SURFACE EMITE LASER DEVICE

Abstract

A surface emitter laser device with a photonic crystal is provided, in which an increase in the oscillation threshold current and the driving current of the surface emitter laser device with a photonic crystal is suppressed or reduced, and which has a stable oscillation mode and excellent beam quality. The surface emitter laser device with a photonic crystal has a surface emitter laser element, a mounting substrate on which the surface emitter laser element is arranged and to which it is electrically connected, and a conductive element bonding or element connecting element that connects the surface emitter laser element and the mounting substrate and reduces strain in the surface emitter laser element due to the mounting substrate.The surface emitter laser element comprises a translucent element substrate, a first semiconductor layer on the element substrate, an active layer on the first semiconductor layer, a second semiconductor layer with a conductivity opposite to the first semiconductor layer, an air hole layer provided in the first or second semiconductor layer, which has an air hole arranged in two-dimensional periodicity or in a plane, and a light reflection layer provided on the second semiconductor layer, which has a reflective surface, and has a light emission surface on a surface side opposite to the side of the first semiconductor layer of the element substrate.

Description

TECHNICAL AREA

[0001] The present invention relates to a surface emitter laser device and in particular to a surface emitter laser device with a surface emitter laser element with a photonic crystal. TECHNICAL BACKGROUND

[0002] In recent years, the development of photonic crystal surface emitting lasers (PCSEL = photonic crystal surface emitting lasers) using photonic crystals (PC) has progressed.

[0003] For example, patent literature 1 discloses the formation of a photonic crystal layer with a uniform size and a uniform refractive index period by forming air holes with two-dimensional periodicity in a guide layer or conduction layer, wherein concave parts having facets with a predetermined surface orientation are formed in upper parts of openings of the air holes, and wherein the concave parts are flattened by mass transport.

[0004] Additionally, the non-patented literature discloses the shaping of diffracted light from a surface emitter laser with a photonic crystal, a wave profile of diffracted radiation that is diffracted in a photonic crystal layer and emitted in a direction perpendicular to the photonic crystal layer, and so on. Citation list of patent literature Patent literature 1: Japanese patent no. 7101370 Non-patent literature 1: Y. Liang et al.,: Phys. Rev. B Vol. 84, 195119 (2011) Summary of the invention: Technical problem

[0005] However, in one case where the surface emitter laser element with photonic crystal was mounted on a circuit board or a heat sink, a problem arose in that voltage was generated in the surface emitter laser element with photonic crystal, increasing the oscillation threshold current, decreasing the light emission efficiency, and making the oscillation mode unstable.

[0006] In particular, in a case where a drive with continuous current conduction or flowing current (CW drive) is implemented, there was a problem in that the drive current increased due to voltage inherent in the surface emitter laser element with photonic crystal, with the power conversion efficiency decreasing while the amount of heat generation increasing, and therefore insufficient output could be obtained, and the oscillation mode was unstable.

[0007] An objective of the present invention is to provide a surface emitter laser device with a photonic crystal, wherein an increase in an oscillation threshold current and a driving current of a surface emitter laser element with a photonic crystal is suppressed, and which has a stable oscillation mode and excellent beam quality. Solution to the problem

[0008] A surface emitter laser device according to a first embodiment of the present invention has the following features: a surface emitter laser element; a mounting substrate on which the surface emitter laser element is arranged and which is electrically connected to the surface emitter laser element; and an element connecting element made of a conductive connecting material, which connects the surface emitter laser element and the mounting substrate and reduces stress in the surface emitter laser element due to the mounting substrate, wherein the surface emitter laser element has the following features: a translucent element substrate, a first semiconductor layer that is provided on the element substrate, an active layer that is provided on the first semiconductor layer, a second semiconductor layer of a second conductivity type, opposite or different from the first semiconductor layer provided on the active layer, an air hole layer which is a photonic crystal layer provided in the first semiconductor layer or the second semiconductor layer and which has an air hole arranged with a two-dimensional periodicity in a plane parallel to the active layer, and a light reflection layer that is provided on the second semiconductor layer and has a reflective surface, and a light emission surface which is provided on one surface side opposite a surface of the element substrate on which the first semiconductor layer is provided. Brief description of the drawings Fig. Figure 1 is a cross-sectional view illustrating a cross-section of a surface emitter laser device of a first embodiment. Fig. Figure 2A is a cross-sectional view that schematically illustrates an example of the structure of a PCSEL element of the first embodiment. Fig. 2B is an enlarged cross-sectional view that schematically illustrates the arrangement of the air hole pairs in the photonic crystal layer shown in Fig. 2A are illustrated. Fig. 3A is a top view schematically illustrating a top surface of the PCSEL element located in Fig. 2A is illustrated. Fig. Figure 3B is a cross-sectional view that schematically illustrates a cross-section of the photonic crystal layer in a plane parallel to an n-side conduction layer. Fig. 3C is a top view that schematically illustrates a bottom side of the PCSEL element. Fig. Figure 4 is a view that schematically illustrates a cross-section of the shaped photonic crystal layer perpendicular to a crystal layer. Fig. 5A is a scanning electron microscope image of the surface illustrating primary holes 14H1 and secondary holes 14H2 drilled into a GAn layer (n-side conduction layer) in a case where a photonic crystal layer is formed. Fig. Figure 5B is a view illustrating a scanning electron microscope (SEM) image of a surface of the shaped main air holes 14K1 and the secondary air holes 14K2. Fig. Figure 6 is a cross-sectional view that schematically illustrates a cross-section of the arrangement of the main air hole 14K1 and the secondary air hole 14K2 in the depth direction of the double grid structure. Fig. Figure 7 illustrates the current output characteristics of a PCSEL element before and after mounting it in a surface emitter laser device 5 of Example 1 (EMB1). Fig. Figure 8 is a curve representation illustrating oscillation spectra before and after assembly in a case where a current of 3.0 A is applied to a PCSEL element in the surface emitter laser device of Example 1. Fig. Figure 9A is a view illustrating a photonic band of a PCSEL element. Fig. Figure 9B is a view illustrating a Γ-point spectrum before oscillation (lower part) and a spectrum immediately after oscillation (upper part). Fig. Figure 10A is a view illustrating an FFP prior to assembly in a case where a current of 3.0 A is applied to a PCSEL element in the surface emitter laser device of Example 1. Fig. Figure 10B is a view illustrating an FFP after assembly in a case where a current of 3.0 A is applied to a PCSEL element in the surface emitter laser device of Example 1. Fig. Figure 11 is a view illustrating current output characteristics of a PCSEL element before and after mounting in a surface emitter laser device of Comparative Example 1 (CMP1). Fig. Figure 12 illustrates oscillation spectra before and after mounting in a case where a current of 3.0 A is applied to the PCSEL element in the surface emitter laser device of comparison example 1. Fig. Figure 13A is a view illustrating an FFP prior to assembly in a case where a current of 3.0 A is applied to the PCSEL element in the surface emitter laser device of Comparative Example 1. Fig. Figure 13B is a view illustrating an FFP after assembly in a case where a current of 3.0 A is applied to the PCSEL element in the surface emitter laser device of Comparative Example 1. Fig. Figure 14 is a view illustrating a base material which is a graphite laminated board. Fig. Figure 15 is a curve representation illustrating current output characteristics of a PCSEL element before and after mounting in a surface emitter laser device of Example 2 (EMB2). Fig. Figure 16 illustrates oscillation spectra before and after assembly in a case where a current of 3.0 A is applied to the PCSEL in the surface emitter laser device of Example 2. Fig. Figure 17A illustrates oscillation spectra prior to assembly in a case where a current of 3.0 A is applied to the PCSEL in the surface emitter laser device of Example 2. Fig. Figure 17B illustrates oscillation spectra after assembly in a case where a current of 3.0 A is applied to the PCSEL in the surface emitter laser device of Example 2. Fig. Table 18A illustrates a base material of the mounting substrate, connection conditions and oscillation characteristics of the PCSEL element before and after mounting the surface emitter laser device of Example 1. Fig. Table 18B illustrates a base material of the mounting substrate, connection conditions and oscillation characteristics of the PCSEL element before and after mounting the surface emitter laser device of Example 2. Fig. Table 18C illustrates a base material of the mounting substrate, connection conditions and oscillation characteristics of the PCSEL element before and after mounting the surface emitter laser device of comparison example 1. Fig. Table 19 illustrates the values ​​of materials used in Examples 1 and 2 and Comparative Example 1. Fig. Figure 20 is a curve representation that records a rate of change of a threshold current in relation to a strain quantity ε applied to a PCSEL element by fixing it to a fixing substrate (base material). Fig. Figure 21 is a view illustrating stresses σ applied to GAN at the time of attachment to a fixing substrate in cases where GAN, diamond and three-layer graphite are used as the base material of a fixing substrate. Description of exemplary implementations

[0009] Preferred embodiments of the present invention are described below; however, these embodiments can be suitably modified and combined. Furthermore, essentially identical or equivalent parts are described in the following description and in the accompanying drawings, using the same reference numerals. First embodiment 1. Structure of the surface emitter laser device with photonic crystal

[0010] Fig. Figure 1 is a cross-sectional view illustrating a cross-section of a surface emitter laser device 5 of the present embodiment. The surface emitter laser device 5 comprises a surface emitter laser element with a photonic crystal or PCSEL element 10 (PCSEL = photonic crystal surface emitting laser), further comprising an element connecting element 31, a mounting substrate 32, a substrate connecting element 34, a heat sink 35, and a housing 38.

[0011] The surface emitter laser element 10 with photonic crystal (hereinafter also referred to as the PCSEL element) has an internal photonic crystal layer 14P. Furthermore, the PCSEL element 10 has a first electrode 20A (n-electrode) and a second electrode 20B (p-electrode).

[0012] The PCSEL element 10 is attached to the mounting substrate 32 by being bound or bonded to the mounting substrate 32 by the element connecting element 31. In particular, the second electrode 20B of the PCSEL element 10 is connected to and electrically connected to a wiring electrode 33, which is a conductive layer on the mounting substrate 32, by means of the element connecting element 31.

[0013] The mounting substrate 32 is connected to the heat sink 35 by the substrate connecting element 34. Furthermore, the wiring electrode 33 of the mounting substrate 32 is electrically connected to the heat sink 35 by a connecting wire W2.

[0014] Furthermore, in the present embodiment, the heat sink 35 is a conductor and acts as an anode electrode of the surface emitter laser device 5. However, the connection type is not limited to this. For example, the wiring electrode 33 can be configured to be connected to an anode electrode (second terminal, not illustrated) of the surface emitter laser device 5.

[0015] Furthermore, the first electrode 20A of the PCSEL element 10 is electrically connected to the first terminal 37 (cathode electrode) of the surface emitter laser device 5 via the connecting wire W2. Therefore, the PCSEL element 10 emits light by applying a voltage between the first terminal 37 and the second terminal.

[0016] The components described above are included in the housing 38 to form the surface emitter laser device 5. Mounting substrate

[0017] A diamond substrate with a thickness of 500 µm and excellent heat dissipation properties was used as a base material 32A of the mounting substrate 32 (substructure). Other examples of the base material 32A of the mounting substrate 32 could include aluminum nitride (AlN), silicon carbide (SiC), aluminum oxide (Al₂O₃), copper-aluminum nitride-copper (Cu-Aln-Cu), copper-tungsten (CuW), GaN, graphite, or similar materials.

[0018] Furthermore, in the present embodiment, a metal film coating layer made of nickel / palladium / gold (Ni / Pd / Au) was used as the wiring electrode 33 of the mounting substrate 32. Element connection element

[0019] The element bonding element 31 was a paste material (MAX102, manufactured by NIHON HANDA Co., Ltd.) in which fine silver particles (silver nanoparticles) were mixed in an organic solvent, or a paste material (AuRoFUSE, manufactured by Tanaka Kikinzoku Kogyo KK) in which fine gold particles (gold nanoparticles) were mixed. The paste material can be sintered at 200°C, and the PCSEL element 10 and the mounting substrate 32 can be bonded to each other at a sufficiently lower temperature compared to the sintering temperature of 320°C of the gold-tin alloy (AuSn) used as a bonding material in the prior art. This means that the thermal stress required to bond the PCSEL element 10 can be suppressed or reduced.

[0020] In particular, the bonding or connecting material was applied to the mounting substrate 32, and then the PCSEL element 10 was subjected to a load of approximately 1.5 kfg / cm. 2 The mounting substrate 32, on which the PCSEL element 10 was mounted under load, was inserted into a sintering furnace, heated to 200°C in an N2 atmosphere and sintered for one hour.

[0021] Furthermore, the sintering temperature can range from 80°C to 320°C. If the temperature is too low, the fine metal particles will not sinter, while if the temperature is too high, the element's characteristics will deteriorate. For example, the IV characteristics will be negatively affected. Additionally, the sintering time is the period during which the organic solvent contained in element 31 evaporates during the sintering process, and this time can range from, for example, 2 minutes to 8 hours.

[0022] Furthermore, in the present example, a paste material is used in which silver or gold nanoparticles have been mixed; however, a paste material containing at least one type of fine metal particle (nanoparticle), such as gold (Au), silver (Ag), and copper (Cu), can be used. It is preferable to use the fine metal particles on the nanometer scale in the element connecting element 31, from the perspective that the bonding temperature of the PCSEL element 10 of the mounting substrate 32 can be reduced.

[0023] As described above, in the case of fine metal particles where contact parts between the particles are connected (connected by a transition) by sintering at a low temperature, and which have properties of high conductivity and high heat dissipation, other fine particles besides the metal nanoparticles described above can also be used.

[0024] Furthermore, it is preferable that the element connecting element 31 has a smaller modulus of elasticity than the modulus of elasticity of the fastening substrate 32. The modulus of elasticity of the element connecting element 31 is particularly preferably 100 or less and even more preferably 70 or less.

[0025] Furthermore, in a case where the PCSEL element 10 is attached to the mounting substrate 32, a joining process at ambient temperature can be used. For example, the connecting surfaces of the second electrode 20B and the wiring electrode 33 of the PCSEL element 10 are activated by Ar and H2 plasma, and then the second electrode 20B and the wiring electrode 33 are pressurized at ambient temperature. Accordingly, the PCSEL element 10 and the mounting substrate 32 can be joined together. Substrate connecting element

[0026] An indium alloy (component ratio: In 0.52-Sn 0.48) was used for the substrate bonding element 34. Specifically, the substrate bonding material was applied to the heat sink 35, the heat sink 35 was heated to 120°C to soften the bonding element, and the mounting substrate 32, on which the PCSEL element 10 was mounted, was pressurized to bond the heat sink 35 and the mounting substrate 32 together. Heat sink

[0027] The heat sink 35 is made of copper (Cu) with excellent thermal conductivity. A Peltier cooling device is arranged on the back side of the heat sink 35 (opposite the surface to a connection area with the mounting substrate 32), and the back side is kept at a predetermined constant temperature. Sealing gas

[0028] The surface emitter laser device 5 was sealed by a housing 38, and dry nitrogen was used as an internal sealing gas. A nitrogen-oxygen gas mixture, dry air, or similar gases can be used as the sealing gas.

[0029] In a case where the wavelength of the emitted light of the PCSEL element 10 is shorter than 420 nm, the formation of a carbide originating from the remaining organic matter can be suppressed by mixing with a few percent oxygen. 2. Structure of the surface emitter laser element

[0030] The surface emitter laser element with photonic crystal has a resonator layer in a direction parallel to a light-emitting semiconductor structure layer (n-side conduction layer, a light-emitting layer, and a p-side conduction layer, forming a light-emitting element, and is an element which emits coherent light in a direction perpendicular to the resonator layer.

[0031] This means that in the PCSEL element, light waves propagating in a plane parallel to a photonic crystal layer are diffracted due to a diffraction effect of the photonic crystal, forming a two-dimensional resonance mode, and they are also diffracted in a direction perpendicular to the parallel plane. Therefore, in the PCSEL element, the light extraction direction is a direction perpendicular to the resonance direction (which is a plane parallel to the photonic crystal layer).

[0032] Fig. Figure 2A is a cross-sectional view that schematically illustrates an example of the structure of a surface emitter laser element 10 with a photonic crystal layer (PCSEL element 10) according to the embodiment of the present invention. Furthermore, Fig. 2B an enlarged cross-sectional view, schematically showing a photonic crystal layer 14P in Fig. 2A and a pair of air holes 14K illustrates light arranged in the photonic crystal layer 14P.

[0033] As in Fig. As illustrated in Figure 2A, a semiconductor structure layer 11 is formed on a translucent element substrate 12. Furthermore, semiconductor layers are laminated perpendicular to a central axis CX of the semiconductor structure layer 11.

[0034] Additionally, the semiconductor structure layer 11 is made of a hexagonal nitrite semiconductor. In the present embodiment, the semiconductor structure layer 11 is, for example, made of a GAn-based semiconductor.

[0035] In particular, the semiconductor structure layer 11 is made up of a plurality of semiconductor layers, namely an n-cladding layer or n-coating layer (a first coating layer of a first conductivity type) 13, an n-side conduction layer (first conduction layer) 14, which is a conduction layer provided on the n-side, a light distribution setting layer 23, an active layer (ACT) 15, a p-side conduction layer (second conduction layer) 16, which is a conduction layer provided on the p-side, an electron blocking layer (EBL) 17, a p-cladding layer or p-coating layer (a second coating layer of a second conductivity type) 18, and a p-contact layer 19 are formed on the element substrate 12 in this order.

[0036] Furthermore, the first conductivity type and the second conductivity type can be a p-type and an n-type respectively, although the case where the first conductivity type is an n-type and the second conductivity type, which is a conductivity type opposite or different from the first conductivity type, is a p-type, can be described.

[0037] The elemental substrate 12 is a hexagonal GaN single crystal and has a high transmittance for light emitted from the active layer 15. Specifically, the elemental substrate 12 is a hexagonal GaN single crystal substrate whose main surface (crystal growth surface) is a +c plane, which is a {0001} plane in which Ga atoms are arranged at the outermost surface. A back surface (light emission surface) is a -c plane, which is a (000-1) plane in which N atoms are arranged at the outermost surface. The -c plane is resistant to oxidation or similar processes and is therefore suitable as a light emission surface.

[0038] The element substrate 12 is not limited to this; for example, a substrate whose main surface is offset by approximately 1° in the m-axis direction is preferably used. For example, the substrate which is offset by approximately 0.3 to 0.7° in the m-axis direction can achieve growth or growth with a mirror finish under a wide range of growing conditions.

[0039] A substrate surface (back side or light emission surface) on which a light emission region 20L, which leads to the main surface ( Fig. 3C) indicates that the “-c-plane”, which is the (000-1)-plane, has N atoms arranged on the outermost surface. The -c-plane is resistant to oxidation or similar processes and is therefore suitable as a light-emitting surface.

[0040] The following describes configurations, such as the layer thickness of each semiconductor layer; however, these configurations are only examples and can be modified and applied as appropriate.

[0041] The n-cladding or n-coating layer 13 is, for example, an n-AL. 0,04 Ga 0,96 N-layer with an Al composition or Al content of 4% and a layer thickness of 2 µm. The composition ratio of aluminum (Al) is based on a composition in which one refractive index is smaller than that of a layer (the n-side conduction layer 14) adjacent to the side of the active layer 15.

[0042] The n-side conduction layer 14 consists of a lower conduction layer 14A, a photonic crystal layer (PC layer) 14P, which is an air-hole layer, and an embedded layer 14B. As shown in Fig. As illustrated in Figure 2B, the photonic crystal layer 14P has a layer thickness d PC , and the embedded layer 14B has a layer thickness d EMB For example, the layer thickness d is PC of the photonic crystal layer 14P 40 to 180 mm.

[0043] Furthermore, in the present description, the photonic crystal layer 14P refers to a layer portion from the upper end to the lower end of the air holes in the n-side conduction layer 14 (see Fig. 2B). Therefore, the layer thickness d PC The height of the photonic crystal layer 14P is equal to the height of the air holes.

[0044] The lower conduction layer 14A is, for example, n-GaN with a layer thickness of 100 to 400 nm. The photonic crystal layer 14P is n-GaN with a layer thickness (or a depth of the air holes 14K) of 40 to 180 nm.

[0045] The embedded layer 14B is made of n-GaN, n-InGaN, or undoped GaN or undoped InGaN. Alternatively, the embedded layer 14B can be a layer in which these semiconductor layers are laminated. The embedded layer 14B has, for example, a layer thickness d EMB from 50 to 150 nm. Furthermore, the embedded layer 14B is made up of a first embedded layer 14B1 and a second embedded layer 14B2.

[0046] The light distribution adjusting layer 23, which is formed on the embedded layer 14B, is an undoped in 0,03 Ga 0,97 N-layer and has, for example, a layer thickness of 50 nm.

[0047] Furthermore, the n-side semiconductor layer, which has the n-side conduction layer 14 and the light distribution setting layer 23, is also referred to as a first semiconductor layer, however, the light distribution setting layer 23 may not be provided.

[0048] The active layer 15, which is a light-emitting layer, is, for example, a multiple quantum well (MQW) layer with two quantum well layers. A barrier layer and the quantum well layer of the MQW are GaN (layer thickness: 6.0 nm) and InGaN (layer thickness: 4.0 nm), respectively. Furthermore, the center emission wavelength of the active layer 15 is 440 nm.

[0049] Furthermore, it is preferable that the active layer be located 15-180 nm or less (i.e., within the air hole period PC) of the photonic crystal layer 14P. In this case, a high resonance effect is obtained through the photonic crystal layer 14P.

[0050] The p-side conduction layer 16 consists of a p-side conduction layer (1) 16A, which is an undominated In 0,02 Ga 0,98N layer (layer thickness 70 nm) and a p-side conduction layer (2) 16B is an undoped GaN layer (layer thickness 180 nm).

[0051] The p-side conduction layer 16 is an undoped layer. However, taking into account light absorption, it can be doped with a dopant (Mg: magnesium or similar) to achieve good electrical conductivity. Furthermore, the in composition and layer thickness of the p-side conduction layer (1) 16A can be selected appropriately to adjust the electric field distribution in an oscillation operating mode.

[0052] The electron blocking layer (EBL) 17 is an AL 0,2 Ga 0,8 N-layer of the p-type, which is doped with magnesium (Mg) and has, for example, a layer thickness of 15 nm.

[0053] The p-coating layer 18 is a Mg-doped p-Al 0,06 Ga 0,94The N-layer has, for example, a layer thickness of 600 nm. The Al composition of the p-coating layer 18 is preferably selected such that its refractive index is smaller than that of the p-side conduction layer 16. The p-coating layer 18 acts as a first p-coating layer.

[0054] Furthermore, the p-contact layer 19 is a Mg-doped p-GaN layer and has, for example, a layer thickness of 20 nm. The carrier density of the p-contact layer 19 is specified at a concentration that allows an ohmic connection to be formed with a translucent electrode 29, which is a translucent conductor layer provided on the surface of the p-contact layer 19. Instead of p-type GaN, p-type InGaN or undoped InGaN can be used. Alternatively, a layer in which a GaN layer and an InGaN layer are laminated can be used.

[0055] Furthermore, the layer, which consists of the p-side conduction layer 16, the electron blocking or electron barrier layer 17, the p-coating layer 18 and the p-contact layer 19, is also referred to as the second semiconductor layer.

[0056] Furthermore, in the present description, the terms "n-side" and "p-side" do not necessarily mean that these are of an n-type and a p-type, respectively. For example, the n-side conduction layer means a conduction layer that is located closer to the n-side than to the active layer, and it can be an undoped layer (or an I-layer).

[0057] Furthermore, the n-coating layer 13 can have multiple layers instead of a single layer, and in this case, not all layers need to be n-layers (n-doped layers); they can include an undoped layer (I-layer). The same applies to the conduction layer 16 and the p-coating layer 18.

[0058] Furthermore, it is not necessary to provide all of the semiconductor layers described above, and there can be a configuration in which a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and an active layer (light-emitting layer) located between these layers are provided.

[0059] Furthermore, in the present embodiment a case is described where the photonic crystal layer 14P (air hole layer) is provided in the first semiconductor layer (n-type semiconductor layer), however a configuration can be used in which the photonic crystal layer is provided in the second semiconductor layer (p-type semiconductor layer).

[0060] The translucent electrode 29 (anode), which establishes an ohmic contact with the p-contact layer 19, is provided on the p-contact layer 19. Furthermore, the translucent electrode 29 acts not only as an electrode layer, but also as a second p-cladding or p-coating layer.

[0061] The translucent electrode 29 has a round shape with a diameter RA centered on the central axis CX of the semiconductor structure layer 11. In particular, the translucent electrode 29 has, for example, a diameter RA = 300 µm in a top view (that is, in a case where it is viewed from a direction perpendicular to the semiconductor structure layer 11).

[0062] The translucent electrode 29 is formed from a translucent conductor and is, for example, made of indium tin oxide (ITO). Furthermore, the translucent electrode 29 is not limited to ITO, and a translucent conductor such as zinc tin oxide (ZTO), GZO (ZnO:Ga), or AZO (ZnO:Al) can be used.

[0063] On the translucent electrode 29, an Ag / Au layer, formed from a silver layer (Ag layer) and a gold layer (Au layer) formed on the Ag layer, is shaped as a p-electrode 20B (second electrode). That is, the p-electrode 20B acts as a light-reflecting layer, and the interface between the translucent electrode 29 and the Ag layer of the p-electrode 20B is a reflective surface SR. Furthermore, the reflective surface SR is positioned parallel to the photonic crystal layer 14.

[0064] Furthermore, Pd, Al, an Al alloy, a dielectric distributed Bragg reflector (DBR), or similar materials can be used as the p-electrode 20B. Additionally, a pillow or pad electrode, or similar material, can be provided at the p-electrode 20B.

[0065] The side surface and the top surface of the semiconductor structure layer 11 and the side surfaces of the translucent electrode 29 and the p-electrode 20B are covered with an insulating film 21, such as SiO2. In addition, the insulating film 21 is shaped so that it overlaps the p-electrode 20B and covers the edge of the top surface of the p-electrode 20B.

[0066] The insulating film 21 also acts as a protective film, shielding the aluminum (Al) crystal layer that forms the PCSEL element 10 from corrosive gases, etc. Furthermore, the insulating film 21 prevents short circuits or similar issues caused by deposits and creeping solder during fastening, thus improving reliability and yield. The insulating film 21 material is not limited to SiO2; other materials include ZrO2, HfO2, TiO2, Al2O3, and SiN. x , Si etc. can be selected.

[0067] A ring-shaped cathode electrode 20A (first electrode) is formed on the back side of the element substrate 20 (see Fig. 3C). In addition, an antireflection coating layer (AR coating layer) 27 is formed within the cathode electrode 20A.

[0068] The cathode electrode 20A is made of Ti / Au and is in ohmic contact with the element substrate 12. In addition to Ti / Au, the electrode material can be selected from Ti / Al, Ti / Rh, Ti / Al / Pt / Au, Ti / Pt / Au or similar.

[0069] The light emitted from the active layer 15 is diffracted by the photonic crystal layer (PC layer) 14B. The light (directly diffracted light Ld: first diffracted light) that is diffracted by the photonic crystal layer 14P and emitted directly from the photonic crystal layer 14P, and the light (reflected diffracted light Lr: second diffracted light) that is emitted due to diffraction of the photonic crystal layer 14P and reflected by a light reflection layer 32, are directed outwards from the light emission region 20L ( Fig. 3C) emits from a rear side (emission surface) 12 R of the element substrate 12.

[0070] Fig. Figure 3A is a top view schematically illustrating the top surface of PCSEL element 10. Furthermore, Fig. 3B a cross-sectional view which schematically illustrates a cross-section of the photonic crystal layer 14P in a plane parallel to the n-side conduction layer 14, and Fig. Figure 3C is a top view that schematically illustrates a bottom side of PCSEL element 10.

[0071] As in Fig. As illustrated in Figure 3B, the air holes 14K in the photonic crystal layer 14P are provided, for example, by being arranged periodically in a rectangular air hole formation region 14R.

[0072] As in Fig. As illustrated in Figure 3C, an anode region RA is shaped so that it is contained within the air hole formation region 14R.

[0073] The cathode electrode 20A is provided as a ring-shaped electrode outside the p-electrode 20B, which does not overlap with the p-electrode 20B, in a case when viewed in a vertical direction with respect to the photonic crystal layer 14P.

[0074] The region within the cathode region 20A is a light emission region 20L. Furthermore, a bonding pad 20C, which is electrically connected to the cathode electrode 20A and connected to a wire to supply power from the outside, is provided. Structure of the photonic crystal layer

[0075] Fig. Figure 4 is a view that schematically illustrates a cross-section of the shaped photonic crystal layer 14P perpendicular to a crystal layer. The photonic crystal layer 14P of the present embodiment is a photonic crystal layer with a double lattice in which a pair of air holes 14K, consisting of a main air hole 14K1 and a secondary air hole 14K2, is arranged at each of the square lattice points. Furthermore, in a case where the main air hole 14K1 and the secondary air hole 14K2 cannot be specifically distinguished from each other, they can be referred to together as the air hole 14K.

[0076] In particular, the centers of gravity CD1 of the main air holes 14K1 are arranged in a square grid pattern with period PC in two directions (x-direction and y-direction) that are perpendicular to each other. Furthermore, the centers of gravity CD2 of the secondary air holes 14K2 are also arranged in a similar manner in a square grid pattern, with air hole period PC in both the x-direction and the y-direction.

[0077] The principal axes of the main air hole 14K1 and the secondary air hole 14K2 are parallel to a <11-20> direction of the crystal orientation, and the minor axes or secondary axes of the main air hole 14K1 and the secondary air hole 14K2 are parallel to a <1-100> direction.

[0078] Furthermore, the center of gravity CD2 of the secondary air hole 14K2 is separated from the center of gravity CD1 of the main air hole 14K1 by Δx and Δy. Here, Δx = Δy was defined. This means that the center of gravity CD2 of the secondary air hole 14K2 is located away from the center of gravity CD1 of the main air hole 14K1 in the <1-100> direction.

[0079] In particular, the period PC was set to 176.8 nm, and the distances Δx and Δy between the centers of gravity of the main air holes 14K1 and the secondary air holes 14K2 were set such that they satisfy Δx = Δy = 0.46 PC.

[0080] Fig. 5A is a scanning electron microscope (SEM) image of a surface illustrating the main holes 14H1 and the secondary holes 14H2 drilled in a GaN layer (n-side conduction layer 14) in a case in which a photonic crystal layer 14P is formed.

[0081] The main hole 14H1 and the secondary hole 14H2 have an elongated columnar shape with a central axis perpendicular to the crystal layer. Furthermore, in cases where the main hole 14H1 and the secondary hole 14H2 are not specifically distinguishable from each other, they can be collectively referred to as hole 14H.

[0082] The main hole 14H1 and the secondary hole 14H2 are embedded and blocked by mass transport, and the first embedded layer 14B1 is formed. Subsequently, the main air hole 14K1 and the secondary air hole 14K2 are formed by embedding through the second embedded layer 14B2.

[0083] Fig. Figure 5B is a view illustrating a surface SEM image of the formed main air holes 14K1 and secondary air holes 14K2. In a case where the holes 14H are embedded in group III nitrite, the shapes of the holes 14H are deformed into shapes configured with thermally stable surfaces by mass transport, and air holes 14K are formed.

[0084] This means that in a +c-plane substrate, the shape of the inner side surface of hole 14H changes to a (1-100) plane (i.e., an m-plane). That is, the shape changes from a long column shape to an air hole 14K with a long hexagonal column shape, whose side surfaces are configured with the m-plane.

[0085] The shaped main air hole 14K1 had a long hexagonal column shape with a major axis of 72.5 nm and a minor axis of 43.5 nm, with a major / minor axis ratio of 1.67. The secondary air hole 14K2 had a major axis of 44.6 nm and a minor axis of 38.3 nm, with a major / minor axis ratio of 1.16, and had an elongated hexagonal column shape that was closer to a regular hexagonal column than the main air hole 14K1.

[0086] Furthermore, it was confirmed that the distances Δx and Δy between the centers of gravity of the main air hole 14K1 and the secondary air hole 14K2 were 81.6 nm (Δx = Δy = 0.46 PC) and that this had not changed since before embedding. Additionally, it was also confirmed that the principal axes of the main air hole 14K1 and the secondary air hole 14K2 were parallel to the <11-20> axis (i.e., the a-axis).

[0087] Furthermore, the air hole filling rates (filling factors) FF1 and FF2 of the main air hole 14K1 and the secondary air hole 14K2 were calculated such that FF1 = 8.8% and FF2 = 4.2%. The air hole filling rate here represents the fraction of the area occupied by each air hole per unit area in a two-dimensional regular arrangement. Specifically, in a case where the areas of the main air hole 14K1 and the secondary air hole 14K2 in the photonic crystal layer 14P are fixed at S1 and S2, respectively, the air hole filling rates FF1 and FF2 of the main air hole 14K1 and the secondary air hole 14K2 are given by the following expressions. FF1=S1 / PC2,FF2=S2 / PC2. Separation distance between diffraction surface and reflection surface

[0088] In the PCSEL element 10 of the present embodiment, a separation distance dr is set between a diffraction surface WS and a reflection surface SR (see Fig. 2A). This is configured to suppress or prevent losses due to diffraction in the vertical direction in the photonic crystal layer 14P by controlling interference between directly diffracted light Ld, which is emitted directly from the diffraction surface WS, and reflected diffracted light Lr, which is diffracted in the +z direction, reflected from the reflection surface SR and emitted.

[0089] Furthermore, the coupled-wave theory, for example, from non-patent literature 1, can be used to calculate the position of the diffraction surface WS (or the wave source), which is the diffraction position of the diffracted wave through the photonic crystal layer 14P, and the emitted wave, which is diffracted and emitted in the vertical direction of the photonic crystal layer 14P. Therefore, the separation distance dr between the diffraction surface WS and the reflection surface SR can be calculated using the position of the diffraction surface WS.

[0090] The position of the diffraction surface WS in the photonic crystal layer 14P of the PCSEL element 10 of the present embodiment was estimated by the method described in the non-patent literature 1. That is, it was estimated that the diffraction surface WS is approximately 7 nm closer to the side of the active layer 15 than the centroid of the photonic crystal layer 14P.

[0091] In a case where a phase difference between the first diffracted light (directly diffracted light Ld), which was diffracted by the diffracting surface WS, and the second diffracted light (reflected diffracted light Lr), which was diffracted by the diffracting surface WS and reflected by the reflecting surface SR, is denoted by θ (degrees), a wavelength of the first diffracted light is denoted by λ, and an average refractive index of the crystal layer from the diffracting surface WS to the reflecting surface SR is denoted by n avedenoted by, and an integer of zero or more is denoted by m, where a separation distance dr is represented by expression (1). dr={(θ / 360)+0.5+m}λ / 2nave

[0092] Furthermore, provided that the phase difference θ satisfies expression (2), the light intensities of the interference light of the directly diffracted light Ld and of the reflected diffracted light Lr are smaller than the light intensity of the directly diffracted light Ld. cosθ<0

[0093] In other words, this means that the emitted light is attenuated by the interference between the directly diffracted light Ld and the reflected diffracted light Lr, and the radiation loss (loss in the vertical direction) is reduced.

[0094] Furthermore, the photonic crystal layer 14P preferably has a thickness (d PC), which is such that the length of the optical path of the photonic crystal layer is less than a wavelength to prevent interference (mutual attenuation) from occurring within the photonic crystal layer 14P.

[0095] Therefore, it is possible to obtain a two-dimensional surface emitter laser element with a photonic crystal (PCSEL element) which can be driven with a low current. Arrangement of main air holes and secondary air holes of double grid structure

[0096] Fig. Figure 6 is a cross-sectional view that schematically illustrates cross-sections of the main air hole 14K1 and the secondary air hole 14K2 in the depth direction of the double grid structure. Here, the main air hole 14K1 and the secondary air hole 14K2 have different air hole heights (depths). That is, the height of the main air hole 14K1 is h K1and is equal to the thickness of the photonic crystal layer 14P (h K1 = d PC Furthermore, the height of the secondary air hole is 14 K² h. K2 .

[0097] In particular, the lower end of the main air hole 14K1 is positioned lower than the lower end of the secondary air hole 14K2, that is, in the -z direction. The difference between the lower ends of the main air hole 14K1 and the secondary air hole 14K2 is h DOWN Furthermore, the upper end of the secondary air hole 14K2 is lower than the upper end of the main air hole 14K1, and the difference between them is h. UP .

[0098] Here is the difference h UP between the upper ends smaller than the difference h DOWN between the lower ends, and the center of gravity CPC (=C K2 The position of the secondary air hole 14K2 in the depth direction (-z direction) is closer to the side of the active layer 15 than the center of gravity C. K1 of the main air hole 14K1.

[0099] In a nitrite-based PCSEL element, where holes of different sizes are formed simultaneously by a process such as dry etching and embedded to form the main air hole 14K1 and the secondary air hole 14K2, the side faces of the formed main air hole 14K1 and the secondary air hole 14K2 each have a hexagonal columnar structure with m-plane faces. Therefore, the size relationship between the main air hole 14K1 and the secondary air hole 14K2 at any z-direction position in the photonic crystal layer 14P is the same as the size relationship between the holes before embedding.

[0100] Furthermore, in the photonic crystal layer 14P of the nitrite-based PCSEL element, the lower end of the main air hole 14K1, with a large air hole filling rate FF, is located closer to the side of the lower end of the photonic crystal layer 14P than the secondary air hole 14K2; that is, the main air hole 14K1 is deeper than the secondary air hole 14K2. Additionally, the upper end of the secondary air hole 14K2 is formed deeper than the upper end of the main air hole 14K1 due to embedding growth.

[0101] Furthermore, in a case where the active layer 15 is formed after the photonic crystal layer 14P is formed, that is, in a case where the photonic crystal layer 14P is located on the -z-direction side of the active layer 15, the relationship FF1 > FF2 is always satisfied. This means that in a nitrite-based PCSEL element, the wave source (diffraction surface) WS is always located at a position approximately 1 to 10 nm away from the center of mass C. PC (that is, the center of gravity of the main air hole 14K1) is arranged in the z-direction of the photonic crystal layer 14P towards the active layer 15, even in the case of a double lattice structure.

[0102] Therefore, there are regions (regions of h) UP and h DOWN ), in which only the main air hole 14K1 is present in the depth direction (-z direction), and regions (regions of h K2), in which both the main air hole 14K1 and the secondary air hole 14K2 are present, however, the propagating light component that is diffracted in the vertical direction is larger in the region where both the main air hole 14K1 and the secondary air hole 14K2 are present. Accordingly, the wave source (diffraction surface) WS is also located at a position that is in the +z direction (towards the active layer 15) from the center of mass C. PC the photonic crystal layer 14P is shifted.

[0103] Furthermore, the air hole has been described in which the air hole has a hexagonal column shape and the cross-sectional area does not change in the depth direction. In a case where either the main air hole 14K1 or the secondary air hole 14K2 has a shape in which the cross-sectional area changes in the depth direction, it is preferable that the center of gravity of the secondary air hole 14K2 is located closer to the active layer 15 than the center of gravity of the main air hole 14K1. 2. Operational characteristics(1) Example 1

[0104] To evaluate the effect of mounting the mounting substrate 32 on the laser characteristics, the current output characteristics of the PCSEL element 10 were measured before and after mounting. To eliminate the thermal effect and evaluate the characteristics, they were assessed by pulse driving with a pulse width of 100 ns and a repetition rate of 1 kHz (i.e., with a load cycle of 0.01%). Furthermore, the evaluation was always performed at room temperature. This means that when evaluating the current output characteristics, the PCSEL element 10 was driven under pulsed conditions where there was no thermal effect or the thermal effect or influence of heat was negligible.

[0105] The current output characteristics of a PCSEL element 10 before and after mounting in a surface emitter laser device 5 of example 1 (EMB1) with the structure described above are shown in Fig. 7 illustrates. As in Fig. As illustrated in Figure 7, it was found in the present examples that there was no increase in the threshold current of the PCSEL element 10 due to the mounting or attachment to the mounting substrate 32, there was no change in the current output characteristics, and there was no deterioration in the characteristics.

[0106] The oscillation spectra before and after mounting in a case where a current of 3.0 A was applied to the PCSEL element 10 in the surface emitter laser device of Example 1 are shown in Fig. Figure 8 illustrates the oscillation wavelength λ. The oscillation wavelength was 436.24 nm before fastening and 436.32 nm after fastening.

[0107] Here, the oscillation wavelength λ is represented by expression 3 in a case where m is an integer of 1 or more and the effective refractive index is represented by n. eff is referred to as such. λ=m×neff×PC

[0108] Considering that the impulse drive has a very small load and is therefore considered to have no thermal effect or heat influence, it is assumed that there is no change in the effective diffraction index n. eff in the spectral evaluation there is ( Fig. 8) Therefore, expression (3) shows that the change in the oscillation wavelength λ before and after fixing is proportional to the change in the air hole period PC of the photonic crystal layer.

[0109] In the present embodiment, since the oscillation wavelength λ is increased before and after fastening, this is considered to be such that the air hole period PC is increased and tensile strain is applied to the PCSEL element 10 due to the fastening. The strain quantity ε is given by expression (4). ε=ΔPC / PC=Δλ / λ

[0110] In one case where the strain magnitude or extent of strain ε was calculated in the present examples, ε = 0.0018% was achieved.

[0111] Fig. Figure 9A is a view illustrating a photonic band of a PCSEL element. The PCSEL element performs laser oscillation by using the effect of zero group velocity as the Γ-point of the photon band (i.e., the resonance effect).

[0112] In the case of a photonic crystal with a square lattice, four oscillation modes (A, B, C, and D, each from the low-frequency side) are present at the Γ-point, and laser oscillation occurs in each of these modes. Each mode can be evaluated by measuring the spectrum at the Γ-point before the oscillation, that is, the emission spectrum in the direction perpendicular to the surface (perpendicular direction) with respect to the substrate.

[0113] Fig. Figure 9B is a view illustrating a Γ-spot spectrum before oscillation (lower part) and a spectrum immediately after oscillation (upper part). This means that by comparing the Γ-spot spectrum before oscillation with the spectrum after laser oscillation, it is possible to determine the mode in which the PCSEL element oscillates. In the examples presented, the oscillation occurs in mode B. Furthermore, modes C and D are degenerated in the spectrum before oscillation.

[0114] The beam emission patterns (far field patterns: FFP) before and after assembly or fastening in a case where a current of 3.0 A was applied to the PCSEL element 10 in the surface emitter laser device of Example 1 are shown in the Fig. 10A and Fig. 10B illustrates.

[0115] By measuring the spectra before and after the oscillation, information regarding the spectrum of the Fig. 9B was obtained, and it was found that the oscillation occurs in band-edge B mode, both before and after fastening. However, a difference in the appearance level of the high-order band-edge B mode is observed before and after fastening, which is assumed to be due to the strain effect induced by fastening in the PCSEL element. (2) Comparative example 1

[0116] The surface emitter laser device of comparison example 1 (CMP1) differs from the surface emitter laser device 5 of example 1 in the following points, but is the same as example 1 in other points.

[0117] In the surface emitter laser device of Comparative Example 1, a flux-free gold-tin alloy (AuSn) was used as the element connector or element bonding element instead of the element connector 31 of Example 1. The melting point of the gold-tin alloy (AuSn) is approximately 280°C, and it is necessary to apply a higher temperature than this to perform the sintering and bonding.

[0118] In particular, the element bonding material (AuSn) was applied to the mounting substrate 32, then the mounting substrate 32 was heated to 340°C, and the surface emitter laser element was loaded with a force of approximately 1.5 kfg / cm².2 The surface emitter laser element was attached. It was held in the loaded state for 10 seconds and then immediately cooled.

[0119] Furthermore, the surface emitter laser element (PCSEL element) was the same as the PCSEL element 10 in the surface emitter laser device of Example 1 described above, except that the air hole period PC of the photonic crystal layer 14P was 177.5 nm. Evaluation of characteristics

[0120] The current output characteristics of the surface emitter laser element were measured before and after mounting to evaluate the effect of mounting on the substrate via the element connection element (AuSn) on the laser characteristics. To eliminate the thermal effect and evaluate the characteristics, they were assessed by pulse driving with a pulse width of 100 ns and a repetition rate of 1 kHz (i.e., a load of 0.01%), as in Example 1. Furthermore, the evaluation was performed at room temperature in each case.

[0121] The current output characteristics of the PCSEL element 10 before and after mounting in the surface emitter laser device of comparison example 1 (CMP1) with the structure described above are shown in Fig. Figure 11 illustrates this. In comparison example 1, the current output characteristics before mounting were almost the same as those of the surface emitter laser device 5 of example 1. However, the threshold current increased after mounting, and the current output characteristics were significantly worsened, such as a reduction in slope efficiency.

[0122] The oscillation spectra before and after mounting in a case where a current of 3.0 A is applied to the PCSEL element in the surface emitter laser device of comparison example 1 are shown in Fig. Figure 12 illustrates this. As described above, the oscillation wavelength λ of example 1 was 436.24 nm before fastening and was 436.32 nm after fastening.

[0123] In contrast, the oscillation wavelength λ of comparison example 1 was 438.48 nm before fastening and 438.83 nm after fastening. Furthermore, the magnitude of the strain ε, estimated from equation (4), was 0.079%. That is, it was found that a greater stress (tensile strain) was applied to the PCSEL element compared to example 1.

[0124] The beam emission patterns (far field patterns: FFP) before and after mounting in a case where a current of 3.0 A was applied to the PCSEL element in the surface emitter laser device of comparison example 1 are shown in the Fig. 13A and Fig. Figure 13B illustrates this. It can be seen from these FFPs that before attachment, the oscillation occurs in band-edge B mode, while after attachment it occurs in flat-band mode. Here, flat-band mode refers to a mode that differs from photonic band mode B, as in Fig. 9A, illustrated in the Γ-x direction, extends, and refers to an unintended or unwanted oscillation mode in which a laser oscillation occurs from a region other than the Γ-point.

[0125] By also focusing on the oscillation spectrum of Fig. Reference is made to section 12, which takes into account that in the surface emitter laser device of comparison example 1, the extent of the strain ε was large, which weakened the two-dimensional resonance effect of the light in the photonic crystal layer, and the flat-band mode, which is the one-dimensional oscillation mode, appeared. Since the beam quality is significantly worse when oscillating in flat-band mode, oscillation in flat-band mode is not preferable or desirable, even in an application where high light-collecting properties are required. (3) Example 2

[0126] In the surface emitter laser device 5 of Example 2 (EMB2), a graphite-laminated plate was used as the base material 32A of the mounting substrate 32 (sub-mounting). Furthermore, a gold-tin alloy (AuSn) was used for the element connecting element 34 (the same as in Comparing Example 1). Other details are the same as in Example 1.

[0127] Fig. Figure 14 shows a view illustrating base material 32A, which is a graphite-laminated sheet. Base material 32A is a graphite-laminated sheet with a three-layer structure, formed by laminating three graphite sheets GL1, GL2, and GL3 in that order.

[0128] The graphite plate GL1 has a thermal conductivity in an in-plane direction (x-direction) of 7 W / mK and a thermal conductivity in directions perpendicular to the x-direction (y-direction and z-direction) of 1700 W / mK. This means that the graphite plate GL1 is a thermally conductive plate with high thermal conductivity in a specific direction and a high anisotropy of thermal conductivity. In particular, any material with high thermal conductivity in the A- and B-axis directions (y-direction and z-direction) with respect to the c-axis direction (x-direction) in the graphite crystal lattice can be used, and, for example, boron nitride (BN) can also be used.

[0129] The graphite plates GL2 and GL3 are the same thermally conductive plates as the graphite plate GL1, however, the graphite plate GL2 is rotated by 90°, and the graphite plate GL3 is laminated in the same orientation as the graphite plate GL1 ( Fig. 14, right side).

[0130] The base material 32A, which is a graphite-laminated plate, is an isotopic heat diffusion material or heat dissipation material with high thermal conductivity and has a thermal conductivity comparable to that of diamond.

[0131] Although the graphite-laminated plate has been described as having a three-layer structure, the present invention is not limited to this. It is preferred that a plurality of graphite plates be laminated in different orientations according to the in-plane anisotropy of the thermal conductivity.

[0132] Fig. Figure 15 is a curve plot illustrating current output characteristics before and after mounting or securing a PCSEL element 10 in a surface emitter laser device 5 of Example 2 (EMB2). Furthermore, the aspect that the evaluation of the characteristics is performed during a pulse drive with a pulse width of 100 ns and a repetition frequency of 1 kHz (a load of 0.01%) is the same as in Example 1 and Comparative Example 1.

[0133] Similarly, in Example 2, where the gold-tin alloy (AuSn) was used as the connecting material, it was found that there was no increase in the threshold current of the PCSEL element 10 due to its attachment to the mounting substrate 32, no change in the current output characteristics, and no deterioration of the characteristics. Therefore, by using the element connecting element 31, which relieves or reduces the stress applied to the PCSEL element 10, it is possible to significantly suppress or reduce the deterioration of the characteristics of the PCSEL element 10, particularly in the case of CW propulsion.

[0134] The oscillation spectra before and after mounting in a case where a current of 3.0 A is applied to the PCSEL element 10 in the surface emitter laser device 5 of Example 2 are shown in Fig. Figure 16 illustrates this. Furthermore, the field-free particle (FFP) emission patterns before and after mounting (fastening??) are shown in the figure below. In one case, a current of 3.0 A was applied to the PCSEL element 10. Fig. 17A and Fig. 17B illustrates.

[0135] The spectra and radiation emission patterns of FFPs before and after oscillation confirmed that the oscillation occurs in the band-edge-B mode before and after mounting or fastening. 3. Theoretical Analysis and Considerations

[0136] Threshold current and changes in oscillation mode with respect to strain magnitude

[0137] To estimate the strain magnitude or extent of the strain that does not degrade the laser characteristics, a large number of samples were produced and subjected to the element fixation process. Fig. 18A, Fig. 18B and Fig. 18C illustrate the base materials of the mounting substrates of the surface emitter laser devices, the bonding or connection conditions and the oscillation characteristics before and after mounting the PCSEL elements in Example 1 (EBM1), in Example 2 (EBM2) and in Comparative Example 1 (CMP1).

[0138] Furthermore, the bonding temperature is represented by Tm, the oscillation wavelengths before and after bonding are represented by λ1 and λ2, the oscillation thresholds before and after bonding are represented by Ith1 and Ith2, respectively, and the oscillation modes before and after bonding are represented by OM1 and OM2. Here, B represents the oscillation modes OM1 and OM2. Fig. 18A and Fig. 18C represents an oscillation mode B, and Flat represents a flatband mode.

[0139] Furthermore, the physical property values ​​of materials used in Examples 1 and 2 and in Comparison Example 1 are in Fig. Figure 19 illustrates this. Furthermore, the three-layer graphite is based on technical data from Thermo Fisher Scientific, Inc., and the Ag nanoparticles are based on technical data from HIHON HANDA Co., Ltd. “MAX102”. Since there is no thermal physical property value for Au nanoparticles, the thermal properties of Au were used. A submicron Au nanoparticle compound material (manufactured by TANAKA Precious Metals: AuRoFUSE) was used as the element bonding or element bonding material (NanoAg) of Example 1. Because the compound material, which is made of nanoparticles, is a porous body, the Young's modulus of the submicron Au nanoparticle compound material is smaller than that of Au.

[0140] Furthermore, the curve representation, in which a rate of change of the threshold current with respect to the magnitude of the strain ε, which is recorded on the PCSEL element by attaching it to the mounting substrate (base material), is in Fig. Figure 20 illustrates this. Here, the magnitude of the strain ε was estimated from the magnitude of the change in the oscillation wavelength λ before and after fastening (ε = ΔPC / PC = Δλ / λ: expression (4)).

[0141] In detail, the values ​​are recorded for the case where the base material 32A of the fastening substrate 32 is diamond and the element connecting element 34 is an Au nanoparticle (Example 1), the case where the base material 32A is diamond and the element connecting element is an Ag nanoparticle (Example 1), the case where the base material 32A is a graphite-laminated plate and the element connecting element 34 is AuSn (Example 2), and the case where the base material of the fastening material is diamond and the element connecting element is AuSn (Comparison Example 1).

[0142] It's out Fig. 20. It was observed that in a case where the magnitude of the strain ε present in the PCSEL element exceeds 0.04%, the threshold current increases. It is considered that this is because the lattice constant (air hole period PC) of the photonic crystal layer changes due to the tensile stress generated in the PCSEL element, leading to an increase in the resonator loss.

[0143] Furthermore, the oscillation mode changes from band-edge mode (Band B) to flat-band mode when the strain exceeds 0.05%. This is thought to occur because applying a strong tensile stress to the photonic crystal layer weakens the two-dimensional coupling of light propagation within the layer, and resonance through primary coupling becomes the dominant oscillation mode.

[0144] In a case where the degree of strain ε increases further from 0.05%, the threshold current also increases in flatband mode. Furthermore, in flatband mode, the beam quality, i.e., the light-collecting properties of the beam, is significantly degraded.

[0145] When considering both (tensile strain and compressive strain) in a case where the extent of strain ε is positive or negative, the extent of strain ε is preferably 0.05% or less and particularly preferably 0.04% or less. Furthermore, considering the variation of the threshold current ( Fig. 20) the extent of the elongation ε, in particular preferably 0.03% or less. Voltage applied to the PCSEL element

[0146] Fig. Figure 21 illustrates stresses σ applied to GaN (i.e., the base material of the PCSEL element or the element substrate) at the time of attachment to a mounting substrate, in cases where GaN, diamond, and three-layer graphite are used as a base material of the mounting substrate.

[0147] Furthermore, the stress σ applied to GaN is represented by expression (5) using physical property values ​​that are in Fig. 19 are illustrated. σ={tbEaEb / (taEa−tbEb)}(αa−αb)ΔT

[0148] Here, the thermal expansion coefficients for GaN and the base material are given by α. a or α b The E-modules are each designated with E a and E b denoted by , and the thicknesses are each denoted by t a and t b designated.

[0149] As in Fig.Figure 20 illustrates that fastening can be carried out in a case where the stress due to fastening is 100MPa or less, without increasing the oscillation threshold.

[0150] Diffraction and extent of strain of the photonic crystal layer

[0151] In a two-dimensional surface emitter laser element with a photonic crystal (PCSEL element), a resonance effect is achieved by utilizing the effect that the group velocity becomes zero at the Γ-point of the two-dimensional photonic crystal. This means that the resonator of the two-dimensional PCSEL element is a two-dimensional photonic crystal layer. Furthermore, the light diffracted by the photonic crystal outwards from the resonator is necessarily diffracted in a vertical direction with respect to the photonic crystal layer.

[0152] As described above, the strain in the photonic crystal layer (air-hole layer) changes the air-hole period and also alters the position of the diffraction surface WS, thereby preventing interference or counter-interference between the directly diffracted light Ld and the reflected diffracted light Lr. Therefore, it is important to suppress or reduce the extent of the strain ε to an extremely small value.

[0153] Furthermore, the photonic crystal layer 14P described above has a double lattice structure in which pairs of air holes, each comprising a main air hole and a secondary air hole of a smaller size (including one air hole diameter) and depth than the main air hole, are arranged at lattice points. Additionally, the center of gravity of the secondary air hole is located closer to the active layer on one side of the photonic crystal layer 14P than the center of gravity of the main air hole.

[0154] The strain in the photonic crystal layer (air-hole layer) alters the air-hole period; however, the interval between the primary and secondary air holes (the distance between the centers of gravity Δx and Δy) also changes due to the strain, so the effect on the threshold current and the oscillation mode is also significant. Therefore, the effect of suppressing or reducing the magnitude of the strain ε is greater than that in the case of a single lattice.

[0155] As described in detail above, according to the present invention it is possible to provide a surface emitter laser device with a photonic crystal in which an increase in an oscillation threshold current and driving current of an attached PCSEL element is suppressed or reduced and which has a stable oscillation mode and excellent beam quality.

[0156] Furthermore, the numerical values ​​in the exemplary embodiments described above are only illustrative and can be modified and applied as appropriate. Although a PCSEL element with a double lattice structure has been presented as an example, the present invention can be applied to a PCSEL element with a single lattice structure and, more generally, to a PCSEL element with a multiple lattice structure.

[0157] Furthermore, the present invention has been illustrated by way of example with respect to a photonic crystal layer in which the air hole has a hexagonal column shape, but it can also be applied to a case where the air hole of the photonic crystal layer has a column shape, a rectangular shape, a polygonal shape or an irregular column shape, such as a teardrop shape.

[0158] In the present examples, a PCSEL element 10 is attached to a mounting substrate 32; however, a plurality of PCSEL elements 10 can be attached to a mounting substrate 32 according to the present invention. For example, a plurality of the PCSEL elements 10 can be arranged in a 3 x 3 matrix and attached to a mounting substrate. Furthermore, a PCSEL element attached to a mounting substrate 32 can be arranged in a matrix and used as an emitter.

[0159] A diamond substrate or a graphite-laminated plate was used as the mounting substrate 32, however a composite or bonded substrate can also be used in which the A and B axis directions in the graphite crystal lattice are arranged such that they are perpendicular or inclined to the surface of the diamond substrate on which the element is mounted. Description of reference symbols 5 Surface emitter laser device 10 PCSEL elements 12 element substrate 13 first cladding or coating layer 14 first management or leadership layer 14A lower management or control layer' 14B embedded layer 14K air hole / air hole pair 14K1 / 14K2 Main air hole / Secondary air hole 14P photonic crystal layer (air hole layer) 15 active layer 16 second management layer 17 Electron blocking layer or electron barrier layer 18 second coating layer 19 Contact layer 20A first electrode 20B second electrode 20L light emission region 27 Anti-reflective film 29 translucent conductor layer 31 element bonding or element connecting element 32 Mounting substrate 33 wiring electrode (coating layer) 34 Substrate bonding or substrate connecting element 35 Heat sink 38 cases CD1, CD2 Focus the separation distance Ld direct diffracted light Lr reflected diffracted light SR reflective surface QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 7101370

[0004] Cited non-patent literature

[0000] Y. Liang et al,: Phys. Rev. B Vol. 84, 195119 (2011

[0004]

Claims

[1] Surface emitter laser device comprising: a surface emitter laser element; a mounting substrate on which the surface emitter laser element is arranged and which is electrically connected to the surface emitter laser element; and an element connecting element made of a conductive connecting material, which connects the surface emitter laser element and the mounting substrate and reduces strain in the surface emitter laser element due to the mounting substrate, wherein the surface emitter laser element has the following features: a translucent elemental substrate, a first semiconductor layer that is provided on the element substrate, an active layer that is provided on the first semiconductor layer, a second semiconductor layer with a conductivity type opposite to the first semiconductor layer provided on the active layer, an air hole layer, which is a photonic crystal layer provided in the first semiconductor layer or the second semiconductor layer and has an air hole arranged with a two-dimensional periodicity or periodic arrangement in a plane parallel to the active layer, and a light reflection layer provided on the second semiconductor layer and having a reflective surface, and wherein a light emission surface is provided on a surface side opposite a surface of the element substrate on which the first semiconductor layer is provided. [2] Surface emitter laser device according to claim 1, where, in a case where an air hole period of the air hole layer of the surface emitter laser element is designated by PC2, and an air hole period of the air hole layer before the surface emitter laser element is connected to the mounting substrate by the element connecting element is designated by PC1, the extent of a change in the air hole period, ΔPC = PC2 - PC1, is within + / - 0.04%. [3] Surface emitter laser device according to claim 1, wherein the thermal stress α acting between the surface emitter laser element and the mounting substrate satisfies σ ≤ 100 MPa. [4] Surface emitter laser device according to claim 1, wherein the mounting substrate has a base material and a conductive layer provided on the base material, where the base material is diamond, and wherein the element connecting element comprises metal nanoparticles. [5] Surface emitter laser device according to claim 1, wherein the mounting substrate has a base material and a conductive layer provided on the base material, and the base material is a graphite-laminated board. [6] Surface emitter laser device according to claim 5, wherein the graphite-laminated plate is a graphite-laminated plate in which a plurality of graphite plates are laminated in different orientations according to an in-plane anisotropy of thermal conductivity. [7] Surface emitter laser device according to claim 1, wherein the air-hole layer has a diffraction surface which diffracts standing wave light present in the air-hole layer in a direction perpendicular to the air-hole layer, and in a case where a phase difference between a first diffracted light which is diffracted by the diffraction surface and a second diffracted light which is diffracted by the diffraction surface and reflected by the reflection surface is denoted by θ (degrees), a wavelength of the first diffracted light is denoted by λ, and an average refractive index of a crystal layer from the diffraction surface to the reflection surface is denoted by n ave where is denoted, and an integer of 0 or more is denoted by m, a separation distance dr between the diffraction surface and the reflection surface is represented by the following expression dr={(θ / 360)+0.5+m}λ / 2nave where the phase difference θ satisfies the following cosθ<0 [8] Surface emitter laser device according to claim 1, wherein the air hole layer has a multiple grid structure in which pairs of air holes, each having a main air hole and a secondary air hole with a smaller size and depth than the main air hole, are arranged at each of the grid points. [9] Surface emitter laser device according to any one of claims 1 to 8, wherein the air hole layer has a thickness such that the length of an optical path of the air hole layer is less than a wavelength. [10] Surface emitter laser device according to any one of claims 1 to 8, wherein the air hole layer has a multiple grid structure in which pairs of air holes, each having a main air hole and a secondary air hole with a smaller size and depth than the main air hole, are arranged at each of the grid points, and wherein a center of gravity position of the secondary air hole in a depth direction of the air hole layer is closer to the active layer on one side than a center of gravity position of the main air hole.

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