JP5152393B2 - Group III nitride semiconductor laser device and method of manufacturing group III nitride semiconductor laser device - Google Patents

Description

  The present invention relates to a group III nitride semiconductor laser device and a method for manufacturing a group III nitride semiconductor laser device.

  Non-Patent Document 1 describes a semiconductor laser fabricated on a c-plane sapphire substrate. A mirror surface of the semiconductor laser is formed by dry etching. A photomicrograph of the resonant mirror surface of the laser is published, and it is described that the roughness of the end surface is about 50 nm.

  Non-Patent Document 2 describes a semiconductor laser fabricated on a (11-22) plane GaN substrate. A mirror surface of the semiconductor laser is formed by dry etching.

  Non-Patent Document 3 describes a gallium nitride based semiconductor laser. In order to use the m-plane as a cleaved facets for a laser resonator, it has been proposed to generate laser light polarized in the off direction of the c-axis of the substrate. Specifically, this document describes that the well width is increased on the nonpolar plane and the well width is decreased on the semipolar plane.

Jpn.J.Appl.Phys.Vol. 35, (1996) L74-L76 Appl.Phys.Express 1 (2008) 091102 Jpn.J.Appl.Phys.Vol. 46, (2007) L789

  According to the band structure of a gallium nitride semiconductor, there are several transitions that can cause laser oscillation. According to the inventor's knowledge, in a group III nitride semiconductor laser device using a semipolar surface supporting substrate whose c-axis is inclined in the direction of the m-axis, the laser beam is guided along a plane defined by the c-axis and the m-axis. We believe that the threshold current can be lowered when extending the waveguide. In the direction of this laser waveguide, the mode with the smallest transition energy (difference between conduction band energy and valence band energy) can be laser-oscillated, and when this mode can be oscillated, the threshold is set. The current can be lowered.

  However, in this laser waveguide orientation, a conventional cleavage plane such as c-plane, a-plane or m-plane cannot be used for the resonator mirror. For this reason, the dry etching surface of the semiconductor layer has been formed using reactive ion etching (RIE) for the fabrication of the resonator mirror. A resonator mirror formed by the RIE method is desired to be improved in terms of perpendicularity to a laser waveguide, flatness of a dry etching surface, or ion damage. In addition, derivation of process conditions for obtaining a good dry etching surface at the current technical level is a heavy burden.

  As far as the inventor knows, in the same group III nitride semiconductor laser element formed on the above semipolar plane, a laser waveguide extending in the c-axis tilt direction (off direction) and dry etching have so far been made. Both the end face for the resonator mirror formed without using the above are not achieved.

  The present invention has been made in view of such circumstances. It is an object of the present invention to provide a group III nitride having a laser resonator that enables a low threshold current on the semipolar plane of a support base inclined from the c-axis to the m-axis direction of hexagonal group III nitride. An object of the present invention is to provide a semiconductor laser device, and to provide a method for manufacturing the group III nitride semiconductor laser device.

  A group III nitride semiconductor laser device according to one aspect of the present invention includes: (a) a support base made of a hexagonal group III nitride semiconductor and having a semipolar main surface; and the semipolar main surface of the support base A laser structure including the semiconductor region provided; and (b) an electrode provided on the semiconductor region of the laser structure. The semiconductor region includes a first cladding layer made of a gallium nitride semiconductor of a first conductivity type, a second cladding layer made of a gallium nitride semiconductor of a second conductivity type, the first cladding layer, and the first cladding layer. The first cladding layer, the second cladding layer and the active layer are arranged along a normal axis of the semipolar main surface. The active layer includes a gallium nitride based semiconductor layer, and the c-axis of the hexagonal group III nitride semiconductor of the support base is the normal axis in the direction of the m axis of the hexagonal group III nitride semiconductor. The laser structure is inclined at a finite angle ALPHA, and the laser structure intersects the mn plane defined by the m-axis and the normal axis of the hexagonal group III nitride semiconductor. The group III nitride semiconductor laser The laser resonator of the element includes the first and second fractured surfaces, the laser structure includes first and second surfaces, and the first surface is a surface opposite to the second surface. The first and second fractured surfaces extend from an edge of the first surface to an edge of the second surface.

  According to this group III nitride semiconductor laser device, the first and second fractured surfaces serving as laser resonators are in the mn plane defined by the m axis and the normal axis of the hexagonal group III nitride semiconductor. Since they intersect, a laser waveguide extending in the direction of the intersecting line between the mn plane and the semipolar plane can be provided. Therefore, a group III nitride semiconductor laser device having a laser resonator that enables a low threshold current can be provided.

  In the group III nitride semiconductor laser device according to the present invention, an angle formed between the normal axis and the c axis of the hexagonal group III nitride semiconductor is in a range of 45 degrees to 80 degrees or 100 degrees to 135 degrees. It is preferable that

  In this group III nitride semiconductor laser device, there is a high possibility that the end face formed by pressing is an m-plane at angles less than 45 degrees and greater than 135 degrees. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained.

  In the group III nitride semiconductor laser device according to the present invention, an angle formed between the normal axis and the c axis of the hexagonal group III nitride semiconductor is in a range of not less than 63 degrees and not more than 80 degrees, or not less than 100 degrees and not more than 117 degrees. More preferably.

  In this group III nitride semiconductor laser device, in the range of 63 degrees to 80 degrees or 100 degrees to 117 degrees, there is a high possibility that the end face formed by pressing is nearly perpendicular to the substrate main surface. Become. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained.

  In the group III nitride semiconductor laser device according to the present invention, the thickness of the support base is preferably 400 μm or less. This group III nitride semiconductor laser device is suitable for obtaining a high-quality fractured surface for a laser resonator.

  In the group III nitride semiconductor laser device according to the present invention, the thickness of the support base is more preferably 50 μm or more and 100 μm or less. When the thickness is 50 μm or more, handling becomes easy and production yield is improved. If it is 100 micrometers or less, it is further suitable in order to obtain the good-quality split surface for a laser resonator.

  In the group III nitride semiconductor laser device according to the present invention, the laser light from the active layer is polarized in the a-axis direction of the hexagonal group III nitride semiconductor. In this group III nitride semiconductor laser device, a band transition capable of realizing a low threshold current has polarization.

  In the group III nitride semiconductor laser device according to the present invention, the light in the LED mode of the group III nitride semiconductor laser device includes the polarization component I1 in the direction of the a-axis of the hexagonal group III nitride semiconductor and the hexagonal The polarization component I2 is included in a direction in which the c-axis of the crystal group III nitride semiconductor is projected onto the principal surface, and the polarization component I1 is larger than the polarization component I2. According to this group III nitride semiconductor laser element, light having a large emission intensity in the LED mode can be laser-oscillated using the laser resonator.

  In the group III nitride semiconductor laser device according to the present invention, the semipolar main surface includes {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1. } Any of the surfaces is preferred.

  According to this group III nitride semiconductor laser device, the first and second flatness and perpendicularity sufficient to configure the laser resonator of the group III nitride semiconductor laser device on these typical semipolar planes. Two end faces can be provided.

  In the group III nitride semiconductor laser device according to the present invention, the semipolar main surface includes {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1. } A plane having a slight inclination in a range of −4 degrees or more and +4 degrees or less in the m-plane direction from any semipolar plane of the plane is also suitable as the main plane.

  According to this group III nitride semiconductor laser device, the flatness and perpendicularity sufficient to configure the laser resonator of the group III nitride semiconductor laser device on the slightly inclined surface from these typical semipolar planes. First and second end surfaces of the first and second end surfaces can be provided.

In the group III nitride semiconductor laser device according to the present invention, the stacking fault density of the support base is preferably 1 × 10 ⁴ cm ⁻¹ or less.

According to this group III nitride semiconductor laser device, since the stacking fault density is 1 × 10 ⁴ cm ⁻¹ or less, there is a low possibility that the flatness and / or the perpendicularity of the fractured section will be disturbed due to accidental circumstances.

  In the group III nitride semiconductor laser device according to the present invention, the support base may be made of any one of GaN, AlGaN, AlN, InGaN, and InAlGaN.

  According to this group III nitride semiconductor laser device, when using a substrate made of these gallium nitride semiconductors, the first and second end faces that can be used as a resonator can be obtained. When an AlN substrate or an AlGaN substrate is used, the degree of polarization can be increased, and light confinement can be enhanced by a low refractive index. When an InGaN substrate is used, the lattice mismatch rate between the substrate and the light emitting layer can be reduced, and the crystal quality can be improved.

  The group III nitride semiconductor laser device according to the present invention may further include a dielectric multilayer film provided on at least one of the first and second fractured faces.

  Also in this group III nitride semiconductor laser device, an end face coat can be applied to the fracture surface. The reflectance can be adjusted by the end face coating.

  In the group III nitride semiconductor laser device according to the present invention, the active layer may include a quantum well structure provided to generate light having a wavelength of 360 nm to 600 nm. This group III nitride semiconductor laser device can obtain a group III nitride semiconductor laser device that effectively utilizes polarized light in the LED mode by utilizing a semipolar plane, and can obtain a low threshold current.

  In the group III nitride semiconductor laser device according to the present invention, it is more preferable that the active layer includes a quantum well structure provided to generate light having a wavelength of 430 nm or more and 550 nm or less. This group III nitride semiconductor laser device can improve quantum efficiency by reducing the piezoelectric field and improving the crystal quality of the light emitting layer region by utilizing a semipolar plane, and can generate light with a wavelength of 430 nm to 550 nm. Is preferred.

  In the group III nitride semiconductor laser device according to the present invention, an end surface of the support base and an end surface of the semiconductor region appear in each of the first and second fractured surfaces, and the active layer of the semiconductor region The angle formed between the end face in FIG. 5 and the reference plane perpendicular to the m-axis of the support base made of the hexagonal nitride semiconductor is (ALPHA) in the first plane defined by the c-axis and m-axis of the group III nitride semiconductor. −5) An angle in the range of not less than ALPHA + 5 degrees.

  This group III nitride semiconductor laser device has an end surface that satisfies the above-described perpendicularity with respect to an angle taken from one of the c-axis and the m-axis to the other.

  In the group III nitride semiconductor laser device according to the present invention, the angle is preferably in the range of −5 degrees or more and +5 degrees or less in the first plane and the second plane orthogonal to the normal axis.

  This group III nitride semiconductor laser device has an end face that satisfies the above-described perpendicularity with respect to an angle defined in a plane perpendicular to the normal axis of the semipolar plane.

  In the group III nitride semiconductor laser device according to the present invention, the electrode extends in the direction of a predetermined axis, and the first and second fractured surfaces intersect the predetermined axis.

  Another aspect of the present invention relates to a method for fabricating a group III nitride semiconductor laser device. This method includes (a) a step of preparing a substrate made of a hexagonal group III nitride semiconductor and having a semipolar main surface; and (b) a semiconductor region formed on the semipolar main surface and the substrate. Forming a substrate product having a laser structure, an anode electrode, and a cathode electrode comprising (c) a first surface of the substrate product in the direction of the a-axis of the hexagonal group III nitride semiconductor; A step of partially scribing; and (d) separating the substrate product by pressing the substrate product against a second surface to form another substrate product and a laser bar. The first surface is a surface opposite to the second surface, the semiconductor region is located between the first surface and the substrate, and the laser bar extends from the first surface to the first surface. The first and second end faces extending to the second face and formed by the separation, wherein the first and second end faces constitute a laser resonator of the group III nitride semiconductor laser element, An anode electrode and a cathode electrode are formed on the laser structure, and the semiconductor region is formed of a first cladding layer made of a first conductivity type gallium nitride semiconductor and a second conductivity type gallium nitride semiconductor. A second clad layer; and an active layer provided between the first clad layer and the second clad layer, the first clad layer, the second clad layer, and the active layer. Are arranged along the normal axis of the semipolar principal surface. The active layer includes a gallium nitride based semiconductor layer, and the c-axis of the hexagonal group III nitride semiconductor of the substrate is in the direction of the m axis of the hexagonal group III nitride semiconductor with respect to the normal axis. The first and second end faces intersect the mn plane defined by the m-axis and the normal axis of the hexagonal group III nitride semiconductor.

  According to this method, after the first surface of the substrate product is scribed in the direction of the a-axis of the hexagonal group III nitride semiconductor, the substrate product is separated by pressing the substrate product against the second surface. To form another substrate product and laser bar. Therefore, the first and second end faces are formed on the laser bar so as to intersect the mn plane defined by the m-axis and the normal axis of the hexagonal group III nitride semiconductor. According to this end face formation, the first and second end faces are provided with a mirror mirror surface having sufficient flatness, perpendicularity, or ion damage sufficient to constitute a laser resonator of the group III nitride semiconductor laser element. The

  In this method, the laser waveguide extends in the direction of the c-axis inclination of the hexagonal group III nitride, and the cavity mirror end face that can provide this laser waveguide is not used as a dry etching surface. Is formed.

  In the method according to the present invention, in the step of forming the substrate product, the substrate is subjected to processing such as slicing or grinding so that the thickness of the substrate is 400 μm or less, and the second surface is It can be a processed surface formed by processing. Alternatively, it can be a surface including an electrode formed on the processed surface.

  In the method according to the present invention, in the step of forming the substrate product, the substrate is polished so that the thickness of the substrate is 50 μm or more and 100 μm or less, and the second surface is formed by the polishing. It can be a polished surface. Alternatively, it can be a surface including an electrode formed on the polished surface.

  With the substrate having such a thickness, the first and second end faces having sufficient flatness, perpendicularity, or ion damage sufficient to constitute a laser resonator of the group III nitride semiconductor laser element can be formed with high yield. .

  In the method according to the present invention, the angle ALPHA may be in the range of 45 degrees to 80 degrees and 100 degrees to 135 degrees. If the angle is less than 45 degrees or more than 135 degrees, there is a high possibility that the end face formed by pressing is an m-plane. Further, when the angle is more than 80 degrees and less than 100 degrees, desired flatness and perpendicularity cannot be obtained.

  In the method according to the present invention, more preferably, the angle ALPHA can be in the range of 63 degrees to 80 degrees and 100 degrees to 117 degrees. If the angle is less than 63 degrees or more than 117 degrees, the m-plane may appear in a part of the end face formed by pressing. Further, when the angle is more than 80 degrees and less than 100 degrees, desired flatness and perpendicularity cannot be obtained.

  In the method according to the present invention, the semipolar principal surface is any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. Preferably there is.

  Even in these typical semipolar planes, it is possible to provide the first and second end faces without flatness, perpendicularity, or ion damage sufficient to constitute a laser resonator of the group III nitride semiconductor laser element.

  In the method according to the present invention, the semipolar principal surface is any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. A plane having a slight inclination in a range of −4 degrees or more and +4 degrees or less in the m-plane direction from the semipolar plane is also suitable as the main surface.

  Even on these slightly inclined surfaces from the typical semipolar plane, the first and second layers do not have sufficient flatness, perpendicularity, or ion damage that can constitute a laser resonator of the group III nitride semiconductor laser device. Can provide end face.

  In the method according to the present invention, the scribe is performed using a laser scriber, a scribe groove is formed by the scribe, and the length of the scribe groove is defined by the a-axis of the hexagonal group III nitride semiconductor and the scribe groove. It is shorter than the length of the intersection line between the a-n plane defined by the normal axis and the first plane.

  According to this method, another substrate product and a laser bar are formed by cleaving the substrate product. This cleaving is caused by using a scribe groove that is shorter than the cleaving line of the laser bar.

  In the method according to the present invention, the end face of the active layer in each of the first and second end faces is in the hexagonal direction with respect to a reference plane perpendicular to the m-axis of the support base made of the hexagonal nitride semiconductor. An angle in the range of (ALPHA-5) degrees or more and (ALPHA + 5) degrees or less can be formed on a plane defined by the c-axis and m-axis of the crystal group III nitride semiconductor.

  According to this method, the end face having the above-described perpendicularity can be formed with respect to an angle taken from one of the c-axis and the m-axis to the other.

  In the method according to the present invention, the substrate may be made of any one of GaN, AlN, AlGaN, InGaN, and InAlGaN. According to this method, when using a substrate made of these gallium nitride based semiconductors, the first and second end faces usable as a resonator can be obtained.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, the laser resonance that enables a low threshold current on the semipolar plane of the support base in which the c-axis of the hexagonal group III nitride is inclined in the direction of the m-axis. There is provided a group III nitride semiconductor laser device having a cavity, and according to the present invention, a method for producing the group III nitride semiconductor laser device is provided.

FIG. 1 is a drawing schematically showing a structure of a group III nitride semiconductor laser device according to the present embodiment. FIG. 2 is a drawing showing a band structure in an active layer in a group III nitride semiconductor laser device. FIG. 3 is a drawing showing the polarization of light emission in the active layer of the group III nitride semiconductor laser device. FIG. 4 is a drawing showing the relationship between the end face of the group III nitride semiconductor laser device and the m-plane of the active layer. FIG. 5 is a process flow diagram showing the main steps of the method of manufacturing the group III nitride semiconductor laser device according to the present embodiment. FIG. 6 is a drawing schematically showing main steps of a method for producing a group III nitride semiconductor laser device according to the present embodiment. FIG. 7 is a drawing showing a scanning electron microscope image of the resonator end face while showing the {20-21} plane in the crystal lattice. FIG. 8 is a drawing showing the structure of the laser diode shown in Example 1. FIG. 9 is a diagram showing the relationship between the obtained degree of polarization ρ and the threshold current density. FIG. 10 is a drawing showing the relationship between the inclination angle of the c-axis in the m-axis direction of the GaN substrate and the oscillation yield. FIG. 11 is a diagram showing the relationship between stacking fault density and oscillation yield. FIG. 12 is a diagram showing the relationship between the substrate thickness and the oscillation yield. FIG. 13 is a view showing an angle formed by the (20-21) plane and another plane orientation (index). FIG. 14 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-6) plane, and the (−1016) plane. FIG. 15 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-7) plane, and the (−1017) plane. FIG. 16 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-8) plane, and the (−1018) plane.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the group III nitride semiconductor laser device and the method for manufacturing the group III nitride semiconductor laser device of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

  FIG. 1 is a drawing schematically showing a structure of a group III nitride semiconductor laser device according to the present embodiment. Although group III nitride semiconductor laser device 11 has a gain guide type structure, the embodiment of the present invention is not limited to the gain guide type structure. The group III nitride semiconductor laser device 11 includes a laser structure 13 and an electrode 15. The laser structure 13 includes a support base 17 and a semiconductor region 19. The support base 17 is made of a hexagonal group III nitride semiconductor and has a semipolar main surface 17a and a back surface 17b. The semiconductor region 19 is provided on the semipolar main surface 17 a of the support base 17. The electrode 15 is provided on the semiconductor region 19 of the laser structure 13. The semiconductor region 19 includes a first cladding layer 21, a second cladding layer 23, and an active layer 25. The first cladding layer 21 is made of a first conductivity type gallium nitride semiconductor, and is made of, for example, n-type AlGaN, n-type InAlGaN, or the like. The second cladding layer 23 is made of a second conductivity type gallium nitride based semiconductor, for example, p-type AlGaN, p-type InAlGaN, or the like. The active layer 25 is provided between the first cladding layer 21 and the second cladding layer 23. The active layer 25 includes a gallium nitride based semiconductor layer, and this gallium nitride based semiconductor layer is, for example, a well layer 25a. The active layer 25 includes barrier layers 25b made of a gallium nitride semiconductor, and the well layers 25a and the barrier layers 25b are alternately arranged. The well layer 25a is made of, for example, InGaN, and the barrier layer 25b is made of, for example, GaN, InGaN, or the like. The active layer 25 can include a quantum well structure provided to generate light having a wavelength of 360 nm to 600 nm. Use of a semipolar plane is suitable for generation of light having a wavelength of 430 nm or more and 550 nm or less. The first cladding layer 21, the second cladding layer 23, and the active layer 25 are arranged along the normal axis NX of the semipolar principal surface 17a. In the group III nitride semiconductor laser device 11, the laser structure 13 includes the first fractured surface 27 and the first section 27 intersecting the mn plane defined by the m axis and the normal axis NX of the hexagonal group III nitride semiconductor. 2 split sections 29 are included.

  Referring to FIG. 1, an orthogonal coordinate system S and a crystal coordinate system CR are depicted. The normal axis NX is directed in the direction of the Z axis of the orthogonal coordinate system S. The semipolar principal surface 17a extends in parallel to a predetermined plane defined by the X axis and the Y axis of the orthogonal coordinate system S. FIG. 1 also shows a representative c-plane Sc. The c-axis of the hexagonal group III nitride semiconductor of the support base 17 is inclined at a finite angle ALPHA with respect to the normal axis NX in the m-axis direction of the hexagonal group III nitride semiconductor.

  Group III nitride semiconductor laser device 11 further includes an insulating film 31. The insulating film 31 covers the surface 19 a of the semiconductor region 19 of the laser structure 13, and the semiconductor region 19 is located between the insulating film 31 and the support base 17. The support base 17 is made of a hexagonal group III nitride semiconductor. The insulating film 31 has an opening 31a. The opening 31a extends in the direction of the intersection line LIX between the surface 19a of the semiconductor region 19 and the mn plane, and has, for example, a stripe shape. The electrode 15 is in contact with the surface 19a (for example, the second conductivity type contact layer 33) of the semiconductor region 19 through the opening 31a, and extends in the direction of the intersection line LIX. In the group III nitride semiconductor laser device 11, the laser waveguide includes the first cladding layer 21, the second cladding layer 23, and the active layer 25, and extends in the direction of the intersection line LIX.

  In the group III nitride semiconductor laser device 11, the first fractured surface 27 and the second fractured surface 29 intersect the mn plane defined by the m-axis and the normal axis NX of the hexagonal group III nitride semiconductor. To do. The laser resonator of the group III nitride semiconductor laser device 11 includes first and second fractured faces 27 and 29, and a laser waveguide is provided from one of the first fractured face 27 and the second fractured face 29 to the other. It is extended. The laser structure 13 includes a first surface 13a and a second surface 13b, and the first surface 13a is a surface opposite to the second surface 13b. The first and second fractured surfaces 27 and 29 extend from the edge 13c of the first surface 13a to the edge 13d of the second surface 13b. The first and second fractured surfaces 27 and 29 are different from conventional cleavage planes such as c-plane, m-plane, or a-plane.

  According to the group III nitride semiconductor laser device 11, the first and second fractured surfaces 27 and 29 constituting the laser resonator intersect with the mn plane. Therefore, it is possible to provide a laser waveguide extending in the direction of the intersecting line between the mn plane and the semipolar plane 17a. Therefore, the group III nitride semiconductor laser device 11 has a laser resonator that enables a low threshold current.

  The group III nitride semiconductor laser device 11 includes an n-side light guide layer 35 and a p-side light guide layer 37. The n-side light guide layer 35 includes a first portion 35a and a second portion 35b, and the n-side light guide layer 35 is made of, for example, GaN, InGaN, or the like. The p-side light guide layer 37 includes a first portion 37a and a second portion 37b, and the p-side light guide layer 37 is made of, for example, GaN, InGaN, or the like. The carrier block layer 39 is provided, for example, between the first portion 37a and the second portion 37b. Another electrode 41 is provided on the back surface 17b of the support base 17, and the electrode 41 covers, for example, the back surface 17b of the support base 17.

  FIG. 2 is a drawing showing a band structure in an active layer in a group III nitride semiconductor laser device. FIG. 3 is a drawing showing the polarization of light emission in the active layer 25 of the group III nitride semiconductor laser device 11. FIG. 4 is a drawing schematically showing a cross section defined by the c-axis and the m-axis. Referring to FIG. 2A, there are three possible transitions between the conduction band and the valence band near the Γ point of the band structure BAND. The A band and the B band are relatively small energy differences. The light emission due to the transition Ea between the conduction band and the A band is polarized in the a-axis direction, and the light emission due to the transition Eb between the conduction band and the B band is polarized in the direction projected on the principal plane. Regarding the laser oscillation, the threshold value of the transition Ea is smaller than the threshold value of the transition Eb.

  Referring to FIG. 2B, a light spectrum in the LED mode in the group III nitride semiconductor laser device 11 is shown. The light in the LED mode includes a polarization component I1 in the direction of the a-axis of the hexagonal group III nitride semiconductor and a polarization component I2 in a direction of projecting the c-axis of the hexagonal group III nitride semiconductor on the main surface, The polarization component I1 is larger than the polarization component I2. The degree of polarization ρ is defined by (I1−I2) / (I1 + I2). By using the laser resonator of this group III nitride semiconductor laser device 11, light in a mode with a large emission intensity can be laser-oscillated in the LED mode.

  As shown in FIG. 3, dielectric multilayer films 43 a and 43 b provided on at least one of the first and second fractured surfaces 27 and 29, or each of them, may be further provided. An end face coat can also be applied to the fracture surfaces 27 and 29. The reflectance can be adjusted by the end face coating.

  As shown in FIG. 3B, the laser light L from the active layer 25 is polarized in the a-axis direction of the hexagonal group III nitride semiconductor. In this group III nitride semiconductor laser device 11, the band transition capable of realizing a low threshold current has polarization. The first and second fractured surfaces 27 and 29 for the laser resonator are different from conventional cleavage planes such as c-plane, m-plane or a-plane. However, the first and second fractured surfaces 27 and 29 have flatness and perpendicularity as mirrors for the resonator. Therefore, using the first and second split sections 27 and 29 and the laser waveguide extending between the split sections 27 and 29, the c-axis is mainly used as shown in FIG. Low threshold laser oscillation is possible by using light emission of transition Ea stronger than light emission of transition Eb polarized in the direction projected onto the surface.

In the group III nitride semiconductor laser device 11, the end surface 17c of the support base 17 and the end surface 19c of the semiconductor region 19 appear in each of the first and second fractured surfaces 27 and 29, and the end surface 17c and the end surface 19c are It is covered with a dielectric multilayer film 43a. An angle BETA formed by the normal vector NA of the end face 17c of the support substrate 17 and the end face 25c of the active layer 25 and the m-axis vector MA of the active layer 25 is defined by the c-axis and m-axis of the group III nitride semiconductor. A component (BETA) ₁ defined in one plane S1, a first plane S1 (not shown for ease of understanding, but referred to as “S1”) and a second plane S2 orthogonal to the normal axis NX (understand For the sake of simplicity, it is defined by the component (BETA) ₂ defined in (not shown but referred to as “S2”). The component (BETA) ₁ is preferably in the range of (ALPHA-5) degrees to (ALPHA + 5) degrees in the first plane S1 defined by the c-axis and m-axis of the group III nitride semiconductor. This angle range is shown in FIG. 4 as an angle formed by a representative m-plane _SM and the reference plane F _A. A representative m-plane _SM is depicted from the inside to the outside of the laser structure in FIG. 4 for ease of understanding. The reference plane F _A extends along the end face 25c of the active layer 25. This group III nitride semiconductor laser device 11 has an end surface that satisfies the above-described perpendicularity with respect to an angle BETA taken from one of the c-axis and the m-axis to the other. In addition, the component (BETA) ₂ is preferably in the range of −5 degrees or more and +5 degrees or less in the second plane S2. Here, BETA ² = (BETA) ₁ ² + (BETA) ₂ ² . At this time, the end faces 27 and 29 of the group III nitride semiconductor laser device 11 satisfy the above-described perpendicularity with respect to an angle defined in a plane perpendicular to the normal axis NX of the semipolar surface 17a.

  Referring again to FIG. 1, in the group III nitride semiconductor laser device 11, the thickness DSUB of the support base 17 is preferably 400 μm or less. This group III nitride semiconductor laser device is suitable for obtaining a high-quality fractured surface for a laser resonator. In the group III nitride semiconductor laser device 11, the thickness DSUB of the support base 17 is more preferably 50 μm or more and 100 μm or less. This group III nitride semiconductor laser device 11 is further suitable for obtaining a high-quality fractured surface for the laser resonator. Moreover, handling becomes easy and production yield can be improved.

  In the group III nitride semiconductor laser device 11, the angle ALPHA formed by the normal axis NX and the c axis of the hexagonal group III nitride semiconductor is preferably 45 degrees or more, and preferably 80 degrees or less. The angle ALPHA is preferably 100 degrees or more, and preferably 135 degrees or less. If the angle is less than 45 degrees or more than 135 degrees, there is a high possibility that the end face formed by pressing is an m-plane. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained.

  In group III nitride semiconductor laser device 11, the angle ALPHA formed by normal axis NX and c-axis of the hexagonal group III nitride semiconductor is preferably 63 degrees or more and 80 degrees or less. It is preferable. The angle ALPHA is preferably 100 degrees or more, and is preferably 117 degrees or less. If the angle is less than 63 degrees or more than 117 degrees, the m-plane may appear in a part of the end face formed by pressing. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained.

  The semipolar principal surface 17a can be any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. Furthermore, a surface slightly inclined from these surfaces within a range of −4 degrees or more and +4 degrees or less is also suitable as the main surface. In these typical semipolar surfaces 17a, the first and second end surfaces 27 and 29 having sufficient flatness and perpendicularity that can constitute the laser resonator of the group III nitride semiconductor laser device 11 can be provided. In addition, in the range of angles over these typical plane orientations, an end face exhibiting sufficient flatness and perpendicularity can be obtained.

In the group III nitride semiconductor laser device 11, the stacking fault density of the support base 17 can be 1 × 10 ⁴ cm ⁻¹ or less. Since the stacking fault density is 1 × 10 ⁴ cm ⁻¹ or less, there is a low possibility that the flatness and / or perpendicularity of the fractured section will be disturbed due to accidental circumstances. The support base 17 can be made of any one of GaN, AlN, AlGaN, InGaN, and InAlGaN. When these gallium nitride semiconductor substrates are used, end faces 27 and 29 that can be used as resonators can be obtained. When an AlN or AlGaN substrate is used, the degree of polarization can be increased, and light confinement can be enhanced by a low refractive index. When an InGaN substrate is used, the lattice mismatch rate between the substrate and the light emitting layer can be reduced, and the crystal quality can be improved.

  FIG. 5 is a drawing showing the main steps of the method for producing a group III nitride semiconductor laser device according to the present embodiment. Referring to FIG. 6A, a substrate 51 is shown. In step S101, a substrate 51 for preparing a group III nitride semiconductor laser device is prepared. The c-axis (vector VC) of the hexagonal group III nitride semiconductor of the substrate 51 is inclined at a finite angle ALPHA with respect to the normal axis NX in the m-axis direction (vector VM) of the hexagonal group III nitride semiconductor. ing. Therefore, the substrate 51 has a semipolar main surface 51a made of a hexagonal group III nitride semiconductor.

  In step S102, a substrate product SP is formed. In FIG. 6A, the substrate product SP is depicted as a substantially disk-shaped member, but the shape of the substrate product SP is not limited to this. In order to obtain the substrate product SP, first, in step S103, the laser structure 55 is formed. The laser structure 55 includes a semiconductor region 53 and a substrate 51. In step S103, the semiconductor region 53 is formed on the semipolar main surface 51a. In order to form the semiconductor region 53, a first conductivity type gallium nitride based semiconductor region 57, a light emitting layer 59, and a second conductivity type gallium nitride based semiconductor region 61 are sequentially grown on the semipolar main surface 51a. The gallium nitride based semiconductor region 57 can include, for example, an n-type cladding layer, and the gallium nitride based semiconductor region 61 can include, for example, a p-type cladding layer. The light emitting layer 59 is provided between the gallium nitride based semiconductor region 57 and the gallium nitride based semiconductor region 61, and may include an active layer, a light guide layer, an electron blocking layer, and the like. The gallium nitride based semiconductor region 57, the light emitting layer 59, and the second conductivity type gallium nitride based semiconductor region 61 are arranged along the normal axis NX of the semipolar principal surface 51a. These semiconductor layers are epitaxially grown. The semiconductor region 53 is covered with an insulating film 54. The insulating film 54 is made of, for example, silicon oxide. An opening 54 a of the insulating film 54 is provided. The opening 54a has, for example, a stripe shape.

  In step S <b> 104, the anode electrode 58 a and the cathode electrode 58 b are formed on the laser structure 55. In addition, before forming the electrode on the back surface of the substrate 51, the back surface of the substrate used for crystal growth is polished to form a substrate product SP having a desired thickness DSUB. In the formation of the electrodes, for example, the anode electrode 58a is formed on the semiconductor region 53, and the cathode electrode 58b is formed on the back surface (polishing surface) 51b of the substrate 51. The anode electrode 58a extends in the X-axis direction, and the cathode electrode 58b covers the entire back surface 51b. Through these steps, the substrate product SP is formed. The substrate product SP includes a first surface 63a and a second surface 63b located on the opposite side thereof. The semiconductor region 53 is located between the first surface 63 a and the substrate 51.

  In step S105, as shown in FIG. 6B, the first surface 63a of the substrate product SP is scribed. This scribing is performed using a laser scriber 10a. A scribe groove 65a is formed by scribing. In FIG. 6B, five scribe grooves have already been formed, and the formation of the scribe groove 65b is advanced using the laser beam LB. The length of the scribe groove 65a is shorter than the length of the intersection line AIS between the a-n plane and the first plane 63a defined by the a-axis and the normal axis NX of the hexagonal group III nitride semiconductor. The laser beam LB is irradiated on a part of the AIS. By irradiation with the laser beam LB, a groove extending in a specific direction and reaching the semiconductor region is formed in the first surface 63a. The scribe groove 65a can be formed at one edge of the substrate product SP, for example.

  In step S106, as shown in FIG. 6C, the substrate product SP is separated by pressing the substrate product SP against the second surface 63b to form the substrate product SP1 and the laser bar LB1. The pressing is performed using a breaking device such as a blade 69. The blade 69 includes an edge 69a extending in one direction and at least two blade surfaces 69b and 69c defining the edge 69a. The substrate product SP1 is pressed on the support device 71. The support device 71 includes a support surface 71a and a recess 71b, and the recess 71b extends in one direction. The recess 71b is formed in the support surface 71a. The substrate product SP1 is positioned on the recess 71b on the support device 71 by aligning the direction and position of the scribe groove 65a of the substrate product SP1 with the extending direction of the recess 71b of the support device 71. The edge of the breaking device is aligned with the extending direction of the recess 71b, and the edge of the breaking device is pressed against the substrate product SP1 from the direction intersecting the second surface 63b. The intersecting direction is preferably substantially perpendicular to the second surface 63b. Thereby, the substrate product SP is separated to form the substrate product SP1 and the laser bar LB1. By pressing, the laser bar LB1 having the first and second end faces 67a and 67b is formed, and these end faces 67a and 67b are at least perpendicular to the light emitting layer and applicable to the resonant mirror of the semiconductor laser. It has flatness.

  The formed laser bar LB1 has first and second end surfaces 67a and 67b formed by the above separation, and each of the end surfaces 67a and 67b extends from the first surface 63a to the second surface 63b. Exists. Therefore, the end faces 67a and 67b constitute a laser resonator of the group III nitride semiconductor laser element and intersect the XZ plane. This XZ plane corresponds to the mn plane defined by the m-axis and the normal axis NX of the hexagonal group III nitride semiconductor.

  According to this method, after scribing the first surface 63a of the substrate product SP in the direction of the a-axis of the hexagonal group III nitride semiconductor, the substrate product SP is pressed against the second surface 63b. The product SP is separated to form a new substrate product SP1 and a laser bar LB1. Therefore, the first and second end faces 67a and 67b are formed on the laser bar LB1 so as to intersect the mn plane. This end face formation provides sufficient flatness and perpendicularity to the extent that a laser resonator of the group III nitride semiconductor laser element can be formed on the first and second end faces 67a and 67b.

  Further, in this method, the formed laser waveguide extends in the direction of the inclination of the c-axis of the hexagonal group III nitride. A resonator mirror end face capable of providing this laser waveguide is formed without using a dry etching surface.

  According to this method, a new substrate product SP1 and a laser bar LB1 are formed by cleaving the substrate product SP1. In step S107, separation by pressing is repeated to produce a large number of laser bars. This cleaving is caused by using a scribe groove 65a shorter than the breaking line BRAK of the laser bar LB1.

  In step S108, a dielectric multilayer film is formed on the end faces 67a and 67b of the laser bar LB1 to form a laser bar product. In step S109, the laser bar product is separated into individual semiconductor laser chips.

  In the manufacturing method according to the present embodiment, the angle ALPHA can be in the range of 45 degrees to 80 degrees and 100 degrees to 135 degrees. If the angle is less than 45 degrees or more than 135 degrees, there is a high possibility that the end face formed by pressing is an m-plane. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained. More preferably, the angle ALPHA can be in the range of 63 degrees to 80 degrees and 100 degrees to 117 degrees. If the angle is less than 45 degrees or more than 135 degrees, the m-plane may appear in a part of the end face formed by pressing. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained. The semipolar principal surface 51a can be any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. Furthermore, a surface slightly inclined from these surfaces within a range of −4 degrees or more and +4 degrees or less is also suitable as the main surface. In these typical semipolar planes, it is possible to provide an end face for the laser resonator with sufficient flatness and perpendicularity that can constitute the laser resonator of the group III nitride semiconductor laser device.

  The substrate 51 can be made of any one of GaN, AlN, AlGaN, InGaN, and InAlGaN. When these gallium nitride semiconductor substrates are used, an end face that can be used as a laser resonator can be obtained. The substrate 51 is preferably made of GaN.

  In step S104 for forming the substrate product SP, the semiconductor substrate used for crystal growth was subjected to processing such as slicing or grinding so that the substrate thickness was 400 μm or less, and the second surface 63b was formed by polishing. It can be a machined surface. With this substrate thickness, end faces 67a and 67b free from flatness, perpendicularity, or ion damage sufficient to constitute a laser resonator of the group III nitride semiconductor laser device can be formed with high yield. More preferably, the second surface 63b is a polished surface formed by polishing, and is polished to have a substrate thickness of 100 μm or less. In order to handle the substrate product SP relatively easily, the substrate thickness is preferably 50 μm or more.

In the laser end face manufacturing method according to the present embodiment, the angle BETA described with reference to FIG. 3 is also defined for the laser bar LB1. In the laser bar LB1, the component (BETA) ₁ of the angle BETA ₁ is in a first plane (surface corresponding to the first plane S1 in the description with reference to FIG. 3) defined by the c-axis and the m-axis of the group III nitride semiconductor. It is preferably in the range of (ALPHA-5) degrees to (ALPHA + 5) degrees. The end faces 67a and 67b of the laser bar LB1 satisfy the above-described perpendicularity with respect to the angle component of the angle BETA taken from one of the c-axis and the m-axis to the other. Further, the component (BETA) ₂ of the angle BETA is preferably in the range of −5 degrees or more and +5 degrees or less on the second plane (the plane corresponding to the second plane S2 shown in FIG. 3). At this time, the end faces 67a and 67b of the laser bar LB1 satisfy the above-described perpendicularity with respect to the angle component of the angle BETA defined by the plane perpendicular to the normal axis NX of the semipolar surface 51a.

  The end faces 67a and 67b are formed by a break by pressing against a plurality of gallium nitride based semiconductor layers epitaxially grown on the semipolar surface 51a. Because of the epitaxial film on the semipolar surface 51a, the end surfaces 67a and 67b are not cleaved surfaces with a low index such as the c-plane, m-plane, or a-plane that have been used as resonator mirrors. However, in the break of the lamination of the epitaxial film on the semipolar surface 51a, the end surfaces 67a and 67b have flatness and perpendicularity applicable as resonator mirrors.

Example 1
A semipolar plane GaN substrate was prepared as follows, and the perpendicularity of the fractured surface was observed. As the substrate, a {20-21} plane GaN substrate cut out at an angle of 75 degrees in the m-axis direction from a (0001) GaN ingot grown thick by the HVPE method was used. The main surface of the GaN substrate was mirror-finished and the back surface was polished and finished in a satin state. The thickness of the substrate was 370 μm.

  On the back side of the matte state, a diamond pen was used to put a marking line perpendicular to the direction in which the c-axis was projected onto the main surface of the substrate, and then pressed to cleave the substrate. In order to observe the perpendicularity of the obtained fractured surface, the substrate was observed from the a-plane direction using a scanning electron microscope.

  FIG. 7A is a scanning electron microscope image obtained by observing the fractured surface from the a-plane direction, and the right end surface is the fractured surface. It can be seen that the split section has flatness and perpendicularity with respect to the semipolar principal surface.

(Example 2)
In Example 1, in a GaN substrate having a semipolar {20-21} plane, a fractured surface obtained by pressing with a marking line perpendicular to the direction in which the c-axis is projected onto the substrate main surface is formed on the substrate main surface. On the other hand, it was found to have flatness and perpendicularity. Therefore, in order to investigate the usefulness of this split section as a laser resonator, the laser diode shown in FIG. 8 was grown by metal organic vapor phase epitaxy as follows. Trimethylgallium (TMGa), trimethylaluminum (TMAl), trimethylindium (TMIn), ammonia (NH ₃ ), and silane (SiH ₄ ) were used as raw materials. A substrate 71 was prepared. A substrate 71 is cut from a (0001) GaN ingot grown thick by HVPE using a wafer slicing device at an angle in the range of 0 to 90 degrees in the m-axis direction, and an inclination angle ALPHA of the c-axis in the m-axis direction. However, a GaN substrate having a desired off angle in the range of 0 to 90 degrees was produced. For example, when cut at an angle of 75 degrees, a {20-21} plane GaN substrate is obtained, which is indicated by reference numeral 71a in the hexagonal crystal lattice shown in FIG. 7B.

  Before the growth, the substrate was observed by the cathodoluminescence method in order to investigate the stacking fault density of the substrate. In cathodoluminescence, the emission process of carriers excited by an electron beam is observed, but if a stacking fault exists, carriers are not re-emitted in the vicinity, and thus are observed as dark lines. The density per unit length of the dark line (linear density) was determined and defined as the stacking fault density. Here, in order to investigate the stacking fault density, the cathodoluminescence method of nondestructive measurement was used, but a transmission electron microscope of destructive measurement may be used. In the transmission electron microscope, when the sample cross section is observed from the a-axis direction, a defect extending in the m-axis direction from the substrate toward the sample surface is a stacking fault included in the support base, and as in the case of the cathodoluminescence method. The line density of stacking faults can be determined.

  After this substrate 71 was placed on the susceptor in the reactor, an epitaxial layer was grown by the following growth procedure. First, n-type GaN 72 having a thickness of 1000 nm was grown. Next, an n-type InAlGaN cladding layer 73 having a thickness of 1200 nm was grown. Subsequently, after growing an n-type GaN guide layer 74a having a thickness of 200 nm and an undoped InGaN guide layer 74b having a thickness of 65 nm, a three-period MQW 75 composed of a GaN thickness of 15 nm / InGaN thickness of 3 nm was grown. Subsequently, an undoped InGaN guide layer 76a having a thickness of 65 nm, a p-type AlGaN blocking layer 77 having a thickness of 20 nm, and a p-type GaN guide layer 76b having a thickness of 200 nm were grown. Next, a p-type InAlGaN cladding layer 77 having a thickness of 400 nm was grown. Finally, a p-type GaN contact layer 78 having a thickness of 50 nm was grown.

After an insulating film 79 of SiO ₂ was formed on the contact layer 78, a stripe window having a width of 10 μm was formed by wet etching using photolithography. Here, contact windows in the stripe direction were formed in the following two ways. Laser stripes are (1) in the M direction (the contact window is along a predetermined plane defined by the c-axis and m-axis) and (2) in the A direction: <11-20> direction. .

  After forming the stripe window, a p-side electrode 80a made of Ni / Au and a pad electrode made of Ti / Al were deposited. Next, the back surface of the GaN substrate (GaN wafer) was polished with diamond slurry to produce a substrate product with the back surface in a mirror state. At this time, the thickness of the substrate product was measured using a contact-type film thickness meter. The thickness may be measured by a microscope from a sample cross section. As the microscope, an optical microscope or a scanning electron microscope can be used. An n-side electrode 80b made of Ti / Al / Ti / Au was formed on the back surface (polished surface) of the GaN substrate (GaN wafer) by vapor deposition.

  A laser scriber using a YAG laser having a wavelength of 355 nm was used to manufacture the resonator mirror for these two types of laser stripes. When a break is made using a laser scriber, it is possible to improve the oscillation chip yield compared to the case where diamond scribe is used. The following conditions were used for forming the scribe grooves: laser light output 100 mW; scanning speed 5 mm / s. The formed scribe groove was, for example, a groove having a length of 30 μm, a width of 10 μm, and a depth of 40 μm. A scribe groove was formed by directly irradiating the epitaxial surface with laser light through an insulating film opening portion of the substrate at a pitch of 800 μm. The resonator length was 600 μm.

  Using a blade, a resonant mirror was prepared by cleaving. A laser bar was produced by breaking on the back side of the substrate by pressing. More specifically, FIG. 7 (b) and FIG. 7 (c) show the relationship between the crystal orientation and the cleavage plane for the {20-21} -plane GaN substrate. FIG. 7B shows a case where laser stripes are provided in the (1) M direction, and end faces 81a and 81b for the laser resonator are shown together with the semipolar surface 71a. The end surfaces 81a and 81b are substantially orthogonal to the semipolar surface 71a, but are different from conventional cleavage surfaces such as the conventional c-plane, m-plane, or a-plane. FIG. 7C shows a case where laser stripes are provided in the (2) <11-20> direction, and end faces 81c and 81d for the laser resonator are shown together with the semipolar surface 71a. The end surfaces 81c and 81d are substantially orthogonal to the semipolar surface 71a and are composed of a-planes.

  As a result of observing the fractured surface formed by the break with a scanning electron microscope, no remarkable unevenness was observed in each of (1) and (2). From this, the flatness (size of irregularities) of the fractured surface is estimated to be 20 nm or less. Further, the perpendicularity of the cut surface to the sample surface was within a range of ± 5 degrees.

A dielectric multilayer film was coated on the end face of the laser bar by vacuum deposition. The dielectric multilayer film was configured by alternately laminating SiO ₂ and TiO ₂ . Each film thickness was adjusted in the range of 50 to 100 nm and designed so that the central wavelength of the reflectance was in the range of 500 to 530 nm. The reflective surface on one side was set to 10 periods, the design value of reflectivity was designed to about 95%, the reflective surface on the other side was set to 6 periods, and the design value of reflectivity was about 80%.

  Evaluation by energization was performed at room temperature. As a power source, a pulse power source having a pulse width of 500 ns and a duty ratio of 0.1% was used, and electricity was applied by dropping a needle on the surface electrode. When measuring the optical output, the light emission from the end face of the laser bar was detected by a photodiode, and the current-optical output characteristic (IL characteristic) was examined. When measuring the emission wavelength, the light emitted from the end face of the laser bar was passed through an optical fiber, and the spectrum was measured using a spectrum analyzer as a detector. When examining the polarization state, the polarization state was examined by rotating the light emitted from the laser bar through the polarizing plate. When observing the LED mode light, the light emitted from the surface was measured by arranging the optical fiber on the laser bar surface side.

  As a result of confirming the polarization state after oscillation in all lasers, it was found that the laser beam was polarized in the a-axis direction. The oscillation wavelength was 500 to 530 nm.

The polarization state of LED mode (spontaneously emitted light) was measured with all lasers. The polarization component in the a-axis direction was defined as I1, the polarization component in the direction in which the m-axis was projected onto the principal surface was defined as I2, and (I1-I2) / (I1 + I2) was defined as the degree of polarization ρ. Thus, FIG. 9 was obtained as a result of investigating the relationship between the obtained degree of polarization ρ and the minimum value of the threshold current density. From FIG. 9, it can be seen that, when the degree of polarization is positive, (1) the laser current in the direction of the laser stripe M greatly reduces the threshold current density. That is, it can be seen that the threshold current density is greatly reduced when the degree of polarization is positive (I1> I2) and the waveguide is provided in the off direction.
The data shown in FIG. 9 is as follows.
Threshold current Threshold current polarization degree, (M direction stripe), (<11-20> stripe)
0.08 64 20
0.05 18 42
0.15 9 48
0.276 7 52
0.4 6

As a result of examining the relationship between the inclination angle of the c-axis in the m-axis direction of the GaN substrate and the oscillation yield, FIG. 10 was obtained. In this example, the oscillation yield was defined as (number of oscillation chips) / (number of measurement chips). FIG. 10 is a plot of a substrate having a stacking fault density of 1 × 10 ⁴ (cm ⁻¹ ) or less and a laser stripe of (1) M direction laser. FIG. 10 shows that the oscillation yield is very low when the off angle is 45 degrees or less. As a result of observing the end face state with an optical microscope, it was found that at an angle smaller than 45 degrees, the m-plane appeared in most of the chips and verticality could not be obtained. It can also be seen that when the off angle is in the range of 63 degrees to 80 degrees, the verticality is improved and the oscillation yield is increased to 50% or more. From these facts, the optimum range of the off-angle of the GaN substrate is 63 degrees or more and 80 degrees or less. Similar results can be obtained even in the range of 100 degrees to 117 degrees, which is the angle range in which the crystallographically equivalent end faces are provided.
The data shown in FIG. 10 is as follows.
Inclination angle, yield
10 0.1
43 0.2
58 50
63 65
66 80
71 85
75 80
79 75
85 45
90 35

As a result of investigating the relationship between the stacking fault density and the oscillation yield, FIG. 11 was obtained. The definition of the oscillation yield is the same as described above. From FIG. 11, it can be seen that when the stacking fault density exceeds 1 × 10 ⁴ (cm ⁻¹ ), the oscillation yield rapidly decreases. In addition, as a result of observing the end face state with an optical microscope, it was found that the sample having a reduced oscillation yield did not have a flat split surface with severe end face unevenness. The cause is thought to be a difference in the ease of cracking due to the presence of stacking faults. For this reason, the stacking fault density contained in the substrate needs to be 1 × 10 ⁴ (cm ⁻¹ ) or less.
The data shown in FIG. 11 is as follows.
Stacking fault density (cm ⁻¹ ), yield
500 80
1000 75
4000 70
8000 65
10000 20
50000 2

As a result of investigating the relationship between the substrate thickness and the oscillation yield, FIG. 12 was obtained. The definition of the oscillation yield is the same as described above. Moreover, in FIG. 12, the stacking fault density of the substrate is 1 × 10 ⁴ (cm ⁻¹ ) or less, and the laser stripe is plotted in the (1) M direction laser. From FIG. 12, when the substrate thickness is thinner than 100 μm and thicker than 50 μm, the oscillation yield is high. This is because if the substrate thickness is thicker than 100 μm, the perpendicularity of the fractured surface deteriorates. On the other hand, when the thickness is less than 50 μm, handling is difficult and the chip is easily broken. For these reasons, the optimal thickness of the substrate is 50 μm or more and 100 μm or less.
The data shown in FIG. 12 is as follows.
Substrate thickness, yield
48 10
80 65
90 70
110 45
150 48
200 30
400 20

(Example 3)
In Example 2, a plurality of epitaxial films for a semiconductor laser were grown on a GaN substrate having a {20-21} plane. As described above, the end face for the optical resonator was formed by forming and pressing the scribe groove. In order to find candidates for these end faces, a plane orientation different from the a-plane was formed by calculation at an angle close to 90 degrees with respect to the (20-21) plane. Referring to FIG. 13, the following angles and plane orientations have an angle in the vicinity of 90 degrees with respect to the (20-21) plane.
Specific plane index, angle with respect to {20-21} plane (−1016): 92.46 degrees;
(-1017): 90.10 degrees;
(-1018): 88.29 degrees.

  FIG. 14 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-6) plane, and the (−1016) plane. FIG. 15 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-7) plane, and the (−1017) plane. FIG. 16 is a drawing showing atomic arrangements in the (20-21) plane, the (−101-8) plane, and the (−1018) plane. As shown in FIGS. 14 to 16, the local atomic arrangement indicated by the arrow indicates a charge-neutral atomic arrangement, and an electrically neutral atomic arrangement appears periodically. The reason why a plane that is relatively perpendicular to the growth plane can be obtained is that this charge-neutral atomic arrangement appears periodically, which suggests that the generation of the split section is relatively stable. There is sex.

  According to various experiments including Examples 1 to 3 described above, the angle ALPHA can be in the range of 45 degrees to 80 degrees and 100 degrees to 135 degrees. In order to improve the oscillation chip yield, the angle ALPHA can be in the range of 63 degrees to 80 degrees and 100 degrees to 117 degrees. It can be any of a typical semipolar principal surface, {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. Furthermore, it can be a slightly inclined surface from these semipolar surfaces. For example, the semipolar principal surface is the m-plane direction from any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. Further, it can be a slightly inclined surface that is turned off within a range of −4 degrees or more and +4 degrees or less.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

DESCRIPTION OF SYMBOLS 11 ... Group III nitride semiconductor laser element, 13 ... Laser structure, 13a ... 1st surface, 13b ... 2nd surface, 13c, 13d ... Edge, 15 ... Electrode, 17 ... Support base | substrate, 17a ... Semipolar main Surface, 17b ... Back surface of supporting substrate, 17c ... End surface of supporting substrate, 19 ... Semiconductor region, 19a ... Surface of semiconductor region, 19c ... End surface of semiconductor region, 21 ... First cladding layer, 23 ... Second cladding layer, 25 ... Active Layer, 25a ... well layer, 25b ... barrier layer, 27, 29 ... broken section, ALPHA ... angle, Sc ... c-plane, NX ... normal axis, 31 ... insulating film, 31a ... insulating film opening, 35 ... n-side light guide Layer, 37 ... p-side light guide layer, 39 ... carrier block layer, 41 ... electrode, 43a, 43b ... dielectric multilayer, MA ... m-axis vector, BETA ... angle, DSUB ... support substrate thickness, 51 ... substrate, 51a ... Semipolar main surface SP ... substrate product, 57 ... gallium nitride based semiconductor region, 59 ... light emitting layer, 61 ... gallium nitride based semiconductor region, 53 ... semiconductor region, 54 ... insulating film, 54a ... insulating film opening, 55 ... laser structure, 58a ... Anode electrode, 58b ... Cathode electrode, 63a ... First surface, 63b ... Second surface, 10a ... Laser scriber, 65a ... Scribe groove, 65b ... Scribe groove, LB ... Laser beam, SP1 ... Substrate product, LB1 ... Laser bar, 69 ... Blade, 69a ... Edge, 69b, 69c ... Blade surface, 71 ... Support device, 71a ... Support surface, 71b ... Recess

Claims (24)

A group III nitride semiconductor laser device comprising:
A support structure made of a hexagonal group III nitride semiconductor and having a semipolar main surface; and a laser structure including a semiconductor region provided on the semipolar main surface of the support base;
An electrode provided on the semiconductor region of the laser structure,
With
The semiconductor region includes a first cladding layer made of a gallium nitride semiconductor of a first conductivity type, a second cladding layer made of a gallium nitride semiconductor of a second conductivity type, the first cladding layer, and the first cladding layer. An active layer provided between the two clad layers,
The first cladding layer, the second cladding layer, and the active layer are arranged along a normal axis of the semipolar principal surface,
The active layer includes a gallium nitride based semiconductor layer,
The c-axis of the hexagonal group III nitride semiconductor of the support base is inclined at a finite angle ALPHA with respect to the normal axis in the m-axis direction of the hexagonal group III nitride semiconductor, The angle ALPHA is in the range of 45 degrees to 80 degrees or 100 degrees to 135 degrees,
The laser structure includes first and second fractured surfaces intersecting an mn plane defined by the m-axis and the normal axis of the hexagonal group III nitride semiconductor,
The laser resonator of the group III nitride semiconductor laser device includes the first and second split sections,
The laser structure includes first and second surfaces, wherein the first surface is a surface opposite the second surface;
It said first and second fractured is to extend from the edge of each of the first surface to an edge of the second surface,
In each of the first and second fractured faces, an end face of the support base and an end face of the semiconductor region appear,
The angle formed between the end face of the active layer of the semiconductor region and the reference plane orthogonal to the m-axis of the support base made of the hexagonal group III nitride semiconductor is determined by the c-axis and m-axis of the group III nitride semiconductor. An angle in the range of (ALPHA-5) degrees or more and (ALPHA + 5) degrees or less is formed in the first plane defined, and the angle is -5 degrees or more in the second plane orthogonal to the first plane and the normal axis. A group III nitride semiconductor laser device characterized by being in a range of +5 degrees or less .   2. The group III nitride according to claim 1, wherein the first and second fractured faces are different from a cleavage plane such as a c-plane, m-plane, or a-plane of a hexagonal group III nitride semiconductor. Semiconductor laser device.   The angle formed by the normal axis and the c-axis of the hexagonal group III nitride semiconductor is in a range of 63 degrees to 80 degrees or 100 degrees to 117 degrees. Item III nitride semiconductor laser device according to Item 2.   4. The group III nitride semiconductor laser device according to claim 1, wherein a thickness of the support base is 400 μm or less. 5.   The group III nitride semiconductor laser device according to any one of claims 1 to 4, wherein a thickness of the support base is 50 µm or more and 100 µm or less.   The laser light from the active layer is polarized in the direction of the a-axis of the hexagonal group III nitride semiconductor, according to any one of claims 1 to 5. Group III nitride semiconductor laser device. The light in the LED mode of the group III nitride semiconductor laser element has a polarization component I1 in the direction of the a-axis of the hexagonal group III nitride semiconductor and the c-axis of the hexagonal group III nitride semiconductor as principal surfaces. Including the polarization component I2 in the direction projected onto
7. The group III nitride semiconductor laser device according to claim 1, wherein the polarization component I1 is larger than the polarization component I2.   The semipolar principal surface is -4 degrees or more +4 from any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. 8. The group III nitride semiconductor laser device according to claim 1, wherein the III-nitride semiconductor laser device is a slightly inclined surface that is turned off within a range of less than or equal to a degree.   The semipolar principal surface is any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. The group III nitride semiconductor laser device according to any one of claims 1 to 8. 10. The group III nitride semiconductor laser device according to claim 1, wherein a stacking fault density of the support base is 1 × 10 ⁴ cm ⁻¹ or less.   11. The group III nitride semiconductor laser device according to claim 1, wherein the support base is made of any one of GaN, AlGaN, AlN, InGaN, and InAlGaN.   The group III nitride according to any one of claims 1 to 11, further comprising a dielectric multilayer film provided on at least one of the first and second fractured faces. Semiconductor laser device.   The group III nitride according to any one of claims 1 to 12, wherein the active layer includes a light emitting region provided to generate light having a wavelength of 360 nm to 600 nm. Semiconductor laser element.   The group III nitride according to any one of claims 1 to 13, wherein the active layer includes a quantum well structure provided to generate light having a wavelength of 430 nm to 550 nm. Semiconductor laser device. The first and second fractured faces have L of 6, 7, 8 and are -5 degrees from the plane indicated by (-1, 0, 1, L) or (1, 0, -1, -L). The group III nitride semiconductor laser device according to any one of claims 1 to 14 , including a region within a range of ~ 5 degrees. A method for producing a group III nitride semiconductor laser device, comprising:
Preparing a substrate composed of a hexagonal group III nitride semiconductor and having a semipolar main surface;
Forming a substrate structure having a laser structure including a semiconductor region formed on the semipolar main surface and the substrate, an anode electrode, and a cathode electrode;
Partially scribing the first surface of the substrate product in the direction of the a-axis of the hexagonal III-nitride semiconductor;
Separating the substrate product by pressing against the second surface of the substrate product to form another substrate product and a laser bar ;
With
The first surface is a surface opposite to the second surface;
The semiconductor region is located between the first surface and the substrate;
The laser bar has first and second end surfaces extending from the first surface to the second surface and formed by the separation,
The first and second end faces constitute a laser resonator of the group III nitride semiconductor laser element,
The anode electrode and the cathode electrode are formed on the laser structure;
The semiconductor region includes a first cladding layer made of a gallium nitride semiconductor of a first conductivity type, a second cladding layer made of a gallium nitride semiconductor of a second conductivity type, the first cladding layer, and the first cladding layer. An active layer provided between the two clad layers,
The first cladding layer, the second cladding layer, and the active layer are arranged along a normal axis of the semipolar principal surface,
The active layer includes a gallium nitride based semiconductor layer,
The c-axis of the hexagonal group III nitride semiconductor of the substrate is inclined at a finite angle ALPHA with respect to the normal axis in the m-axis direction of the hexagonal group III nitride semiconductor. ALPHA is in the range of 45 degrees to 80 degrees or 100 degrees to 135 degrees,
The first and second end faces intersect an mn plane defined by the m-axis and the normal axis of the hexagonal group III nitride semiconductor ,
The end face of the active layer in each of the first and second end faces is the hexagonal group III nitride with respect to a reference plane perpendicular to the m-axis of the support base made of the hexagonal group III nitride semiconductor. A method of manufacturing a group III nitride semiconductor laser device, wherein an angle in a range of (ALPHA-5) degrees or more and (ALPHA + 5) degrees or less is formed on a plane defined by the c-axis and m-axis of a semiconductor. 17. The group III nitride according to claim 16 , wherein the first and second end faces are different from a cleavage plane such as c-plane, m-plane, or a-plane of a hexagonal group III nitride semiconductor. A method of manufacturing a semiconductor laser device. 18. The method for manufacturing a group III nitride semiconductor laser device according to claim 16 , wherein the angle ALPHA is in a range of 63 degrees to 80 degrees or 100 degrees to 117 degrees. . In the step of forming the substrate product, the substrate is subjected to processing such as slicing or grinding so that the thickness of the substrate is 400 μm or less,
The second surface is a processed surface formed by the processing, or a surface including an electrode formed on the processed surface, according to any one of claims 16 to 18. A method for producing the group III nitride semiconductor laser device described. In the step of forming the substrate product, the substrate is polished so that the thickness of the substrate is 50 μm or more and 100 μm or less,
The second surface is a polished surface formed by the polishing, or the a surface including an electrode formed on the polishing surface, it in any one of claims 16 to claim 19, characterized in A method for producing the group III nitride semiconductor laser device described. The scribe is performed using a laser scriber,
A scribe groove is formed by the scribe, and the length of the scribe groove is an intersection of the a-n plane defined by the a-axis and the normal axis of the hexagonal group III nitride semiconductor and the first surface. 21. The method for producing a group III nitride semiconductor laser device according to claim 16 , wherein the group III nitride semiconductor laser device is shorter than a length of the line. The semipolar principal surface is any one of {20-21} plane, {10-11} plane, {20-2-1} plane, and {10-1-1} plane. A method for producing a group III nitride semiconductor laser device according to any one of claims 16 to 21 . The first and second end faces have L of 6, 7, 8 and are -5 degrees from the plane indicated by (-1, 0, 1, L) or (1, 0, -1, -L). The method for producing a group III nitride semiconductor laser device according to any one of claims 16 to 22 , comprising a region within a range of +5 degrees. The group III nitride semiconductor laser device according to any one of claims 16 to 23 , wherein the substrate is made of any one of GaN, AlGaN, AlN, InGaN, and InAlGaN. Method.