Photonic crystal surface emitting laser and manufacturing method thereof

Abstract

A photonic crystal surface emitting laser is provided with: an active layer; a photonic crystal layer; and a first semiconductor layer, the photonic crystal layer having a base material and a plurality of holes periodically arranged in the base material, the holes extending from one surface of the photonic crystal layer to an opposing surface of the photonic crystal layer, the first semiconductor layer being provided on the one surface of the photonic crystal layer, the first semiconductor layer being provided on the other surface of the photonic crystal layer, and the second semiconductor layer being provided on the other surface of the photonic crystal layer. The length of the hole in the < 110 > direction of the photonic crystal layer is smaller than the length of the hole in the < 1-10 > direction of the photonic crystal layer.

Description

Technical Field

[0001] The present disclosure relates to a photonic crystal surface emitting laser and a method for manufacturing the same. The present disclosure claims priority based on Japanese application No. 2022-121596 filed on July 29, 2022, and all the contents described in the Japanese application are cited. Background Art

[0002] Photonic crystal surface emitting lasers (PCSEL: Photonic-crystal Surface Emitting Laser) are being used (Patent Documents 1 to 3, etc.) which are made by stacking photonic crystals and active layers with optical gain. Photonic crystals contain a periodic structure with a refractive index different from that of the base material. By diffracting light within the plane of the photonic crystal, the light oscillates at a wavelength based on the period and is emitted in the normal direction of the surface. The resonator extends within the plane, so compared with the end-emitting laser, PCSEL is superior in single-mode operation and high output.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-180120

[0006] Patent Document 2: Japanese Patent Application Publication No. 2008-243962

[0007] Patent Document 3: International Publication No. 2017 / 150387 Summary of the invention

[0008] The photonic crystal surface emitting laser involved in the present disclosure comprises: an active layer; a photonic crystal layer; and a first semiconductor layer, wherein the photonic crystal layer has a base material and a plurality of holes periodically arranged in the base material, wherein the holes extend from one surface of the photonic crystal layer to an opposite surface of the photonic crystal layer, and the first semiconductor layer is arranged on the one surface of the photonic crystal layer. <110> The length of the holes in the <1-10> direction is smaller than the length of the holes in the <1-10> direction of the photonic crystal layer.

[0009] The method for manufacturing a photonic crystal surface emitting laser disclosed in the present invention comprises: a step of forming a plurality of vacancies, wherein the plurality of vacancies are periodically arranged in a base material of a photonic crystal layer and extend from one surface of the photonic crystal layer to an opposite surface; a step of forming a first semiconductor layer on the one surface of the photonic crystal layer; and a step of forming an active layer, wherein the photonic crystal layer <110> The length of the holes in the <1-10> direction is smaller than the length of the holes in the <1-10> direction of the photonic crystal layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 FIG. 1 is a cross-sectional view showing an example of the photonic crystal surface emitting laser according to the first embodiment.

[0011] Figure 2A FIG. 1 is a top view showing an example of a photonic crystal surface emitting laser.

[0012] Figure 2B FIG. 1 is a bottom view showing an example of a photonic crystal surface emitting laser.

[0013] Figure 3 This is an enlarged cross-sectional view of a photonic crystal surface emitting laser.

[0014] Figure 4A is a top view of the photonic crystal layer.

[0015] Figure 4B This is an enlarged view of the photonic crystal layer.

[0016] Figure 5A This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0017] Figure 5B This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0018] Fig. 6A This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0019] Figure 6B This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0020] Fig. 7A This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0021] Figure 7B This is a cross-sectional view illustrating an example of a method for manufacturing a photonic crystal surface emitting laser.

[0022] Fig. 8A FIG. 1 is a plan view showing a photonic crystal surface emitting laser according to Comparative Example 1 as an example.

[0023] Figure 8B FIG. 1 is a plan view showing a photonic crystal surface emitting laser according to Comparative Example 2. FIG.

[0024] Fig. 9 FIG. 1 is a cross-sectional view showing a photonic crystal surface emitting laser according to a modified example.

[0025] Fig.10FIG. 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a second embodiment.

[0026] Fig.11 FIG. 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a third embodiment.

[0027] Fig.12 FIG. 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a fourth embodiment.

[0028] Fig.13 FIG. 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a fifth embodiment.

[0029] Fig.14 FIG. 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a sixth embodiment. DETAILED DESCRIPTION

[0030] [Problems to be Solved by the Present Disclosure]

[0031] Holes are provided in the mother material of the photonic crystal layer. The refractive index of the holes is different from that of the mother material, so that diffraction of light can be achieved. However, dislocations are generated in the semiconductor layer provided on the photonic crystal layer having the holes. Due to the dislocations, the crystallinity of the semiconductor layer is reduced, and the characteristics of the PCSEL are degraded. Therefore, the purpose is to provide a photonic crystal surface emitting laser and a method for manufacturing the same that can suppress dislocations in the semiconductor layer.

[0032] [Effects of the present disclosure]

[0033] According to the present disclosure, it is possible to provide a photonic crystal surface emitting laser capable of suppressing degradation of characteristics and a method for manufacturing the same.

[0034] [Description of Embodiments of the Present Disclosure]

[0035] First, the contents of the embodiments of the present disclosure are listed and described.

[0036] One method disclosed herein is (1) a photonic crystal surface emitting laser, the photonic crystal surface emitting laser comprising: an active layer; a photonic crystal layer; and a first semiconductor layer, the photonic crystal layer having a base material and a plurality of holes periodically arranged in the base material, the holes extending from one surface of the photonic crystal layer to an opposite surface of the photonic crystal layer, the first semiconductor layer being arranged on the one surface of the photonic crystal layer, <110> The length of the vacant hole in the <1-10> direction of the photonic crystal layer is smaller than the length of the vacant hole in the <1-10> direction of the photonic crystal layer. <110> The growth rate in the <1-10> direction is higher than that in the <1-10> direction. <110> The direction grows rapidly, and the holes are closed rapidly. By closing the holes, dislocations are suppressed, and the degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0037] (2) In the above (1), the planar shape of the hole may have a first symmetry axis and a second symmetry axis, the length of the hole in the direction of the first symmetry axis is smaller than the length of the hole in the direction of the second symmetry axis, and the first symmetry axis is parallel to the photonic crystal layer. <110> The angle between the first axis of symmetry and <110> The angle between the directions is 30°, so <110> The first semiconductor layer is along the <110> The holes are quickly closed, so dislocations are suppressed and degradation of the properties of the photonic crystal surface emitting laser is suppressed.

[0038] (3) In the above (1) or (2), the first symmetry axis and the <110> Direction parallel. <110> The first semiconductor layer is along the <110> The holes are quickly closed, so dislocations are suppressed and degradation of the properties of the photonic crystal surface emitting laser is suppressed.

[0039] (4) In any one of the above (1) to (3), the planar shape of the hole may be an ellipse, and the short axis of the hole may be elliptical. <110> Parallel. <110> The first semiconductor layer is along the <110> The holes are quickly closed, so dislocations are suppressed and degradation of the properties of the photonic crystal surface emitting laser is suppressed.

[0040] (5) Based on any one of the above (1) to (4), the photonic crystal layer, the first semiconductor layer, and the photonic crystal layer may be stacked in sequence. The holes are closed by the first semiconductor layer. The first semiconductor layer can be made thinner and the active layer can be made closer to the photonic crystal layer. The light is combined more strongly between the active layer and the photonic crystal layer. The light is diffracted, and it is easy to perform laser oscillation at a desired wavelength.

[0041] (6) In any one of (1) to (4) above, the active layer, the photonic crystal layer, and the first semiconductor layer may be stacked in this order. Deterioration of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0042] (7) In any one of (1) to (6) above, the plurality of holes may be arranged in a square lattice in the plane of the photonic crystal layer, and the ratio of the holes to the area of ​​the square lattice may be greater than 3% and less than 30%. Deterioration of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0043] (8) Based on any one of the above (1) to (7), the photonic crystal layer may have a plurality of first cavities and a plurality of second cavities, the plurality of first cavities and the plurality of second cavities are periodically arranged in the base material, and in at least one of the first cavities and the second cavities, the photonic crystal layer <110> The length of the first semiconductor layer along the <1-10> direction is smaller than the length of the photonic crystal layer along the <1-10> direction. <110> At least one of the first hole and the second hole is quickly closed, so dislocation is suppressed and degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0044] (9) In any one of the above (1) to (8), the photonic crystal layer may include InGaAsP or AlInGaAs, and the first semiconductor layer may include InP. Holes are provided in InGaAsP. The first semiconductor layer of InP is provided along <110> The photonic crystal grows rapidly in the direction of the photon and the holes are closed, and the degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0045] (10) A method for manufacturing a photonic crystal surface emitting laser, the method comprising: a step of forming a plurality of vacancies, wherein the plurality of vacancies are periodically arranged in a base material of a photonic crystal layer and extend from one surface of the photonic crystal layer to an opposite surface; a step of forming a first semiconductor layer on the one surface of the photonic crystal layer; and a step of forming an active layer, wherein the photonic crystal layer <110> The length of the vacant hole in the <1-10> direction of the photonic crystal layer is smaller than the length of the vacant hole in the <1-10> direction of the photonic crystal layer. <110> The growth rate in the <1-10> direction is higher than that in the <1-10> direction. <110> The direction grows rapidly, and the holes are closed rapidly. By closing the holes, dislocations are suppressed, and the degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0046] [Details of the embodiments of the present disclosure]

[0047] Hereinafter, specific examples of the photonic crystal surface emitting laser and its manufacturing method according to the embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, the present disclosure is not limited to these examples, but is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0048] <First Embodiment>

[0049] (Photonic Crystal Surface Emitting Laser)

[0050] Figure 1 FIG. 1 is a cross-sectional view showing an example of a photonic crystal surface emitting laser 100 according to the first embodiment. Figure 2A FIG. 1 is a top view showing an example of a photonic crystal surface emitting laser 100. Figure 2B It is a bottom view.

[0051] like Figure 1 As shown, a photonic crystal surface emitting laser (PCSEL) 100 includes a substrate 10 , a cladding layer 12 , a photonic crystal layer 14 , a cladding layer 16 (first semiconductor layer), an active layer 18 , a cladding layer 20 , and a contact layer 22 .

[0052] The semiconductor layers are stacked along the Z axis. On the substrate 10, the cladding layer 12, the photonic crystal layer 14, the cladding layer 16, the active layer 18, the cladding layer 20, and the contact layer 22 are stacked in this order. The surface of each layer extends parallel to the XY plane. The X axis, the Y axis, and the Z axis are orthogonal to each other.

[0053] The contact layer 22 and the cladding layer 20 are provided with a groove 23. The groove 23 extends from the upper surface of the contact layer 22 to the middle of the cladding layer 20. The bottom surface of the groove 23 is recessed than the upper surface of the contact layer 22 and the upper surface of the cladding layer 20. Figure 2A As shown, the planar shape of the groove 23 is, for example, a circular ring.

[0054] like Figure 1 As shown in FIG. 2 , an insulating film 24 is provided on the upper surface of the contact layer 22. The insulating film 24 covers the upper surface of the contact layer 22 and is also provided inside the groove 23. The insulating film 24 is formed of an insulator such as silicon nitride (SiN) or silicon dioxide (SiO2). The insulating film 24 has an opening 24a and an opening 24b. The contact layer 22 is exposed from the opening 24a and the opening 24b. Figure 2A As shown, the planar shape of the opening 24a is, for example, a ring. The opening 24a is located outside the groove 23. The planar shape of the opening 24b is, for example, a circle. The opening 24b is located inside the groove 23.

[0055] like Figure 1As shown in FIG. 2 , an electrode 26 is provided on the insulating film 24. The electrode 26 is a P-type electrode, and can be formed of, for example, titanium (Ti), platinum (Pt), gold (Au), or other metals. The electrode 26 is provided on the entire upper surface of the insulating film 24, and contacts the upper surface of the contact layer 22 inside the opening 24a. That is, the electrode 26 is electrically connected to the contact layer 22. Figure 1 and Figure 2A As shown, the end portion (outer periphery) of the electrode 26 is provided at the same position as the end portion of the opening 24a.

[0056] An electrode 28 is provided on the surface of the substrate 10 opposite to the surface on which the cladding layer 12 is provided. The electrode 28 is an n-type electrode and can be formed of, for example, gold (Au), germanium (Ge), nickel (Ni), or other metals. The electrode 28 has an opening 28a at the center in the XY plane. Figure 2B As shown, the planar shape of the opening 28a is, for example, circular. The substrate 10 is exposed from the opening 28a. The opening 28a functions as a portion (aperture) for emitting light.

[0057] The substrate 10, the cladding layer 12 and the cladding layer 16 are formed of, for example, n-type indium phosphide (n-InP). The n-type dopant is, for example, silicon (Si). The thickness of the cladding layer 12 is, for example, 500 nm. The thickness of the cladding layer 16 is, for example, 100 nm.

[0058] The cladding layer 20 is formed of, for example, p-type indium phosphide (p-InP). The contact layer 22 is formed of, for example, p-type indium gallium arsenide (p-InGaAs). The p-type dopant is, for example, zinc (Zn). The thickness of the cladding layer 20 is, for example, 3 μm. The thickness of the contact layer 22 is, for example, 300 nm.

[0059] The photonic crystal layer 14 is formed of, for example, n-type indium gallium arsenide phosphide (InGaAsP) or aluminum indium gallium arsenide (AlInGaAs). The thickness of the photonic crystal layer 14 is, for example, 300 nm.

[0060] The active layer 18 includes a plurality of well layers and barrier layers, and has a multi-quantum well structure (MQW: Multi Quantum Well). The well layers and barrier layers are formed, for example, of undoped indium gallium arsenic phosphide (InGaAsP) or aluminum gallium indium arsenide (AlGaInAs). The above materials are examples, and each layer can be formed of other materials, or a combination of the above materials and other materials.

[0061] The refractive index of active layer 18 is, for example, 3.5. The refractive index of cladding layer 12, cladding layer 16 and cladding layer 20 is, for example, 3.2. The refractive index of InGaAsP, the base material of photonic crystal layer 14, is higher than that of cladding layer 12, cladding layer 16 and cladding layer 20, and is, for example, 3.4.

[0062] Figure 3 1 is an enlarged cross-sectional view of the photonic crystal surface emitting laser 100, showing the cladding layer 12 to the cladding layer 20. Figure 3 As shown, the photonic crystal layer 14 has a plurality of cavities 30. The cavities 30 extend from the surface of the photonic crystal layer 14 on which the cladding layer 16 is provided (in Figure 3 The upper surface in the figure) faces the opposite surface of the photonic crystal layer 14 (in Figure 3 The hole 30 extends from the bottom surface (in the middle) to, for example, the middle of the photonic crystal layer 14. The inside of the hole 30 is air. The refractive index of the hole 30 is different from the refractive index of the base material of the photonic crystal layer 14.

[0063] Figure 4A and Figure 4B is a top view of the photonic crystal layer 14 . Figure 4A A plane containing a plurality of holes is shown. Figure 4B An empty hole is shown. Figure 4A and Figure 4B In the photonic crystal layer 14, <110> Direction is upward. <1-10> Direction is right. <100> Direction relative to <110> direction and <1-10> direction are tilted 45°.

[0064] like Figure 4A As shown, a plurality of holes 30 are periodically arranged on the upper surface of the photonic crystal layer 14. The plurality of holes 30 are arranged in a square lattice. Figure 4A The square grid is shown by dashed lines. The sides of the square grid are relative to <110> direction and <1-10> direction tilted 45°, towards <100> Direction. The holes 30 and the square grid are along <100> The number of the holes 30 is, for example, several tens or several hundreds.

[0065] The distance (period) a between the centers of adjacent holes 30 is equal to the length of a side of a square grid. The distance a is determined by the oscillation wavelength. For example, when the oscillation wavelength is 1300 nm, the distance a is about 400 nm.

[0066] like Figure 4B As shown, the hole 30 is elliptical and has a short axis 32 (first symmetry axis) and a long axis 34 (second symmetry axis). The hole 30 is linearly symmetrical with respect to the short axis 32 and linearly symmetrical with respect to the long axis 34. <110> The major axis 34 is parallel to the <1-10> direction. The minor axis 32 and the major axis 34 are parallel to the <1-10> direction. <100> The direction is tilted 45°.

[0067] The length L1 of the minor axis 32 is smaller than the length L2 of the major axis 34. The length L1 of the minor axis 32 is, for example, 60 nm to 150 nm, for example, 120 nm. The length L2 of the major axis 34 is, for example, 100 nm to 355 nm, for example, 280 nm.

[0068] The area of ​​a hole 30 is equal to the area a of a square grid. 2 The occupied ratio (area filling rate) is, for example, 3% or more and 30% or less.

[0069] Voltage is applied to the photonic crystal surface emitting laser 100 from the electrodes 26 and 28. The active layer 18 has optical gain and generates light by injecting carriers. The photonic crystal layer 14 has a plurality of holes 30 arranged periodically, so the refractive index also changes periodically. Light is Bragg diffracted within the plane of the photonic crystal layer 14. Light having a wavelength corresponding to the period of the holes 30 is amplified and performs laser oscillation. The laser is emitted in the normal direction (Z-axis direction) of the photonic crystal layer 14. In Figure 1 In the example of FIG. 2 , the lower surface of the electrode 26 is mirror-finished to reflect light. The opening 28a of the electrode 28 serves as a light emission portion (aperture), and light is emitted from the aperture.

[0070] (Manufacturing method)

[0071] FIG. 5A to FIG. 7B 1 is a cross-sectional view showing an example of a method for manufacturing the photonic crystal surface emitting laser 100. Figure 5A As shown, for example, by metal organic chemical vapor deposition (MOCVD), the cladding layer 12 and the photonic crystal layer 14 are epitaxially grown in this order on the substrate 10. In this process, the base material (InGaAsP) of the photonic crystal layer 14 is formed, but the vacancy 30 is not formed.

[0072] FIG. 5B to FIG. 6B Yes Figure 3 Such an enlarged picture. Figure 5B As shown, a mask 31 is provided on the upper surface of the photonic crystal layer 14. The mask 31 is formed of an insulator such as SiN. An insulating film is formed on the upper surface of the photonic crystal layer 14. An anti-etching pattern is formed by an electron beam or the like, and the anti-etching pattern is transferred to the insulating film, thereby forming the mask 31. The mask 31 has a plurality of openings 31a. The upper surface of the photonic crystal layer 14 is exposed from the openings 31a. The planar shape of the openings 31a is an ellipse corresponding to the vacant hole 30. The short axis of the openings 31a is oriented toward <110> Direction. The major axis is oriented in the <1-10> direction.

[0073] like Fig. 6AAs shown, a plurality of holes 30 are formed in the photonic crystal layer 14 by reactive ion etching (RIE) or the like. The etching is performed, for example, halfway through the photonic crystal layer 14 and does not proceed to the bottom surface of the photonic crystal layer 14. The holes 30 are elliptical in shape corresponding to the opening 31a (see Figure 4A and Figure 4B ). After etching is completed, the mask 31 is removed.

[0074] like Figure 6B As shown, cladding layer 16, active layer 18, cladding layer 20, and contact layer 22 are epitaxially grown on photonic crystal layer 14. Holes 30 are closed by cladding layer 16. The inside of holes 30 is not filled with cladding layer 16 and becomes a hollow.

[0075] <110> The growth rate of the coating layer 16 in the direction <100> The growth rate in the direction and the growth rate in the <1-10> direction are large. Figure 4B As shown, the short axis 32 of the hole 30 is <110> The cladding layer 16 grows rapidly along the direction of the short axis 32 of the pore 30. <110> The cladding layer 16 grown in the direction closes the upper side of the void 30. On the cladding layer 16, the active layer 18, the cladding layer 20, and the contact layer 22 are grown.

[0076] like Fig. 7A As shown in FIG. 1 , the insulating film 24 is formed by, for example, a plasma CVD method. The groove 23 is provided in the insulating film 24 by resist patterning (resist pattern not shown) and etching.

[0077] like Figure 7B As shown, an electrode 26 is provided on the contact layer 22 by vacuum deposition and lift-off, for example. An electrode 28 is provided on the lower surface of the substrate 10. The photonic crystal surface emitting laser 100 is formed through the above steps.

[0078] Fig. 8A FIG. 1 is a top view showing the photonic crystal surface emitting laser according to Comparative Example 1, and shows a portion of the photonic crystal layer 14 including one hole 30R1. Fig. 8A As shown, the major axis 34 of the hole 30R1 is oriented toward <100> In other words, the hole 30R1 is oriented from Figure 3 The hole 30 of B is rotated 45° to the left. Figure 4A and Figure 4B Similarly to the example, assume that one side of the pore 30 is arranged in a 400 nm square grid. <110> The length L3 in the direction is 170nm, which is Figure 4B The length L1 of the minor axis 32 of the hole 30 in the cavity is large.

[0079] Figure 8BFIG. 1 is a top view showing a photonic crystal surface emitting laser according to Comparative Example 2, and shows a portion of the photonic crystal layer 14 including one hole 30R2. Figure 8B As shown, the major axis 34 of the hole 30R1 is oriented toward <110> In other words, the hole 30R2 is oriented from Figure 3 The hole 30 of B is rotated 90° to the left. Figure 4A and Figure 4B Similarly to the example, assume that one side of the pore 30 is arranged in a 400 nm square grid. <110> The length L4 in the direction is equal to the length of the major axis 34, for example, 280 nm. Figure 4B The length L1 of the minor axis 32 of the hole 30 in the cavity is large.

[0080] The crystal growth of the semiconductor layer on the vacancy proceeds from the edge of the vacancy toward the upper part of the vacancy to block the vacancy. In III-V semiconductors such as InP-based semiconductors and GaAs-based semiconductors, the growth rate along the <1-10> direction is low due to the relationship of the atomic structure, and the growth rate along the <1-10> direction is high. <110> The direction has a high growth rate. When a GaAs-based semiconductor layer is crystal-grown on a hole having a shape of a major axis and a minor axis, if there is a difference in the growth rate of the major axis and the minor axis, crystal defects (dislocations) are easily generated. When a GaAs-based semiconductor is crystal-grown on the hole 30R1, the difference between the growth rate relative to the major axis and the growth rate relative to the minor axis is small. Therefore, it is possible to crystal-grow a cladding layer with fewer dislocations. That is, the hole 30R1 can be closed by a good GaAs-based semiconductor layer with fewer dislocations. However, the inventors have discovered that in semiconductor layers different from the GaAs system, the difference in materials leads to different forms of crystal growth. For example, in InP-based semiconductors, closing the holes in a short time is more conducive to suppressing crystal defects in the cladding layer than reducing the difference in growth rate relative to the major axis and the growth rate relative to the minor axis. For example, the InP cladding layer 16 has a low growth rate along the <1-10> direction and a high growth rate along the <1-10> direction. <110> direction has a high growth rate. Fig. 8A In the example <110> The length L3 in the direction is greater than the length L1 in the example of FIG. 4 . Figure 8B In the example <110> The length L4 in the direction is greater than the length L1. It takes a long time to close the hole. In the experiment using the InP semiconductor, there is a risk of dislocation in the cladding layer 16 on the hole 30R1 and the cladding layer 16 on the hole 30R2. There is a possibility that the characteristics of the photonic crystal surface emitting laser will deteriorate due to the dislocation in the cladding layer 16.

[0081] According to the first embodiment, the photonic crystal layer 14 has a plurality of pores 30. <110> The length L1 in the <1-10> direction is smaller than the length L2 in the <1-10> direction. <110> The growth rate of the coating layer 16 in the direction <100> The growth rate in the direction of <1-10> is high. <110> The photonic crystal surface emitting laser 100 grows rapidly in the same direction, and the vacant holes 30 are quickly closed by the cladding layer 16. By closing the vacant holes 30, it is not easy to generate dislocations in the cladding layer 16. The degradation of the characteristics of the photonic crystal surface emitting laser 100 caused by dislocations is suppressed. By suppressing dislocations, the crystallinity of the cladding layer 16 and the layers above the cladding layer 16 (such as the active layer 18) is improved. The characteristics of the photonic crystal surface emitting laser 100 are improved. For example, the threshold current can be reduced, the output can be increased, etc. The long-term reliability is also improved.

[0082] like Figure 4B As shown, the planar shape of the hole 30 is an ellipse having two symmetry axes (a short axis 32 and a long axis 34). The length L1 of the hole 30 in the direction of the short axis 32 is smaller than the length L2 of the hole 30 in the direction of the long axis 34. <110> The direction in which the growth rate of the cladding layer 16 is high is parallel to the direction of the short axis 32 of the vacant hole 30, so the cladding layer 16 grows rapidly in the direction of the short axis 32 compared to other directions. The vacant hole 30 is quickly closed by the cladding layer 16. Thus, dislocations of semiconductor layers such as the cladding layer 16 can be suppressed. By suppressing dislocations, the characteristics of the photonic crystal surface emitting laser 100 are improved.

[0083] like Figure 1 As shown, the photonic crystal layer 14, the cladding layer 16 and the active layer 18 are stacked in this order. The vacancies 30 of the photonic crystal layer 14 are closed by the cladding layer 16. The active layer 18 grows on the cladding layer 16. The vacancies 30 are quickly closed, so it is not easy to generate dislocations in the cladding layer 16 and the active layer 18 on the photonic crystal layer 14. The surface of the cladding layer 16 is flatter than the surface of the photonic crystal layer 14. The active layer 18 grows on a flat surface and therefore has high crystallinity.

[0084] By rapidly growing the cladding layer 16 and closing the holes 30, the generation of dislocations in the cladding layer 16 can be suppressed. Even if the cladding layer 16 is set to be as thin as, for example, more than 50nm and less than 200nm, the generation of dislocations is suppressed. By making the cladding layer 16 thinner, the distance between the active layer 18 and the photonic crystal layer 14 becomes smaller. The combination of light between the active layer 18 and the photonic crystal layer 14 becomes stronger. The light generated in the active layer 18 is strongly affected by the photonic crystal layer 14. By diffracting the light, it is easy to perform laser oscillation at a desired wavelength. That is, the output of the laser increases.

[0085] like Figure 4AAs shown, a plurality of holes 30 are arranged in a square lattice. The area ratio of the holes 30 to the area of ​​one square lattice is 5% or more and 20% or less. By diffracting light, laser oscillation can be performed. The area ratio of the holes 30 can also be, for example, 3% or more, 10% or more, 15% or less, or 30% or less.

[0086] When the resonance wavelength is 1300nm, the length a of one side of the square lattice is 400nm. The length L1 of the short axis 32 of the hole 30 is greater than 60nm and less than 150nm. The length L2 of the long axis 34 is greater than 100nm and less than 355nm. The length L1 of the short axis 32 is within the above range and is smaller than the length L2. The above dimensions can also be changed according to the resonance wavelength.

[0087] The photonic crystal layer 14 is formed of, for example, InGaAsP or AlInGaAs. The photonic crystal layer 14 is a semiconductor layer containing the compound semiconductor described above. The cladding layer 16 contains InP, for example, formed of n-type InP. The growth rate varies depending on the direction of the crystal. The cladding layer 16 is <110> By orienting the short axis 32 of the pore 30 toward <110> direction, the vacant hole 30 can be quickly closed by the cladding layer 16. By growing the photonic crystal layer 14 along the <110> A semiconductor having a high growth rate in the direction, such as InP, can quickly close the vacancies 30 .

[0088] As shown in FIG. 2 , holes 30 may extend to the middle of photonic crystal layer 14 , or may penetrate photonic crystal layer 14 and extend to cladding layer 12 .

[0089] (Variation Example)

[0090] Fig. 9 FIG. 1 is a cross-sectional view showing a photonic crystal surface emitting laser 110 according to a modified example. The description of the same structure as the first embodiment will be omitted. Fig. 9 As shown, substrate 10, cladding layer 12, active layer 18, cladding layer 16, photonic crystal layer 14, and cladding layer 20 are stacked in this order. Active layer 18 is disposed between cladding layer 12 and photonic crystal layer 14.

[0091] like Figure 4A and Figure 4B As shown, the photonic crystal layer 14 has elliptical holes 30. The short axis 32 is oriented toward <110> Since the vacancy 30 can be closed quickly, the generation of dislocations is suppressed. The characteristics of the photonic crystal surface emitting laser 110 are improved.

[0092] <Second Embodiment>

[0093] Fig.101 is a plan view showing an example of a photonic crystal surface emitting laser according to the second embodiment, and enlarges a hole 30 in a photonic crystal layer 14. A description of the same configuration as that of the first embodiment will be omitted. Fig.10 The holes 30 and the square grid are arranged from Figure 4B The position of the hole 30 and the square grid in the figure is rotated counterclockwise by an angle θ. The minor axis 32 of the hole 30 is relative to <110> The minor axis 32 is inclined in the direction of <110> The angle θ between the directions is, for example, 30° or less.

[0094] and Figure 4A and Figure 4B In the same manner as in the example of , it is assumed that one side of the holes 30 is arranged in a square lattice of 400 nm. Fig.10 The empty hole 30 <110> The length L5 in the <1-10> direction is 139 nm, which is smaller than the length L6 in the <1-10> direction.

[0095] According to the second embodiment, the pores 30 <110> The length L5 in the direction is smaller than the length L6 in the <1-10> direction. <110> The pores 30 grow rapidly in the direction of the cavities 30, and the cavities 30 are closed. By closing the cavities 30, dislocations are less likely to occur in the cladding layer 16. Deterioration in the characteristics of the photonic crystal surface emitting laser is suppressed.

[0096] Short shaft 32 and <110> The angle θ between the directions is, for example, 30° or less. By setting the angle θ to be 30° or less, the length L5 becomes smaller. The pores 30 can be quickly closed by the coating layer 16. The angle θ can also be, for example, 35° or less, 20° or less, 10° or less, or 5° or less. The smaller the angle θ, the closer the short axis 32 is to the <110> direction. The smaller the angle θ is, the Fig.10 The length L5 becomes smaller. If the angle θ is 0°, then Figure 4B In this way, the short axis 32 and <110> When θ = 0°, the length L5 is parallel to Figure 4B The smaller the length L5 is, the faster the hole 30 can be closed.

[0097] The shape of the hole 30 is determined by the shape of the opening 31a of the mask 31 used for etching. By making the opening 31a elliptical, the hole 30 also becomes elliptical. <110> Direction parallel, such as Figure 4B As shown, the short axis 32 of the hole 30 is also <110> If the short axis of the opening 31a is parallel to <110> The direction is tilted at an angle θ, then Fig.10 As shown, the short axis 32 of the hole 30 also extends from <110> The direction is tilted by an angle θ.

[0098] Fig.10In the example, the minor axis 32 is oriented from <110> The minor axis 32 may also be oriented in the direction of the left rotation angle θ. <110> The direction is rotated to the right by an angle θ.

[0099] <Third Embodiment>

[0100] Fig.11 1 is a top view of a photonic crystal surface emitting laser according to the third embodiment, showing a square lattice in the photonic crystal layer 14. The same structure as the first embodiment will be omitted. Two holes are provided in a square lattice, hole 30 (first hole) and hole 36 (second hole). The planar shape of each of the hole 30 and the hole 36 is an ellipse.

[0101] The hole 36 is smaller than the hole 30 and is similar to the hole 30. The minor axis 32 of the hole 30 and the minor axis 37 of the hole 36 are <110> The major axis 34 of the pore 30 and the major axis 38 of the pore 36 are parallel to the <1-10> direction. For example, the pore 30 has Figure 4B The short axis 37 of the hole 36 is shorter than the short axis 32 of the hole 30. The long axis 38 of the hole 36 is shorter than the long axis 34 of the hole 30.

[0102] According to the third embodiment, the minor axes of the holes 30 and 36 are <110> The coating layer 16 is parallel to the <110> The growth rate is high in the direction. The holes 30 and 36 are quickly closed by the cladding layer 16. Dislocations are suppressed, and degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0103] The photonic crystal layer 14 has two holes in one square lattice, namely, hole 30 and hole 36. The number of holes provided in one square lattice may be two or more, for example, three or more, or four or more. In at least one hole, <110> The length in the <1-10> direction is smaller than the length in the <1-10> direction. For example, the planar shape of at least one of the plurality of holes is set to an ellipse. The short axis of the hole on the ellipse is oriented from <110> The direction is within the range of an angle θ or less.

[0104] exist Fig.11 In the embodiment, both of the two holes, hole 30 and hole 36, are elliptical. Alternatively, one or both of the two holes, hole 30 and hole 36, may be in a shape other than an ellipse. A shape other than an ellipse refers to a polygonal shape as shown in the fourth to sixth embodiments.

[0105] <Fourth Embodiment>

[0106] Fig.121 is a plan view showing an example of a photonic crystal surface emitting laser according to a fourth embodiment, and shows one square lattice in a photonic crystal layer 14. A description of the same configuration as that of the first embodiment will be omitted.

[0107] The photonic crystal layer 14 is provided with a hole 40. The planar shape of the hole 40 is a rectangle. The hole 40 has a short axis 41 and a long axis 42. The short axis 41 is shorter than the long axis 42. <110> The major axis 42 is parallel to the <1-10> direction.

[0108] According to the fourth embodiment, the minor axis 41 of the hole 40 is <110> Direction parallel. Through the coating layer 16 along <110> The pores 40 grow rapidly in the cladding layer 16, and the pores 40 are rapidly closed by the cladding layer 16. Closing the pores 40 makes it difficult for dislocations to occur in the cladding layer 16. By suppressing dislocations, degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0109] <Fifth Embodiment>

[0110] Fig.13 1 is a plan view showing an example of a photonic crystal surface emitting laser according to a fifth embodiment, and shows one square lattice in a photonic crystal layer 14. A description of the same configuration as that of the first embodiment will be omitted.

[0111] The photonic crystal layer 14 is provided with a hole 44. The planar shape of the hole 44 is a rhombus. The hole 44 has a short axis 45 and a long axis 46. The short axis 45 is shorter than the long axis 46. <110> The major axis 46 is parallel to the <1-10> direction.

[0112] According to the fifth embodiment, the minor axis 45 of the hole 44 is <110> Direction parallel. Through the coating layer 16 along <110> The pores 44 grow rapidly in the cladding layer 16, and the pores 44 are rapidly closed by the cladding layer 16. Closing the pores 44 makes it difficult for dislocations to occur in the cladding layer 16. By suppressing dislocations, degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0113] In the first to fifth embodiments, the hole has two symmetry axes. The hole is linearly symmetrical with respect to each of the two symmetry axes. The hole can be strictly linearly symmetrical, or it can deviate from the linear symmetry, for example, within the range of manufacturing error. The shape of the hole is determined by the accuracy of etching, etc. Depending on the accuracy of etching, etc., the hole sometimes deviates slightly from the linear symmetry.

[0114] <Sixth Implementation Method>

[0115] Fig.14 1 is a plan view showing an example of a photonic crystal surface emitting laser according to the sixth embodiment, and shows one square lattice in the photonic crystal layer 14. The description of the same configuration as that of the first embodiment will be omitted.

[0116] The photonic crystal layer 14 is provided with a hole 50. The planar shape of the hole 50 is a triangle. One side 51 of the hole 50 is <110> The vertex of the hole 50 that faces the side 51 is the vertex 52. The line segment that passes through the vertex 52 and bisects the side 51 is the line segment 53. The line segment 53 is parallel to the <1-10> direction. The side 51 is shorter than the line segment 53.

[0117] According to the sixth embodiment, the side 51 of the hole 50 is <110> The direction is parallel and shorter than the line segment 53 in the <1-10> direction. <110> The pores 50 grow rapidly in the cladding layer 16, and the pores 50 are rapidly closed by the cladding layer 16. By closing the pores 50, dislocations are less likely to occur in the cladding layer 16. By suppressing dislocations, degradation of the characteristics of the photonic crystal surface emitting laser is suppressed.

[0118] As shown in the first embodiment, the planar shape of the hole may be an ellipse. As shown in the fourth to sixth embodiments, the planar shape of the hole may be a polygon. The vertices of the polygon may include curves.

[0119] As mentioned above, although the embodiment of this disclosure is described in detail, this disclosure is not limited to the specific embodiment involved, and various deformation|transformation and changes are possible within the scope of the summary of this disclosure described in a claim.

[0120] Description of Reference Numerals

[0121] 10: substrate;

[0122] 12, 16, 20: coating layer;

[0123] 14: Photonic crystal layer;

[0124] 18: active layer;

[0125] 22: contact layer;

[0126] 23: slot;

[0127] 24: Insulation film;

[0128] 24a, 24b, 28a, 31a: opening;

[0129] 26, 28: electrodes;

[0130] 31: mask;

[0131] 30, 30R1, 30R2, 36, 40, 50: empty holes;

[0132] 32, 37, 45: short axis;

[0133] 34, 38, 46: major axis;

[0134] 51: edge;

[0135] 52: Vertex;

[0136] 53: Line segment;

[0137] 100, 110: Photonic crystal surface emitting laser.

Claims

1. A photonic crystal surface emitting laser, wherein: The photonic crystal surface emitting laser comprises: Active layer; a photonic crystal layer; and a first semiconductor layer, The photonic crystal layer includes a base material and a plurality of holes periodically arranged in the base material. The holes extend from one surface of the photonic crystal layer to an opposite surface of the photonic crystal layer. The first semiconductor layer is disposed on the one surface of the photonic crystal layer, The length of the holes in the <110> direction of the photonic crystal layer is smaller than the length of the holes in the <1-10> direction of the photonic crystal layer.

2. The photonic crystal surface emitting laser according to claim 1, wherein: The planar shape of the hole has a first symmetry axis and a second symmetry axis, The length of the hole in the direction of the first symmetry axis is smaller than the length of the hole in the direction of the second symmetry axis. An angle formed by the first symmetry axis and the <110> direction of the photonic crystal layer is 30° or less.

3. The photonic crystal surface emitting laser according to claim 2, wherein: The first symmetry axis is parallel to the <110> direction.

4. The photonic crystal surface emitting laser according to claim 3, wherein: The plane shape of the hole is an ellipse, The short axis of the hole is parallel to the <110>.

5. The photonic crystal surface emitting laser according to claim 1 or 2, wherein: The photonic crystal layer, the first semiconductor layer, and the photonic crystal layer are sequentially stacked.

6. The photonic crystal surface emitting laser according to claim 1 or 2, wherein: The active layer, the photonic crystal layer, and the first semiconductor layer are stacked in sequence.

7. The photonic crystal surface emitting laser according to claim 1 or 2, wherein: The plurality of holes are arranged in a square lattice in the plane of the photonic crystal layer. The ratio of the pores to the area of ​​the square lattice is 3% or more and 30% or less.

8. The photonic crystal surface emitting laser according to claim 1 or 2, wherein: The photonic crystal layer has a plurality of first vacancies and a plurality of second vacancies, The plurality of first pores and the plurality of second pores are periodically arranged in the base material. In at least one of the first hole and the second hole, the length of the photonic crystal layer in the <110> direction is smaller than the length of the photonic crystal layer in the <1-10> direction.

9. The photonic crystal surface emitting laser according to claim 1 or 2, wherein: The photonic crystal layer comprises indium gallium arsenic phosphide or aluminum indium gallium arsenic, The first semiconductor layer includes indium phosphide.

10. A method for manufacturing a photonic crystal surface emitting laser, wherein: The method for manufacturing the photonic crystal surface emitting laser comprises: A step of forming a plurality of cavities, wherein the plurality of cavities are periodically arranged in a base material of the photonic crystal layer and extend from one surface of the photonic crystal layer to an opposite surface; forming a first semiconductor layer on the one surface of the photonic crystal layer; as well as The process of forming an active layer, The photonic crystal layer <110> The length of the holes in the <1-10> direction is smaller than the length of the holes in the <1-10> direction of the photonic crystal layer.

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