Surface emitting laser element

Abstract

This surface-emitting laser element is provided with: a first semiconductor layer provided on a translucent substrate; an active layer on the first semiconductor layer; a second semiconductor layer on the active layer; a photonic crystal layer which is included in the first semiconductor layer and which has pores arranged in a two-dimensional periodic manner in a plane parallel to the active layer; and a light reflecting layer provided on the second semiconductor layer and having a reflecting surface. The back surface of the substrate has a light emission surface, the photonic crystal layer has a diffraction surface which is a wave source when fixed light is diffracted in a direction orthogonal to the photonic crystal layer, and the distance between the diffraction surface and the reflection surface is set so that the light emission surface is substantially equal to the light emission surface. The light intensity of interference light generated by interference between first diffracted light diffracted from the diffraction surface to the light emission surface side and second diffracted light diffracted from the diffraction surface to the light reflection layer side and reflected by the reflection surface is made smaller than the light intensity of the first diffracted light.

Description

Technical Field

[0001] The present invention relates to a surface emitting laser element, and in particular to a surface emitting laser element having a photonic crystal. Background Art

[0002] In recent years, the development of photonic crystal surface-emitting lasers (PC) using photonic crystals has been advanced.

[0003] For example, Patent Document 1 discloses a photonic crystal surface emitting laser having a cladding layer with a variable Al composition, which can enhance optical confinement of light parallel to the photonic crystal layer and reduce loss.

[0004] In addition, Patent Document 2 discloses a surface emitting laser which uses a p-type In x Ga 1-x A photonic crystal layer is formed in the N layer, the purpose of which is to reduce the light absorption caused by Mg and lower the oscillation threshold.

[0005] Patent Document 3 discloses a surface emitting laser having a first photonic crystal layer and a second photonic crystal layer, and making them have the same optical thickness. That is, a surface emitting laser is disclosed, which weakens the light diffracted by each photonic crystal in a direction perpendicular to the photonic crystal layer by interference, thereby reducing the light component diffracted in the perpendicular direction.

[0006] Furthermore, Non-Patent Document 1 discloses a formulation of diffracted light of a photonic crystal surface emitting laser and a wave pattern of diffracted radiation that is diffracted in a photonic crystal layer and emitted in a direction perpendicular to the photonic crystal layer.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2008-227095

[0010] Patent Document 2: Japanese Patent Application Publication No. 2010-232488

[0011] Patent Document 3: Japanese Patent Application Publication No. 2014-67945

[0012] Non-patent literature

[0013] Non-patent document 1: Y. Liang et al.: Phys. Rev. B vol. 84, 195119 (2011) Summary of the invention

[0014] Problems to be solved by the invention

[0015] However, the prior art described in the above-mentioned patent documents 1 and 2 cannot reduce the resonator loss in the vertical direction. In addition, the prior art described in patent document 3 is difficult to accurately control the thickness of the photonic crystal layer, thereby making it difficult to have a desired beam shape (FFP: Far Field Pattern) and reduce the intensity of light diffracted in the vertical direction.

[0016] In addition, in order to realize wearable devices such as smart glasses, a small and low-power laser source that can be driven with a low current is required. On the other hand, for the output of light, low output is required from the perspective of direct incidence to the human eye. Therefore, especially in applications such as wearable devices, a small, low-power and low-output laser source is required.

[0017] An object of the present invention is to provide a surface-emitting laser element capable of reducing emission loss, lowering oscillation threshold current, and reducing drive current.

[0018] Means for solving problems

[0019] A surface emitting laser device according to one embodiment of the present invention includes:

[0020] Light-transmitting substrate;

[0021] A first semiconductor layer, which is disposed on the substrate;

[0022] an active layer disposed on the first semiconductor layer;

[0023] a second semiconductor layer disposed on the active layer;

[0024] a photonic crystal layer included in the first semiconductor layer and having pores arranged two-dimensionally periodically in a plane parallel to the active layer; and

[0025] a light reflecting layer, which is disposed on the second semiconductor layer and has a reflecting surface,

[0026] The back side of the substrate has a light emitting surface,

[0027] The photonic crystal layer has a diffraction surface, which is a wave source when the light fixed in the photonic crystal layer is diffracted in a direction orthogonal to the photonic crystal layer.

[0028] The separation distance between the diffraction surface and the reflection surface is set so that the light intensity of interference light generated by the interference between the first diffraction light diffracted from the diffraction surface to the light emitting surface side and the second diffraction light diffracted from the diffraction surface to the light reflecting layer side and reflected by the reflection surface is smaller than the light intensity of the first diffraction light. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A 1 is a cross-sectional view schematically showing an example of the structure of the PCSEL element 10 according to the first embodiment of the present invention.

[0030] Figure 1B It is schematically shown Figure 1A FIG. 1 is a partially enlarged cross-sectional view of a photonic crystal layer 14P (pore layer) and pores 14K arranged in the photonic crystal layer 14P.

[0031] Figure 2A is a plan view schematically showing the upper surface of the PCSEL element 10 .

[0032] Figure 2B 1 is a cross-sectional view schematically showing a cross section of the photonic crystal layer 14P on a surface parallel to the n-side guide layer 14 .

[0033] Figure 2C 1 is a plan view schematically showing the bottom surface of the PCSEL element 10 .

[0034] Figure 3A 1 is a plan view schematically showing the main opening K1 and the sub-opening K2 of the resist, and the holes 14H1 and 14H2 after etching.

[0035] Figure 3B The figure shows a surface SEM (Scanning Electron Microscope) image after the holes 14H1 and 14H2 are formed.

[0036] Figure 4A Schematically shows a cross section of the formed photonic crystal layer 14P, taken along a line perpendicular to the crystal layer.

[0037] Figure 4B 14K1 and 14K2 are diagrams showing a surface SEM image after the main pores 14K1 and the sub-pores 14K2 are formed.

[0038] Figure 5 It is a table showing the pore period PC, the separation distance dr from the wave source WS to the reflection surface SR, and the like of the manufactured elements Ex. 1 to 9.

[0039] Figure 6 It is shown Figure 5 Table showing threshold current density, slope efficiency, and phase difference θ between direct diffracted light Ld and reflected diffracted light Lr of the element shown.

[0040] Figure 7 The threshold current density Jth (kA / cm2) is plotted against the separation distance dr (nm) of Ex. 1 to 9. 2 )’s picture.

[0041] Figure 8 is a graph showing Γ relative to the thickness of the p-cladding layer 18 act , Γ PC .

[0042] Fig. 9 αi is a graph showing the value of αi with respect to the thickness of the p-cladding layer 18 .

[0043] Fig.10 1 to 9, which are obtained based on the distance dr, and which are related to the phase difference θ between the direct diffracted light Ld and the reflected diffracted light Lr.

[0044] Fig.11 This is a diagram showing changes in the vertical loss α′ with respect to the reflectivity R normalized to the value of R=0 when the phase difference θ=180°.

[0045] Fig.12 2 is a graph showing the differential of the loss α′ with respect to the reflectivity R (dα′ / dR).

[0046] Fig.13 14K1 is a cross-sectional view schematically showing the arrangement cross section of the main air holes 14K1 and the sub-air holes 14K2 in the depth direction of the twin lattice structure. DETAILED DESCRIPTION

[0047] Hereinafter, preferred embodiments of the present invention will be described, but they may be appropriately changed and combined. In the following description and drawings, substantially the same or equivalent parts are denoted by the same reference numerals for description.

[0048] [First embodiment]

[0049] 1. Structure of Photonic Crystal Surface Emitting Laser

[0050] A photonic crystal surface emitting laser (hereinafter also referred to as PCSEL) is an element that has a resonator layer in a direction parallel to the semiconductor light-emitting structure layers (n-side guide layer, light-emitting layer, p-side guide layer) that constitute the light-emitting element, and radiates coherent light in a direction orthogonal to the resonator layer.

[0051] That is, in a photonic crystal surface emitting laser (PCSEL), a light wave propagating in a plane parallel to the photonic crystal layer is diffracted due to the diffraction effect of the photonic crystal to form a two-dimensional resonance mode, and is also diffracted in a direction perpendicular to the parallel plane. That is, in a photonic crystal surface emitting laser, the light extraction direction is a vertical direction relative to the resonance direction (in a plane parallel to the photonic crystal layer).

[0052] Figure 1A1 is a cross-sectional view schematically showing an example of the structure of a photonic crystal surface emitting laser element (hereinafter referred to as a PCSEL element) 10 according to an embodiment of the present invention. Figure 1B It is schematically shown Figure 1A FIG. 1 is an enlarged cross-sectional view of a photonic crystal layer 14P and a pair of air holes 14K arranged in the photonic crystal layer 14P.

[0053] like Figure 1A As shown, the semiconductor structure layer 11 is formed on a light-transmitting substrate 12. In addition, semiconductor layers are vertically stacked along the central axis CX of the semiconductor structure layer 11.

[0054] In addition, the semiconductor structure layer 11 is composed of a hexagonal nitride semiconductor. In this embodiment, the semiconductor structure layer 11 is composed of, for example, a GaN-based semiconductor.

[0055] In more detail, a semiconductor structure layer 11 composed of a plurality of semiconductor layers is formed on a substrate 12, namely, an n-cladding layer (a first cladding layer of a first conductivity type) 13, a guiding layer arranged on the n-side, namely, an n-side guiding layer (a first guiding layer) 14, a light distribution adjustment layer 23, an active layer (ACT) 15, a guiding layer arranged on the p-side, namely, a p-side guiding layer (a second guiding layer) 16, an electron blocking layer (EBL: Electron Blocking Layer) 17, a p-cladding layer (a second cladding layer of a second conductivity type) 18, and a p-contact layer 19 are sequentially formed.

[0056] Furthermore, the case where the first conductivity type is the n-type and the second conductivity type which is the opposite conductivity type to the first conductivity type is the p-type is described, but the first conductivity type and the second conductivity type may be the p-type and the n-type, respectively.

[0057] The substrate 12 is a hexagonal GaN single crystal, and is a substrate with a high transmittance of light emitted from the active layer 15. More specifically, the substrate 12 is a hexagonal GaN single crystal substrate whose main surface (crystal growth surface) is the {0001} plane, i.e., the +c plane, on which Ga atoms are arranged on the outermost surface. The back surface (light emitting surface) is the (000-1) plane, i.e., the -c plane, on which N atoms are arranged on the outermost surface. The -c plane is resistant to oxidation, etc., and is therefore suitable as a light emitting surface.

[0058] The substrate 12 is not limited thereto, and is preferably a so-called front substrate, or a substrate whose main surface is offset by about 1° in the m-axis direction. For example, a substrate offset by about 0.3 to 0.7° in the m-axis direction can achieve mirror growth under a wide range of growth conditions.

[0059] The substrate surface (back surface, light emitting surface) provided with the light emitting region 20L opposite to the main surface is the (000-1) surface with N atoms arranged on the outermost surface, that is, the "-c" surface. The -c surface is resistant to oxidation and is therefore suitable as a light extraction surface.

[0060] The composition, layer thickness and other structures of each semiconductor layer are described below, but these are merely examples and can be appropriately changed for application.

[0061] The n-cladding layer 13 is, for example, n-Al having an Al content of 4%. 0.04 Ga 0.96 The N layer has a thickness of 2 μm and an aluminum (Al) composition ratio such that the refractive index is smaller than that of the layer adjacent to the active layer 15 side (ie, the n-side guide layer 14).

[0062] The n-side guide layer 14 is composed of a lower guide layer 14A, a photonic crystal layer (PC layer) 14P as an air-hole layer, and an embedded layer 14B. Figure 1B As shown, the photonic crystal layer 14P has a layer thickness d PC , the embedding layer 14B has a layer thickness d EMB For example, the thickness d of the photonic crystal layer 14P is PC It is 40~180nm.

[0063] In this specification, the photonic crystal layer 14P refers to the layer portion from the upper end to the lower end of the pore in the n-side guide layer 14 (see Figure 1B ). Therefore, the layer thickness d of the photonic crystal layer 14P is PC Equal to the height of the pore.

[0064] The lower guide 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 the depth of the pores 14K) of 40 to 180 nm.

[0065] The buried layer 14B is composed of n-GaN, n-InGaN, or undoped GaN or undoped InGaN. Alternatively, the buried layer 14B may be a layer formed by stacking these semiconductor layers. The layer thickness d of the buried layer 14B is EMB It is, for example, 50 to 150 nm. In addition, the embedded layer 14B is composed of a first embedded layer 14B1 and a second embedded layer 14B2.

[0066] The light distribution adjustment layer 23 formed on the embedding layer 14B is an undoped In 0.03 Ga 0.97 The N layer has a thickness of 50 nm, for example.

[0067] In addition, the n-side guide layer 14 and the light distribution adjusting layer 23 are also referred to as a first semiconductor layer, but the light distribution adjusting layer 23 may not be provided.

[0068] The active layer 15 as a light-emitting layer is, for example, a multi-quantum well (MQW) layer having two quantum well layers. The barrier layer and quantum well layer of the MQW are GaN (layer thickness 6.0 nm) and InGaN (layer thickness 4.0 nm), respectively. In addition, the light emission center wavelength of the active layer 15 is 440 nm.

[0069] In addition, the active layer 15 is preferably arranged within 180 nm (ie, within the period PC of the pores) of the photonic crystal layer 14P. In this case, the resonance effect generated by the photonic crystal layer 14P is better.

[0070] The p-side guide layer 16 is made of undoped In 0.02 Ga 0.98 It is composed of an N layer (thickness 70 nm), namely a p-side guide layer (1) 16A, and an undoped GaN layer (thickness 180 nm), namely a p-side guide layer (2) 16B.

[0071] Considering the light absorption caused by the dopant (Mg: magnesium, etc.), the p-side guide layer 16 is an undoped layer, but it can be doped to obtain good conductivity. In addition, in order to adjust the electric field distribution in the oscillation operation mode, the In composition and layer thickness of the p-side guide layer (1) 16A can be appropriately selected.

[0072] The electron blocking layer (EBL) 17 is a p-type Al doped with magnesium (Mg). 0.2 Ga 0.8 The N layer has a layer thickness of 15 nm, for example.

[0073] The p-cladding layer 18 is Mg-doped p-Al 0.06 Ga 0.94 The N layer has a layer thickness of 600 nm, for example. The Al composition of the p-cladding layer 18 is preferably selected so that the refractive index is smaller than that of the p-side guide layer 16. The p-cladding layer 18 functions as a first p-cladding layer.

[0074] In addition, the p-contact layer 19 is a Mg-doped p-GaN layer, for example, having a layer thickness of 20 nm. The carrier density of the p-contact layer 19 is a concentration that enables ohmic bonding with the light-transmitting conductive layer, i.e., the light-transmitting electrode 31, disposed on the surface thereof. Alternatively, p-type or undoped InGaN may be used instead of p-type GaN. Alternatively, a layer of GaN layers and InGaN layers may be stacked.

[0075] Furthermore, a layer composed of the p-side guide layer 16 , the electron blocking layer 17 , the p-cladding layer 18 , and the p-contact layer 19 is also referred to as a second semiconductor layer.

[0076] In this specification, "n-side" and "p-side" do not necessarily mean n-type or p-type. For example, an n-side guide layer refers to a guide layer disposed on the n-side of an active layer, and may be an undoped layer (or i-layer).

[0077] In addition, the n-cladding layer 13 may not be a single layer but may be composed of a plurality of layers. In this case, not all layers need to be n layers (n-doped layers) but may include undoped layers (i layers). The same is true for the p-side guide layer 16 and the p-cladding layer 18.

[0078] In addition, all the above-mentioned semiconductor layers do not need to be provided, and a structure having a first semiconductor layer of a first conductivity type including a photonic crystal layer, a second semiconductor layer of a second conductivity type, and an active layer (light-emitting layer) sandwiched between these layers is sufficient.

[0079] A light-transmitting electrode 31 (anode) is provided on the p-contact layer 19 and is in ohmic contact with the p-contact layer 19. The light-transmitting electrode 31 functions not only as an electrode layer but also as a second p-cladding layer.

[0080] The light-transmitting electrode 31 has a circular shape with a diameter RA centered on the central axis CX of the semiconductor structure layer 11. Specifically, the light-transmitting electrode 31 has a diameter of RA=300 μm, for example, in a plan view.

[0081] The light-transmitting electrode 31 is formed of a light-transmitting conductor, such as indium tin oxide (ITO). The light-transmitting electrode 31 is not limited to ITO, and light-transmitting conductors such as zinc tin oxide (ZTO), GZO (ZnO:Ga), and AZO (ZnO:Al) may also be used.

[0082] An Ag / Au layer composed of a silver (Ag) layer and a gold (Au) layer formed on the Ag layer is formed on the light-transmitting electrode 31 as a p-electrode 20B (second electrode). That is, the p-electrode 20B functions as a light-reflecting layer, and the interface between the light-transmitting electrode 31 and the Ag layer of the p-electrode 20B is a reflection surface SR. In addition, the reflection surface SR is provided in parallel with the photonic crystal layer 14P.

[0083] Alternatively, Pd, Al, Al alloy, dielectric DBR (Distributed Bragg Reflector), etc. may be used as the p-electrode 20B. Alternatively, a pad electrode, etc. may be provided on the p-electrode 20B.

[0084] The side and upper surfaces of the semiconductor structure layer 11, and the side surfaces of the light-transmitting electrode 31 and the p-electrode 20B are covered with an insulating film 21 such as SiO2. The insulating film 21 is formed so as to straddle the p-electrode 20B and cover the edge of the upper surface of the p-electrode 20B.

[0085] The insulating film 21 acts as a protective film to protect the crystal layer containing aluminum (Al) constituting the PCSEL element 10 from being affected by corrosive gases, etc. In addition, the insulating film 21 prevents short circuits caused by attachments and solder climbing during installation, which is conducive to improving reliability and yield. The material of the insulating film 21 is not limited to SiO2, and ZrO2, HfO2, TiO2, Al2O3, SiN x , Si, etc.

[0086] A circular cathode electrode 20A (first electrode) is formed on the back surface of the substrate 12. In addition, an anti-reflection (AR) coating 27 is formed on the inner side of the cathode electrode 20A.

[0087] The cathode electrode 20A is made of Ti / Au and is in ohmic contact with the substrate 12. The electrode material may be Ti / Al, Ti / Rh, Ti / Al / Pt / Au, Ti / Pt / Au, or the like in addition to Ti / Au.

[0088] The radiated light from the active layer 15 is diffracted by the photonic crystal layer (PC layer) 14P. The light diffracted by the photonic crystal layer 14P and directly emitted from the photonic crystal layer 14P (direct diffracted light Ld: first diffracted light), and the light diffracted by the photonic crystal layer 14P and emitted and reflected by the light reflecting layer 32 (reflected diffracted light Lr: second diffracted light) are emitted from the light emitting region 20L (such as the back side (emitting surface) 12R) of the substrate 12. Figure 2C ) is ejected to the outside.

[0089] Figure 2A 1 is a plan view schematically showing the upper surface of the PCSEL element 10. In order to make the image clear and easy to understand, the upper surface is schematically shown in a state where the pad electrode 33 is removed.

[0090] also, Figure 2B is a cross-sectional view schematically showing a cross section of the photonic crystal layer 14P at a surface parallel to the n-side guide layer 14 , Figure 2C 1 is a plan view schematically showing the bottom surface of the PCSEL element 10 .

[0091] like Figure 2B As shown, in the photonic crystal layer 14P, pores 14K are periodically arranged in, for example, a rectangular pore forming region 14R.

[0092] like Figure 2C As shown, the anode region RA is formed so as to be included in the pore forming region 14R. In addition, the cathode electrode 20A is provided as a ring-shaped electrode outside the p-electrode 20B so as not to overlap with the p-electrode 20B when viewed in a direction perpendicular to the photonic crystal layer 14P.

[0093] The region inside the cathode electrode 20A is a light emitting region 20L. In addition, a bonding pad 20C is provided which is electrically connected to the cathode electrode 20 and is connected to a wire for power supply from the outside.

[0094] 2. Fabrication method and structure of photonic crystal layer

[0095] The following is an explanation of the process of making the photonic crystal layer. The MOVPE (Metalorganic Vapor Phase Epitaxy) method is used as the crystal growth method. In addition, the following uses the case where the photonic crystal layer 14P is a double-lattice photonic crystal layer as an example to explain its formation method, but a single-lattice photonic crystal layer and a poly-lattice photonic crystal layer can also be formed in the same way.

[0096] (a) Pore formation

[0097] First, n-type Al with an Al content of 4% is grown on the substrate 12. 0.04 Ga 0.96 The N layer serves as the n-cladding layer 13. Then, an n-type GaN layer is grown on the n-cladding layer 13. This grown layer is a preparatory layer for forming the lower guide layer 14A and the photonic crystal layer 14P.

[0098] After forming the above-mentioned preparation layer, the substrate is taken out from the chamber of the MOVPE device, and fine holes (pores) are formed on the surface of the growth layer. After the surface is cleaned by washing, a silicon nitride film (SiN) is formed by plasma CVD. x ). A resist for electron beam drawing is applied thereon and placed in an electron beam drawing apparatus to pattern a two-dimensional periodic structure.

[0099] Figure 3A 1 is a plan view schematically showing the main opening K1 and the sub-opening K2 of the resist, and the holes 14H1 and 14H2 after etching. Figure 3A As shown, patterning is performed such that opening pairs consisting of an elliptical main opening K1 and a sub-opening K2 smaller than the main opening K1 are arranged two-dimensionally in a square lattice shape at a period PC in the resist surface. In order to make the drawings clear, the openings are shown with hatching.

[0100] More specifically, the centroids CD1 of the main openings K1 are arranged in two orthogonal directions (x and y) in a square lattice with a period PC. Similarly, the centroids CD2 of the sub-openings K2 are arranged in a square lattice with a period PC in the x and y directions.

[0101] The major axes of the main opening K1 and the sub-opening K2 are parallel to the <11-20> direction of the crystal orientation, and the minor axes of the main opening K1 and the sub-opening K2 are parallel to the <1-100> direction.

[0102] In addition, the center of gravity CD2 of the sub-opening K2 is spaced apart from the center of gravity CD1 of the main opening K1 by Δx and Δy. Here, Δx=Δy. That is, the center of gravity CD2 of the sub-opening K2 is spaced apart from the center of gravity CD1 of the main opening K1 in the <1-100> direction.

[0103] In addition, the distances Δx and Δy between the centers of gravity of the main opening K1 and the sub-opening K2 are set to Δx=Δy=0.4PC. After the patterned resist is developed, the SiN is selectively treated by an ICP-RIE (Inductive Coupled Plasma-Reactive Ion Etching) device. x Thus, the main openings K1 and the auxiliary openings K2 are arranged in a square lattice shape with a period PC to penetrate the SiN x Film formation.

[0104] Furthermore, since the oscillation wavelength (λ) is set to 438 nm, the period (pore interval) PC is PC=177.5 nm.

[0105] Next, the resist is removed and the patterned SiN x The film acts as a hard mask to form holes (pores) on the GaN surface. By dry etching GaN in the depth direction using chlorine-based gas and argon gas in an ICP-RIE device, vertically excavated elliptical columnar pores, namely main holes 14H1 and auxiliary holes 14H2, are formed on the GaN surface.

[0106] In order to distinguish the holes formed by etching the GaN surface from the air holes in the photonic crystal layer 14P, they are referred to as main holes and auxiliary holes. In addition, when the main holes 14H1 and auxiliary holes 14H2 are not particularly distinguished, they are sometimes collectively referred to as holes 14H.

[0107] In addition, the shape of the hole 14H is not limited to the elliptical column shape, and may be a cylindrical shape, a polygonal shape, or the like.

[0108] Figure 3B The figure shows a surface SEM (Scanning Electron Microscope) image after the holes 14H1 and 14H2 are formed.

[0109] The major diameter of the main hole 14H1 was 138.9 nm, the minor diameter was 63.2 nm, and the major diameter / minor diameter ratio was 2.20. The minor diameter of the secondary hole 14H2 was 66.3 nm, the minor diameter was 59.1 nm, and the major diameter / minor diameter ratio was 1.12.

[0110] In addition, it is known that the main holes 14H1 and the auxiliary holes 14H2 are arranged in a square lattice with a period PC of 177.5 nm. At this time, the distances Δx and Δy between the centers of gravity of the main holes 14H1 and the auxiliary holes 14H2 are 81.6 nm (Δx = Δy = 0.46 PC). In addition, the major axes of the main holes 14H1 and the auxiliary holes 14H2 are parallel to the <11-20> axis (i.e., the a-axis).

[0111] (b) Formation of embedded layer

[0112] The substrate having the holes 14H formed therein is cleaned and introduced again into the reactor of the MOVPE apparatus, and ammonia (NH 3 ), trimethylgallium (TMG) and NH 3 are supplied to close the openings of the holes 14H, thereby forming the first embedded layer 14B1 .

[0113] That is, the first embedded layer 14B1 is formed at the first temperature (920° C.), at which temperature the shape of the pores 14H is deformed into a shape consisting of a thermally stable surface due to mass transfer.

[0114] In the first temperature region, N atoms are attached to the outermost surface of the growth substrate, so that an N polar surface can be selectively grown. Therefore, a {1-101} facet can be selectively grown on the surface. The opposite {1-101} facets collide with each other, so that the hole 14H is closed and embedded, thereby forming a first embedded layer 14B1.

[0115] Next, after the main hole 14H1 and the auxiliary hole 14H2 are closed, a second embedded layer 14B2 with a thickness of 50 nm is grown. The growth of the second embedded layer 14B2 is performed as follows: after the substrate temperature (growth temperature) is lowered to 820°C (second embedded temperature), triethylgallium (TEG), trimethylindium (TMI) and NH3 are supplied. In addition, the second embedded temperature is a temperature lower than the first embedded temperature.

[0116] In addition, the In composition of the second embedded layer 14B2 in this embodiment is 3% (ie, Ga 0.97 In 0.03 N layer). The second embedded layer 14B2 also functions as a light distribution adjustment layer for adjusting the coupling efficiency (light field) between light and the photonic crystal layer 14P.

[0117] The above embedding process forms a photonic crystal layer 14P of a double lattice structure, in which a pore pair 14K consisting of a main pore 14K1 and a sub-pore 14K2 is arranged at each square lattice point. The pore diameter and depth (height) of the sub-pore 14K2 are smaller than those of the main pore 14K1.

[0118] In addition, when the main air holes 14K1 and the auxiliary air holes 14K2 are not particularly distinguished, they may be collectively referred to as air holes 14K.

[0119] Figure 4A 14H is a diagram schematically showing a cross section of the photonic crystal layer 14P formed perpendicular to the crystal layer. When holes are embedded in the group III nitride, the shape of the hole 14H is deformed into a shape of a thermally stable surface due to mass transfer, forming a pore 14K.

[0120] That is, in the +c-plane substrate, the inner side of the hole 14H changes shape toward the (1-100) plane (ie, m-plane), that is, the shape changes from an elliptical column to an oblate hexagonal columnar air hole 14K whose side surface is composed of the m-plane.

[0121] Figure 4B 14K1 and 14K2 are diagrams showing a surface SEM image after the main pores 14K1 and the sub-pores 14K2 are formed.

[0122] The main pore 14K1 formed has a long diameter of 72.5 nm and a short diameter of 43.5 nm, and has an oblate hexagonal prism shape with a long diameter / short diameter ratio of 1.67. In addition, the auxiliary pore 14K2 has a long diameter of 44.6 nm and a short diameter of 38.3 nm, and has an oblate hexagonal prism shape with a long diameter / short diameter ratio of 1.16, which is closer to a regular hexagonal prism than the main pore 14K1.

[0123] The distances Δx and Δy between the centers of gravity of the main pore 14K1 and the auxiliary pore 14K2 were 81.6 nm (Δx = Δy = 0.46 PC), which was confirmed to be unchanged from before embedding. In addition, the major axes of the main pore 14K1 and the auxiliary pore 14K2 were confirmed to be parallel to the <11-20> axis (i.e., the a-axis).

[0124] In addition, the pore filling rates (filling factors) FF1 and FF2 of the main pores 14K1 and the auxiliary pores 14K2 are calculated, and FF1 = 8.8% and FF2 = 4.2%. The pore filling rate refers to the ratio of the area occupied by each pore per unit area in a two-dimensional regular arrangement. Specifically, when the areas of the main pores 14K1 and the auxiliary pores 14K2 in the photonic crystal layer 14P are S1 and S2 respectively, the pore filling rates FF1 and FF2 of the main pores 14K1 and the auxiliary pores 14K2 are given by the following formulas.

[0125] FF1=S1 / PC 2 , FF2=S2 / PC 2

[0126] Through the above steps, the formation of the n-side guide layer 14 including the photonic crystal layer 14P as a pore layer is completed.

[0127] 3. Component characteristics and theoretical research

[0128] (a) Component characteristics

[0129] PCSEL devices 10 with different thicknesses of the p-cladding layer 18 (first p-cladding layer) were produced, and device characteristics thereof were evaluated. The semiconductor layers other than the p-cladding layer 18 had the same structure, such as components and thicknesses.

[0130] Figure 5 This is a table showing the pore period PC, the thickness of the p-cladding 18, the thickness of the translucent electrode 31 (ITO), and the separation distance dr from the wave source WS to the p-electrode 20B (i.e., the reflecting surface SR) of the elements Examples.1 to 9 (hereinafter referred to as Ex. 1 to 9) of the manufactured embodiments.

[0131] also, Figure 6 It is shown Figure 5 Table showing threshold current density, slope efficiency, and phase difference θ between direct diffracted light Ld and reflected diffracted light Lr of the element shown.

[0132] Figure 7 The threshold current density Jth (kA / cm2) is plotted against the separation distance dr (nm) of the above elements. 2 )’s picture.

[0133] like Figure 6 and Figure 7 As shown in FIG. 1 , it can be seen that, for the spacing distance dr of the elements 1 to 9 of the present example, the threshold current density Jth tends to decrease monotonically with respect to the spacing distance dr.

[0134] In addition, for example, according to non-patent document 1, the diffraction position of the diffraction wave generated by the photonic crystal layer 14P, that is, the position of the wave source WS (or the diffraction surface), and the radiation wave that is diffracted and radiated in the vertical direction of the photonic crystal layer 14P can be calculated using the coupled wave theory. Therefore, the separation distance dr between the wave source WS and the reflection surface SR can be calculated using the position of the wave source WS.

[0135] (b) Resonator loss in the vertical direction

[0136] Assuming that the resonator loss in the direction perpendicular to the photonic crystal layer 14P is αv, the resonator loss in the horizontal direction is αp, the absorption loss caused by the material is αi, the gain of the active layer is g, and the proportion of the electromagnetic field distribution existing in the active layer is Γ act In the case of , the gain condition of oscillation in the photonic crystal surface emitting laser is expressed by the following equation (1).

[0137] In addition, below, the resonator loss αv in the vertical direction, the resonator loss αp in the horizontal direction, and the absorption loss αi due to the material are also represented as follows.

[0138] [Mathematical formula 1]

[0139] α⊥ , α / / , α i

[0140] [Mathematical formula 2]

[0141] Γ act g=α ⊥ +α / / +α i (1) In the structure of the above-mentioned PCSEL element 10 (Ex. 1 to 9), the ratios (optical confinement rates) of the electromagnetic field distribution existing in the active layer and the photonic crystal layer in the electromagnetic field distribution of the fundamental mode are Γ act , Γ PC When Γ is set relative to the thickness of the p-cladding layer 18 (first p-cladding layer) act , Γ PC Shown in Figure 8 .

[0142] When the thickness of the p-cladding layer 18 is 300 nm or more, Γ act , Γ PC It does not depend on the thickness of the p-cladding layer 18. That is, in the elements Ex. 1 to 9, the left side of the equation (1) does not change.

[0143] In addition, the photonic crystal layer 14P of the same structure is used in the elements Ex.1 to 9. If Γ PC If there is no change, the same resonance effect of the photonic crystal layer can be obtained in each element. In other words, the resonator loss αp in the horizontal direction becomes the same value in each element.

[0144] In addition, the main material absorption in the resonance wavelength occurs in the Mg-doped layer, the InGaN layer in the contact layer, and the ITO layer. Assume that the absorption coefficients in each layer are 100, 50,000, and 2,600 cm-1, respectively. -1 When the ratio of the electromagnetic field distribution in each layer is multiplied by the ratio of the electromagnetic field distribution in each layer, and the sum of them is taken as the absorption loss αi, the αi relative to the thickness of the p-cladding layer 18 is shown in Fig. 9 .

[0145] like Fig. 9 As shown in FIG. 1 , when the thickness of the p-cladding layer 18 is 300 nm or more, αi does not depend on the thickness of the p-cladding layer 18. Therefore, it can be said that the change in the threshold current density Jth with respect to the spacing distance dr ( Figure 7 ) is due to the change in the resonator loss αv in the vertical direction in equation (1).

[0146] (c) Threshold current density

[0147] The resonant light propagating in the photonic crystal layer 14P is diffracted by the photonic crystal in a direction perpendicular to the photonic crystal layer 14P. At this time, it can be considered that the resonant light is diffracted at the position of the wave source WS existing in the photonic crystal layer 14P.

[0148] The position of the wave source WS in the photonic crystal layer 14P in the embodiment can be estimated by the method described in Non-Patent Document 1. That is, the wave source WS is estimated to be located 7 nm closer to the active layer 15 from the center of the photonic crystal layer 14P.

[0149] The electric field amplitude and energy intensity of the light diffracted in the vertical direction by the wave source WS in the photonic crystal layer 14P, that is, the direct diffraction light Ld diffracted and directly emitted toward the back side (emitting surface) 12R (-z direction) of the substrate 12, and the reflected diffraction light Lr diffracted in the +z direction and reflected by the reflecting surface SR and emitted are respectively expressed by the following formulas.

[0150] [Mathematical formula 3]

[0151] E0e ikz ,|E0e ikz | 2

[0152] If diffraction occurs equally in the +z direction and the -z direction, the electric field amplitudes of the direct diffracted light Ld and the reflected diffracted light Lr are equal, which is expressed by the following equation.

[0153] [Formula 4]

[0154]

[0155] The electric field amplitude when the light is reflected by the reflection surface SR and returns to the wave source WS is expressed by the following equation.

[0156] [Formula 5]

[0157]

[0158] Wherein, R is the energy reflectivity of the reflecting surface SR, and θ is the phase difference between the direct diffracted light Ld and the reflected diffracted light Lr in the wave source WS.

[0159] Therefore, when the direct diffracted light Ld and the reflected diffracted light Lr interfere at the wave source WS, the electric field amplitude of the light that contributes to the emission is expressed by the following equation (2).

[0160] [Mathematical formula 6]

[0161]

[0162] On the other hand, the electric field amplitude of the light component absorbed by the reflecting surface SR in the reflected and diffracted light Lr is expressed by the following equation.

[0163] [Mathematical formula 7]

[0164]

[0165] Therefore, light diffracted by the wave source WS in the photonic crystal layer 14P and lost by the resonator is expressed by the following equation (3).

[0166] [Mathematical formula 8]

[0167]

[0168] That is, if the interference between the direct diffracted light Ld and the reflected diffracted light Lr affects the resonator loss, the loss αv in the vertical direction is (1+R 1 / 2 cosθ) times.

[0169] At this time, the gain condition of oscillation is expressed by the following equation (4).

[0170] [Mathematical formula 9]

[0171]

[0172] When the thickness of the active layer 15 is as thin as several nm, the threshold current and the threshold gain are approximately proportional to each other. Therefore, using the proportionality constant A, the threshold current density Jth can be expressed by the following equation (5).

[0173] [Formula 10]

[0174]

[0175] In addition, if

[0176] [Mathematical formula 11]

[0177] α ⊥ , α / / , α i

[0178] It remains constant regardless of the current.

[0179] Then let [Mathematical formula 12]

[0180] B=α ⊥ +α / / +α i

[0181] The threshold current density Jth can be expressed by the following formula (6).

[0182] [Mathematical formula 13]

[0183]

[0184] Fig.101 to 9, which is a graph showing the threshold current density Jth with respect to the phase difference θ between the direct diffracted light Ld and the reflected diffracted light Lr, obtained based on the separation distance dr from the wave source WS to the reflecting surface SR for the PCSEL element 10 (Ex. 1 to 9).

[0185] When the wave number of the emitted light is k and the optical path length is x, the phase difference θ can be expressed by the following equation (7).

[0186] [Formula 14]

[0187]

[0188] also, Fig.10 Calculated values ​​(dashed line) of the threshold current density Jth obtained by equation (6) when A=0.75, B=2.63, and R=0.85 are shown in FIG. 1 , and the results are very consistent with the calculated values.

[0189] That is, by adjusting the distance dr between the wave source WS and the reflection surface SR, the loss αv of the propagating light caused by the photonic crystal layer 14P can be reduced.

[0190] Therefore, it is possible to reduce the loss caused by diffraction of light propagating in the vertical direction from the photonic crystal layer 14P and reduce the threshold current density. In other words, it is possible to provide a two-dimensional photonic crystal surface emitting laser that can be driven with a low current.

[0191] (d) Loss in the vertical direction (a unique feature of PCSEL)

[0192] The fact that interference of diffracted light emitted in a direction perpendicular to the photonic crystal layer can be utilized is a unique feature of photonic crystal lasers. This feature will be described below.

[0193] In a general end laser or vertical cavity surface emitting laser (VCSEL), it is difficult to control the loss of the resonator outside the resonator, that is, by using light emitted from the resonator by diffraction.

[0194] On the other hand, in a two-dimensional photonic crystal surface emitting laser, the resonance effect is obtained by utilizing the effect that the group velocity at the Γ point of the two-dimensional photonic crystal is 0. That is, the resonator of the two-dimensional photonic crystal surface emitting laser is a two-dimensional photonic crystal layer. Therefore, the light diffracted to the outside of the resonator by the photonic crystal must be diffracted in a direction perpendicular to the photonic crystal layer.

[0195] Therefore, by configuring a reflection plane parallel to the photonic crystal layer, the optical path length of the light diffracted by the resonator can be uniquely determined. That is, the loss of the resonator can be controlled by utilizing the diffracted light from the resonator, so that the gain required for oscillation can be reduced. In other words, low current driving is possible.

[0196] (e) Range of separation distance dr

[0197] As described above, it is shown that by controlling the interference between the direct diffracted light Ld and the reflected diffracted light Lr by the distance dr between the wave source WS and the reflecting surface SR, it is possible to control the loss caused by diffraction in the direction perpendicular to the photonic crystal layer 14P.

[0198] In order to reduce the threshold current density compared to the case where there is no reflection by the reflection surface SR, the spacing distance dr may be determined so that the right side of the equation (4) is smaller than the right side of the equation (1).

[0199] That is, it only needs to satisfy the following formula (8).

[0200] [Mathematical formula 15]

[0201]

[0202] For the separation distance dr, according to formula (7), when the phase difference is θ, the wavelength of the diffracted light is λ, and the average refractive index of the crystal layer from the wave source WS (diffraction surface) to the reflection surface SR is n ave When m is an integer greater than 0, it can be represented by the following formula (9).

[0203] [Formula 16]

[0204]

[0205] Therefore, according to equation (8), if the phase difference θ satisfies the following equation (10), the loss caused by diffraction in the vertical direction can be reduced compared to the case where there is no interference between the direct diffracted light Ld and the reflected diffracted light Lr.

[0206] [Mathematical formula 17]

[0207] cosθ<0 (10)

[0208] That is, under this condition, the light intensity of the interference light of the direct diffracted light Ld and the reflected diffracted light Lr is smaller than the light intensity of the direct diffracted light Ld.

[0209] In other words, this means that the outgoing light is weakened by the interference between the direct diffracted light Ld and the reflected diffracted light Lr, and the radiation loss (loss in the vertical direction) αv becomes smaller.

[0210] In addition, in order to prevent interference (mutual weakening) within the photonic crystal layer 14P, the photonic crystal layer 14P preferably has a thickness (d PC ).

[0211] Therefore, a two-dimensional photonic crystal surface emitting laser capable of low-current driving can be obtained.

[0212] (f) p-cladding layer thickness

[0213] The interference between the direct diffracted light Ld and the reflected diffracted light Lr is determined by the separation distance dr between the wave source WS and the reflecting surface SR.

[0214] As described above, the PCSEL elements 10 (Ex. 1 to 9) have the same structure such as composition and thickness except for the thickness of the p-cladding layer 18 (first p-cladding layer). Therefore, the conditions for the thickness of the p-cladding layer 18 will be studied below.

[0215] Specifically, the thickness of the p-cladding layer 18 may be such that the distance dr from the wave source WS to the reflection surface SR shown in the equation (9) satisfies the equation (10).

[0216] However, refer to Fig. 9 It is known that when the thickness of the p-cladding layer 18 is about 150 nm or less, the loss αi due to material absorption increases. This is because the thinning of the p-cladding layer 18 weakens the confinement of the core layer (active layer and guide layer) on the electromagnetic field distribution of the fundamental mode.

[0217] That is, the fundamental mode is distributed more in the doped layer, the contact (InGaN) layer and the light-transmitting electrode layer (ITO), and the light absorption becomes larger. That is, the thickness of the p-cladding layer 18 is preferably 150 nm or more.

[0218] (g) Reflectivity of the reflecting surface SR

[0219] According to equation (4), the effective loss in the direction perpendicular to the photonic crystal layer 14P is (1+R 1 / 2 cosθ)αv, whose magnitude varies according to the reflectivity R of the reflecting surface SR. When the phase difference θ between the direct diffracted light Ld and the reflected diffracted light Lr is 180°, the change of the loss α' in the vertical direction normalized to the value of R=0 with respect to the reflectivity R is shown in Fig.11 .from Fig.11 It can be seen that the loss α′ changes more sharply when the reflectivity R is lower, and can be greatly reduced according to the reflectivity R.

[0220] Fig.12 The differential of the loss α' with respect to the reflectivity R (i.e., dα' / dR) is shown. When the reflectivity R changes from 0 to about 0.05, dα' / dR decreases significantly. Therefore, if the reflectivity R is greater than 0.05, the effective loss in the vertical direction in the photonic crystal layer 14P can be greatly reduced. That is, the reflectivity R is preferably greater than 0.05.

[0221] In addition, according to Fig.12When the reflectivity R is greater than 0.6, dα' / dR no longer changes relative to R. Thus, by making the reflectivity R greater than 0.6, the effective loss in the vertical direction in the photonic crystal layer can be kept low. That is, the reflectivity R is more preferably greater than 0.6.

[0222] (h) Photonic crystal layer with double lattice structure

[0223] Fig.13 14K1 is a cross-sectional view schematically showing the arrangement cross section of the main pore 14K1 and the auxiliary pore 14K2 in the depth direction of the dual lattice structure. The main pore 14K1 and the auxiliary pore 14K2 have different pore heights. That is, the height of the main pore 14K1 is h K1 , which is equal to the thickness of the photonic crystal layer 14P (h K1 =d PC ). In addition, the height of the auxiliary air hole 14K2 is h K2 .

[0224] More specifically, the lower end of the main air hole 14K1 is deeper than the lower end of the auxiliary air hole 14K2, that is, located in the -z direction. The difference between the lower ends of the main air hole 14K1 and the auxiliary air hole 14K2 is h DOWN In addition, the upper end of the secondary air hole 14K2 is deeper than the upper end of the main air hole 14K1, and the difference is h UP .

[0225] Among them, the difference between the upper and lower ends h UP Difference from lower end h DOWN The center C of the secondary air hole 14K2 in the depth direction (-z direction) is small. PC (=C K2 ) is located at the center C of the main pore 14K1 K1 Closer to the active layer 15 side.

[0226] In the nitride-based PCSEL element, holes of different sizes are simultaneously formed by dry etching or the like. When the holes are embedded to form the main pore 14K1 and the auxiliary pore 14K2, the main pore 14K1 and the auxiliary pore 14K2 are formed in a hexagonal prism structure whose side faces are m-planes. Therefore, no matter at which z-direction position of the photonic crystal layer 14P, the size relationship between the main pore 14K1 and the auxiliary pore 14K2 is the same as the size relationship of the holes before embedding.

[0227] Then, in the photonic crystal layer 14P of the nitride-based PCSEL element, the lower end of the main pore 14K1 having a large pore filling rate FF is located closer to the lower end side of the photonic crystal layer 14P than the sub-pore 14K2, that is, the main pore 14K1 is deeper than the sub-pore 14K2. In addition, due to the embedded growth, the upper end of the sub-pore 14K2 is formed deeper than the upper end of the main pore 14K1.

[0228] Furthermore, when the active layer 15 is formed after the photonic crystal layer 14P is formed, that is, when the photonic crystal layer 14P is provided on the -z direction side of the active layer 15, the relationship FF1>FF2 is necessarily satisfied. That is, in the nitride-based PCSEL element, even in the case of a double lattice structure, the wave source (diffraction plane) WS is necessarily present at a position 1000 m from the center C in the z direction of the photonic crystal layer 14P. PC (ie, the center of the main pore 14K1) is separated from the active layer 15 by, for example, about 0 to 10 nm.

[0229] Therefore, there is a region (h UP and h DOWN ), and the area where both the main pore 14K1 and the auxiliary pore 14K2 exist (h K2 ), but the propagation light component diffracted in the vertical direction is larger in the area where both the main air hole 14K1 and the auxiliary air hole 14K2 exist. Therefore, the wave source (diffraction surface) WS also exists at a position larger than the center C of the photonic crystal layer 14P. PC The position is more biased toward the +z direction (active layer 15 side).

[0230] In addition, the above description is about a pore having a hexagonal prism shape and a constant cross-sectional area in the depth direction. In the case where either the main pore 14K1 or the sub-pore 14K2 has a shape in which the cross-sectional area changes in the depth direction, it is preferred that the center of gravity of the sub-pore 14K2 is located closer to the active layer 15 than the center of gravity of the main pore 14K1.

[0231] As described above in detail, according to the present invention, it is possible to provide a photonic crystal surface emitting laser element capable of reducing emission loss, lowering oscillation threshold current, and reducing drive current.

[0232] The numerical values ​​in the above embodiments are merely examples and can be appropriately changed for application. In addition, although a dual-lattice PCSEL element is exemplified, the present invention can also be applied to a single-lattice PCSEL element and a general poly-lattice PCSEL element.

[0233] Furthermore, the present invention exemplifies a photonic crystal layer in which pores have a hexagonal prism shape, but the present invention can also be applied to a case in which the pores of the photonic crystal layer have an irregular column shape such as a cylindrical shape, a rectangular shape, a polygonal shape, or a teardrop shape.

[0234] Explanation of symbols

[0235] 10: PCSEL components;

[0236] 12: Substrate;

[0237] 13: first cladding;

[0238] 14: first guide layer;

[0239] 14A: lower guide layer;

[0240] 14B: embedding layer;

[0241] 14K: stoma / stoma pair;

[0242] 14K1 / 14K2: main / secondary air hole;

[0243] 14P: photonic crystal layer (pore layer);

[0244] 15: active layer;

[0245] 16: second guide layer;

[0246] 17; electron blocking layer;

[0247] 18: Second cladding;

[0248] 19: contact layer;

[0249] 20A: first electrode;

[0250] 20B: second electrode;

[0251] 20L: light emission area;

[0252] 27: Anti-reflective film;

[0253] 31: light-transmitting conductive layer;

[0254] CD1, CD2: center of gravity;

[0255] dr: separation distance;

[0256] Ld: directly diffracted light;

[0257] Lr: reflected diffracted light;

[0258] SR: Reflective surface.

Claims

1. A surface-emitting laser element, comprising: Light-transmitting substrate; A first semiconductor layer, which is disposed on the substrate; an active layer disposed on the first semiconductor layer; a second semiconductor layer disposed on the active layer; a photonic crystal layer included in the first semiconductor layer and having pores arranged two-dimensionally and periodically in a plane parallel to the active layer; as well as a light reflecting layer, which is disposed on the second semiconductor layer and has a reflecting surface, The back side of the substrate has a light emitting surface, The photonic crystal layer has a diffraction surface, which is a wave source when the light fixed in the photonic crystal layer is diffracted in a direction orthogonal to the photonic crystal layer. The separation distance between the diffraction surface and the reflection surface is set so that the light intensity of interference light generated by the interference between the first diffraction light diffracted from the diffraction surface to the light emitting surface side and the second diffraction light diffracted from the diffraction surface to the light reflecting layer side and reflected by the reflection surface is smaller than the light intensity of the first diffraction light.

2. The surface-emitting laser element according to claim 1, wherein: The diffraction surface is located closer to the active layer than the center of the photonic crystal layer in the depth direction.

3. The surface-emitting laser element according to claim 1, wherein The first semiconductor layer, the active layer and the second semiconductor layer are semiconductor layers of a Group III nitride system, and the first semiconductor layer and the second semiconductor layer are n-type and p-type semiconductor layers, respectively.

4. The surface-emitting laser element according to claim 1, wherein Assuming that the phase difference between the first diffracted light and the second diffracted light is θ, the wavelength of the first diffracted light is λ, and the average refractive index of the crystal layer from the diffraction surface to the reflection surface is n ave , assuming that the separation distance is dr, and assuming that m is an integer greater than 0, the separation distance dr is represented by the following formula: [Mathematical formula 1] The phase difference θ satisfies: [Mathematical formula 2], cosθ<0 (10).

5. The surface-emitting laser element according to claim 1, wherein The second semiconductor layer is a p-type semiconductor layer, and a light-transmitting conductive layer is provided between the reflective surface and the second semiconductor layer.

6. The surface-emitting laser element according to claim 1, wherein: The second semiconductor layer includes a guiding layer and a cladding layer having a refractive index lower than that of the guiding layer, and the thickness of the cladding layer is greater than or equal to 150 nm.

7. The surface-emitting laser element according to claim 1, wherein: The reflectivity of the reflecting surface to the second diffracted light is greater than or equal to 0.

05.

8. The surface-emitting laser element according to claim 1, wherein: The reflectivity of the reflecting surface to the second diffracted light is greater than or equal to 0.

6.

9. The surface-emitting laser element according to claim 1, wherein The reflection surface is parallel to the photonic crystal layer.

10. The surface-emitting laser element according to claim 1, wherein The photonic crystal layer has a thickness such that an optical path length of the photonic crystal layer is less than 1 wavelength.

11. The surface-emitting laser element according to any one of claims 1 to 10, wherein The photonic crystal layer has a double lattice structure, in which main pores and secondary pores with smaller pore diameters and heights than the main pores are arranged at lattice points, and the center of gravity of the secondary pores in the depth direction is closer to the active layer side than the center of gravity of the main pores.

Images