diagram for explaining the range of angles between the cleavage lines of a laser diode bar and pattern lines; FIG. [Figure 10A] 4 is a schematic diagram for explaining the range of angles formed by cleavage lines, pattern lines, and a-axis direction lines. FIG. [Figure 10B] FIG. 11 is another schematic diagram for explaining the range of angles formed by the cleavage lines, the pattern lines, and the a-axis direction lines. [Figure 11] FIG. 2 is a schematic diagram for explaining the crystal structure of GaN as viewed from the c-axis direction. [Figure 12] FIG. 2 is a schematic diagram for explaining the off-angle of a GaN substrate. [Figure 13A] FIG. 2 is a schematic diagram showing an example of the direction of an off-angle in a GaN substrate. [Figure 13B] FIG. 2 is a schematic diagram showing another example of the direction of an off-angle in a GaN substrate. [Figure 13C] FIG. 13 is a schematic diagram showing yet another example of the direction of the off-angle in a GaN substrate. [Figure 14] 4 is a schematic diagram for explaining the relationship between the angle between the cleavage line and the pattern line and the range of the off-angle direction. FIG. [Figure 15A] 11 is a plan view showing an example of a p-side electrode pattern according to Modification 1. FIG. [Figure 15B] 13 is a plan view showing another example of a p-side electrode pattern according to Modification 1. FIG. [Figure 16] 10 is a flowchart showing a method for manufacturing a laser diode bar according to a second embodiment. [Figure 17A] 1 is a schematic diagram for explaining the positional relationship between an orientation flat line and an a-axis direction line. FIG. [Figure 17B] 1 is a schematic diagram for explaining the positional relationship between an orientation flat line, an a-axis direction line, and a pattern line. [Figure 17C] 1 is a schematic diagram for explaining the positional relationship between an orientation flat line, an a-axis line, a pattern line, and a cleavage line. FIG. [Figure 18A] FIG. 13 is a diagram showing a relationship between a predicted value of a deviation amount of a cleavage position at an end of a laser diode bar after a process correction and an actual deviation amount of a cleavage position at an end of a laser diode bar after a cleaving process. [Figure 18B] FIG. 13 is a diagram showing the relationship between the predicted value of the angle deviation after the process correction and the actual value of the angle deviation after the cleavage process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0015] (Embodiment 1) [Method of manufacturing laser diode bars] FIG. 1 is a flow chart showing a method for manufacturing a laser diode bar according to the first embodiment. FIG. 2A is a plan view of a GaN substrate after a GaN laminate is formed. FIG. 2B is a cross-sectional view taken along line IIB-IIB in FIG. 2A. FIG. 3A is a plan view of a GaN substrate after an emitter is formed. FIG. 3B is a plan view of a block after an emitter is formed. FIG. 3C is a cross-sectional view taken along line IIIC-IIIC in FIG. 3B. FIG. 3D is an enlarged view of a portion surrounded by a dashed line in FIG. 3C. FIG. 4 is a plan view showing a GaN substrate after being divided into a plurality of blocks. FIG. 5 is a schematic diagram for explaining a process of forming a cleavage groove. FIG. 6A is a schematic diagram for explaining a cleavage process as viewed from one direction. FIG. 6B is a schematic diagram for explaining a cleavage process as viewed from another direction. FIG. 7 is a perspective view of a laser diode bar.

[0016] For ease of explanation, the insulating layer 6, the n-side electrode 7, and the p-side electrode 8 are omitted in Figures 3B and 3C. Also, in Figure 7, the laser diode bar 40 is illustrated without showing the structure of the emitter 30. Also, the thicknesses of the layers and the dimensional ratios of the parts shown in Figures 2B, 3D, and 7 are different from the actual ones.

[0017] In the following description, the thickness direction of the GaN substrate 1 is sometimes referred to as the Z direction, and the arrangement direction of the emitters 30 in the laser diode bars 40 formed on the GaN substrate 1 before division is sometimes referred to as the X direction. The direction perpendicular to the X direction and the Z direction is sometimes referred to as the Y direction. In the Z direction, the side on which the p-side electrode 8 is formed is sometimes referred to as the top or upper side, and the side on which the n-side electrode 7 is formed is sometimes referred to as the bottom or lower side. The GaN substrate 1, the block 20, and the laser diode bars 40 viewed from above are sometimes referred to as the top view.

[0018] In the GaN substrate 1, the surface on which the GaN laminate 10 is formed is called the front surface, and the opposing surface, ie, the surface on which the n-side electrode 7 is formed, is called the back surface.

[0019] In this specification, "orthogonal," "parallel," or "same" means orthogonal, parallel, or the same, including manufacturing tolerances of each part that makes up the laser diode bar 40, and does not mean that the objects being compared are strictly orthogonal, parallel, or the same.

[0020] In manufacturing the laser diode bar 40, first, the GaN substrate 1 is prepared as shown in step S1 of Fig. 1. Next, the angular deviation between the a-axis line L3 and the orientation flat line L0 is measured (step S2).

[0021] The GaN substrate 1 is a GaN single crystal substrate having a c-plane as a main surface (see FIG. 11). Therefore, the surface of the GaN substrate 1 is a c-plane. As described later, in order to improve the quality of the GaN laminate 10, the substrate is often tilted by about 0.1 to 1.0° from the strict c-plane, but since the off-angle is sufficiently small, it is conveniently called a c-plane substrate in this specification. As shown in FIG. 2A, a part of the outer periphery of the GaN substrate 1 is linear, and this part is called an orientation flat (hereinafter, referred to as an orientation flat) 1a. The orientation flat 1a indicates the crystal orientation of the GaN substrate 1, and in this embodiment, the orientation flat 1a is formed so that the linear part is parallel to the a-axis direction of the GaN substrate (see FIG. 11). However, since the GaN substrate 1 is very hard compared to a Si substrate, a GaAs substrate, etc., the processing accuracy of the orientation flat 1a is low. Therefore, the degree of agreement between the actual a-axis direction and the direction indicated by the orientation flat 1a is not high. This will be described further later.

[0022] In the following description, a virtual line along a straight portion of the orientation flat 1a may be referred to as the orientation flat line L0, or simply as the virtual line L0. A virtual line parallel to the primary surface of the GaN substrate 1 and along a crystal axis intersecting with a cleavage plane described later may be referred to as the third virtual line L3. In this embodiment, the third virtual line L3 is generally along the a-axis direction of the GaN substrate 1 even when the primary surface of the GaN substrate 1 is inclined from the c-plane. In other words, the third virtual line L3 can be said to be a virtual line obtained by projecting the a-axis direction of the GaN substrate 1 onto the primary surface of the GaN substrate. In the following description, this third virtual line L3 will be referred to as the a-axis direction line L3.

[0023] In step S2, the angular deviation between the a-axis line L3 and the orientation flat line L0 is evaluated using a device capable of measuring crystal orientation, such as an X-ray diffraction device. The angular deviation value may be substituted for the measured value by the inventors by using the evaluation value from the substrate manufacturer.

[0024] Next, a GaN laminate 10 is formed on the surface of the GaN substrate 1 by epitaxial growth (step S3). As shown in FIG. 2B, the GaN laminate 10 includes an n-type AlGaN cladding layer 2 (hereinafter simply referred to as the n-type cladding layer 2), an active layer 3, a p-type AlGaN cladding layer 4 (hereinafter simply referred to as the p-type cladding layer 4), and a p-type GaN contact layer 5 (hereinafter simply referred to as the p-type contact layer 5). The composition ratio of Al and Ga in the n-type cladding layer 2 and the p-type cladding layer 4 is appropriately determined according to the characteristics of the laser light emitted from the emitter 30 (see FIG. 3C). The active layer 3 is a known multiple quantum well (MQW) layer, and is formed by alternately stacking InGaN layers and GaN layers, or InGaN layers having different In and Ga composition ratios. The composition ratio of In and Ga in the active layer 3 is also appropriately determined according to the characteristics of the laser light emitted from the emitter 30. Further, depending on the laser characteristic specifications, further layers such as an InGaN guide layer (not shown) may be added.

[0025] Next, a mask pattern (not shown) is formed on the surface of the GaN laminate 10 (Step S4). The mask pattern is obtained by patterning an insulating film such as SiO2 formed on the surface of the GaN laminate 10 into a predetermined shape using photolithography and dry etching.

[0026] Using this mask pattern as an etching mask, GaN laminate 10 is patterned to obtain emitter prototype 31 (step S5). In practice, the process from mask pattern formation to etching of GaN laminate 10 is performed two or three times to form ridge portion 11, separation groove 12, and first groove 13 shown in Figures 3B to 3D. When the etching process is performed twice, separation groove 12 and first groove 13 are formed simultaneously.

[0027] After the emitter prototype 31 is formed, an insulating film such as SiO2 is formed on the surface of the GaN substrate 1, and the insulating film is patterned using photolithography and dry etching so that only the surface of the ridge portion 11 is exposed. Then, a p-side contact electrode (not shown) is formed to make ohmic contact with the p-type contact layer 5 on the surface of the ridge portion 11. Then, a metal multilayer film is deposited on the surface of the GaN substrate 1 using another mask pattern as a mask. Next, the other mask pattern is removed by wet etching or the like, and the portion of the other metal multilayer film that covers the other mask pattern is removed by a lift-off method. Through the above steps, the p-side electrode 8 is formed (step S6).

[0028] Next, the GaN substrate 1 is polished to a thickness of 100 μm or less (step S7). Commercially available GaN substrates are usually about 400 μm thick, but to achieve stable cleavage in the subsequent cleavage step, it is preferable for the GaN substrate 1 to be as thin as possible, and a thickness of about 80±20 μm is preferable in terms of a balance with ease of handling.

[0029] Thereafter, another mask pattern is formed on the rear surface of the GaN substrate 1 by photolithography, and then a metal multilayer film different from the p-side electrode 8 is deposited on the rear surface of the GaN substrate 1. Next, the mask pattern is removed by wet etching or the like, and the portion of the metal multilayer film covering the insulating film is removed by a lift-off method. Through the above steps, the n-side electrode 7 is formed (step S8).

[0030] The p-side electrodes 8 formed in step S6 are patterned into an array at intervals in each of the X and Y directions (see FIGS. 8 and 9). Each of these patterned p-side electrodes 8 may be referred to as a p-side electrode pattern 8. Note that the p-side electrodes 8 may be provided continuously in the X direction. In this case, one p-side electrode pattern 8 is provided in common for multiple emitters 30.

[0031] The emitter prototype 31 shown in FIGS. 3B to 3D is of the emitter 30 shown in FIG. 3E and has a structure constituted only by the nitride semiconductor layer before the insulating layer 6, the n-side electrode 7, and the p-side electrode 8 are formed.

[0032] The ridge portion 11, together with the insulating layer 6 shown in Fig. 3E, is formed for the purpose of injecting current only into the active layer 3 immediately below the ridge portion 11 and confining light immediately below the ridge portion 11. In this manner, current and light are confined to a specific portion of the active layer 3, and when the injected current exceeds a threshold value, laser oscillation occurs and laser light is emitted from the emitter 30 (see Fig. 7).

[0033] The ridge portion 11 includes a p-type contact layer 5 and a p-type cladding layer 4. The p-type cladding layer 4 has a protrusion 4a.

[0034] When forming the ridge portion 11, the p-type contact layer 5 is entirely removed in the area other than the ridge portion 11, the p-type cladding layer 4 is partially removed, and portions 4b of the p-cladding layer are included on both sides of the ridge portion 11.

[0035] The separation grooves 12 are provided to separate the emitters 30 adjacent to each other in the X direction and to reduce warpage of the laser diode bar 40. In the example shown in Fig. 3B, the separation grooves 12 are formed so as not to overlap the cleavage planes of the laser diode bar 40. However, in order to most effectively suppress warpage of the block 20, and in turn the laser diode bar 40, in the X direction, it is preferable that the separation grooves 12 are formed continuously in all the laser diode bars 40 within the block 20 along the Y direction.

[0036] In the example shown in Figures 3C and 3D, the separation groove 12 is formed so as to reach the surface of the GaN stack 10, i.e., the surface of the p-type contact layer 5, to the GaN substrate 1; however, the separation groove 12 may be formed so that its bottom reaches partway through the n-type cladding layer 2, or may be formed so as to reach the inside of the GaN substrate 1.

[0037] The first groove 13 is provided not only for the purpose of forming the ridge portion 11 but also for the purpose of relieving stress applied to the cleavage plane when the block 20 is cleaved to form the laser diode bar 40. In addition, only the ridge portion 11 becomes a protrusion in areas other than the cleavage plane, and the pedestal portion 14 having the same height as the ridge portion 11 is left without being removed by etching in order to prevent defects such as chipping during the process. Therefore, in the example shown in Figs. 3B and 3C, the first groove 13 is formed in a portion that straddles the portion that becomes the cleavage plane of the laser diode bar 40 and on both sides of the ridge portion. In addition, the depth of the first groove 13 is up to the middle of the p-type cladding layer 4. However, the first groove 13 may be formed continuously in all the laser diode bars 40 along the Y direction inside the block 20, and may have a shape without the pedestal portion 14.

[0038] As shown in FIG. 3C, the width of the emitter prototype 31 in the X direction is W1, and the width of the separation groove 12 in the X direction is W S Then, the width W of the emitter 30 in the X direction is E is the width W1 and the width W SThe width of first groove 13 in the X direction is W2. The thickness of p-type cladding layer 4 is T1, and the thickness in the Z direction from the interface between active layer 3 and p-type cladding layer 4 to the bottom surface of first groove 13 is T2.

[0039] Next, as shown in Fig. 4, the GaN substrate 1 is divided into a plurality of blocks 20 (step S9). Each block 20 includes a plurality of emitters 30. For ease of explanation, the shape of the p-side electrode pattern 8 is simplified in Fig. 4, and as described above, the actual p-side electrode pattern 8 is formed in a state in which it is divided at a predetermined interval in the Y direction as well. Also, in Fig. 4, the number of p-side electrodes 8 included in one block 20 is different from the actual number.

[0040] At regular intervals in the Y direction, cleavage grooves 50 of a predetermined length are formed along the X direction from an end face of the block 20 perpendicular to the X direction (step S10). As shown in Fig. 5, for one block 20, a plurality of cleavage grooves 50 are formed along the Y direction at intervals equal to the resonator length L (see Fig. 7) of the emitter 30. For ease of explanation, the p-side electrode pattern 8 is omitted in Fig. 5, but in reality, the p-side electrode pattern 8 is formed to pass between adjacent p-side electrode patterns 8 in the Y direction (see Fig. 8).

[0041] The cleavage grooves 50 are formed by irradiating a laser beam of a predetermined output from the surface of the GaN laminate 10 in the block 20 along the X direction over a predetermined length. The wavelength of the laser beam in this case is a wavelength that is absorbed by the GaN laminate 10, and specifically, is preferably shorter than the emission wavelength of the active layer 3. Although not shown, auxiliary grooves (not shown) may be provided for each cavity length L, and the cleavage grooves 50 may be formed by irradiating the laser beam through the auxiliary grooves.

[0042] Next, the block 20 is cleaved starting from the cleavage grooves 50 (step S11). The cleavage process in step S11 is performed using jigs such as a cleavage table 60 and a cutting blade 80, which will be described later. This will be further described with reference to Figures 6A and 6B.

[0043] 6A and 6B is a support table on which a groove 61 extending linearly in one direction is provided. Protective sheets 70 are attached to both the front and back surfaces of the block 20 on which the cleavage grooves 50 are formed. Next, the block 20 is set on the cleavage table 60 so that the length direction of the cleavage grooves 50 and the extension direction of the grooves 61 are aligned and the cleavage grooves 50 face the grooves 61.

[0044] With block 20 set on cleavage table 60, a cleavage cutting blade 80 is pressed against protective sheet 70 attached to the back surface of block 20 along the extension direction of groove 61 to press block 20. Starting from the tip of cleavage groove 50, a force of a predetermined value or more is applied to GaN substrate 1, whereby GaN substrate 1 including GaN laminate 10 is cleaved in the length direction of cleavage groove 50, in this case, the X direction.

[0045] Incidentally, the cleavage groove 50 is formed on the surface of the GaN substrate 1, or more precisely, the GaN laminate 10, but it is also possible to form the cleavage groove on the back surface side in terms of manufacturing. However, in order to prevent damage to the active layer 3 in the cleavage process as much as possible, it is preferable to form the groove on the front surface side. By forming the cleavage groove 50 at a predetermined depth from the front surface of the GaN laminate 10 and pressing and dividing the GaN substrate 1 from the back surface along the cleavage groove 50 with the cutting blade 80, it is possible to prevent excessive pressure from being applied to the active layer 3, which would cause damage to the active layer 3.

[0046] Next, in the laser diode bar 40, an end face coating film 9A is formed on one of a pair of cleavage faces facing each other in the Y direction, and an end face coating film 9B is formed on the other (step S12). In the following description, the side of the laser diode bar 40 on which the end face coating film 9A is formed may be referred to as the front end face or front, and the side on which the end face coating film 9B is formed may be referred to as the rear end face or rear. The terms "front" and "rear" refer to the Y direction. The block 20 and the GaN substrate 1 before the laser diode bar 40 is extracted by cleavage may also be referred to as the front or rear in the Y direction.

[0047] The surfaces on which the end face coating films 9A and 9B are formed correspond to the resonator end faces of the emitter 30, and in this embodiment, as shown in Fig. 7, the surface on which the end face coating film 9A is formed corresponds to the surface on which the emission point 32 of the laser light is located. Note that in Fig. 7, the number of emitters 30 included in the laser diode bar 40 differs from the actual number. The actual number of emitters 30 is, for example, about 30 to 60.

[0048] Through the processes shown in steps S1 to S12, the laser diode bar 40 is completed (step S13).

[0049] [Findings that led to this disclosure] 1, a cleavage plane is formed along the m-plane of the GaN substrate 1. This cleavage plane is the cleavage plane of the laser diode bar 40, and a straight line along the cleavage plane is parallel to the a-axis line L3 in the top view (see FIG. 11).

[0050] In addition, in the GaN substrate 1 whose main surface is the c-plane, the orientation flat line L0 is formed so as to be parallel to the a-axis direction line L3. A mask pattern for patterning the GaN substrate 1 and the p-side electrode pattern 8 is formed using the orientation flat line L0 as a reference line. In the following description, a straight line along the cleavage plane of the laser diode bar 40 in a top view may be referred to as a cleavage line L1 or a first virtual line L1. In addition, in a top view, a virtual line passing through the midpoints of the front end faces of the multiple p-side electrode patterns 8 may be referred to as a pattern line L2 or a second virtual line L2. In addition, in a top view, a virtual line passing through the midpoints of the rear end faces of the multiple p-side electrode patterns 8 may be referred to as a pattern line L4 or a fourth virtual line L4 (see FIG. 9).

[0051] On the other hand, as mentioned above, GaN substrate 1 is hard, and therefore the processing precision of orientation flat 1a is low. As a result, the parallelism between orientation flat line L0 and a-axis line L3 is low, and the two often do not coincide with each other.

[0052] The inventors of the present application have found that poor parallelism between the orientation flat line L0 and the a-axis line L3 leads to a large angular misalignment between the cleavage line L1 and the pattern line L2, and that a large angular misalignment makes the laser diode bar 40 more susceptible to characteristic defects. This will be further described below with reference to the drawings.

[0053] Fig. 8 is a schematic diagram for explaining the angular deviation between the cleavage lines and pattern lines of a laser diode bar, and Fig. 9 is a schematic diagram for explaining the range of the angle between the cleavage lines and pattern lines of a laser diode bar.

[0054] In the following description, the virtual line L j A virtual line L based on i and virtual line L j The angle between them is θ ij (i and j are integers from 0 to 3, and i ≠ j). For convenience of explanation, in this specification, θ ij The rotation direction of is positive when viewed from above in a counterclockwise direction and negative when viewed from above in a clockwise direction.

[0055] As shown in FIG. 8, the cleavage line L1 and the pattern line L2 do not coincide with each other, and the angle between them (-θ 12 ) becomes greater than a predetermined value, the front end face of the p-side electrode pattern 8 protrudes from the cleavage line L1 at one end of the laser diode bar 40. As a result, a part of the p-side electrode pattern 8 may cover the cleavage plane of the laser diode bar 40. When this happens, the emitter 30 located at the part of the cleavage plane covered by the p-side electrode pattern 8 does not emit light, and no laser light is emitted.

[0056] When the laser diode bar 40 is used as a laser light source, high-power laser light is obtained by combining laser light emitted from multiple emitters 30. If a light emission defect occurs in some of the emitters 30, laser light of the desired power cannot be obtained, and the laser diode bar 40 itself becomes a defective product.

[0057] As a result of various investigations, the inventors of the present application have concluded that |θ 12 It has been found that, when | satisfies the relationship shown in formula (1), the occurrence of defective characteristics of the laser diode bars 40 can be prevented, and a decrease in the yield of the laser diode bars 40 can be suppressed.

[0058] |θ 12 | <tan -1 (2(DA) / W) ···(1) Here, the length D is half the distance between adjacent p-side electrode patterns 8 in the Y direction in the block 20, as shown in FIG. 9. Ideally, the length D is a distance between the center line L C This corresponds to the distance between the center line L and the end face of the p-side electrode pattern 8 facing the center line L. C corresponds to the designed cleavage line L1.

[0059] Also, A is a positive constant and corresponds to the lower limit of the distance along the Y direction between the designed cleavage plane of the laser diode bar 40 and the end face of the p-side electrode pattern 8. Also, D≧A. In other words, the block 20 is cleaved so as not to be shorter than the length A from the end face of the p-side electrode pattern 8.

[0060] |θ 12 By making | satisfy the relationship shown in formula (1), the cleavage line L1 and the pattern line L2 do not intersect within the range of the length W in the X direction of the laser diode bar 40. In other words, the p-side electrode pattern does not cover the cleavage surface at the end of the laser diode bar 40, and light emission defects of the emitter 30 at the end of the laser diode bar 40 can be prevented.

[0061] In addition, when the angle deviation with respect to the a-axis direction line L3 is taken into consideration, the angle θ 12 It was found that the range is more preferable.

[0062] Fig. 10A is a schematic diagram for explaining the range of angles formed by the cleavage lines, the pattern lines, and the a-axis lines, and Fig. 10B is another schematic diagram for explaining the range of angles formed by the cleavage lines, the pattern lines, and the a-axis lines.

[0063] The angle between the pattern line L2 and the a-axis direction line L3 is defined as θ 32 Then, the angle θ 12 and angle θ 32 It was found that the angles of the cleavage lines L1 and L3 are preferably rotated in the same direction with respect to the pattern line L2. In other words, it was found that the direction of the angular shift of the cleavage lines L1 with respect to the pattern line L2 is preferably the same as the direction of the angular shift of the a-axis line L3 with respect to the pattern line L2.

[0064] Angle θ 12 and angle θ 32 When the above-mentioned relationship is satisfied between the p-side electrode pattern 8 and the cleavage line L1, the cleavage line L1 and the a-axis direction line L3 are shifted in the same direction with respect to the pattern line L2. When the above-mentioned relationship is satisfied while satisfying the relationship shown in formula (1), the cleavage direction is corrected to the extension direction of the a-axis direction line L3, which is the original cleavage direction, in a state where the cleavage line L1 is not in contact with the p-side electrode pattern 8, and an improvement in the cleavage yield can be expected. In other words, it is possible to reliably prevent the emission failure of the emitter 30 at the end of the laser diode bar 40, and further the occurrence of characteristic failure due to cracks or steps on the cleavage surface of the laser diode bar 40, and suppress a decrease in the yield of the laser diode bar 40.

[0065] The angle between the cleavage line L1 and the a-axis line L3 is θ 13 The angle between the a-axis direction line L3 and the pattern line L2 is θ 32 When this is done, as shown in FIG. |θ 13 |<0.5×|θ 32 | (2) It is preferable that the following relationship is satisfied. In FIG. 10B, the cleavage line L 1+is an angle θ counterclockwise with respect to the a-axis direction line L3 13 The cleavage line L is an imaginary line that is shifted by 1- is an angle θ clockwise with respect to the a-axis direction line L3 13 It is a virtual line shifted by only

[0066] Angle θ 13 and angle θ 32 When the relationship shown in formula (2) holds between the cleavage lines L1 and L3, it can be said that the cleavage lines L1 and L3 are close to each other with the pattern line L2 as a reference. In other words, the angular deviation between the actual cleavage plane and the designed cleavage plane is small. As a result, by satisfying the relationship shown in formula (2) while satisfying the relationship shown in formula (1), it is possible to reliably prevent the occurrence of poor light emission of the emitter 30 and thus poor characteristics of the laser diode bar 40 caused by poor workmanship due to cracks or steps on the cleavage plane of the laser diode bar 40, and suppress a decrease in the yield of the laser diode bar 40.

[0067] In order to improve the cleavage yield of the laser diode bar 40, in addition to the relationship between the cleavage line L1, the pattern line L2, and the a-axis direction line L3 described above, the off angle θ OFF As a result of the investigation by the present inventors, it became clear that the off angle θ OFF The off-angle θ is the inclination angle of the c-axis with respect to the primary surface of the GaN substrate 1. OFF and the off angle θ OFF and angle θ 12 The relationship between the above will be further explained with reference to the drawings.

[0068] Fig. 11 is a schematic diagram illustrating the crystal structure of GaN as viewed from the c-axis direction. Fig. 12 is a schematic diagram illustrating the off-angle of a GaN substrate. Fig. 13A is a schematic diagram illustrating an example of the direction of the off-angle in a GaN substrate. Fig. 13B is a schematic diagram illustrating another example of the direction of the off-angle in a GaN substrate. Fig. 13C is a schematic diagram illustrating yet another example of the direction of the off-angle in a GaN substrate. In Figs. 13A to 13C, the arrows shown on GaN substrate 1 indicate the off-direction, which will be described later.

[0069] As shown in Fig. 11, the c-axis, m-axis, and a-axis of a hexagonal GaN crystal are mutually orthogonal. The c-axis is orthogonal to the c-plane, the m-axis is orthogonal to the m-plane, and the a-axis is orthogonal to the a-plane. If the primary surface of the GaN substrate 1 is the c-plane, the off-angle θ OFF is zero. However, as mentioned above, in order to form a high-quality GaN laminate 10, a c-plane substrate with an off-axis angle of about 0.1 to 1.0° from the c-plane is often used as the GaN substrate 1. Furthermore, due to the influence of warping and the like that occurs during the manufacturing process of the GaN substrate, the magnitude and direction of the off-angle at which the primary surface is inclined with respect to the c-plane usually vary somewhat within the plane of the substrate. For this reason, within the plane of the GaN substrate 1, the off-angle θ OFF Also, the off direction θ OFF-D also has a finite value that differs depending on the location.

[0070] 12, in an off-axis substrate, the c-axis is inclined with respect to the c-axis direction, m-axis direction, and a-axis direction when the primary surface is a non-off-axis c-plane. When the off-axis c-axis direction is expressed as a standardized vector, the length of the vector obtained by projecting this vector onto the primary surface (XY plane) of the GaN substrate 1 represents the magnitude of the off-axis angle. On the other hand, the a-axis direction in the XY plane is taken as the reference direction, and the angle between the reference direction and the projected vector is taken as θ OFF-D Let θ OFF-D It can be said that the off-direction θ represents the direction of the projection vector based on the a-axis direction. OFF-D The vector shown in FIG. 13A is the above-mentioned projection vector, and is in the off direction θ OFF-Dcontains both m-axis and a-axis components and has slightly different directions within the substrate plane. In addition, the magnitude of the off-angle θ OFF also have slightly different magnitudes in the substrate plane and are expressed as the lengths of the projected vectors.

[0071] Furthermore, when the main surface of the GaN substrate 1 is tilted from the c-plane, the m-plane may also be tilted from its original direction. Specifically, when the off-direction is the a-axis direction, the m-plane, which is the cleavage plane, only rotates in a plane perpendicular to the m-axis, so there is no movement of the m-plane due to the off-direction. However, when the off-direction has an m-axis component, the m-plane has a slight inclination from the top to the bottom of the laser diode bar 40 due to the rotation in the a-axis direction. Note that, in different GaN substrates 1, the off-direction may be mainly in the m-axis direction as shown in FIG. 13B, or may be mainly in the a-axis direction as shown in FIG. 13C. Also, as shown in FIGS. 13A to 13C, the off-direction is not constant within the main surface of the GaN substrate 1. The main off-direction of the GaN substrate 1 can be specified during the manufacture of the substrate, such as the a-axis direction, the m-axis direction, or an intermediate direction between them. However, this is due to the specified off-angle, in-plane variation centered on the off-direction, warpage of the seed crystal, and the like, and is unavoidable as an in-plane off-direction characteristic of the GaN substrate 1.

[0072] FIG. 14 is a schematic diagram for explaining the relationship between the angle between the cleavage line and the pattern line and the range of the off-angle direction.

[0073] According to the study by the present inventors, the off direction θ OFF-D and angle θ 12 It has been found that it is preferable to satisfy the relationship shown in Fig. 14 between and Specifically, it has been found that it is preferable to satisfy any one of the following conditions 1 to 4.

[0074] (Condition 1) Angle θ 12 is positive and 0(°)<θ OFF―D <90(°).

[0075] (Condition 2) Angle θ 12is positive and 180(°)<θ OFF―D <270(°).

[0076] (Condition 3) Angle θ 12 is negative and 90(°)<θ OFF―D <180(°).

[0077] (Condition 4) Angle θ 12 is negative and 270(°)<θ OFF―D <360(°).

[0078] Off direction θ OFF―D and angle θ 12 If any one of conditions 1 to 4 is satisfied, the cleavage line L1 is in the off-direction θ OFF―D In other words, when the main surface of the GaN substrate 1 is regarded as four quadrants divided by the line pattern L2 and imaginary lines perpendicular to the line pattern L2, the cleavage line L1 is located in the same direction as the off-direction θ OFF―D is located in the same quadrant.

[0079] For example, when the GaN substrate 1 shown in FIG. 13A is used, the off-direction has components in both the m-axis direction and the a-axis direction. In addition, the off-direction in the main surface varies within the surface, but the off-direction θ OFF-D , 0(°)<θ OFF <90(°). At the same time, it was revealed that cleavage defects are reduced and yields are improved when the a-axis direction line L3, which is the original cleavage direction, is shifted in the same direction as the pattern line L2. This is presumably because, when the shift direction with respect to the pattern and the off-direction of the GaN substrate 1 are oriented in the same rotation direction, the stress applied to the GaN laminate 10 during cleavage is reduced, making cleavage defects less likely to occur. This makes it less likely that damage will occur to the active layer 3, and improves the manufacturing yield of the laser diode bar 40.

[0080] As shown in step S2 of Fig. 1, the angular deviation between the orientation flat line L0 and the a-axis line L3 is measured in advance. Therefore, when forming a mask pattern in steps S4 and S6, this angular deviation can be used as a correction term to correct the direction of the pattern line L2 with respect to the orientation flat line L0. When using the GaN substrate shown in Fig. 13A for this angle correction, the angle θ between the pattern line L2 and the a-axis line L3 is 32 It is preferable to correct the angle θ so that it becomes slightly positive. On the other hand, when using a substrate with an off-direction distribution such as the GaN substrate 1 shown in FIG. 13B or the GaN substrate 1 shown in FIG. 13C, the off-direction differs depending on the substrate surface. For this reason, the angle θ between the pattern line L2 and the a-axis direction line L3 32 Since the directions of and do not coincide throughout the entire surface, 32 It is desirable to make a correction so that

[0081] From the above, it is most preferable for the GaN substrate 1 to have a substrate specification in which the off-direction is the same in all four quadrants as shown in FIG. 13A and the off-direction is close to the a-axis direction. OFF-E Then, the off-axis direction of the substrate is 0<θ OFF-D <2θ OFF-E It is desirable that the range is within.

[0082] [Effects, etc.] As described above, the laser diode bar 40 according to this embodiment has a plurality of emitters 30. The laser diode bar 40 is obtained by cleaving the GaN substrate 1 on which the plurality of emitters 30 are formed at intervals in the X direction, which is the arrangement direction of the emitters 30 in the laser diode bar 40. Each of the plurality of emitters 30 has a p-side electrode pattern 8.

[0083] The direction parallel to the main surface of the GaN substrate 1 and perpendicular to the X direction is defined as the Y direction. The length of the laser diode bar 40 in the X direction is defined as W, and the interval between the adjacent p-side electrode patterns 8 in the Y direction before cleavage is defined as 2D. FIG. 9 shows the case of D=D0. D0 is the shorter of the distance along the Y direction from one cleavage plane in the laser diode bar 40 to the front end face of the p-side electrode pattern 8, or the distance along the Y direction from another cleavage plane opposite to the one cleavage plane to the rear end face of the p-side electrode pattern 8. In FIG. 9, the distance along the Y direction between the front end face of the p-side electrode pattern 8 and the cleavage plane close to the front end face is defined as D0, but there are also cases where the distance along the Y direction between the rear end face of the p-side electrode pattern 8 and the cleavage plane close to the rear end face is D0.

[0084] When viewed from above, the angle θ between a second imaginary line passing through the midpoints of the front end faces of the multiple p-side electrode patterns 8, i.e., the pattern line L2, and a cleavage line L1, which is a first imaginary line along the cleavage plane of the laser diode bar 40 12 satisfies the relationship shown in equation (1).

[0085] |θ 12 | <tan -1 (2(DA) / W) ···(1) Here, A is a positive constant and D≧A.

[0086] By configuring the laser diode bar 40 in this manner, it is possible to prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This makes it possible to prevent poor light emission of the emitters 30 at the end of the laser diode bar 40, and thus poor characteristics of the laser diode bar 40, and suppress a decrease in the yield of the laser diode bar 40.

[0087] Moreover, in order to reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8, it is preferable that the following relationship be established.

[0088] The primary surface of the GaN substrate 1 is a c-plane or a plane tilted at a predetermined angle from the c-plane. The angle between the pattern line L2 and an a-axis direction line L3, which is a third imaginary line obtained by projecting the a-axis direction of the GaN substrate 1 onto the primary surface of the GaN substrate 1, is defined as θ 32 Then, the angle θ 12 and angle θ 32 and are preferably rotated in the same direction with respect to the pattern line L2. The predetermined angle is a few degrees or less, and preferably 1.0 degree or less.

[0089] In other words, it is preferable that the direction of the angular shift of the cleavage lines L1 with respect to the pattern lines L2 is the same as the direction of the angular shift of the a-axis lines L3 with respect to the pattern lines L2.

[0090] The angle between the cleavage line L1 and the a-axis line L3 is θ 13 The angle between the a-axis direction line L3 and the pattern line L2 is θ 32 When |θ 13 | and |θ 32 It is preferable that | satisfies the relationship shown in formula (2).

[0091] |θ 13 |<0.5×|θ 32 | (2) The a-axis direction of the GaN substrate 1 is taken as a reference, and the counterclockwise direction is taken as a positive direction and the clockwise direction is taken as a negative direction when viewed from above. The length of a vector that extends in the c-axis direction with respect to the primary surface of the GaN substrate 1 and has a normalized length and is projected onto the primary surface of the GaN substrate 1 is defined as the magnitude of the off-angle θ. OFF The a-axis direction on the primary surface of the GaN substrate 1 is taken as the reference direction, and the angle between the reference direction and the projection vector is taken as the off-direction θ OFF-D Then, the magnitude of the off angle θ OFF and the off direction θ OFF-D It is preferable that any one of the following conditions 1 to 4 is satisfied.

[0092] (Condition 1) Angle θ 12 is positive and 0(°)<θ OFF-D <90(°).

[0093] (Condition 2) Angle θ 12 is positive and 180(°)<θ OFF-D <270(°).

[0094] (Condition 3) Angle θ 12 is negative and 90(°)<θ OFF-D <180(°).

[0095] (Condition 4) Angle θ 12 is negative and 270(°)<θ OFF-D <360(°).

[0096] When such a relationship is established, the off-axis direction θ caused by the substrate off-axis angle based on the pattern line L2 is OFF-D Since the direction of inclination of the cleavage plane of the laser diode bar 40 due to the cleavage is the same as the direction of the cleavage line L1, cleavage defects are unlikely to occur. This makes it difficult for damage to occur in the active layer 3, and improves the manufacturing yield of the laser diode bar 40.

[0097] When viewed from above, a pattern line L4 is a fourth imaginary line passing through the midpoints of the rear end faces of the p-side electrode patterns 8, and the angle θ between the pattern line L4 and the cleavage line L1 is 14 Then, the angle θ 14 It is preferable that the relationship shown in formula (3) is satisfied.

[0098] |θ 14 | <tan -1 (2(DA) / W) ···(3) Here, A is a positive constant and D≧A.

[0099] By configuring the laser diode bar 40 in this manner, it is possible to reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents poor light emission of the emitter 30 at the end of the laser diode bar 40, and ultimately poor characteristics of the laser diode bar 40, and suppresses a decrease in the yield of the laser diode bar 40. Note that the a-axis direction line L3 in the GaN substrate 1 is basically in the same direction within the main surface, so that |θ 12 If | satisfies the relationship shown in equation (1), then basically, |θ 14 | satisfies the relationship shown in equation (3).

[0100] Moreover, it is preferable that the length W is 5 mm or more and 20 mm or less. If the length W is shorter than 5 mm, the number of emitters 30 included in the laser diode bar 40 cannot be made sufficiently large. For example, only a dozen or so emitters 30 can be mounted, making it difficult to obtain high-output laser light. On the other hand, if the length W is longer than 20 mm, |θ 12 In terms of manufacturing, it becomes difficult for | to satisfy the relationship shown in equation (1).

[0101] Furthermore, the constant A is preferably 2 μm or more and 10 μm or less. If A becomes too small, the cleavage line L1 may come closer to the pattern line L2, but it is known that if the cleavage line L1 comes closer than a certain distance, a force may be applied to the cleavage line L1 that attracts it to the pattern due to stress from the laminated film that constitutes the electrode pattern. How close the cleavage lines L1 can come is also influenced by the material and thickness of the laminated film of the electrode pattern, so the optimal value differs depending on the surrounding structure, but according to the study by the inventors of the present application, it has been found that the constant A is preferably 2 μm or more, and more preferably about 5 μm. If the constant A is too large, θ 12 Since the tolerance for the thickness becomes smaller, a maximum of about 10 μm is preferable.

[0102] A separation groove 12 is provided between adjacent emitters 30, and the width of the emitter 30 in the X direction is W E The width of the separation groove 12 in the X direction is WS Then, the width W E and width W S It is preferable that and satisfy the relationship shown in formula (4).

[0103] 5≦100×(W S / W E )<80 ···(4) By providing the separation groove 12, the warping of the block 20 and therefore the laser diode bar 40 is reduced, so that the block 20 can be easily cleaved. E and width W S By satisfying the relationship shown in formula (4), it is possible to reliably reduce warpage of the laser diode bar 40. In order to reliably reduce warpage of the laser diode bar 40, the separation groove 12 in the laser diode bar 40 more preferably has a length along the Y direction that is 80% or more of the cavity length L of the emitter 30, and may be continuous throughout the Y direction.

[0104] When the thickness direction of the GaN substrate 1 is taken as the Z direction, the emitter 30 has a structure in which an n-type cladding layer 2, an active layer 3, and a p-type cladding layer 4 are laminated in this order along the Z direction. The p-type cladding layer 4 has at least a protrusion 4a protruding in the Z direction and first grooves 13 provided on both sides of the protrusion.

[0105] The width in the X direction of the emitter prototype 31 in the vicinity of the end face of the laser diode bar 40 shown in FIGS. 3B and 3C, that is, the width W in the X direction of the emitter 30 E The width W of the separation groove 12 in the X direction S When the value obtained by subtracting this is taken as W1 and the width of the first groove 13 in the X direction is taken as W2, it is preferable that the width W1 and the width W2 satisfy the relationship shown in formula (5).

[0106] 50≦100×(2W2 / W1)≦100 (5) By increasing the width of the first groove 13, the occurrence of cracks due to stress is reduced in the lower part of the ridge portion 11, and the block 20 can be easily cleaved. Furthermore, by making the width W1 and the width W2 satisfy the relationship shown in formula (4), the occurrence of cracks due to stress can be reliably reduced. Here, the vicinity of the end face generally refers to a portion where the p-side electrode pattern 8 is not present. The width of the first groove 13 in a portion away from the end face where the p-side electrode pattern 8 is formed may be narrower than that in the vicinity of the end face. By narrowing the width of the first groove 13 as shown in FIG. 3B and FIG. 3C and leaving a part of it at the same height as the ridge portion 11, it is possible to provide a protective function against chipping of the ridge portion 11.

[0107] Furthermore, when the thickness of the p-type cladding layer 4 is T1 and the thickness along the Z direction from the interface between the active layer 3 and the p-type cladding layer 4 to the bottom surface of the first groove 13 is T2, it is preferable that the thicknesses T1 and T2 satisfy the relationship shown in formula (6), and it is more preferable that they satisfy the relationship shown in formula (6A).

[0108] 50≦100×(T2 / T1)<100 (6) 80≦100×(T2 / T1)<100 (6A) By making the thicknesses T1 and T2 satisfy the relationship shown in formula (6) or formula (6A), the occurrence of cracks due to stress can be reliably reduced, and the block 20 can be easily cleaved.

[0109] When the cavity length of the emitter 30 is L and the shorter of the distance along the Y direction from one cleavage surface in the laser diode bar 40 to the front end surface of the p-side electrode pattern 8 or the distance along the Y direction from another cleavage surface opposite the one cleavage surface to the rear end surface of the p-side electrode pattern 8 is D0, it is preferable to satisfy the relationship shown in formula (7).

[0110] D0≦0.2L (7) In particular, when the cavity length L is short, as the distance D0 increases, the contact area between the p-side electrode 8 and the p-type contact layer 5 of the emitter 30 decreases, and the ohmic resistance between the p-side electrode 8 and the emitter 30 increases to a predetermined value or more. In this case, the threshold current increases, and there is a risk that the output of the laser light emitted from the emitter 30 may decrease.

[0111] On the other hand, when the distance D0 satisfies the relationship shown in formula (7), an increase in the ohmic resistance between the p-side electrode 8 and the emitter 30 and a decrease in the output of the laser light emitted from the emitter 30 can be suppressed.

[0112] The method for manufacturing the laser diode bar 40 according to this embodiment includes at least the following first to seventh steps.

[0113] In the first step (Step S1 in FIG. 1), a GaN substrate 1 having an orientation flat 1a is prepared.

[0114] In the second step (Step S3 in FIG. 1), a GaN stack 10 having a plurality of nitride semiconductor layers is formed on the surface of the GaN substrate 1.

[0115] In the third step (steps S4 and S5 in FIG. 1), the GaN laminate 10 is processed using a mask pattern to form a plurality of emitter prototypes 31.

[0116] In a fourth step (step S6 in FIG. 1), after the third step is performed, a p-side electrode pattern 8 is formed on the surface of each of the plurality of emitter prototypes 31 using another mask pattern.

[0117] In a fifth step (step S9 in FIG. 1), after the fourth step is performed, the GaN substrate 1 is divided into blocks 20 of a predetermined size each including a plurality of emitters 30.

[0118] In a sixth step (step S10 in FIG. 1), a plurality of cleavage grooves 50 are formed at predetermined intervals from one end face of the block 20 along the X direction perpendicular to the one end face and in the Y direction parallel to the one end face.

[0119] In the seventh step (steps S11 to S13 in FIG. 1), the block 20 is cleaved starting from the cleavage grooves 50 to obtain the laser diode bars 40.

[0120] In the fourth step, the p-side electrode patterns 8 are provided at intervals along the X direction and at intervals along the Y direction. The p-side electrode patterns 8 may be continuous in the X direction across multiple emitters 30 inside the laser diode bar 40, but are preferably separated at intervals from each other for the purpose of reducing warping and inspecting the characteristics of each emitter 30 in advance.

[0121] In the block 20, when the interval between adjacent p-side electrode patterns 8 in the Y direction is 2D, in the seventh step, the angle θ between the pattern line L2 and the cleavage line L1 in the top view is 12 The block 20 is cleaved so that the relationship shown in formula (1) is satisfied.

[0122] This makes it possible to prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This makes it possible to prevent poor light emission of the emitters 30 at the end of the laser diode bar 40, and thus poor characteristics of the laser diode bar 40, and suppress a decrease in the yield of the laser diode bars 40.

[0123] In addition, the angle θ between the pattern line L4 and the cleavage line L1 14 It is preferable that the relationship shown in the above-mentioned formula (3) is satisfied.

[0124] This can reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents poor light emission of the emitters 30 at the end of the laser diode bar 40, and thus poor characteristics of the laser diode bar 40, and suppresses a decrease in the yield of the laser diode bars 40.

[0125] In the sixth step, it is preferable to form only one cleavage groove 50 between the p-side electrode patterns 8 adjacent to each other in the Y direction in the block 20.

[0126] In the conventional method disclosed in Patent Document 1, broken scribe lines are formed along the planned dividing lines of the laser diode bar 40, and then cleavage is performed. This makes it possible to stabilize the shape of the laser diode bar 40. However, if the cleavage direction is forcibly corrected using this method, damage is caused to the cleavage plane, which may cause poor light emission in the emitter 30 at the damaged portion.

[0127] On the other hand, as shown in this embodiment, by providing only one cleavage groove 50 on one of the end faces parallel to the Y direction in the block 20, the probability that cleavage of the block 20 will occur from the cleavage groove 50 along the a-axis direction line L3, which is the original cleavage direction, instead of the pattern line L2, increases. This makes it possible to prevent damage to the cleavage surface, and suppress the occurrence of poor light emission of the emitter 30 and therefore poor characteristics of the laser diode bar 40. Also, a decrease in the manufacturing yield of the laser diode bar 40 can be suppressed.

[0128] In addition, the off-angle θ of the GaN substrate 1 OFF and the off direction θ OFF-D It is preferable that any one of the above-mentioned conditions 1 to 4 is satisfied.

[0129] By doing this, the off angle θ OFF and the off direction θ OFF-DSince the direction of the inclination of the cleavage plane of the laser diode bar 40, which depends on the cleavage angle θ, is the same as the direction of the cleavage line L1, cleavage defects are unlikely to occur. This makes it possible to prevent damage to the active layer 3 and to improve the manufacturing yield of the laser diode bar 40.

[0130] In addition, the angle θ between the pattern line L4 and the cleavage line L1 14 It is preferable that the relationship shown in formula (3) is satisfied.

[0131] This can reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents poor light emission of the emitters 30 at the end of the laser diode bar 40, and thus poor characteristics of the laser diode bar 40, and suppresses a decrease in the yield of the laser diode bars 40.

[0132] <Variation 1> Fig. 15A is a plan view showing an example of a p-side electrode pattern according to Modification 1. Fig. 15B is a plan view showing another example of a p-side electrode pattern according to Modification 1. For ease of explanation, in Figs. 15A and 15B, the same reference numerals are used for the same parts as in embodiment 1, and detailed explanations thereof will be omitted.

[0133] 15A and 15B is fabricated by the manufacturing method shown in embodiment 1. On the other hand, the laser diode bar 40 of this modification differs from the laser diode bar 40 of embodiment 1 shown in FIG. 9 in the following points.

[0134] First, in the example shown in FIG. 12 is set so as to satisfy the formula (1) and the relationship shown in the following formula (8).

[0135] |θ 12 | <tan -1 (2(D1-A1) / W) ···(8) In addition, the number of emitters 30 included in the laser diode bar 40 is n, and m is an integer between 1 and n. If the p-side electrode pattern 8 with the longest length in the Y direction is the first p-side electrode pattern 8, the length L in the Y direction of the m-th p-side electrode pattern 8 is m is set so as to satisfy the relationship shown in equation (9).

[0136] L m <L-2A1―2(D1-A1)×(m / n) ···(9) Here, A1 is half the distance between the first p-side electrode patterns 8 adjacent to each other in the Y direction in the block 20, and A1 ≧ A. Also, D1 is half the distance between the n-th p-side electrode patterns 8 adjacent to each other in the Y direction in the block 20.

[0137] Angle θ 12 By satisfying the relationships shown in formulas (1) and (8), it is possible to reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents the emitter 30 from failing to emit light at the end of the laser diode bar 40, and in turn the characteristics of the laser diode bar 40 from failing, thereby suppressing a decrease in the yield of the laser diode bar 40. Furthermore, the length L of the m-th p-side electrode pattern 8 in the Y direction can be reduced by m However, by satisfying the relationship shown in formula (9), the size of the p-side electrode pattern 8 can be maximized. Also, in the block 20, the electrode width of the p-side electrodes 8 adjacent to each other in the Y direction at the cleavage start portion can be narrowed, thereby improving the alignment accuracy of the mask pattern when forming the p-side electrode pattern 8.

[0138] As shown in FIG. 15B, the length of the p-side electrode pattern 8 in the Y direction changes only on one side, and the angle θ 12 satisfies formulas (1) and (10), and the length L of the m-th p-side electrode pattern 8 in the Y direction is m may be set so as to satisfy the formula (11).

[0139] 0<θ 12 | <tan -1(2(D1-A1) / W) ···(10) L m <L-2A1―(D1-A1)×(m / n) ···(11) In the example shown in FIG. 15B, in the block 20, the distance between the n-th p-side electrode patterns 8 adjacent to each other in the Y direction is A1+D1.

[0140] (Embodiment 2) Fig. 16 is a flow chart showing a method for manufacturing a laser diode bar according to embodiment 2. Fig. 17A is a schematic diagram for explaining the positional relationship between the orientation flat lines and the a-axis lines. Fig. 17B is a schematic diagram for explaining the positional relationship between the orientation flat lines, the a-axis lines, and the pattern lines. Fig. 17C is a schematic diagram for explaining the positional relationship between the orientation flat lines, the a-axis lines, the pattern lines, and the cleavage lines.

[0141] In the flowchart of this embodiment shown in FIG. 16, steps S21 to S33 are similar to steps S1 to S13 in the flowchart shown in FIG. 1, so detailed description thereof will be omitted.

[0142] In the method for manufacturing the laser diode bar 40 shown in this embodiment, when the laser diode bar 40 is manufactured through a series of steps S21 to S33, θ is calculated from information on the amount of angular deviation between the orientation flat line L0 and the a-axis direction line L3 when forming a mask pattern that is the basis of the pattern line L2. 32 A step (step S24) of forming a pattern by performing rotation correction so that the deviation angle θ between the pattern line L2 and the a-axis direction line L3 by the formed mask pattern is less than a certain value. 32 The method further includes a step of determining whether or not the difference is within an allowable range (step S25).

[0143] In addition, when performing step S25, the angle deviation amount (angle θ 32 As shown in FIG. 17A, the angle θ 30Next, as shown in FIG. 17B, in steps S24 and S25, the angle deviation amount θ between the orientation flat line L0 and the pattern line L2 is 20 By evaluating θ 32 The angle θ 20 is evaluated using an image recognition device having a camera, etc.

[0144] By performing rotation correction when forming the pattern line L2, the θ 32 can be made close to zero and below a certain value, and θ in Eq. (1) 12 θ 32 By adding such a manufacturing process, in the cleavage process (steps S31 and S32), the cleavage line L1 acts to split along the a-axis line L3 as shown in FIG. 17C, so that it is possible to satisfy the formula (1) and almost completely eliminate cleavage defects.

[0145] In the determination process of step S25, the angle θ 32 If it is outside the allowable range, the mask pattern is removed once, and when step S24 is performed again, the angle θ 32 Correct the correction value so that it falls within the allowable range.

[0146] To verify whether the correction has been performed correctly, in step S33, the angle deviation between the cleavage line L1 and the pattern line L2 (angle θ 12 ) is calculated (see Figure 17C). 12 The angle θ is evaluated using an image recognition device having a camera or the like. 32 and angle θ 12 and the correlation between the predicted and actual values ​​of the deviation of the cleavage position can be examined.

[0147] 18A is a diagram showing the relationship between the predicted value of the deviation of the cleavage position between the left and right ends of the laser diode bar after the process correction and the actual deviation of the cleavage position between the left and right ends of the laser diode bar after the cleavage process. The horizontal axis of FIG. 18A corresponds to the predicted value of the deviation of the cleavage position and is evaluated during the process. 32 The vertical axis corresponds to the actual value of the deviation of the cleavage position, and is used to evaluate the quality of the cleavage in step S33. When the bar width W is 10 mm, the deviation of the cleavage line L1 along the Y direction is shown across the entire width of the laser diode bar 40, with the pattern line L2 as the reference.

[0148] 18B is a diagram showing the relationship between the predicted value of the angle deviation after the process correction and the actual value of the angle deviation after the cleavage process. 32 The vertical axis corresponds to the evaluation value of the angle θ from the actual deviation of the cleavage line L1. 12 This corresponds to the calculated value.

[0149] By performing the correction process and the judgment process in steps S24 and S25, the amount of angle deviation can be suppressed to 0.05° or less. 32 and performance value θ 12 An almost one-to-one correlation can be seen between the two. In addition, the amount of deviation in workmanship is within 10 μm, which is within the level where formula (1) can be easily satisfied.

[0150] As is clear from Figures 18A and 18B, it was found that there is a linear correlation between the predicted value and the actual value of the deviation amount of the cleavage position. 32 The predicted and actual values ​​of θ 12 In other words, because the cleavage phenomenon occurs along the a-axis direction, the cleavage line L1 has a tendency to split along the a-axis line L3, and it can be confirmed from the actual prototype data that if the a-axis line L3 is evaluated in advance and the pattern line L2 is formed under conditions that do not inhibit cleavage, the cleavage line L1 will be formed along the a-axis line L3.

[0151] In the cleavage phenomenon, it is difficult to completely align the cleavage line L1 and the a-axis line L3. However, the angle θ 32 The direction of the pattern line L2 based on the orientation flat line L0, in other words, the angle θ between the orientation flat line L0 and the pattern line L2, is set so that the angle θ 20 By manufacturing the laser diode bar 40 while correcting the above, the direction of the cleavage line L1 and the direction of the a-axis line L3 can be made close to each other.

[0152] In addition, as a means of stabilizing the yield, 32 Based on the evaluation value, during the formation of cleavage grooves 50 in steps S30 and S31 and the cleavage on the cleavage table 60, it is also possible to adjust the process so that the extension direction of cleavage grooves 50 and the extension direction of cleavage groove 61 of cleavage groove 60 are aligned along the a-axis line L3.

[0153] These corrective operations in the manufacturing process can reduce cleavage defects and reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents light emission defects of the emitters 30 at the end of the laser diode bar 40, and thus characteristic defects of the laser diode bar 40, and suppresses a decrease in the yield of the laser diode bars 40.

[0154] As described above, the method for manufacturing the laser diode bar 40 according to this embodiment includes an eighth step in addition to the first to seventh steps shown in the first embodiment.

[0155] In the eighth step (step S25 in FIG. 17), after the mask pattern is formed (step S24 in FIG. 17) after the second step (step S23 in FIG. 17), the angle θ 10 It is determined whether or not the value is within a predetermined acceptable range.

[0156] If the result of the determination in the eighth step is negative, the mask pattern is removed, and when step S24 is performed again, the angle θ 32 Correct the correction value so that it falls within the allowable range.

[0157] <Variation 2> In the second embodiment, in step S25 of FIG. 32 is within the allowable range, but instead, the angle θ 12 It may be determined whether or not the relationship shown in formula (1) is actually satisfied.

[0158] Angle θ 12 If the relationship shown in formula (1) is satisfied, the process proceeds directly to the next step S26, where the laser diode bar 40 is manufactured. 12 does not satisfy the relationship shown in formula (1), the mask pattern is removed and step S24 is performed again, and the angle θ 12 A correction is performed so that equation (1) is satisfied, and a mask pattern is formed.

[0159] In this way, it is possible to reduce cleavage defects and reliably prevent the cleavage plane from being covered by a part of the p-side electrode pattern 8 at the end of the laser diode bar 40. This reliably prevents light emission defects of the emitters 30 at the end of the laser diode bar 40, and thus characteristic defects of the laser diode bar 40, and suppresses a decrease in the yield of the laser diode bars 40. [Industrial Applicability]

[0160] The laser diode bar of the present disclosure is useful because it can prevent the p-side electrode pattern from covering the cleavage plane, thereby suppressing the occurrence of characteristic defects at the ends of the laser diode bar and the decrease in manufacturing yield. [Explanation of symbols]

[0161] 1 GaN substrate 1a Orientation Flat 2 n-type cladding layer 3 Active layer 4 p-type cladding layer 4a Convex part 4b Part of p cladding layer 5 p-type contact layer 6 Insulating layer 7 n-side electrode 8 p side electrode 9A, 9B End surface coating film 10 GaN stack 11 Ridge 12 Separation groove 13 First groove 14 Pedestal 20 blocks 30 Emitter 31 Emitter prototype 32 Light Point 40 Laser Diode Bar 50 Cleavage groove 60 Cleavage stand 61 Groove on cleavage base 70 Protective Sheet 80 cutting blade L0 Orientation Flat Line (Virtual Line) L1 cleavage line (first imaginary line) L2 pattern line (second virtual line) L3a axial line (third virtual line) L C Center line (imaginary line) between p-side electrode patterns (Y direction) L4 pattern line (rear end surface reference, 4th virtual line) θ OFF GaN substrate off-angle θ OFF-D Inclination direction of the off-angle of the GaN substrate projected onto the XY plane (off-direction)

Claims

1. 1. A laser diode bar having multiple emitters, comprising: the laser diode bar is obtained by cleaving a GaN substrate on which a plurality of the emitters are formed; Each of the plurality of emitters has a p-side electrode pattern, The arrangement direction of the emitters in the laser diode bar is defined as an X direction, the direction parallel to the main surface of the GaN substrate and perpendicular to the X direction is defined as a Y direction, the length of the laser diode bar in the X direction is defined as W, and the interval between the p-side electrode patterns adjacent to each other in the Y direction before the laser diode bar is cleaved is defined as 2D. When viewed from above, an angle θ is formed between a second imaginary line passing through the midpoints of the front end faces of the plurality of p-side electrode patterns and a first imaginary line along the cleavage plane of the laser diode bar. １２ but, |θ １２ |<tan －１ ・・・(1) (A is a positive constant and D ≥ A) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

2. 2. The laser diode bar of claim 1, a primary surface of the GaN substrate is a c-plane or a plane inclined at a predetermined angle from the c-plane; The angle between the second virtual line and a third virtual line obtained by projecting the a-axis direction of the GaN substrate onto the main surface is defined as θ. ３２ When A laser diode bar characterized in that the direction of angular shift of the first virtual line relative to the second virtual line is the same as the direction of angular shift of the third virtual line along the a-axis direction of the GaN substrate relative to the second virtual line.

3. 3. The laser diode bar according to claim 2, The angle between the first virtual line and the third virtual line is θ １３ The angle between the third virtual line and the second virtual line is θ ３２ Then, |θ １３ | and |θ ３２ |What is |θ １３ |<0.5×|θ ３２ | ・・・(2) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

4. 2. The laser diode bar of claim 1, With the a-axis direction of the GaN substrate as a reference, the counterclockwise direction in a top view is defined as positive, and the clockwise direction is defined as negative. Furthermore, the length of a vector that extends in the c-axis direction with respect to the main surface of the GaN substrate and has a normalized length projected onto the main surface of the GaN substrate is defined as the magnitude of the off-angle θ. ＯＦＦ The a-axis direction on the principal surface is taken as a reference direction, and the angle between the reference direction and the projection vector is taken as an off-direction θ ＯＦＦ－Ｄ When the off angle is set as θ ＯＦＦ and the off direction θ ＯＦＦ－Ｄ satisfies any one of conditions 1 to 4, The condition 1 is the angle θ １２ is a positive value and 0 (°) < θ ＯＦＦ－Ｄ < 90 (°), The condition 2 is the angle θ １２ is a positive value and 180 (°) < θ ＯＦＦ－Ｄ < 270 (°), The condition 3 is that the angle θ １２ is a negative value and 90(°)<θ ＯＦＦ－Ｄ < 180 (°), The condition 4 is that the angle θ １２ is a negative value and 270 (°) < θ ＯＦＦ－Ｄ <360(°).

5. 2. The laser diode bar of claim 1, When viewed from above, an angle θ between a fourth virtual line passing through the midpoints of the rear end surfaces of the p-side electrode patterns and the first virtual line １４ but, |θ １４ |<tan －１ ・・・(3) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

6. 2. The laser diode bar of claim 1, A laser diode bar, wherein the length W is 5 mm or more and 20 mm or less.

7. 2. The laser diode bar of claim 1, A separation groove is provided between adjacent emitters, The width of the emitter in the X direction is W Ｅ and the width of the separation groove in the X direction is W Ｓ When 5≦100×(W Ｓ / W Ｅ )<80 ・・・(4) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

8. 8. The laser diode bar of claim 7, When the thickness direction of the GaN substrate is the Z direction, the emitter includes a structure in which an n-type cladding layer, an active layer, and a p-type cladding layer are stacked in this order along the Z direction, The p-type cladding layer has at least a convex portion protruding in the Z direction and a first groove provided on both sides of the convex portion, Said width W Ｅ From the width W Ｓ The value obtained by subtracting １ and the width of the first groove in the X direction is W ２ When 50≦100×(2W ２ / W １ )≦100 ・・・(6) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

9. 2. The laser diode bar of claim 1, The cavity length of the emitter is L, and the shorter of the distance along the Y direction from one of the cleavage planes to the front end surface of the p-side electrode pattern or the distance along the Y direction from another of the cleavage planes opposite to the one of the cleavage planes to the rear end surface of the p-side electrode pattern is D. ０ When D ０ ≦0.2L ・・・(7) A laser diode bar, characterized in that the above relationship is satisfied.

10. 2. The laser diode bar of claim 1, The number of the emitters included in the laser diode bar is n, an integer between 1 and n is m, the p-side electrode pattern with the longest length in the Y direction is the first, and the interval between the first adjacent p-side electrode patterns 8 in the Y direction before division is 2A. １ Before division, the interval between the n-th p-side electrode patterns 8 adjacent to each other in the Y direction is set to 2D １ When The angle θ １２ teeth, |θ １２ |<tan －１ (2() １ -A １ ) / W) ・・・(8) (A １ ≧A) 4. A laser diode bar further comprising:

11. 11. The laser diode bar of claim 10, The length L of the m-th p-side electrode pattern in the Y direction ｍ teeth, L ｍ <L-2A １ ―2(D １ -A １ )×(m / n) ・・・(9) A laser diode bar characterized in that the relationship shown in the formula (1) is satisfied.

12. A first step of providing a GaN substrate having an orientation flat; a second step of forming a GaN stack having a plurality of nitride semiconductor layers on a primary surface of the GaN substrate; A third step of processing the GaN stack using a mask pattern to form a plurality of emitter prototypes; a fourth step of forming a p-side electrode pattern on each surface of the plurality of emitter prototypes using another mask pattern after the third step is performed; a fifth step of dividing the GaN substrate into blocks of a predetermined size each including a plurality of emitters after the fourth step is performed; a sixth step of forming a plurality of cleavage grooves at predetermined intervals from one end surface of the block along an X direction perpendicular to the one end surface and in a Y direction parallel to the one end surface; and a seventh step of cleaving the block along the cleavage grooves to obtain a laser diode bar. In the fourth step, the p-side electrode patterns are provided at intervals along the Y direction, In the block, when the interval between the p-side electrode patterns adjacent to each other in the Y direction is 2D, In the seventh step, an angle θ between a second imaginary line passing through the midpoints of the front end faces of the plurality of p-side electrode patterns and a first imaginary line along the cleavage plane of the laser diode bar is １２ The block is cleaved so that the relationship shown in formula (1) is satisfied. The formula (1) is |θ １２ |<tan －１ (2(D-A) / W) (A is a positive constant and D≧A) 4. A method for producing a laser diode bar, comprising:

13. 13. The method for producing a laser diode bar according to claim 12, The sixth step comprises forming the cleavage groove at only one location between the p-side electrode patterns adjacent to each other in the Y direction.

14. 13. The method for producing a laser diode bar according to claim 12, The method further includes a step of identifying an a-axis direction of the GaN substrate projected onto the primary surface as a third virtual line in the first step; In the third step, a mask pattern is formed as a reference for forming the emitter prototype using a virtual line along a straight portion of the orientation flat as a reference line, and another virtual line parallel to the second virtual line is derived from the mask pattern; Before processing the emitter prototype in the third step, when it is assumed that the first virtual line and the third virtual line are parallel and the second virtual line and the other virtual line are parallel, the angle θ between the second virtual line and the first virtual line is １２ An eighth step of determining whether is within a predetermined acceptable range; If the result of the determination in the eighth step is negative, the angle θ １２ a third step of correcting an angle between the first imaginary line and another imaginary line so that the angle is within the tolerance range.

15. 15. The method of claim 14, further comprising the steps of: In the determination of the eighth step, the angle θ １２ whether or not is within the allowable range is determined based on whether or not the relationship shown in formula (1) is satisfied.

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