JP2013041918A - Semiconductor light-emitting device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a semiconductor light-emitting device, for example, an end-face emission type superluminescent diode with high power.SOLUTION: A semiconductor light-emitting device includes a substrate 101 and a stacked structure that is formed on the substrate 101 and is composed of a plurality of semiconductor layers including an optical guide layer 120. The stacked structure has a stripe-shaped optical waveguide 113 selectively provided on the top portion, and a light-emission end face 115 composed of the end face of the stacked structure. The angle θ formed between the stacked surface of the optical guide layer 120 and the light-emission end face 115 is not equal to 90°.

Description

  The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device composed of an edge-emitting superluminescent diode (SLD) and a method for manufacturing the same.

  Light emitting diodes (LEDs), semiconductor laser elements (LDs), and semiconductor light emitting elements such as SLDs are used in IT technologies such as communication and optical disk devices because they have excellent features such as small size, low cost, and high output. In addition, it is used in a wide range of technical fields such as medical equipment or some lighting devices.

  In recent years, in particular, in order to reduce the size, thickness, and power consumption of display devices such as liquid crystal projectors and liquid crystal displays, development of display devices using an SLD as a light source has been actively conducted. As a light source in such a display device, a light source capable of emitting so-called RGB light of red light, green light, and blue light having a wavelength of about 420 nm to 660 nm is required. For this reason, in a conventional display device, there are a configuration in which three types of LEDs (red / green / blue LEDs) each emitting RGB light are combined, or a white LED that obtains white light by combining a phosphor material with a blue LED. Has been developed. In the case of a projection display device such as a liquid crystal projector, the light emitted from the light source has high directivity and the light intensity of the light source itself is high in order to project the light from the light source as an image more efficiently. Is preferred. In order to realize such a highly directional light-emitting element, development of an SLD that emits visible light is in progress.

  Among SLDs, gallium nitride (GaN) -based semiconductor elements are mainly used for SLDs that emit green light from blue light having a wavelength of 420 nm to 550 nm. Further, gallium arsenide (GaAs) SLD is mainly used for SLD emitting red light having a wavelength of 550 nm to 660 nm. Furthermore, research and development of SLDs that can emit red light from green light using GaN-based semiconductors are underway.

  By the way, in order to increase the emission intensity of the SLD, it is necessary to reduce the reflectance of the end face from which light is emitted. This is because if the reflectance at the emission end face is high, laser oscillation occurs and the operation as an SLD cannot be maintained.

  Further, in the application using the SLD as the light source as described above, it is important that the SLD can be manufactured at a low cost. In order to reduce the cost of the SLD, it is particularly important to reduce the chip area and increase the number that can be obtained from a wafer of a predetermined size (the number that can be obtained).

  FIG. 9 shows an SLD according to a conventional example (see, for example, Patent Document 1). As shown in FIG. 9, the SLD 200 according to the conventional example has a stacked structure in which semiconductor layers 2 to 10 are sequentially stacked on a substrate 1. In the upper part of the laminated structure, the optical waveguide is bent by an angle θ in the laminated surface to reduce the light reflectance at the light emitting end face (front end face 110). In this way, by shifting the angle formed by the optical waveguide with the front end surface 110 from 90 °, the ratio of light (returned light) that is reflected by the front end surface 110 and returns to the optical waveguide to cause laser oscillation is reduced. Thereby, it is possible to perform a stable operation without causing laser oscillation in the SLD.

Japanese Patent No. 4106210

Diode Laser and Photonic Integrated Circuits, 1st edition, page 46, Eq. (2.45) JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 10, NO. 2, FEBRUARY 1992, PP.215

  As described above, in the conventional SLD shown in FIG. 9, the optical waveguide and the front end surface 110 form an angle θ within the stacked surface of the stacked structure, and the light reflectance at the front end surface 110 is reduced. SLD operation is obtained.

  Incidentally, a semiconductor light emitting element such as an SLD is manufactured on a cleaved semiconductor substrate or an insulating substrate (hereinafter referred to as a wafer). Here, a large number, usually several thousand to several tens of thousands, of SLD elements are collectively produced on a wafer, and a plurality of SLD elements are obtained by cleaving the wafer for each element. The cleavage of the wafer is performed in two stages. That is, there are a primary cleavage in which a plurality of SLDs are arranged in a bar shape by substantially cutting the optical waveguide, and a secondary cleavage in which the SLDs arranged in a bar shape are further separated into elements for each chip.

  In the primary cleavage step, the rear end face is formed by cleaving the optical waveguide to face the light emitting end face with the optical waveguide formed at the top of the laminated structure interposed therebetween. Since the cleavage plane is generally a parallel plane, the light exit end face and the optical waveguide are crossed at an angle different from 90 ° in order to reduce the end face reflectivity. For this reason, it is set as the structure which inclines at least one part of an optical waveguide with respect to a light-projection end surface within the surface of the surface of a laminated structure. Thereafter, in the secondary cleavage step, the SLDs arranged in a bar shape are cleaved in the direction parallel to the optical waveguide to separate each element. Here, the non-inclined region in the optical waveguide is parallel to the secondary cleavage surface, and the inclined region forms an angle θ with the secondary cleavage surface. The angle formed by the primary cleavage surface and the secondary cleavage surface is substantially 90 ° from the viewpoint of ease of processing and handling. From this, when the non-inclined region in the optical waveguide is arranged in the center portion of the chip, the light emission end face depends on the length and the inclination angle of the inclined region in the optical waveguide. As a result, a deviation occurs in the side surface direction of the chip.

  This shift in the side surface direction becomes more conspicuous when the angle formed by the optical waveguide with the light emitting end surface is increased to increase the output of the SLD. Here, in order to increase the output of a semiconductor light emitting element such as an SLD, it is important to sufficiently dissipate the element to prevent a temperature rise due to operation. In order to prevent the temperature rise of the SLD element, it is important to ensure heat radiation by sufficiently separating the optical waveguide from the side surface of the chip.

  For this reason, in an SLD with an inclined optical waveguide, in order to keep the distance from the side surface of the chip at the side of the optical waveguide equal to or greater than the case where there is no inclination, the chip area is increased by increasing the secondary cleavage interval. Need to be increased. However, when the chip area is increased, there arises a problem that the number of chips taken from one wafer is reduced.

  An object of the present invention is to solve the above-described problems and to efficiently obtain a semiconductor light-emitting device, for example, a high-power edge-emitting superluminescent diode (SLD).

  In order to achieve the above object, the present invention tilts the semiconductor light emitting device in a direction perpendicular to the substrate, rather than tilting the angle formed with the light emitting end surface of the optical waveguide in the side surface direction (lateral direction) of the substrate. The configuration is to be

  Specifically, a semiconductor light emitting device according to the present invention includes a substrate and a stacked structure formed on the substrate and including a plurality of semiconductor layers including a light guide layer, and the stacked structure is selectively formed on the upper portion. The angle θ1 formed by the laminated surface of the light guide layer and the light emitting end surface is θ1 ≠ 90 °.

  According to the semiconductor light emitting device of the present invention, the angle θ1 formed by the laminated surface and the light emitting end face in the light guide layer is θ1 ≠ 90 °, so that the light reflectance at the light emitting end face can be reduced. In addition, since the optical waveguide is displaced in a direction perpendicular to the substrate (chip), there is no displacement in the side surface direction of the chip. Therefore, the semiconductor light emitting device can be formed efficiently.

  As described above, in the conventional example, the angle between the optical waveguide and the light emitting end face is different from 90 ° on the upper surface (in the laminated face) of the laminated structure, thereby reducing the end face reflectance and reducing the SLD. Getting the action. On the other hand, in the present invention, the end face reflectance is reduced by forming the light guide layer at an angle different from 90 ° with respect to the light emitting end face in the stacking direction of the stacked structure. That is, since the inclination of the optical waveguide is provided in the stacking direction of the stacked structure, it is not necessary to widen the interval between the plurality of light emitting devices on the wafer. As a result, an SLD can be obtained without increasing the chip area. In addition, the optical waveguide is inclined with respect to the end surface on the upper surface of the laminated structure in combination with the inclination of the light guide layer in the lamination direction. Thereby, the reflectance can be further reduced as compared with the case of tilting only in the stacking direction or on the surface, and the region where the SLD operation can be performed can be enlarged under the same chip area.

  Here, the light guide layer refers to a layer through which light generated in the stacked structure propagates, and the light emitting layer and a plurality of semiconductor layers formed near the top and bottom of the light emitting layer are collectively referred to as a light guide layer. . Examples of such a semiconductor laminated structure include an n-side cladding layer and a p-side cladding layer, or an n-side guide layer and a p-side guide layer. Further, the angle θ1 formed by the laminated surface and the light emitting end face in the light guide layer is a continuous line drawn by continuously plotting the center point when the light guide layer is viewed in the laminated direction in the optical waveguide direction. Of the angles formed by the line and the light exit end face, the angle is smaller than 90 °.

  In the semiconductor light emitting device of the present invention, at least a part of the light guide layer has a curved portion having a concave shape on the substrate side, and an angle formed between the reflection end surface opposite to the light emission end surface and the laminated surface of the light guide layer is θ2. (However, when θ2 ≦ 90 °), it is preferable to have a relationship of θ1 <θ2.

  In the curved optical waveguide, the stacking direction refers to a direction perpendicular to the main surface (upper surface) of the substrate.

  In this case, a curved portion having a cross-sectional shape corresponding to the curved portion in the light guide layer may be formed on the substrate.

  If it does in this way, since a laminated structure takes over the shape of the curved part formed in the board | substrate, it becomes possible to bend a light guide layer reliably.

  In the semiconductor light emitting device of the present invention, the laminated structure may be made of a III-V group compound semiconductor.

  In this way, a desired wavelength can be generated.

  In the first method for manufacturing a semiconductor light emitting device according to the present invention, the top surface of the substrate is 90% relative to the surface of the substrate opposite to the stacked structure by selectively etching the top surface of the substrate. A step of tilting to have an angle of −−θ1 and a step of forming a laminated structure on the tilted substrate.

  In the second method for manufacturing a semiconductor light emitting device according to the present invention, the upper surface of the substrate on the light emitting end surface side is mechanically polished on the upper surface of the substrate, so that the upper surface of the substrate is opposite to the surface opposite to the laminated structure. And a step of forming the laminated structure on the inclined substrate.

  According to the manufacturing method of the first or second semiconductor light emitting device, the semiconductor light emitting device of the present invention can be realized with certainty.

  According to the semiconductor light-emitting device and the method for manufacturing the same according to the present invention, for example, a high-power edge-emitting superluminescent diode (SLD) can be efficiently manufactured.

1A to 1C show a semiconductor light emitting device according to a first embodiment of the present invention, FIG. 1A is a plan view, and FIG. 1B is FIG. FIG. 1C is a cross-sectional view taken along line Ic-Ic in FIG. 1A. 2A to 2C are cross-sectional views in order of steps showing the method for manufacturing the semiconductor light emitting device according to the first embodiment of the present invention. 3A and 3B are cross-sectional views in order of steps showing the method for manufacturing the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 4 is a graph obtained by calculating an example of the relationship between the mode reflectance of the front end face and the injection current and the SLD / LD operation mode in the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 5 is a graph showing an example of the relationship between the mode reflectance of the light emitting end face and the inclination angle of the end face of the light guide layer in the semiconductor light emitting device according to the first embodiment of the present invention. 6A to 6C show a semiconductor light emitting device according to the second embodiment of the present invention, FIG. 6A is a plan view, and FIG. 6B is FIG. FIG. 6C is a cross-sectional view taken along line VIc-VIc in FIG. 6A. FIG. 7 is a cross-sectional view illustrating a substrate processing step in the method for manufacturing a semiconductor light emitting device according to the second embodiment of the present invention. 8A to 8C show a semiconductor light emitting device according to the third embodiment of the present invention, FIG. 8A is a plan view, and FIG. 8B is FIG. 8A. FIG. 8C is a cross-sectional view taken along line VIIIc-VIIIc of FIG. 8A. 9A and 9B show a conventional superluminescent diode (SLD), and FIG. 9A is a cross-sectional view taken along the line IXa-IXa in FIG. 9B. b) is a plan view.

(First embodiment)
A superluminescent diode (SLD), which is a semiconductor light emitting device according to a first embodiment of the present invention, will be described with reference to FIGS. 1 (a) to 1 (c).

  As shown in FIGS. 1A to 1C, the SLD according to the first embodiment is a blue SLD having an emission wavelength of 450 nm using a hexagonal gallium nitride (GaN) -based semiconductor.

  As shown in FIG. 1B, in the SLD according to this embodiment, the main surface (upper surface) of the substrate 101 itself is inclined with respect to the m-axis direction. As a result, the entire laminated structure including the light guide layer 120 is inclined with respect to the back surface of the substrate 101, and the angle formed by the light emitting end face 115 on the laminated surface of the light guide layer 120 is deviated from 90 °. As a result, the reflectivity of light at the light emitting end face 115 is reduced, laser oscillation is suppressed, and an SLD operation can be obtained.

  Here, the laminated structure includes an n-type cladding layer 102, an n-type guide layer 103, an active layer (multiple quantum well active layer) 104, a p-type guide layer 105, a carrier overflow suppression ( OFS) layer 106, p-type cladding layer 107, and p-type contact layer 108.

  Further, as shown in FIGS. 1A and 1C, the upper portion of the p-type cladding layer 107 and the p-type contact layer 108 on the p-type cladding layer 107 form a ridge stripe portion whose plane and cross section are both linear. . A region below the ridge stripe portion and centering on the active layer 104 is an optical waveguide 113.

  As described above, the light guide layer 120 refers to a semiconductor layer through which light generated in the stacked structure propagates. The active layer 104 and semiconductor layers formed in the vicinity of the upper and lower sides of the active layer 104, here, The n-type guide layer 103 and the p-type guide layer 105 are collectively referred to as a light guide layer 120.

  Further, symbols c, a, and m in the figure represent the plane orientation of the hexagonal GaN-based crystal. Symbol c represents a normal vector in the plane orientation (0001) plane, that is, the c-axis. Symbol a represents a normal vector between the plane orientation (11-20) plane and its equivalent plane, that is, the a-axis. The symbol m represents a normal vector between the plane orientation (1-100) plane and its equivalent plane, that is, the m-axis. In the present specification, the minus sign “−” attached to the Miller index in the plane orientation represents the inversion of one index following the minus sign for convenience.

Block layers (passivation films) 112 made of silicon oxide (SiO ₂ ) are formed on both sides and on both sides of the ridge stripe portion in the p-type cladding layer 107. A p-side electrode 109 is formed on the upper surface of the ridge stripe portion. Further, the wiring electrode 110 is formed so as to cover the p-side electrode 109 and both side portions of the ridge stripe portion in the block layer 112. An n-side electrode 111 is formed on the surface (back surface) opposite to the laminated structure of the substrate 101.

  As shown in FIG. 1A and FIG. 1B, a high reflection coat in which a plurality of dielectric films are laminated on a rear end face 116 which is an end face opposite to the light emitting end face 115 in the laminated structure. A film 114 is formed.

  Hereinafter, a method of manufacturing the SLD configured as described above will be described with reference to FIGS. 2 (a) to 2 (c), FIG. 3 (a), and FIG. 3 (b).

First, as shown in FIG. 2A, for example, the cross-sectional shape along the m-axis direction of the main surface of the substrate 101 made of n-type hexagonal GaN having a c-plane main surface is It is processed into a triangular wave shape whose length (length in the direction in which the optical waveguide 113 extends = chip length) is L. Here, the length L is set to 800 μm. This length L substantially corresponds to the resonator length of the SLD. In order to process the main surface of the substrate 101 into a triangular wave cross section, a mechanical polishing method may be used. Further, instead of the mechanical polishing method, a planar rectangular etching region reaching the triangular wave bottom is provided. For example, the etching region has a length in the m-axis direction of 800 μm, a depth of the deepest portion is 177 μm, and the a-axis direction is about the width of the wafer.
Thereafter, the substrate 101 may be etched using hot phosphoric acid or potassium hydroxide to expose, for example, the (1-102) plane.

Next, as shown in FIG. 2B, a thickness of 2 μm is formed on the main surface of the substrate 101 having a triangular wave surface by, for example, a metal organic chemical vapor deposition (MOCVD) method. An n-type cladding layer 102 made of n-type Al _0.03 Ga _0.97 N, an n-type guide layer 103 made of n-type GaN having a thickness of 0.1 μm, and a barrier layer made of In _0.02 Ga _0.98 N And a multi-quantum well active layer 104 composed of three periods of quantum well layers composed of In _0.16 Ga _0.84 N, a p-type guide layer 105 composed of p-type GaN having a thickness of 0.1 μm, and a thickness Carrier overflow suppression (OFS) layer 106 made of Al _0.2 Ga _0.8 N with a thickness of 10 nm, p-type Al _0.16 Ga with a thickness of 1.5 nm each _0.84 p-type cladding layer 107 made of a strained superlattice having a thickness of 0.48 μm and composed of 160 periods of an N layer and a GaN layer, and a p-type contact made of p-type GaN having a thickness of 0.05 μm The layer 108 is sequentially grown to form a stacked structure.

  The crystal growth method for forming the stacked structure is not limited to the MOCVD method, but is an SLD made of a GaN-based semiconductor, such as a molecular beam epitaxy (MBE) method or a chemical beam epitaxy (CBE) method. A growth method capable of growing the structure can be used.

In addition, as a raw material in the case of using the MOCVD method, for example, trimethyl gallium (TMG) is used as a Ga raw material, trimethyl indium (TMI) is used as an In raw material, and trimethyl aluminum (TMA) is used as an Al raw material, and ammonia (NH ₃ ) is used as an N raw material. ) May be used. Further, silane (SiH ₄ ) gas may be used for the Si raw material that is an n-type impurity, and biscyclopentadienyl magnesium (Cp ₂ Mg) may be used for the Mg raw material that is a p-type impurity.

Subsequently, a mask film (not shown) made of SiO ₂ having a thickness of 0.3 μm is formed on the p-type contact layer 108 by, eg, thermal CVD. Thereafter, the mask film is patterned into a plurality of stripes having a width of 1.0 μm by lithography and etching.

  Subsequently, the upper portion of the multilayer structure is etched to a depth of 0.35 μm using a mask film by an inductively coupled plasma (ICP) etching method. As a result, a ridge stripe portion is formed from the p-type contact layer 109 and the upper portion of the p-type cladding layer 108. Thereafter, the mask film is removed with hydrofluoric acid.

Subsequently, a block layer (passivation film) 112 made of SiO ₂ having a thickness of 200 nm is formed on the exposed p-type cladding layer 107 again over the entire surface including the ridge stripe portion by thermal CVD.

Subsequently, a resist pattern (not shown) having an opening having a width of 1.3 μm along the ridge stripe portion is formed on the upper surface of the ridge stripe portion in the block layer 112 by lithography. Subsequently, the block layer 112 is etched using the resist pattern as a mask by a reactive ion etching (RIE) method using, for example, trifluoromethane (CHF ₃ ) gas, so that the top surface of the ridge stripe portion is removed. The p-type contact layer 108 is exposed.

  Next, as shown in FIG. 2C, palladium having a thickness of 40 nm is formed on the p-type contact layer 108 exposed at least from the upper surface of the ridge stripe portion by, for example, an electron beam (EB) deposition method. A metal laminated film made of (Pd) and platinum (Pt) having a thickness of 35 nm is formed. Thereafter, a region excluding the ridge stripe portion in the metal laminated film is removed by a lift-off method for removing the resist pattern, and the p-side electrode 109 is formed from the metal laminated film.

  Subsequently, the planar dimension in the direction parallel to the ridge stripe portion is 500 μm, for example, so as to cover the p-side electrode 109 on the block layer 112 by the lithography method and the lift-off method, and the ridge stripe portion. A wiring electrode 110 having a planar dimension of 150 μm in a direction perpendicular to is selectively formed. Here, the wiring electrode 110 is formed of a metal laminated film of titanium (Ti) / platinum (Pt) / gold (Au) having a thickness of 50 nm, 200 nm, and 100 nm, respectively. In general, the substrate 101 is in a wafer state, and the plurality of laser devices are formed in a matrix on the main surface of the substrate 101. Therefore, when the wiring electrode 110 is cut when the substrate 101 in the wafer state is divided into individual laser chips, the p-side electrode 109 in close contact with the wiring electrode 110 may be peeled off from the p-type contact layer 108. Therefore, as shown in FIG. 1A, it is desirable that the wiring electrodes 110 are formed not apart from each other but adjacent to each other.

  Subsequently, mechanical polishing (back surface polishing) using diamond slurry is performed on the back surface of the wafer-like substrate 101 on which the wiring electrodes 110 are formed. Thereby, the thickness of the substrate 101 is reduced to about 100 μm. Thereafter, for example, by an EB vapor deposition method and a lift-off method, a metal stack made of titanium (Ti) with a thickness of 5 nm, platinum (Pt) with a thickness of 10 nm, and gold (Au) with a thickness of 1000 nm is formed on the back surface of the substrate 101. An n-side electrode 111 is formed from the film. For the substrate polishing method, in addition to mechanical polishing by slurry, for example, chemical mechanical polishing using auxiliary KOH solution may be used.

  Next, as shown in FIG. 3A, the substrate 101 in the wafer state is first cleaved along the m-plane, that is, the triangular wave apex and bottom, so that the length L in the m-axis direction becomes 800 μm. To do. Further, the bar-shaped chip is sandwiched by using a spacer (not shown) such as silicon (Si) so that the end face of the cleaved bar-shaped chip is exposed.

  Next, as shown in FIG. 3B, a high reflectivity coating film 114 is formed by laminating a plurality of dielectric films on the rear end surface 116 of the bar-shaped chip, for example, by ECR sputtering.

  Next, as shown in FIG. 1A, the substrate 101 that has been primarily cleaved is secondarily cleaved along the a-plane so that the length in the a-axis direction is 200 μm.

  FIG. 4 shows the mode reflectivity of the front end face (light emission end face 115) and the amount of injected current for the SLD when the light reflectivity of the high reflectivity coat film 114 in the SLD according to the present embodiment is 99%. The result of calculating | requiring the relationship with the operation mode (SLD mode or LD mode) of SLD by the calculation is represented. For this calculation, a basic equation of laser oscillation conditions is used (see Non-Patent Document 1). In general, the light output can be increased by increasing the amount of current injected into the SLD. However, at the same time, laser oscillation easily occurs, and the mode shifts to the LD mode. For this reason, the injection current value (threshold value) for shifting to laser oscillation can be increased by reducing the mode reflectivity of the front end face. That is, the SLD operation is obtained with a high light output. Therefore, it is important to reduce the mode reflectivity of the front end face.

  FIG. 5 shows the calculation of the inclination angle dependence of the front end face of the optical waveguide in the mode reflectivity of the front end face (light emitting end face) when the reflectance of the rear end face is 99% in the SLD according to the present embodiment. The obtained result is shown. The method of Non-Patent Document 2 is used for the calculation. As apparent from FIG. 4 described above, in order to increase the output of the SLD, it is necessary to reduce the mode reflectivity of the front end face. Furthermore, it can be seen from FIG. 5 that the mode reflectivity of the front end face depends on the tilt angle θ. In particular, it is important to control the inclination angle θ at an inclination angle θ of relatively small change from 90 ° = 77.5 °, 74 °, 70.7 °, and 68 °. For this reason, in the first embodiment, the angle θ formed by the light guide layer 120 and the light emitting end face 115 is preferably set to about 77.5 °, 74 °, 70.7 °, and 68 °. The deviation from the angle θ may be ± 0.5 °.

In the first embodiment, a GaN-based substrate belonging to a hexagonal system (such as a GaN substrate or an AlGaN substrate) is used as the growth substrate for the laminated structure, but a substrate capable of growing a GaN-based material, for example, Silicon carbide (SiC), silicon (Si), sapphire (single crystal Al ₂ O ₃ ), zinc oxide (ZnO), or the like can be used.

(Second Embodiment)
Hereinafter, an SLD which is a semiconductor light emitting device according to the second embodiment of the present invention will be described with reference to FIGS. 6 (a) to 6 (c). In FIG. 6, the same components as those shown in FIG.

  As shown in FIG. 6B, the SLD according to the second embodiment is different from the SLD according to the first embodiment in that the main surface of the substrate 101 is inclined and the substrate 101 is replaced with an inclined surface. The main surface side of this is to form a curved portion 101a having a concave shape. Thus, a laminated structure including the light guide layer 120 is grown on the main surface of the substrate 101 having the curved portion 101a having a concave main surface, thereby having a curved shape corresponding to the curved portion 101a of the substrate 101. The light guide layer 120 is formed.

  With this configuration, the light emitting end face 115 side of the laminated structure including the light guide layer 120 is inclined with respect to the back surface of the substrate 101, and the angle θ1 formed with the light emitting end face 115 in the laminated surface of the light guide layer 120 is 90 °. It will shift from. As a result, the reflectivity of light at the light emitting end face 115 is reduced, laser oscillation is suppressed, and an SLD operation can be obtained.

  In the second embodiment, when the angle formed by the rear end surface 116 opposite to the light emitting end surface 115 and the laminated surface of the light guide layer 120 is θ2 (where θ2 ≦ 90 °), the relationship θ1 <θ2 is established. Have.

  FIG. 7 shows a step of forming the curved portion 101a on the substrate 101. As shown in FIG. 7, the main surface of a wafer-like substrate 101 made of n-type hexagonal GaN having a c-plane main surface is periodically bent in the m-axis direction using a roller polishing machine 117 or the like. Part 101a is formed.

  At this time, the formation period of the bending portion 101a is set to twice the chip length L. For example, when the length of the SLD is 1000 μm, the formation cycle may be 2000 μm.

  Thereafter, as in the first embodiment, a laminated structure made of a group III nitride semiconductor is formed by crystal growth on the substrate 101 on which a plurality of curved portions 101a are formed, and a ridge stripe portion and a block are formed. Layers and electrodes are formed. Subsequently, primary cleavage and secondary cleavage are performed to obtain the SLD shown in FIG.

  In the second embodiment, since the curved portion 101a having a concave shape is formed on the light emitting end surface 115 side of the substrate 101, the angle θ1 formed with the light emitting end surface 115 on the laminated surface of the light guide layer 120 is set. It becomes easy to make it smaller.

(Third embodiment)
The SLD according to the third embodiment of the present invention will be described below with reference to FIGS. 8 (a) to 8 (c). In FIG. 8, the same components as those shown in FIG.

  As shown in FIG. 8A, the difference between the SLD according to the third embodiment and the SLD according to the second embodiment is that the optical waveguide 113, that is, the ridge stripe portion, is in the stacking plane of the stacked structure. In this case, it is formed so as to intersect with the exit end face at an angle θ3 different from 90 °.

  With this configuration, not only the light emitting end face 115 side of the laminated structure including the light guide layer 120 is inclined with respect to the back surface of the substrate 101, but also the optical waveguide 113 is inclined in the laminated surface of the laminated structure. Therefore, the reflectance of light at the light emitting end face 115 is further reduced, so that the laser oscillation is further suppressed, so that the SLD operation can be easily obtained.

  In this configuration, since the optical waveguide 113 is inclined even in the lamination plane, the chip area is increased and the cost is increased. However, by combining two inclinations in the in-plane direction and the lamination direction, the reflectance is increased. Can be reduced to the limit, and the optical output of the SLD can be greatly increased.

  Hereinafter, the main part of the manufacturing method of the GaN-based blue SLD configured as described above will be described.

  Similar to the second embodiment, the curved portion 101a is formed on the main surface of the substrate 101 by a mechanical polishing method or the like. Thereafter, similarly to the first embodiment, a laminated structure is formed by crystal growth on the main surface of the substrate 101 on which the curved portion 101 is formed.

Subsequently, a mask film (not shown) made of SiO ₂ having a thickness of 0.3 μm is formed on the p-type contact layer 108 formed on the upper portion of the laminated structure by, for example, thermal CVD. Thereafter, the mask film is patterned into a plurality of stripes having a width of 1.0 μm by lithography and etching. At this time, the planar shape of the stripe of the ridge stripe portion is bent or bent so that the optical waveguide 113 is gradually inclined from the m-axis to the a-axis direction toward the light emitting end face 115. It is preferable that the curvature ratio (curvature radius) is constant. However, the bending ratio is not necessarily constant as long as the loss of guided light does not occur.

  Thereafter, a block layer, electrodes, and the like that cover the side surfaces of the ridge stripe portion are formed. Subsequently, primary cleavage and secondary cleavage are performed to obtain the SLD shown in FIG.

  Note that the configuration in which the ridge stripe portion is curved in the stacked surface of each semiconductor layer can be applied to the configuration in which the main surface of the substrate 101 shown in the first embodiment is a hypotenuse.

  In the second and third embodiments, the angle θ2 formed by the rear end surface 116 and the light guide layer 120 is 90 °, but the angle θ1 formed by the front end surface (light emitting end surface 115) and the light guide layer 120 is , Θ1 <θ2 may be satisfied. Furthermore, if the reflectance of the front end surface 115 is smaller than the reflectance of the rear end surface 116, θ2 may not be 90 °.

  Further, although the gallium nitride (GaN) group III nitride semiconductor is used as the semiconductor material constituting the stacked structure of the SLD, the present invention is not limited thereto, and a gallium arsenide (GaAs) semiconductor can be used. That is, a III-V compound semiconductor can be used in the semiconductor light emitting device according to the present invention.

  The semiconductor light-emitting device and the method for manufacturing the same according to the present invention can efficiently produce, for example, a high-output edge-emitting superluminescent diode (SLD), and a liquid crystal projector with high brightness, low power consumption, and low cost. It can be used for a device or a backlight.

101 Substrate 101a Curved portion 102 n-type cladding layer 103 n-type guide layer 104 active layer (multiple quantum well active layer)
105 p-type guide layer 106 carrier overflow suppression (OFS) layer 107 p-type cladding layer 108 p-type contact layer 109 p-side electrode 110 wiring electrode 111 n-side electrode 112 block layer 113 optical waveguide 114 highly reflective coating film 115 light emitting end face ( Front end face)
116 Rear end face 117 Roller polishing machine 120 Light guide layer

Claims (6)

A substrate,
A laminated structure formed on the substrate and including a plurality of semiconductor layers including a light guide layer;
The laminated structure has a stripe-shaped optical waveguide selectively formed on the upper part, and a light emitting end face composed of an end face of the laminated structure,
The angle θ1 formed by the laminated surface of the light guide layer and the light emitting end surface is:
A semiconductor light-emitting device, wherein θ1 ≠ 90 °. At least a part of the light guide layer has a curved portion having a concave shape on the substrate side,
When the angle formed by the reflection end surface opposite to the light emitting end surface and the laminated surface in the light guide layer is θ2 (where θ2 ≦ 90 °),
2. The semiconductor light emitting device according to claim 1, wherein a relationship of [theta] 1 <[theta] 2 is satisfied.   The semiconductor light emitting device according to claim 2, wherein a curved portion having a cross-sectional shape corresponding to the curved portion of the light guide layer is formed on the substrate.   4. The semiconductor light emitting device according to claim 1, wherein the laminated structure is made of a group III-V compound semiconductor. 5. A method of manufacturing a semiconductor light emitting device according to claim 1,
Selectively etching the upper surface of the substrate to incline the upper surface of the substrate so as to have an angle of 90 ° −θ1 with respect to the surface of the substrate opposite to the stacked structure. When,
And a step of forming the laminated structure on an inclined substrate. A method for manufacturing a semiconductor light emitting device according to any one of claims 1 to 4,
By performing mechanical polishing on the upper surface of the substrate, the upper surface of the substrate on the light emitting end surface side has an angle of 90 ° −θ1 with respect to the surface of the substrate opposite to the laminated structure. Inclining to,
And a step of forming the laminated structure on an inclined substrate.

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