JP2009004538A - Semiconductor laser equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide semiconductor laser equipment of a GaN system, which suppresses deterioration of an active layer and an end face and has high output and high reliability. <P>SOLUTION: Semiconductor laser equipment is provided with a laminated structure where a first clad layer 2, the active layer 4 and a second clad layer 6, which respectively consist of hexagonal GaN-based crystals, are sequentially formed on a substrate 1. Equipment has a stripe-shaped optical waveguide transmitting light inside the laminated structure. The optical waveguide extends into a face parallel to a main face of the laminated structure and has a light emission end face with plane orientation of (0001) at one end part in the optical waveguide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device, and more particularly, to a GaN-based semiconductor laser device that reduces end face deterioration and has high output and high reliability.

  Semiconductor lasers (laser diodes; LDs) have excellent features such as small size, low cost, and high output, so in addition to conventional optical communication and optical information recording, a wide range of technologies such as medicine and lighting Used in the field. In recent years, the development of GaN-based semiconductor lasers with a wavelength of 405 nm has been energetically advanced, particularly for Blu-ray Disc applications, and pure blue laser light with a wavelength of 450 nm to 470 nm has been used for laser display and liquid crystal backlight applications. Development of GaN-based semiconductor lasers for output is also progressing. For example, high output of GaN-based semiconductor lasers is required for the purpose of realizing high speed and multi-layer recording in disk applications and for the purpose of realizing high brightness in displays and backlight applications.

  Here, in order to realize a high output of the semiconductor laser, it is important to overcome the following two degradations.

(1) Active layer deterioration Active layer deterioration is a phenomenon in which the structural change of the active layer occurs mainly due to heat, resulting in a decrease in luminous efficiency. However, the amount of heat generated per unit volume of the active layer is reduced. In order to reduce the temperature rise, it is desirable to reduce the value of the injection current density necessary for obtaining the necessary light output.

(2) End face deterioration End face deterioration is a phenomenon in which the emitting end face of the laser beam is melted and is irreversibly damaged. At the emitting end face, atoms constituting the coating material or atoms present as an atmosphere around the laser element. This is caused by an increase in crystal imperfection that is the origin of laser light absorption due to the occurrence of a chemical reaction due to. That is, when the crystal imperfection increases, light absorption increases, and most of the absorbed light becomes heat, so that a temperature rise occurs at the emission end face. For this reason, a positive feedback occurs in that the temperature further rises due to further increase in light absorption due to shrinkage of the band gap of the semiconductor. As a result, a failure called COD (Catastrophic Optical Damage: COD) occurs in which the crystal at the exit end face melts.

In view of the deterioration of the active layer of (1) above, in view of the propagation of laser light on the surface including the active layer, an edge emitting semiconductor laser device that can increase the volume of the active region and reduce the operating current density is widely used. It has been. For example, in a GaAs semiconductor laser device that outputs red laser light for high-speed recording on a DVD, an end face emission type structure is put to practical use. In addition, the GaN-based semiconductor laser devices that are currently being put into practical use mainly employ an end face emission type structure that facilitates high output, for example, having a waveguide on the (0001) plane. There has been proposed a semiconductor laser device having a mirror formed by high reflection or low reflection coating on the (1-100) plane and (-1100) plane exposed by cleavage (see, for example, Patent Document 1).
Japanese Patent No. 3565202

  However, although the conventional GaN-based semiconductor laser device can overcome the deterioration of the active layer of (1) above, as described in (2) above, the emission end face and the atoms constituting the coating material or the periphery of the laser element The problem of end face degradation caused by a chemical reaction with atoms present as an atmosphere cannot be overcome.

  In view of the above, an object of the present invention is to provide a semiconductor laser device having a structure capable of suppressing active layer deterioration and end face deterioration at once.

  In order to achieve the above object, the present inventor has made various studies. As a result, in the conventional semiconductor laser device, the (1-100) plane and (-1100) plane where the end face deterioration occurs are chemically stable. It has been found that the above chemical reaction is likely to occur due to its low nature. The present invention has been made in view of the above findings, and uses a material having a crystal structure having a relatively high surface and a relatively low surface for chemical stability, and provides chemical stability. By adopting a structure in which the surface having a relatively high surface is the exit end face, a semiconductor laser device capable of suppressing end face deterioration is realized. In addition, it is possible to realize a semiconductor laser device that can simultaneously suppress degradation of the active layer.

  A semiconductor laser device according to an aspect of the present invention includes a stacked structure in which a first cladding layer, an active layer, and a second cladding layer each formed of a hexagonal GaN-based crystal are sequentially formed on a substrate. A semiconductor laser device having a stripe-shaped optical waveguide for propagating light inside a laminated structure, wherein the optical waveguide extends in a plane parallel to the main surface of the laminated structure, and is at least one end of the optical waveguide. The part has a light emitting end face with a plane orientation of (0001).

  A semiconductor laser device according to an embodiment of the present invention has a structure with high active power that can reduce the current density because the active region has a large volume because laser light propagates on a surface including an active layer. Since the laser beam is emitted from the surface having the most chemically stable plane orientation of (0001) in the hexagonal GaN, the deterioration of the end face is suppressed, the high output operation is possible, and the high reliability can be realized.

  In the semiconductor laser device according to one embodiment of the present invention, the plane direction of the main surface of the stacked structure is (0001), and the light emitting end surface is located on the upper surface of one end of the optical waveguide. The side surface of the end portion having the light emitting end surface constitutes a mirror that reflects light propagating through the optical waveguide in the <0001> direction.

  In this case, when the plane orientation of the main surface of the laminated structure is (0001) and the light emitting end surface is located on the upper surface of one end of the optical waveguide, the most chemically stable in hexagonal GaN. A configuration in which laser light is emitted from a plane having a plane orientation of (0001) is realized.

  In this configuration, the side surface of the end portion opposite to the end portion having the light emitting end surface in the optical waveguide is a plane perpendicular to the plane having the plane orientation (0001), and the vertical plane has a higher reflectance. Coating is applied.

  In this way, the ratio of the laser light emitted from the surface having the plane orientation of (0001) increases, while the side surface of the end portion facing the end portion having the light emitting end surface (the side surface has a plane orientation of (0001). ) Is a surface that is inferior in chemical stability to the surface), and the ratio of the light emitted from the surface is reduced. Therefore, deterioration of the end surface is reduced, and a high-output and high-reliability GaN semiconductor laser device is realized. .

  In the semiconductor laser device according to one aspect of the present invention, the plane orientation of the main surface of the stacked structure is (0001), the light emitting end surfaces are located on the upper surfaces of both ends of the optical waveguide, and both end portions of the optical waveguide The side surface constitutes a mirror that reflects light propagating through the optical waveguide in the <0001> direction.

  In this case, the most chemically stable surface in hexagonal GaN when the plane orientation of the main surface of the laminated structure is (0001) and the light emitting end surfaces are located on the upper surfaces of both end portions of the optical waveguide. A configuration is realized in which laser light is emitted from two locations on a plane having an orientation of (0001).

  In the semiconductor laser device according to one embodiment of the present invention, the angle formed between the mirror and the main surface of the stacked structure is larger than 41 ° and smaller than 46 °.

  In this case, since the optical coupling efficiency can be maintained at 60% or more, it is possible to suppress undesirable effects on laser characteristics such as an increase in oscillation threshold and a decrease in efficiency due to a decrease in optical coupling efficiency.

  In the semiconductor laser device according to an aspect of the present invention, the light absorption edge energy of each of the active layer and the second cladding layer is a photon of light that travels in the <0001> direction when light propagating through the optical waveguide is reflected by a mirror. Greater than energy.

  In this way, absorption of light propagating in the <0001> direction is reduced, and a semiconductor laser device with higher output and higher reliability is realized.

  The semiconductor laser device according to one aspect of the present invention further includes a contact layer formed on the second cladding layer, and the light absorption edge energy of the contact layer reflects light propagating through the optical waveguide by the mirror. And is larger than the photon energy of light traveling in the <0001> direction.

  In this way, absorption of light propagating in the <0001> direction is reduced, and a semiconductor laser device with higher output and higher reliability is realized.

  In the semiconductor laser device according to one aspect of the present invention, the contact layer does not exist on the light emitting end face.

  In this way, absorption of light propagating in the <0001> direction is reduced, and a semiconductor laser device with higher output and higher reliability is realized.

  In the semiconductor laser device according to one aspect of the present invention, the plane orientation of the main surface of the stacked structure is orthogonal to (0001), and the light emission end surface is located on the side surface of the end portion of the optical waveguide. The side surface of the end portion that becomes the light emitting end surface of both end portions of the optical fiber constitutes a mirror having a surface orientation of (0001), while the side surface of the end portion that does not become the light emitting end surface of the both end portions of the optical waveguide is In addition, a mirror composed of a plane having a plane orientation of (000-1) is formed and a coating for increasing the reflectance is applied.

  In this way, the surface orientation with relatively high chemical stability increases the laser light emitted from the (0001) plane, while the surface orientation with relatively low chemical stability is (000-1). ), A high-output and high-reliability GaN-based semiconductor laser device is realized.

  The present invention is an edge emitting semiconductor laser device that has a large active region and a low operating current density, and has a structure in which laser light is emitted from a surface with relatively high chemical stability. In addition, the GaN-based semiconductor laser capable of high output operation and high reliability can be realized by reducing the chemical reaction at the light emitting end face and keeping the temperature of the end face portion low.

  First, constituent materials of the semiconductor laser device common to the semiconductor laser devices according to the embodiments of the present invention will be described.

  That is, as a material constituting the semiconductor laser device according to each embodiment, a material made of a crystal having a surface with relatively high chemical stability and a surface with relatively low chemical stability is used. Specifically, a material comprising a hexagonal (wurtzite) crystal having a six-fold symmetry structure is used as a material constituting the GaN-based semiconductor laser.

  Here, the hexagonal GaN crystal is a polar crystal, and even if it is the same (0001) plane, there are two types, that is, a plane in which Ga atoms are arranged and a plane in which N atoms are arranged.

  Therefore, in the present specification, a surface on which Ga atoms are arranged is denoted as a (0001) plane, and a surface on which N atoms are arranged is denoted as a (000-1) surface. The (0001) plane is expressed as + c plane, and the (000-1) plane is expressed as -c plane. Similarly, the (1-100) plane is denoted as + m plane, and the (-1100) plane is denoted as -m plane. In addition, when it only describes with c surface etc., it is the meaning including + c surface and -c surface.

  In the semiconductor laser device, the principal surface is not completely the (0001) plane or the (1-100) plane, and crystals having an angle inclined to about 20 ° may be used. For this reason, in this specification, it describes as (0001) plane etc. including the case where the crystal in which the main surface inclined to about 20 degrees is used. Further, in the present specification, when the main surface is referred to as the (0001) plane, it means that the main surface includes a plane inclined by about ± 5 ° from the (0001) plane.

  Based on the above, the semiconductor laser device according to each embodiment of the present invention will be described below with reference to the drawings.

(First embodiment)
Hereinafter, a semiconductor laser device and a manufacturing method thereof according to the first embodiment of the present invention will be described. Specifically, in the first embodiment, a semiconductor laser device that outputs a blue (wavelength 460 nm) laser beam using a GaN-based semiconductor will be described as an example.

  1A and 1B are views showing the structure of the semiconductor laser device according to the first embodiment of the present invention, in which FIG. 1A is a plan view seen from the <1000> direction, and FIG. FIG. 3A is a cross-sectional view taken along line Ib-Ib in FIG.

  In the semiconductor laser device shown in FIGS. 1A and 1B, the laser light propagating on the + c plane is directed in the <1000> direction by a processing surface that functions as an upper surface reflecting mirror located at one end of the waveguide. This is a top emission type semiconductor laser device that is bent and emits laser light from the + c plane.

First, n-type Al _0.08 GaN is formed on the + c plane of the substrate 1 made of n-type GaN having a c-plane main surface by using, for example, a metal organic chemical vapor deposition (MOCVD) method. A clad layer 2 made of 2 μm is grown. Subsequently, an n-side light guide layer 3 made of an n-GaN layer is grown on the clad layer 2 by 0.1 μm. Subsequently, a quantum well active layer 4 having a three-period structure of an In _0.02 GaN barrier layer and an In _0.15 GaN quantum well layer is grown on the n-side light guide layer 3. Subsequently, a p-side light guide layer 5 made of a p-GaN layer is grown on the active layer 4 by 0.1 μm. Subsequently, Al _0.16 GaN as a carrier overflow suppression layer (OFS layer) is grown to 10 nm, and a p-Al _0.16 GaN layer 1.5 nm and a GaN layer 1.5 nm are formed on the OFS layer by 160 nm. A p-type cladding layer 6 made of a strained superlattice having a thickness of 0.48 μm and a contact layer 7 made of a p-GaN layer having a thickness of 0.05 μm are grown in this order.

  In addition to the MOCVD method described above, a nitride-based blue-violet semiconductor such as a molecular beam epitaxy (MBE method) or a chemical beam epitaxy (CBE method) is used as a method for crystal growth. Other growth methods capable of growing the laser structure may be used. Further, as raw materials when using the MOCVD method, for example, trimethyl gallium as a Ga raw material, trimethyl indium as an In raw material, trimethyl aluminum as an Al raw material, ammonia as an N raw material, silane gas as an Si raw material of n-type impurities, and p-type impurities Biscyclopentadienyl magnesium may be used as the Mg raw material.

Then, for example, by plasma CVD, on the contact layer 7, a silicon oxide film (SiO ₂₎ after allowed to 0.3μm deposited, using photolithography and etching techniques, on the silicon oxide film After forming a resist pattern that exposes the central portion in the Ib-Ib line direction of FIG. 1A, the central portion is formed by reactive ion etching (RIE) using CF ₄ gas, for example, using the resist pattern as a mask. Then, a silicon oxide film 10 exposing the contact layer 7 is formed (see FIG. 1B). Subsequently, the predetermined region is removed by about 0.2 μm by, for example, inductively coupled plasma (ICP) etching using Cl ₂ gas. As a result, as shown in FIGS. 1A and 1B, the contact layer 7 in a predetermined region is removed and a part of the clad layer 6 is removed, so that the upper portion of the clad layer 6 is exposed. The width in the Ib-Ib line direction in the non-etched region excluding the predetermined region is preferably about 8 μm. By doing this, the contact layer 7 having a high light absorption rate is not present in the laser light emission region, which can contribute to high output of the semiconductor laser device. In addition, AlGaN having high resistance but low light absorption may be used instead of GaN used as the material of the contact layer 7, and in this case, it is not necessary to remove a part of the contact layer 7 as described above. Good. Further, the light absorption edge energy of each of the active layer 4, the p-type cladding layer 6, and the contact layer 7 is reflected in the <0001> direction by the light propagating through the optical waveguide being reflected by the processed surface 12 constituting a mirror described later. By adopting a configuration that is larger than the photon energy of the traveling light, absorption of light propagating in the <0001> direction can be reduced, and higher output and higher reliability can be further achieved.

  Next, after forming a resist pattern that exposes a predetermined region on the contact layer 7 and covers the silicon oxide film 10 and a part of the contact layer 7 and the cladding layer 6 using photolithography and etching techniques, For example, using an electron beam (EB) vapor deposition apparatus, a p-type contact electrode 8 made of a Pd / Pt (40 nm / 35 nm) laminate is vacuum-deposited in a predetermined region on the contact layer 7. Subsequently, the Pd / Pt layer on the resist pattern is removed by a lift-off method.

  Here, the length in the <1-100> direction of the region in which the p-type contact electrode 8 is not formed on the cladding layer 6 and the contact layer 7 is the p-type contact electrode when the laser light is emitted in the + c plane direction. The thickness is preferably 1 μm or more so as not to be reflected by 8, and more preferably 5 μm or more in consideration of the cleavage accuracy of the laser chip. However, if the length is longer than 15 μm, the region where current is not injected becomes longer, the loss in the device increases, the threshold value increases, the optical coupling efficiency decreases, and the current-light output characteristics are reduced. Since unexpected nonlinearity may appear, it is preferably 15 μm or less, and more preferably 10 μm or less. Considering the above, the length is more preferably 5 μm or more and 10 μm or less.

  Next, a wiring electrode 9 made of a laminate of Ti / Pt / Au (50 nm / 200 nm / 200 nm) is formed on the p-type electrode 8 and the silicon oxide film 10 using photolithography and EB vapor deposition. However, if the wiring electrode 9 is cut when the elements are separated, the p-type electrode 8 that is in close contact with the wiring electrode 9 may be peeled off from the contact layer 7, so that the wiring electrode 9 is not connected to an adjacent element. It is desirable to form. Subsequently, the thickness of Au constituting the wiring electrode 9 is increased to 10 μm. This makes it possible to mount the element by wire bonding and to effectively dissipate the heat generated in the active layer 4, thereby improving the reliability of the element.

  Next, after the thickness of the substrate 1 is thinned from the back surface to about 100 μm using diamond slurry, Ti / Pt / Au (5 nm / 10 nm / 1000 nm is formed on the back surface of the substrate 1 by using, for example, EB vapor deposition. ) To form an n-type electrode 11.

  Next, the sample is subjected to primary cleavage along the m-plane so that the length in the <1-100> direction in the sample obtained as described above becomes 600 μm.

Next, using a ECR sputtering apparatus, for example, a highly reflective coating 13 made of, for example, a three-period structure of SiO ₂ / Nb ₂ O ₅ is applied to the + m plane on the side surface of the sample. Further, alumina (Al ₂ O ₃ ) may be used as the highly reflective coating 13. In this case, the ratio of the laser beam emitted from the + m plane having a relatively low chemical stability is decreased, and the ratio of the laser beam emitted from the + c plane having a relatively high chemical stability is increased. Therefore, it is possible to realize a highly reliable semiconductor laser device with little end face deterioration even during high output operation. Here, the case where the highly reflective coating 13 is formed on the + m plane has been described, but a distributed feedback Bragg reflector (DBR) may be formed instead of the highly reflective coating 13. On the other hand, a low-reflection coating may be applied to the + c surface for the purpose of reducing the reflectivity of the laser beam on the + c surface serving as the light emitting surface. As the low reflection coating, niobium oxide (Nb ₂ O ₅ ) or alumina (Al ₂ O ₃ ) can be used.

  Next, the focused ion beam (FIB) is used to process the end surface (the -m surface in FIG. 1) opposite to the + m surface on which the highly reflective coating 13 is applied, so that the laser beam is reflected on the upper surface (+ c surface) A processed surface 12 that functions as an upper surface reflecting mirror to be reflected to the side is formed. Here, the machining surface 12 is formed so that the machining angle θ formed with the + c plane is 45 °. FIG. 1B shows the case where the processed surface 12 is formed entirely from the cladding layer 6 to the n-type electrode 11, but the processed depth of the processed surface 12 (depth in the thickness direction of the semiconductor layer). In the case where the laser beam is shallow, a part of the laser beam may be detached from the processing surface 12 and reflected to the + c surface side, resulting in optical loss. Therefore, in order to sufficiently suppress the optical loss, the processing depth The depth is preferably deeper than 0.5 μm, and more preferably deeper than 1 μm. At this time, depending on the processing conditions of the FIB, a material that causes light absorption or scattering, such as an amorphous GaN-based crystal or its oxide, may be formed on the processed surface. In order to reduce the above material formation, for example, the FIB beam intensity may be weakened. Further, the damaged layer may be removed by ionic milling, for example, argon ion milling. Further, a wet etching process for removing a damaged layer such as phosphoric acid, aqua regia, or nitric acid may be performed. Here, the case where the processed surface 12 is formed using FIB has been described. However, any method capable of forming the processed surface 12 having an angle at which the laser beam is totally reflected, for example, dry etching, or You may employ | adopt the method using the wet etching using the hot phosphoric acid or the alkaline solution under UV light irradiation.

  FIG. 2 schematically shows the propagation state of the laser beam and the intensity profile of the laser beam in the vicinity of the processing surface 12 in the semiconductor laser device according to the first embodiment of the present invention.

  As shown in FIG. 2, the laser beam 20 is repeatedly reflected and transmitted through the processed surface 12 and the + c surface (see laser beams 20a, 20b, 20c, and 20d), but the processing angle θ deviates from 45 °. Then, since the reflection direction of the laser beam 20a reflected by the processed surface 12 is deviated from the <0001> direction and the light intensity profile becomes broad, the ratio of the light reflected by the + c plane and coupled to the light guide layer is increased. This results in an increase in the oscillation threshold or a decrease in optical coupling efficiency. Therefore, the processing angle θ of the processing surface 12 is desirably 45 °.

  FIG. 3 shows the semiconductor laser device according to the first embodiment of the present invention, in which the laser beam is reflected in the <0001> direction by the processed surface 12, reflected in the <000-1> direction by the + c plane, The result of calculating the ratio of the light reflected by the processed surface 12 and coupled to the waveguide again is shown.

  As shown in FIG. 3, the optical coupling efficiency when the processing angle θ = 45 ° was 66%. In order not to deteriorate the oscillation threshold value of the laser beam or the characteristics of the optical coupling efficiency, it is desirable to maintain the optical coupling efficiency at 50% or more. Therefore, the processing angle θ of the processing surface 12 is 41 ° <θ <46 °. It is desirable to be.

  Note that the optical coupling efficiency 66% when the processing angle θ = 45 ° is reduced from the laser light reflectance 100% on the processing surface 12 is <0001> of the laser light reflected on the processing surface 12. Due to the spread of light accompanying propagation in the direction, a hemispherical reflecting mirror is provided in the light emission region on the + c plane, and the spread light is collected and reflected in the <000-1> direction. May be adopted. Similarly, a configuration in which a hemispherical condenser lens is provided on the surface of the processing surface 12 that functions as an upper surface reflecting mirror may be employed.

  Thereafter, the semiconductor laser device having the structure shown in FIGS. 1A and 1B is obtained by performing secondary cleavage along the a-plane so that the length in the <11-20> direction is 200 μm.

  As described above, according to the semiconductor laser device according to the first embodiment of the present invention, the laser beam propagating on the + c plane functions as the upper surface reflecting mirror located at one end of the waveguide. Is a top emission type semiconductor laser device that is bent in the <0001> direction and emits laser light from the + c plane.

  In this way, the laser beam is emitted from one end of the + c plane, which has high chemical stability. Therefore, the end face is hardly deteriorated or broken even during high output operation, and high output operation is possible and reliable. A highly reliable semiconductor laser device can be realized.

-Modification-
4A and 4B are views showing the structure of a semiconductor laser device according to a modification of the first embodiment of the present invention, wherein FIG. 4A is a plan view seen from the <1000> direction, (B) is the cross section of the IVb-IVb line | wire of (a), Comprising: It is sectional drawing seen from the <1-100> direction.

  As shown in FIGS. 4A and 4B, the semiconductor laser device according to this modification is provided with a processed surface 12 that functions as an upper surface reflection mirror not only on the + m plane but also on the −m plane using FIB. The semiconductor laser device shown in FIGS. 1 (a) and 1 (b) is characterized in that the processed surface 12 is provided only on the −m plane and the high reflection coating 13 is provided on the + m plane. Is different.

  Further, as described above, since the processed surface 12 is also provided on the + m plane, similarly to the cladding layer 6 and the contact layer 7 on the −m plane side in FIGS. 1A and 1B, FIG. And as shown in (b), it is desirable to expose the cladding layer 6 by removing a part of the contact layer 7 and the cladding layer 6 on the + m plane side. However, when an AlGaN layer is used as the contact layer 7, The same applies to other cases. Other configurations are the same as those of the semiconductor laser device shown in FIGS. 1A and 1B.

  As described above, in the semiconductor laser device shown in FIGS. 4A and 4B, the laser beam propagating on the + c plane is <2 by the two processed surfaces functioning as the upper surface reflecting mirrors located at both ends of the waveguide. This is a top emission semiconductor laser device that is bent in the 0001> direction and emits laser light from the + c plane.

  As described above, since the laser light is emitted from both ends of the + c plane, which has high chemical stability, the end face is hardly deteriorated or broken even during high output operation, and high output operation is possible and high reliability. A semiconductor laser device can be realized.

  Furthermore, in this modification, since the processed surface 12 is formed on both the + m plane and the −m plane using FIB, a process of cleaving is not necessary. As described above, since a large number of optical elements can be integrated on a semiconductor chip without cleavage, a high-power laser array in which optical elements are integrated on the array can be easily realized.

(Second Embodiment)
Hereinafter, a semiconductor laser device and a manufacturing method thereof according to the second embodiment of the present invention will be described. Specifically, in the second embodiment, a semiconductor laser device that outputs a blue (wavelength 460 nm) laser beam using a GaN-based semiconductor will be described as an example.

  FIGS. 5A and 5B are views showing the structure of the semiconductor laser device according to the second embodiment of the present invention, wherein FIG. 5A is a plan view seen from the <1-100> direction. b) is a cross-sectional view taken along the line Vb-Vb in (a), as viewed from the <11-20> direction.

  The semiconductor laser device shown in FIGS. 5A and 5B is formed on the + m plane, that is, the (1-100) plane of the substrate 1 made of n-type GaN whose main surface is the m plane, and −c By providing a highly reflective coating on the surface side, the laser light propagated on the + m plane is reflected by the highly reflective coating and emitted from the + c plane.

  The manufacturing method of the semiconductor laser device according to the present embodiment shown in FIGS. 5A and 5B uses the substrate 1 made of n-type GaN whose main surface is an m-plane, and the main surface is a c-plane. Although different from the manufacturing method of the semiconductor laser device according to the first embodiment using the substrate 1 made of n-type GaN, the other steps are the same. However, in the present embodiment, since the substrate 1 having the m-plane main surface is used and the laser beam is emitted from the + c plane, a part of the contact layer 7 and the cladding layer 6 is used as in the first embodiment. As shown in FIGS. 5A and 5B, after the cladding layer 6 and the contact layer 7 are grown in order, the p-type electrode 8 and the wiring electrode 9 are only formed thereon. It's okay. Further, in the present embodiment, the highly reflective coating 13 is applied to the −c surface, and is easily attacked by phosphoric acid, alkali, aqua regia, and the like, and is emitted from the −c surface having low chemical stability. To realize a highly reliable semiconductor laser device with little degradation of the end face even during high output operation by reducing the ratio of laser light and increasing the ratio of light emitted from the + c plane, which has high chemical stability. Can do. Instead of the high reflection coating 13, a distributed feedback Bragg reflector (DBR) may be formed as in the first embodiment. The primary cleavage is performed along the a-plane so that the length in the <11-20> direction is 600 μm, and the secondary cleavage is performed along the c-plane so that the length in the <0001> direction is 200 μm. Just do it.

  As described above, according to the semiconductor laser device according to the second embodiment of the present invention, the laser beam propagating on the + m plane functions as a reflection mirror located at one end of the waveguide. Since the laser beam is emitted from the + c plane, which is highly chemically stable due to the reflection of the surface, the end face is not easily deteriorated or broken even during high output operation, and high output operation is possible and high reliability. A semiconductor laser device can be realized.

  In the first and second embodiments, the case where a GaN substrate is used as the substrate of the semiconductor laser device has been described. However, as long as hexagonal GaN can be formed on the substrate, for example, sapphire, SiC, Other substrates such as Si may be used. Further, the case where the semiconductor laser device is an electrode stripe type semiconductor laser device has been described as the optical waveguide structure of the semiconductor laser device. However, the same applies to, for example, a buried type semiconductor laser device or a ridge stripe type semiconductor laser device. Needless to say, an effect can be obtained.

  The semiconductor laser device according to the present invention is useful for laser displays, light sources, high-speed optical recording, and the like.

(A) And (b) is a figure which shows the structure of the semiconductor laser apparatus based on the 1st Embodiment of this invention, Comprising: (a) is a top view seen from <1000> direction, (b) is ( It is a cross section taken along the line Ib-Ib of a) and viewed from the <1-100> direction. 2 schematically shows a state of propagation of laser light and an intensity profile of the laser light in the vicinity of a processing surface in the semiconductor laser device according to the first embodiment of the present invention. FIG. 4 is a relationship diagram between optical coupling efficiency and processing angle in the semiconductor laser device according to the first embodiment of the present invention. (A) And (b) is a figure which shows the structure of the semiconductor laser apparatus which concerns on the modification of the 1st Embodiment of this invention, Comprising: (a) is the top view seen from <1000> direction, (b) ) Is a cross-sectional view taken along line IVb-IVb of (a) and viewed from the <1-100> direction. (A) And (b) is a figure which shows the structure of the semiconductor laser apparatus based on the 2nd Embodiment of this invention, Comprising: (a) is the top view seen from <1-100> direction, (b) FIG. 4A is a cross-sectional view taken along the line Vb-Vb in (a) and viewed from the <11-20> direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Clad layer 3 n side light guide layer 4 active layer 5 p side light guide layer 6 clad layer 7 contact layer 8 p-type electrode 9 wiring electrode 10 silicon oxide film 11 n-type electrode 12 processing surface 13 high reflection coating

Claims (9)

A striped optical waveguide that propagates light has a laminated structure in which a first clad layer, an active layer, and a second clad layer each made of hexagonal GaN-based crystals are sequentially formed on a substrate. A semiconductor laser device having a laminated structure,
The optical waveguide extends in a plane parallel to the main surface of the laminated structure,
A semiconductor laser device having a light emitting end face having a plane orientation of (0001) at at least one end in the optical waveguide. The semiconductor laser device according to claim 1,
The plane orientation of the main surface of the laminated structure is (0001),
The light emitting end face is located on the upper surface of one end of the optical waveguide;
The semiconductor laser device, wherein a side surface of the end portion having the light emitting end surface in the optical waveguide constitutes a mirror that reflects light propagating through the optical waveguide in a <0001> direction. The semiconductor laser device according to claim 2,
The side surface of the end portion facing the end portion having the light emitting end surface in the optical waveguide is a surface perpendicular to the surface having a plane orientation of (0001),
A semiconductor laser device, wherein the vertical surface is coated with a coating for increasing the reflectance. The semiconductor laser device according to claim 1,
The plane orientation of the main surface of the laminated structure is (0001),
The light emitting end face is located on the upper surface of both end portions of the optical waveguide,
The side surface of the both ends of the said optical waveguide is a semiconductor laser apparatus which comprises the mirror which reflects the light which propagates the said optical waveguide to <0001> direction. In the semiconductor laser device according to any one of claims 2 to 4,
The semiconductor laser device, wherein an angle formed between the mirror and the main surface of the laminated structure is larger than 41 ° and smaller than 46 °. In the semiconductor laser device according to any one of claims 2 to 4,
The light absorption edge energy of each of the active layer and the second cladding layer is larger than the photon energy of the light propagating in the optical waveguide and reflected in the <0001> direction by the mirror. . In the semiconductor laser device according to any one of claims 2 to 4,
A contact layer formed on the second cladding layer;
The light absorption edge energy of the contact layer is larger than the photon energy of the light propagating in the optical waveguide reflected by the mirror and traveling in the <0001> direction. In the semiconductor laser device according to any one of claims 2 to 4,
The semiconductor laser device, wherein the contact layer does not exist on the light emitting end face. The semiconductor laser device according to claim 1,
The plane orientation of the main surface of the laminated structure is orthogonal to (0001),
The light emitting end surface is located on a side surface of the end of the optical waveguide;
Of the both ends of the optical waveguide, the side surface of the end serving as the light emitting end surface constitutes a mirror having a surface orientation of (0001), while the light emitting end surface of the both ends of the optical waveguide. The side surface of the end portion which does not become a semiconductor laser device is configured with a mirror having a surface orientation of (000-1) and is coated with a coating for increasing the reflectance.

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