WO2011086756A1 - Iii族窒化物半導体レーザ素子、及びiii族窒化物半導体レーザ素子を作製する方法 - Google Patents
Iii族窒化物半導体レーザ素子、及びiii族窒化物半導体レーザ素子を作製する方法 Download PDFInfo
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- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
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Definitions
- 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.
- the m-plane As a cleaved facet for a laser resonator, it has been proposed to generate laser light polarized in the off direction of the c-axis of the substrate.
- this document describes that the well width is increased on the nonpolar plane and the well width is decreased on the semipolar plane.
- the band structure of a gallium nitride semiconductor there are several transitions capable of laser oscillation.
- the laser beam is guided along a plane defined by the c-axis and the m-axis.
- the threshold current can be lowered when extending the waveguide.
- the mode with the smallest transition energy difference between conduction band energy and valence band energy
- the threshold is set. The current can be lowered.
- a conventional cleavage plane such as c-plane, a-plane or m-plane cannot be used for the resonator mirror.
- the dry etching surface of the semiconductor layer has been formed using reactive ion etching (RIE) for the fabrication of the resonator mirror.
- RIE reactive ion etching
- 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.
- derivation of process conditions for obtaining a good dry etching surface at the current technical level is a heavy burden.
- the present invention has been made in view of such circumstances. It is an object of the present invention to provide a III-nitride having a laser resonator that enables a low threshold current on a semipolar plane of a support base inclined from the c-axis to the m-axis of hexagonal 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 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 angle ALPHA is in a range of 45 degrees to 80 degrees or 100 degrees to 135 degrees
- the laser structure includes the hexagonal group III nitride Semiconductor m-axis and said method First and second fractured faces intersecting an mn plane defined by an axis, and the laser resonator of the group III nitride semiconductor laser element comprises the first and second fractured faces, and the laser
- the structure includes first and second surfaces, the second surface is a surface opposite to the first surface, and the semiconductor region is located between the first surface and the support base.
- the first and second fractured sections extend from the edge of the first surface to the edge of the second surface, respectively, and the laser structure is at one end of the first fractured surface,
- a scribing mark extending from an edge of the first surface to an edge of the second surface, the scribing mark being a recess extending from the edge of the first surface to the edge of the second surface;
- a fractured surface is provided at one end of the first fractured surface along a concave scribe mark extending from the edge of the first surface to the edge of the second surface.
- the perpendicularity and flatness of the fractured surface are expected, and the fractured surface can have sufficient perpendicularity and flatness as a resonator mirror. Therefore, a group III nitride semiconductor laser device having a laser resonator that enables a low threshold current can be provided.
- 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 an end surface of the semiconductor region in the active layer and
- the angle formed by the reference plane perpendicular to the m-axis of the support base made of the hexagonal nitride semiconductor is (ALPHA-5) in the first plane defined by the c-axis and the m-axis of the group III nitride semiconductor.
- the angle is in the range of not less than ALPHA and not more than (ALPHA + 5) degrees.
- this group III nitride semiconductor laser device it is possible to have an end face 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.
- the angle is in the range of ⁇ 5 degrees to +5 degrees in the first plane and the second plane perpendicular to the normal axis. According to this group III nitride semiconductor laser device, it is possible to have 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.
- the thickness of the support base is 50 ⁇ m or more and 150 ⁇ m or less. According to this group III nitride semiconductor laser device, if the thickness is 50 ⁇ m or more, handling becomes easy and the production yield is improved. If it is 150 ⁇ m or less, it is possible to obtain a high-quality fractured surface for the laser resonator.
- the angle formed between the normal axis and the c axis of the hexagonal group III nitride semiconductor is in the range of 63 degrees to 80 degrees or 100 degrees to 117 degrees.
- the end surface formed by pressing is nearly perpendicular to the main surface of the substrate in the range of 63 ° to 80 ° or 100 ° to 117 °. Becomes higher. Further, when the angle is more than 80 degrees and less than 100 degrees, the desired flatness and perpendicularity may not be obtained.
- the laser light from the active layer is polarized in the a-axis direction of the hexagonal group III nitride semiconductor.
- the band transition capable of realizing a low threshold current has polarization.
- the light in the LED mode of the group III nitride semiconductor laser device includes a polarization component I1 in the direction of the a-axis of the hexagonal group III nitride semiconductor and the hexagonal group III
- the polarization component I2 is included in a direction in which the c-axis of the group nitride semiconductor is projected onto the principal surface, and the polarization component I1 is larger than the polarization component I2.
- light having a large emission intensity in the LED mode can be laser-oscillated using the laser resonator.
- the semipolar principal surface is composed of ⁇ 20-21 ⁇ plane, ⁇ 10-11 ⁇ plane, ⁇ 20-2-1 ⁇ plane, and ⁇ 10-1-1 ⁇ plane. It is a slightly inclined surface that is off from any surface within a range of ⁇ 4 degrees or more and +4 degrees or less. According to this group III nitride semiconductor laser element, even on a slight inclined surface from these typical semipolar planes, sufficient flatness and vertical enough to constitute a laser resonator of the group III nitride semiconductor laser element It is possible to provide the first and second end faces free from sex or ion damage.
- the semipolar principal surface is composed of ⁇ 20-21 ⁇ plane, ⁇ 10-11 ⁇ plane, ⁇ 20-2-1 ⁇ plane, and ⁇ 10-1-1 ⁇ plane. Either. According to this group III nitride semiconductor laser device, even in these typical semipolar planes, sufficient flatness, perpendicularity, or ion damage sufficient to constitute a laser resonator of the group III nitride semiconductor laser device is obtained. There can be no first and second end faces.
- the stacking fault density of the support base is 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 perpendicularity of the fractured section will be disturbed due to accidental circumstances.
- the support base is made of any one of GaN, AlGaN, AlN, InGaN, and InAlGaN.
- the first and second end faces that can be used as a resonator can be obtained.
- the degree of polarization can be increased, and light confinement can be enhanced by a low refractive index.
- 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 further includes a dielectric multilayer film provided on at least one of the first and second fractured faces.
- the end face coating can be applied to the fracture surface.
- the reflectance can be adjusted by the end face coating.
- the active layer includes a light emitting region provided to generate light having a wavelength of 360 nm to 600 nm. According to this group III nitride semiconductor laser device, by using a semipolar plane, a group III nitride semiconductor laser device using LED mode polarization effectively can be obtained, and a low threshold current can be obtained. it can.
- 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. According to this group III nitride semiconductor laser device, it is possible to improve the quantum efficiency by reducing the piezoelectric field and improving the crystal quality of the light emitting layer region by using the semipolar plane, and emit light having a wavelength of 430 nm or more and 550 nm or less. Can occur.
- a group III nitride semiconductor laser device 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
- the semiconductor region comprising a laser structure including a semiconductor region provided on the semiconductor structure and (b) an electrode provided on the semiconductor region of the laser structure is a first conductivity type gallium nitride based semiconductor.
- the first clad layer, the second clad 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 support base Of the hexagonal system III
- the c-axis of the nitride semiconductor 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, and the angle ALPHA is not less than 45 degrees and not more than 80 degrees.
- the laser structure includes first and second surfaces, the second surface is a surface opposite to the first surface, and the semiconductor region is Located between the first surface and the support base, the laser structure is provided at an end of the laser structure, and the normal axis and the a-axis of the hexagonal group III nitride semiconductor First and second scribe marks extending along a plane defined by: the first and second scribe marks extending from an edge of the first surface to an edge of the second surface.
- the laser resonator of the group III nitride semiconductor laser element has a split section connecting each edge of the first and second scribe marks and each edge of the first and second surfaces, Including the split section.
- a fractured surface is provided at one end of the first fractured surface along a concave scribe mark extending from the edge of the first surface to the edge of the second surface. Therefore, the perpendicularity and flatness of the fractured surface are expected, and the fractured surface can have sufficient perpendicularity and flatness as a resonator mirror. Therefore, a group III nitride semiconductor laser device having a laser resonator that enables a low threshold current can be provided.
- a method for producing a group III nitride semiconductor laser device includes: (a) preparing a substrate made of a hexagonal group III nitride semiconductor and having a semipolar principal surface; and (b) Forming a substrate product having a laser structure including a semiconductor region formed on the semipolar main surface and the substrate, an anode electrode, and a cathode electrode; and (c) the hexagonal group III nitride Partially scribing the first surface of the substrate product in the direction of the a-axis of the semiconductor; and (d) separating the substrate product by pressing the substrate product against the second surface. And forming 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
- the laser bar extends from the first surface to the first surface.
- the first and second end faces 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 first conductivity type gallium nitride semiconductor and a second conductivity type gallium nitride semiconductor.
- the layer is 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 the normal axis in the direction of the m axis of the hexagonal group III nitride semiconductor.
- the angle ALPHA is in a range of 45 degrees to 80 degrees or 100 degrees to 135 degrees, and the first and second end faces are formed in the hexagonal system.
- An end face of the active layer in each of the first and second end faces intersects with the mn plane defined by the m-axis of the group III nitride semiconductor and the normal axis, and the end face of the active layer is made of the hexagonal nitride semiconductor.
- An angle of In the cribing step a plurality of scribe penetrations having a shape extending from the first surface of the substrate product to the second surface and extending in the direction of the a-axis of the hexagonal group III nitride semiconductor.
- a hole is formed along the a-axis of the hexagonal group III nitride semiconductor.
- the scribe through hole is formed by laser irradiation from the first surface or the second surface of the laser structure using a laser scriber.
- laser irradiation may be performed from either the first surface or the second surface. In particular, if laser irradiation is performed from the second surface, damage or debris on the epi surface is reduced.
- a low threshold current can be achieved on the semipolar plane of the support base in which the c-axis of the hexagonal group III-nitride is inclined in the m-axis direction.
- 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. 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 the structure of the laser diode shown in the embodiment.
- FIG. 8 is a diagram for explaining a conventional method of forming a scribe groove.
- FIG. 9 is a view showing a shape of an end face formed by a conventional method of forming a scribe groove as viewed from an epi plane.
- FIG. 10 is a drawing showing the shape of an end face of a group III nitride semiconductor laser device formed by a conventional method of forming a scribe groove as viewed from the side.
- FIG. 11 is a drawing for explaining the shape of the end face of a group III nitride semiconductor laser device formed from conventional scribe grooves.
- FIG. 12 is a diagram for explaining a process of forming an end face of a laser bar manufactured using a conventional scribe groove.
- FIG. 13 is a drawing showing the shape of the scribe through hole according to the present embodiment.
- FIG. 14 is a view showing an angle formed by the (20-21) plane and another plane orientation (index).
- FIG. 15 shows a comparison between the number of elements having an angle deviation of the end face when the conventional scribe groove is used and the number of elements having an angle deviation of the end face when the scribe through hole according to the present embodiment is used. It is drawing for doing.
- FIG. 12 is a diagram for explaining a process of forming an end face of a laser bar manufactured using a conventional scribe groove.
- FIG. 13 is a drawing showing the shape of the scribe through hole according to the present embodiment.
- FIG. 14 is a view showing an angle formed
- FIG. 16 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. 17 is a diagram showing the relationship between stacking fault density and oscillation yield.
- FIG. 18 is a drawing showing atomic arrangements in the (20-21) plane, the ( ⁇ 101-6) plane, and the ( ⁇ 1016) plane.
- FIG. 19 is a drawing showing atomic arrangements in the (20-21) plane, the ( ⁇ 101-7) plane, and the ( ⁇ 1017) plane.
- FIG. 20 is a drawing showing atomic arrangements in the (20-21) plane, the ( ⁇ 101-8) plane, and the ( ⁇ 1018) plane.
- FIG. 1 is a drawing schematically showing a structure of a group III nitride semiconductor laser device according to the present embodiment.
- 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
- 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. By using a semipolar plane, light having a wavelength of 430 nm or more and 550 nm or less can be generated.
- 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.
- 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.
- FIG. 1 an orthogonal coordinate system S and a crystal coordinate system CR are drawn.
- 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.
- the 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.
- the laser waveguide includes first clad layer 21, second clad layer 23, and active layer 25, and extends in the direction of crossing line LIX.
- 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.
- the laser resonator of 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 first fractured face 27 and 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.
- the first and second fractured faces 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.
- the laser structure 13 has, at one end of the first fractured surface 27, a scribe mark SM1 extending from the edge 13c of the element surface 11a of the group III nitride semiconductor laser element 11 to the edge 13d of the element back surface 11b.
- a scribe mark SM2 extending from the edge 13c of the element surface 11a of the group III nitride semiconductor laser element 11 to the edge 13d of the element back surface 11b is provided at the other end of the one split section 27.
- the laser structure 13 has scribe marks SM3 and SM4 on the second fractured face 29 side.
- Scribe marks SM1, SM2, SM3, and SM4 have a concave shape extending from element surface 11a of element III nitride semiconductor laser element 11 to element back surface 11b.
- the scribe marks SM1, SM2, SM3, and SM4 are provided at end portions (end portions intersecting the mn plane) of the laser structure 13, respectively, and the normal axis NX and the hexagonal group III nitride semiconductor are provided. Extending along a plane defined by the a-axis.
- the end portion (end portion intersecting the mn plane) of the laser structure 13 has a first fractured surface 27 and a second fractured surface 29.
- the first fractured surface 27 is a surface connecting the respective edges 13e and 13f of the scribe marks SM1 and SM2 and the respective edges 13c and 13d of the element surface 11a and the element back surface 11b.
- Reference numeral 29 denotes a surface connecting the respective edges of the scribe marks SM3 and SM4 and the respective edges 13c and 13d of the element surface 11a and the element back surface 11b.
- the first and second fractured sections 27 and 29 are provided along the concave scribe marks SM1 extending from the element surface 11a to the element back surface 11b of the group III nitride semiconductor laser element 11. Therefore, the perpendicularity and flatness of the fractured surface are expected, and the first and second fractured surfaces 27 and 29 can be sufficiently perpendicular and flat as a resonator mirror.
- 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 ⁇ 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.
- the threshold value of the transition Ea is smaller than the threshold value of the transition Eb.
- 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 principal surface.
- the polarization component I1 is larger than the polarization component I2.
- the degree of polarization ⁇ is defined by (I1 ⁇ I2) / (I1 + I2).
- dielectric multilayer films 43a and 43b provided on at least one of the first and second fractured surfaces 27 and 29, or on each of them, can be further provided.
- End face coating can also be applied to the first and second fractured surfaces 27 and 29. The reflectance can be adjusted by the end face coating.
- the laser light L from the active layer 25 is polarized in the a-axis direction of the hexagonal group III nitride semiconductor.
- 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.
- the first and second fractured surfaces 27 and 29 have flatness and perpendicularity as mirrors for the resonator. Therefore, as shown in FIG. 3B, the first and second fractured surfaces 27 and 29 and the laser waveguide extending between the first and second fractured surfaces 27 and 29 are used.
- it is possible to oscillate at a low threshold by utilizing the light emission of the transition Ea stronger than the light emission of the transition Eb polarized in the direction in which the c-axis is projected onto the main surface.
- 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.
- the component (BETA) 1 can be 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.
- the component (BETA) 2 can be in the range of not less than ⁇ 5 degrees and not more than +5 degrees in the second plane S2.
- BETA 2 (BETA) 1 2 + (BETA) 2 2 .
- the end surfaces (first and second fractured surfaces 27 and 29) of the group III nitride semiconductor laser device 11 have the above-described perpendicularity with respect to an angle defined by a plane perpendicular to the normal axis NX of the semipolar surface 17a.
- the thickness DSUB of the support base 17 can be 50 ⁇ m or more and 150 ⁇ m or less. Since the supporting base 17 of the group III nitride semiconductor laser device 11 has this thickness, it corresponds to a scribe mark SM for a substrate product (a substrate product SP described later) including the group III nitride semiconductor laser device 11. Formation of a scribe through hole (see a scribe through hole 65a described later shown in FIG. 6) is facilitated. As will be described later, the end face (broken section) obtained using the scribe through hole can be used as a good resonator mirror having sufficient verticality and flatness. Therefore, the first and second fractured surfaces 27 and 29 of the group III nitride semiconductor laser device 11 can be good resonator mirrors.
- the angle ALPHA formed by the normal axis NX and the c-axis of the hexagonal group III nitride semiconductor can be 45 degrees or more, and can be 80 degrees or less. Also, the angle ALPHA can be 100 degrees or more and can be 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.
- the angle ALPHA formed by the normal axis NX and the c-axis of the hexagonal group III nitride semiconductor can be 63 degrees or more, and can be 80 degrees or less. Also, the angle ALPHA can be 100 degrees or more and can be 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 main surface 17a can be any one of ⁇ 20-21 ⁇ plane, ⁇ 10-11 ⁇ plane, ⁇ 20-2-1 ⁇ plane, and ⁇ 10-1-1 ⁇ plane. Further, a plane slightly inclined from these planes within a range of ⁇ 4 degrees or more and +4 degrees or less can also be used as the main surface.
- the first and second end faces (first and second) are sufficiently flat and perpendicular enough to constitute the laser resonator of the group III nitride semiconductor laser device 11.
- Split sections 27, 29 can be provided.
- an end face exhibiting sufficient flatness and perpendicularity can be obtained.
- 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 (first and second fractured surfaces 27 and 29) that can be used as resonators can be obtained.
- the degree of polarization can be increased, and light confinement can be enhanced by a low refractive index.
- 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 a method for producing a group III nitride semiconductor laser device according to the present embodiment.
- a substrate 51 is shown.
- 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.
- a substrate product SP is formed.
- 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.
- the laser structure 55 is formed.
- the laser structure 55 includes a semiconductor region 53 and a substrate 51.
- the semiconductor region 53 is formed on the semipolar main surface 51a.
- 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.
- 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.
- the anode electrode 58a and the cathode electrode 58b are formed on the laser structure 55.
- the back surface of the substrate used for crystal growth is polished to form a substrate product SP having a desired thickness DSUB.
- the anode electrode 58a is formed on the semiconductor region 53
- 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
- the cathode electrode 58b covers the entire back surface 51b.
- 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 plurality of scribe through holes 65a are formed by scribing. In FIG. 6B, several scribe through holes are already formed, and the formation of the scribe through hole 65b is advanced using the laser beam LB.
- the scribe through hole 65a or the like is a through hole penetrating from the first surface 63a to the second surface 63b, and is a hexagonal group III nitride semiconductor as viewed from the first surface 63a (or the second surface 63b). It has a shape extending in the a-axis direction.
- the width of the scribe through hole 65a and the like in the a-axis direction of the hexagonal group III nitride semiconductor is longer than the width of the hexagonal group III nitride semiconductor in the direction orthogonal to the a-axis direction.
- the width of the scribe through hole 65a and the like in the a-axis direction of the hexagonal group III nitride semiconductor can be, for example, 50 ⁇ m or more and 300 ⁇ m or less, and the direction orthogonal to the a-axis direction of the hexagonal group III nitride semiconductor
- the width of the scribe through hole 65a and the like can be, for example, not less than 5 ⁇ m and not more than 15 ⁇ m.
- the plurality of scribe through holes 65a and the like are formed at a pitch of, for example, about 400 ⁇ m along the a-axis direction of the hexagonal group III nitride semiconductor.
- the plurality of rows including the plurality of scribe through holes 65a formed side by side in the a-axis direction of the hexagonal group III nitride semiconductor are surfaces defined by the c-axis and the m-axis of the hexagonal group III nitride semiconductor. Are formed at substantially equal intervals on the substrate product SP.
- the scribe through hole 65a and the like are formed in the scribe mark SM1 of the group III nitride semiconductor laser device 11 by separating the group III nitride semiconductor laser device 11 from the substrate product SP in the first and second breaks described later. Etc.
- the length of the scribe through hole 65a or the like is shorter than the length of the intersection line AIS between the an surface and the first surface 63a defined by the a axis and the normal axis NX of the hexagonal group III nitride semiconductor, Irradiation of the laser beam LB is performed on a part of the intersection line AIS. By irradiation with the laser beam LB, a through hole extending in a specific direction and reaching the semiconductor region is formed in the first surface 63a.
- the scribe through hole 65a and the like can be formed at one edge of the substrate product SP, for example.
- step S106 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. Breaking (primary break) for forming the laser bar LB1 and the like is advanced in the y-axis direction.
- 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 through hole 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 may be 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.
- 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.
- 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.
- 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. According to this end face formation, 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 are provided.
- the formed laser waveguide extends in the direction of the c-axis inclination 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.
- a new substrate product SP1 and a laser bar LB1 are formed by cleaving the substrate product SP1.
- separation by pressing is repeated to produce a large number of laser bars.
- This cleaving is caused by using a scribe through hole 65a which is shorter than the breaking line BRAK of the laser bar LB1.
- 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.
- step S109 the laser bar product is separated into individual semiconductor laser chips (secondary break).
- 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.
- 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 main surface 51a can be any one of ⁇ 20-21 ⁇ plane, ⁇ 10-11 ⁇ plane, ⁇ 20-2-1 ⁇ plane, and ⁇ 10-1-1 ⁇ plane. Further, a plane slightly inclined from these planes within a range of ⁇ 4 degrees or more and +4 degrees or less can also be used 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 can be made of GaN.
- the semiconductor substrate used for crystal growth is subjected to processing such as slicing or grinding so that the substrate thickness is 50 ⁇ m or more and 150 ⁇ m or less, and the second surface 63b is formed by polishing.
- the processed surface can be made.
- the formation of the scribe through hole 65a is facilitated, and the end faces 67a and 67b free of flatness, perpendicularity or ion damage sufficient to constitute the laser resonator of the group III nitride semiconductor laser device are obtained. Can be well formed.
- the angle BETA described with reference to FIG. 3 is also defined for 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 can be 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.
- the component (BETA) 2 of the angle BETA can be 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).
- 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.
- the laser diode shown in FIG. 7 was grown by metal organic vapor phase epitaxy. 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, a ⁇ 20-21 ⁇ plane GaN substrate is obtained when cut out at an angle of 75 degrees.
- the substrate was observed by the cathodoluminescence method in order to investigate the stacking fault density of the substrate.
- 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 was determined and defined as the stacking fault density.
- the cathodoluminescence method of nondestructive measurement was used, but a transmission electron microscope of destructive measurement may be used.
- 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.
- 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.
- a p-type InGaN guide layer 76a having a thickness of 65 nm, a p-type AlGaN blocking layer 77a having a thickness of 20 nm, and a p-type InGaN guide layer 76b having a thickness of 200 nm were grown.
- a p-type InAlGaN cladding layer 77b having a thickness of 400 nm was grown.
- a p-type GaN contact layer 78 having a thickness of 50 nm was grown.
- a stripe window having a width of 10 ⁇ m was formed by wet etching using photolithography.
- the contact window in the stripe direction was formed in the M direction (direction in which the contact window is along a predetermined plane defined by the c-axis and the m-axis).
- a p-side electrode 80a made of Ni / Au and a pad electrode made of Ti / Al were deposited.
- the back surface of the GaN substrate (GaN wafer) was polished to 80 ⁇ m (or 60 ⁇ m) using diamond slurry to produce a substrate product with the back surface in a mirror state.
- 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 with a wavelength of 355 nm was used to manufacture the resonator mirror for the laser stripe.
- a break is made using a laser scriber, it is possible to improve the oscillation chip yield as compared with the case where diamond scribe is used.
- the following methods (A) and (B) were used as a method of forming the scribe through hole 65a and the like from the first surface 63a to the second surface 63b of the substrate product SP: Substrate thickness ( ⁇ m) Laser power (mW) Laser scanning speed (mm / s) Method (A) 80 250 1 Method (B) 60 250 1 Note that, by the following method (C), the scribe grooves SL1 and SL2 formed on the first surface 63a of the substrate product SP but not on the second surface 63b, instead of the scribe through holes (FIG. 8 and the like) Also formed.
- the scribe grooves SL1 and SL2 are grooves formed in the first surface 63a, although not reaching the second surface 63b of the substrate product SP.
- the group III nitride semiconductor laser device having the scribe grooves SL1 and SL2 is particularly referred to as a group III nitride semiconductor laser device 111.
- the formed scribe through hole has a length of 200 ⁇ m and a width of 12 ⁇ m, for example, and the scribe groove has a length of 200 ⁇ m, a width of 8 ⁇ m, and a depth of about 40 ⁇ m, for example.
- 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 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.
- 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.
- the light output the light emission from the end face of the laser bar was detected by a photodiode, and the current-light output characteristic (IL characteristic) was examined.
- 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.
- the polarization state was examined by rotating the light emitted from the laser bar through the polarizing plate.
- the LED mode light the light emitted from the surface was measured by arranging the optical fiber on the laser bar surface side.
- the oscillation wavelength was 500 to 530 nm.
- FIG. 8 is a schematic view of a substrate in which scribe grooves are formed in the substrate product SP by the method (C).
- the scribe groove SL1 for the primary break
- the scribe groove (scribe in the x direction for the secondary break).
- the scribe groove SL2 for the secondary break is formed after the primary break.
- FIG. 9 shows the result of observing the epi plane of the LD (III-nitride semiconductor laser device 111) on the semipolar plane that has been formed into chips after finishing the first and second breaks, by observation with an optical microscope.
- the break traveling direction is the y direction.
- the crack of the break (indicated by reference numeral D1 in the figure) is the direction from the direction perpendicular to the waveguide (y direction) to the direction of the c axis (the direction D2 in which the c axis is projected onto the epiplane; It can be seen that the progress is made by changing the direction (corresponding to the x direction).
- FIG. 10 shows the result of observing the end face (zx cross section) of the LD (group III nitride semiconductor laser device 111) on the semipolar plane.
- FIG. 10A is a view of the surface of the epi plane of the group III nitride semiconductor laser device 111
- FIG. 10B is a group III nitride semiconductor laser in the region D3 shown in FIG.
- FIG. 6 is a view of a side surface of an element 111.
- the image has progressed in a direction perpendicular to the direction indicated by reference sign D5. That is, the c-plane appears below the scribe groove SL1.
- a resonator mirror of a semipolar LD Group III nitride semiconductor laser device 111 having a waveguide provided in the off direction
- a low-index cleavage surface may appear below the scribe groove SL1. It is easily guessed that this is the cause of the defective end face.
- FIG. 11 shows how the state of the end face in the depth direction changes as the crack progresses in the direction perpendicular to the waveguide (y direction).
- the end surface is formed by two surfaces, a surface that is relatively perpendicular to the epitaxial surface formed by the scribe and a c surface that appears below the scribe groove SL1. It has an edge as a line of intersection of two surfaces.
- the above two surfaces constituting the end face gradually Try to connect smoothly to eliminate edges. As a result, the end surface becomes a curved surface.
- the inventor understood the crack propagation mechanism as shown in FIG. 12 based on the results shown in FIG. According to the knowledge of the inventor, it has been found that a straight edge appears on the surface on the side pressed against the blade at the time of break (on the substrate rear surface D8 side) by the pressing of the blade. As described above, the c-plane appears on the back surface D8 side of the scribe groove (region indicated by reference sign D6 in the figure). In the area indicated by reference numeral D7 in the figure, when the crack reaches the area where the scribe groove is not formed (area indicated by reference numeral D7 in the figure), the end surface becomes curved, but the back surface is straightened by the pressing of the blade. Since an edge appears, the crack that appears on the epi plane as a result propagates in the -x direction.
- FIGS. 13A and 13B are optical micrographs of a sample (laser bar LB1 etc.) obtained by the method (A).
- FIG. 13A shows the observation result from the epi plane
- FIG. 13B shows the observation result from the end face.
- the angular deviation of the resonator mirror from the direction perpendicular to the waveguide as seen in FIG. 9 is not confirmed.
- FIG. 13 (b) shows the through holes.
- FIG. 14A shows the result of observing the state of the end face in the vicinity of the waveguide of this sample (laser bar LB1, etc.).
- the end face is substantially perpendicular to the epi plane and is different from the conventional cleavage plane.
- a face index forming an angle near 90 degrees with respect to the (20-21) face was obtained by calculation.
- the following angles and plane indices have an angle in the vicinity of 90 degrees with respect to the (20-21) plane.
- Specific surface index Angle to ⁇ 20-21 ⁇ plane ⁇ 1016) 92.46 degrees ( ⁇ 1017) 90.10 degrees ( ⁇ 1018) 88.29 degrees
- Cleavage of each surface index Depending on the verticality (about ⁇ 5 degrees), such a high index surface may be obtained as an end surface.
- the bar graphs NU11, NU12, and NU13 shown in FIG. 15 represent the results when the scribe through holes 65a are formed by the method (A), and the bar graphs NU21 and NU22 are obtained when the scribe through holes 65a are formed by the method (B). Representing results, bar graphs NU31, NU32, and NU33 represent results when the scribe groove SL1 and the like are formed by the method (C). According to FIG.
- Angular deviation GAMMA is reduced in the sample (laser bar LB1 etc.) obtained by the method (method (A) and method (B)) of forming the scribe through hole 65a etc. it can.
- the data shown in FIG. 15 is as follows.
- the average value and standard deviation of the angular deviation GAMMA in each of the methods (A) to (C) are as follows. Average value Standard deviation method (A) 0.67 0.63 Method (B) 0.63 0.57 Method (C) 1.38 0.57
- the relationship between the c-axis inclination angle in the m-axis direction of the GaN substrate (support base 17) of the group III nitride semiconductor laser device 11 and the oscillation yield was measured using the method (A).
- the measurement results are shown in FIG.
- the oscillation yield was defined as (number of oscillation chips) / (number of measurement chips).
- the measurement results shown in FIG. 16 were obtained using a GaN substrate having a stacking fault density of 1 ⁇ 10 4 (cm ⁇ 1 ) or less. According to FIG. 16, it can be seen that the oscillation yield is extremely low when the off angle is 45 degrees or less.
- the optimum range of the off-angle of the GaN substrate (support base 17) 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. 16 is as follows. Inclination angle, yield 10 0.1 43 0.1 58 43 63 71 66 90 71 96 75 88 79 79 85 52 90 36
- FIG. 17 As a result of examining the relationship between the stacking fault density and the oscillation yield using the method (A), the result shown in FIG. 17 was obtained.
- the definition of the oscillation yield is the same as described above. According to FIG. 17, it can be seen that when the stacking fault density of the GaN substrate (supporting base body 17) exceeds 1 ⁇ 10 4 (cm ⁇ 1 ), the oscillation yield rapidly decreases. Further, 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 end face 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.
- the stacking fault density contained in the GaN substrate (support base 17) needs to be 1 ⁇ 10 4 (cm ⁇ 1 ) or less.
- the laser is irradiated from the epi surface (first surface 63a of the substrate product SP) at the time of scribing to form the scribe through hole 65a and the like reaching the back surface of the substrate. It was confirmed with an optical microscope that damage and debris on the epi surface were reduced by irradiating a laser from the second surface 63b) to form the scribe through hole 65a reaching the epi surface.
- This method may improve the yield of LD (Group III nitride semiconductor laser device 11).
- the data shown in FIG. 17 is as follows. Stacking fault density (cm ⁇ 1 ), yield 500 95 1000 91 4000 72 8000 64 10000 18 50000 3
- FIG. 18 is a drawing showing the atomic arrangement in the (20-21) plane, the ( ⁇ 101-6) plane, and the ( ⁇ 1016) plane.
- FIG. 19 is a drawing showing atomic arrangements in the (20-21) plane, the ( ⁇ 101-7) plane, and the ( ⁇ 1017) plane.
- FIG. 20 is a drawing showing atomic arrangements in the (20-21) plane, the ( ⁇ 101-8) plane, and the ( ⁇ 1018) plane.
- the local atomic arrangement indicated by the arrow indicates a charge-neutral atomic arrangement, and an electrically neutral atomic arrangement appears periodically.
- This charge-neutral atomic arrangement appears periodically, which suggests that the generation of the split section is relatively stable. There is sex.
- 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 ⁇ surface, ⁇ 10-11 ⁇ surface, ⁇ 20-2-1 ⁇ surface, and ⁇ 10-1-1 ⁇ surface. Furthermore, it can be a slightly inclined surface from these semipolar surfaces.
- the semipolar principal surface is an m-plane direction from any one of ⁇ 20-21 ⁇ , ⁇ 10-11 ⁇ , ⁇ 20-2-1 ⁇ , and ⁇ 10-1-1 ⁇ planes. 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.
- a III-nitride semiconductor laser device having a laser resonator that enables a low threshold current on the semipolar plane of the support base in which the c-axis of the hexagonal III-nitride is inclined in the direction of the m-axis; and This is a method for producing this group III nitride semiconductor laser device.
- SYMBOLS 11 Group III nitride semiconductor laser element, 11a ... Element surface, 11b ... Element back surface, 13 ... Laser structure, 13a ... First surface, 13b ... Second surface, 13c, 13d ... Edge, 15 ... Electrode, DESCRIPTION OF SYMBOLS 17 ... Support base
Abstract
Description
図7に示されるレーザーダイオードを有機金属気相成長法により成長した。原料にはトリメチルガリウム(TMGa)、トリメチルアルミニウム(TMAl)、トリメチルインジウム(TMIn)、アンモニア(NH3)、シラン(SiH4)を用いた。基板71を準備した。基板71には、HVPE法で厚く成長した(0001)GaNインゴットからm軸方向に0度から90度の範囲の角度でウェハスライス装置を用いて切り出し、m軸方向へのc軸の傾斜角度ALPHAが、0度から90度の範囲の所望のオフ角を有するGaN基板を作製した。例えば、75度の角度で切り出したとき、{20-21}面GaN基板が得られる。
基板厚さ(μm) レーザ出力(mW) レーザ走査速度(mm/s)
方法(A) 80 250 1
方法(B) 60 250 1
なお、下記の方法(C)によって、スクライブ貫通孔ではなく、基板生産物SPの第1の面63aに形成されているが第2の面63bには至らないスクライブ溝SL1,SL2(図8等を参照)も形成した。スクライブ溝SL1,SL2は、基板生産物SPの第2の面63bには至らないが第1の面63aに形成されている溝である。このスクライブ溝SL1,SL2を有するIII族窒化物半導体レーザ素子を、特に、III族窒化物半導体レーザ素子111、という。
基板厚さ(μm) レーザ出力(mW) レーザ走査速度(mm/s)
方法(C) 80 100 5
400μmピッチで基板の絶縁膜開口箇所を通してエピ表面に直接レーザ光を照射することによって、スクライブ貫通孔及びスクライブ溝を形成した。共振器長は600μmとした。形成されたスクライブ貫通孔は、例えば、長さ200μm、幅12μmであり、スクライブ溝は、例えば、長さ200μm、幅8μm、深さ40μm程度であった。
具体的な面指数 {20-21}面に対する角度
(-1016) 92.46度
(-1017) 90.10度
(-1018) 88.29度
各面指数のへき開性や、スクライブ時のレーザの垂直性(±5度程度)に依存して、このような高指数面が端面として得られている可能性が考えられる。
角度ずれGAMMA 方法(A) 方法(B) 方法(C)
0以上1未満 16 18 9
1以上2未満 8 7 22
2以上3未満 1 0 5
3以上4未満 0 0 0
なお、各方法(A)~(C)における角度ずれGAMMAの平均値、標準偏差は以下の通りである。
平均値 標準偏差
方法(A) 0.67 0.63
方法(B) 0.63 0.57
方法(C) 1.38 0.57
傾斜角、歩留まり
10 0.1
43 0.1
58 43
63 71
66 90
71 96
75 88
79 79
85 52
90 36
積層欠陥密度(cm-1)、歩留まり
500 95
1000 91
4000 72
8000 64
10000 18
50000 3
Claims (17)
- III族窒化物半導体レーザ素子であって、
六方晶系III族窒化物半導体からなり半極性主面を有する支持基体、及び前記支持基体の前記半極性主面上に設けられた半導体領域を含むレーザ構造体と、 前記レーザ構造体の前記半導体領域上に設けられた電極とを備え、
前記半導体領域は、第1導電型の窒化ガリウム系半導体からなる第1のクラッド層と、第2導電型の窒化ガリウム系半導体からなる第2のクラッド層と、前記第1のクラッド層と前記第2のクラッド層との間に設けられた活性層とを含み、
前記第1のクラッド層、前記第2のクラッド層及び前記活性層は、前記半極性主面の法線軸に沿って配列されており、
前記活性層は窒化ガリウム系半導体層を含み、
前記支持基体の前記六方晶系III族窒化物半導体のc軸は、前記六方晶系III族窒化物半導体のm軸の方向に前記法線軸に対して有限な角度ALPHAで傾斜しており、前記角度ALPHAは、45度以上80度以下又は100度以上135度以下の範囲であり、
前記レーザ構造体は、前記六方晶系III族窒化物半導体のm軸及び前記法線軸によって規定されるm-n面に交差する第1及び第2の割断面を含み、
当該III族窒化物半導体レーザ素子のレーザ共振器は前記第1及び第2の割断面を含み、
前記レーザ構造体は第1及び第2の面を含み、前記第2の面は前記第1の面の反対側の面であり、
前記半導体領域は前記第1の面と前記支持基体との間に位置し、
前記第1及び第2の割断面は、それぞれ前記第1の面のエッジから前記第2の面のエッジまで延在し、
前記レーザ構造体は、前記第1の割断面の一端に、前記第1の面のエッジから前記第2の面のエッジまで延在するスクライブ跡を有し、
前記スクライブ跡は、前記第1の面のエッジから前記第2の面のエッジまで延在する凹形状を有する、ことを特徴とするIII族窒化物半導体レーザ素子。 - 前記第1及び第2の割断面の各々には、前記支持基体の端面及び前記半導体領域の端面が現れており、
前記半導体領域の前記活性層における端面と前記六方晶系窒化物半導体からなる支持基体のm軸に直交する基準面との成す角度は、前記III族窒化物半導体のc軸及びm軸によって規定される第1平面において(ALPHA-5)度以上(ALPHA+5)度以下の範囲の角度を成す、ことを特徴とする請求項1に記載されたIII族窒化物半導体レーザ素子。 - 前記角度は、前記第1平面及び前記法線軸に直交する第2平面において-5度以上+5度以下の範囲になる、ことを特徴とする請求項1又は請求項2に記載されたIII族窒化物半導体レーザ素子。
- 前記支持基体の厚さは、50μm以上150μm以下である、ことを特徴とする請求項1~請求項3のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記法線軸と前記六方晶系III族窒化物半導体のc軸との成す角度は、63度以上80度以下又は100度以上117度以下の範囲である、ことを特徴とする請求項1~請求項4のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記活性層からのレーザ光は、前記六方晶系III族窒化物半導体のa軸の方向に偏光している、ことを特徴とする請求項1~請求項5のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 当該III族窒化物半導体レーザ素子におけるLEDモードにおける光は、前記六方晶系III族窒化物半導体のa軸の方向に偏光成分I1と、前記六方晶系III族窒化物半導体のc軸を主面に投影した方向に偏光成分I2を含み、
前記偏光成分I1は前記偏光成分I2よりも大きい、ことを特徴とする請求項1~請求項6のいずれか一項に記載されたIII族窒化物半導体レーザ素子。 - 前記半極性主面は、{20-21}面、{10-11}面、{20-2-1}面、及び{10-1-1}面のいずれかの面から-4度以上+4度以下の範囲でオフした微傾斜面である、ことを特徴とする請求項1~請求項7のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記半極性主面は、{20-21}面、{10-11}面、{20-2-1}面、及び{10-1-1}面のいずれかである、ことを特徴とする請求項1~請求項8のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記支持基体の積層欠陥密度は1×104cm-1以下である、ことを特徴とする請求項1~請求項9のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記支持基体は、GaN、AlGaN、AlN、InGaN及びInAlGaNのいずれかからなる、ことを特徴とする請求項1~請求項10のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記第1及び第2の割断面の少なくともいずれか一方に設けられた誘電体多層膜を更に備える、ことを特徴とする請求項1~請求項11のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記活性層は、波長360nm以上600nm以下の光を発生するように設けられた発光領域を含む、ことを特徴とする請求項1~請求項12のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- 前記活性層は、波長430nm以上550nm以下の光を発生するように設けられた量子井戸構造を含む、ことを特徴とする請求項1~請求項13のいずれか一項に記載されたIII族窒化物半導体レーザ素子。
- III族窒化物半導体レーザ素子であって、
六方晶系III族窒化物半導体からなり半極性主面を有する支持基体、及び前記支持基体の前記半極性主面上に設けられた半導体領域を含むレーザ構造体と、 前記レーザ構造体の前記半導体領域上に設けられた電極とを備え、
前記半導体領域は、第1導電型の窒化ガリウム系半導体からなる第1のクラッド層と、第2導電型の窒化ガリウム系半導体からなる第2のクラッド層と、前記第1のクラッド層と前記第2のクラッド層との間に設けられた活性層とを含み、
前記第1のクラッド層、前記第2のクラッド層及び前記活性層は、前記半極性主面の法線軸に沿って配列されており、
前記活性層は窒化ガリウム系半導体層を含み、
前記支持基体の前記六方晶系III族窒化物半導体のc軸は、前記六方晶系III族窒化物半導体のm軸の方向に前記法線軸に対して有限な角度ALPHAで傾斜しており、前記角度ALPHAは、45度以上80度以下又は100度以上135度以下の範囲であり、
前記レーザ構造体は第1及び第2の面を含み、前記第2の面は前記第1の面の反対側の面であり、
前記半導体領域は前記第1の面と前記支持基体との間に位置し、
前記レーザ構造体は、当該レーザ構造体の端部に設けられており前記法線軸と前記六方晶系III族窒化物半導体のa軸とによって規定される平面に沿って延びる第1及び第2のスクライブ跡を有し、
前記第1及び第2のスクライブ跡は、前記第1の面のエッジから前記第2の面のエッジまで延在する凹形状を有し、
前記レーザ構造体の前記端部は、前記第1及び第2のスクライブ跡のそれぞれのエッジと、前記第1及び第2の面のそれぞれのエッジとを繋ぐ割断面を有し、
当該III族窒化物半導体レーザ素子のレーザ共振器は、前記割断面を含む、
ことを特徴とするIII族窒化物半導体レーザ素子。 - III族窒化物半導体レーザ素子を作製する方法であって、
六方晶系III族窒化物半導体からなり半極性主面を有する基板を準備する工程と、
前記半極性主面上に形成された半導体領域と前記基板とを含むレーザ構造体、アノード電極、及びカソード電極を有する基板生産物を形成する工程と、
前記六方晶系III族窒化物半導体のa軸の方向に前記基板生産物の第1の面を部分的にスクライブする工程と、
前記基板生産物の第2の面への押圧により前記基板生産物の分離を行って、別の基板生産物及びレーザバーを形成する工程と
を備え、
前記第1の面は前記第2の面の反対側の面であり、
前記半導体領域は前記第1の面と前記基板との間に位置し、
前記レーザバーは、前記第1の面から前記第2の面にまで延在し前記分離により形成された第1及び第2の端面を有し、
前記第1及び第2の端面は当該III族窒化物半導体レーザ素子のレーザ共振器を構成し、
前記アノード電極及びカソード電極は、前記レーザ構造体上に形成され、
前記半導体領域は、第1導電型の窒化ガリウム系半導体からなる第1のクラッド層と、第2導電型の窒化ガリウム系半導体からなる第2のクラッド層と、前記第1のクラッド層と前記第2のクラッド層との間に設けられた活性層とを含み、
前記第1のクラッド層、前記第2のクラッド層及び前記活性層は、前記半極性主面の法線軸に沿って配列されており、
前記活性層は窒化ガリウム系半導体層を含み、
前記基板の前記六方晶系III族窒化物半導体のc軸は、前記六方晶系III族窒化物半導体のm軸の方向に前記法線軸に対して有限な角度ALPHAで傾斜しており、
前記角度ALPHAは、45度以上80度以下又は100度以上135度以下の範囲であり、
前記第1及び第2の端面は、前記六方晶系III族窒化物半導体のm軸及び前記法線軸によって規定されるm-n面に交差し、
前記第1及び第2の端面の各々における前記活性層の端面は、前記六方晶系窒化物半導体からなる支持基体のm軸に直交する基準面に対して、前記六方晶系III族窒化物半導体のc軸及びm軸によって規定される平面において(ALPHA-5)度以上(ALPHA+5)度以下の範囲の角度を成し、
前記スクライブする工程では、前記基板生産物の前記第1の面から前記第2の面に貫通し前記六方晶系III族窒化物半導体のa軸の方向に長く延びている形状を有する複数のスクライブ貫通孔を、前記六方晶系III族窒化物半導体のa軸に沿って形成する、ことを特徴とする方法。 - 前記スクライブ貫通孔は、レーザスクライバを用いて、前記レーザ構造体の前記第1の面、あるいは前記第2の面からのレーザ照射によって形成される、ことを特徴とする請求項16に記載された方法。
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JP5201129B2 (ja) * | 2009-12-25 | 2013-06-05 | 住友電気工業株式会社 | Iii族窒化物半導体レーザ素子、及びiii族窒化物半導体レーザ素子を作製する方法 |
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US20110176569A1 (en) | 2011-07-21 |
KR20110106838A (ko) | 2011-09-29 |
TW201134039A (en) | 2011-10-01 |
CN102341977A (zh) | 2012-02-01 |
CN102341977B (zh) | 2013-06-19 |
EP2528175A1 (en) | 2012-11-28 |
US8213475B2 (en) | 2012-07-03 |
KR101285049B1 (ko) | 2013-07-10 |
JP4793494B2 (ja) | 2011-10-12 |
US20120027039A1 (en) | 2012-02-02 |
JP2011146653A (ja) | 2011-07-28 |
US8071405B2 (en) | 2011-12-06 |
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