Vertical Cavity Surface Emitting Devices

Abstract

A vertical cavity surface light emitting device comprises: a substrate, a first multilayer film reflector, a light emitting structure layer and a second multilayer film reflector. The first multilayer film reflector is formed on the substrate. The light emitting structure layer is formed on the first multilayer film reflector. The light emitting structure layer includes a light emitting layer. The second multilayer film reflector is formed on the light emitting structure layer. The second multilayer film reflector constitutes a resonator between the first multilayer film reflector and the second multilayer film reflector. The second multilayer film reflector comprises a first multilayer film, an intermediate film and a second multilayer film. The first multilayer film has a low refractive index film made of a low refractive index material and a high refractive index film made of a high refractive index material having a refractive index higher than that of the low refractive index material. The low refractive index film and the high refractive index film are alternately stacked. The intermediate film covers the upper surface of the first multilayer film. The intermediate film has light transmittance to light emitted from the light emitting layer. The second multilayer film is formed to partially cover the upper surface of the intermediate film. The second multilayer film has a low refractive index film made of a low refractive index material and a high refractive index film made of a high refractive index material. The low refractive index film and the high refractive index film are alternately stacked. The film thickness of the intermediate film is based on 1 / 2 of the wavelength of light emitted from the light emitting layer within the intermediate film.

Description

Technical Field

[0001] The present invention relates to a vertical cavity surface emitting device, such as a vertical cavity surface emitting laser. Background Art

[0002] A vertical cavity surface emitting laser (hereinafter referred to as a surface emitting laser) is a semiconductor laser that includes a reflector formed of a multilayer film stacked on a substrate and emits light in a direction perpendicular to the substrate surface. For example, Patent Document 1 discloses a surface emitting laser using a nitride semiconductor.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5707742 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] For example, in a vertical cavity surface emitting device such as a surface emitting laser, it is preferred that the emission pattern is stable, for example, the far field pattern is stable. Therefore, for example, it is preferred that a resonator configured to generate light in a desired transverse mode is constructed in the vertical cavity surface emitting device. For example, generating a laser beam in a fundamental eigenmode can obtain a far field pattern of a single peak laser beam with a low emission angle and high output power.

[0008] The present invention is made in view of the above problems, and its object is to provide a vertical cavity surface emitting device that can emit light in a stable lateral mode.

[0009] Solutions to the problem

[0010] The vertical cavity surface light emitting device of the present invention comprises a substrate, a first multilayer film reflector, a light emitting structure layer and a second multilayer film reflector. The first multilayer film reflector is formed on the substrate. The light emitting structure layer is formed on the first multilayer film reflector. The light emitting structure layer comprises a light emitting layer. The second multilayer film reflector is formed on the light emitting structure layer. The second multilayer film reflector constitutes a resonator between the first multilayer film reflector and the second multilayer film reflector. The second multilayer film reflector comprises a first multilayer film, an intermediate film and a second multilayer film. The first multilayer film has a low refractive index film made of a low refractive index material and a high refractive index film made of a high refractive index material having a refractive index higher than that of the low refractive index material. The low refractive index film and the high refractive index film are alternately stacked. The intermediate film covers the upper surface of the first multilayer film. The intermediate film has light transmittance to light emitted from the light emitting layer. The second multilayer film is formed to partially cover the upper surface of the intermediate film. The second multilayer film has a low refractive index film made of a low refractive index material and a high refractive index film made of a high refractive index material. The low refractive index film and the high refractive index film are alternately stacked. The film thickness of the intermediate film is based on 1 / 2 of the wavelength of light emitted from the light emitting layer within the intermediate film. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a top view of the surface emitting laser of Example 1.

[0012] Figure 2 is a cross-sectional view of the surface emitting laser of Example 1.

[0013] Figure 3 This is a side view of the second multilayer film reflecting mirror in the surface emitting laser of Example 1.

[0014] Figure 4A 1 is a diagram showing a method for manufacturing the surface emitting laser of Example 1.

[0015] Figure 4B 1 is a diagram showing a method for manufacturing the surface emitting laser of Example 1.

[0016] Figure 5 1 is a diagram showing the degree of mirror loss in the first multilayer film of the second multilayer film reflecting mirror in the surface emitting laser of Example 1. FIG.

[0017] Figure 6 is a top view of the surface emitting laser of Example 2.

[0018] Figure 7 is a cross-sectional view of the surface emitting laser of Example 2.

[0019] Figure 8 is a top view of the surface emitting laser of Example 3.

[0020] Fig. 9 is a cross-sectional view of the surface emitting laser of Example 3.

[0021] Fig.10 This is a side view of the second multilayer film reflecting mirror in the surface emitting laser of Example 3. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be described in detail below. In the following embodiments, the case where the present invention is implemented as a surface emitting laser (semiconductor laser) will be described. However, the present invention is not limited to the surface emitting laser, but can be applied to various vertical cavity surface emitting devices, such as vertical cavity surface emitting diodes.

[0023] Example 1

[0024] Figure 1 is a schematic top view of a vertical cavity surface emitting laser (VCSEL, hereinafter referred to as a surface emitting laser) of Example 1. Figure 2 is a cross-sectional view of the surface emitting laser 10 . Figure 2 is along Figure 1 The cross-sectional view taken along line 2-2 in FIG. Figure 1 and Figure 2 The configuration of the surface emitting laser 10 is described.

[0025] The surface emitting laser 10 includes a substrate 11 and a first multilayer film reflector (hereinafter referred to as the first reflector) 12 formed on the substrate 11. In the present embodiment, the first reflector 12 is formed on the substrate 11 and has a structure in which a first semiconductor film (hereinafter referred to as a high refractive index semiconductor film) H1 and a second semiconductor film (hereinafter referred to as a low refractive index semiconductor film) L1 having a refractive index lower than that of the high refractive index semiconductor film H1 are alternately stacked. In the present embodiment, the first reflector 12 constitutes a distributed Bragg reflector (DBR) made of a semiconductor material.

[0026] In this embodiment, the composition of the substrate 11 is GaN. The substrate 11 is a growth substrate for crystal growth of the first reflector 12. The composition of the high refractive index semiconductor film H1 in the first reflector 12 is GaN, and the composition of the low refractive index semiconductor film L1 is AlInN. In this embodiment, a buffer layer (not shown) composed of GaN is provided between the substrate 11 and the first reflector 12.

[0027] The surface emitting laser 10 includes a light emitting structure layer EM1 formed on a first reflector 12 and including a light emitting layer 14. In the present embodiment, the light emitting structure layer EM1 includes a plurality of semiconductor layers made of nitride semiconductors. The light emitting structure layer EM1 includes an n-type semiconductor layer (first semiconductor layer) 13 formed on the first reflector 12, a light emitting layer (active layer) 14 formed on the n-type semiconductor layer 13, and a p-type semiconductor layer (second semiconductor layer) 15 formed on the light emitting layer 14.

[0028] In this embodiment, the composition of the n-type semiconductor layer 13 is GaN and contains Si as an n-type impurity. The light-emitting layer 14 has a quantum well structure, which includes a well layer composed of InGaN and a barrier layer composed of GaN. The p-type semiconductor layer 15 has a GaN-based composition and contains Mg as a p-type impurity.

[0029] The configuration of the light emitting structure layer EM1 is not limited thereto. For example, the n-type semiconductor layer 13 may include a plurality of n-type semiconductor layers having different compositions from each other. The p-type semiconductor layer 15 may include a plurality of p-type semiconductor layers having different compositions from each other.

[0030] For example, the p-type semiconductor layer 15 may include, for example, an AlGaN layer as an electron blocking layer (not shown), which reduces the electrons injected into the light emitting layer 14 from overflowing to the p-type semiconductor layer 15 at the interface with the light emitting layer 14. The p-type semiconductor layer 15 may include a contact layer (not shown) to form an ohmic contact with the electrode. In this case, for example, the p-type semiconductor layer 15 only needs to include a GaN layer as a capping layer between the electron blocking layer and the contact layer.

[0031] In the present embodiment, the p-type semiconductor layer 15 includes a convex portion 15A on its upper surface. In the present embodiment, the convex portion 15A has a cylindrical shape. The surface emitting laser 10 has an insulating layer (first insulating layer) 16 formed on the upper surface except for the convex portion 15A of the p-type semiconductor layer 15. The insulating layer 16 is light-transmissive to the light emitted from the light-emitting layer 14 and is made of a material (e.g., an oxide, such as SiO2) having a refractive index lower than that of the p-type semiconductor layer 15 (convex portion 15A). The upper end surface of the convex portion 15A of the p-type semiconductor layer 15 is exposed from the insulating layer 16.

[0032] The surface emitting laser 10 includes a light-transmitting electrode layer 17 formed on the insulating layer 16 and connected to the p-type semiconductor layer 15 at the convex portion 15A of the p-type semiconductor layer 15. The light-transmitting electrode layer 17 is a conductive film having light-transmitting properties to the light emitted from the light-emitting layer 14. The light-transmitting electrode layer 17 is in contact with the upper surface of the insulating layer 16 and the upper end surface of the convex portion 15A of the p-type semiconductor layer 15. For example, the light-transmitting electrode layer 17 is made of a metal oxide film such as ITO or IZO.

[0033] The insulating layer 16 serves as a current limiting layer that limits the current injected into the light emitting structure layer EM1 via the light-transmitting electrode layer 17. Specifically, the upper surface area outside the convex portion 15A in the p-type semiconductor layer 15 serves as a high resistance area having a higher resistance than other areas due to being covered by the insulating layer 16. Therefore, the current path in the light emitting structure layer EM1 is limited by the area of ​​the convex portion 15A of the p-type semiconductor layer 15.

[0034] The surface emitting laser 10 includes an insulating layer (second insulating layer) 18 formed on the light-transmitting electrode layer 17. For example, the insulating layer 18 is made of a metal oxide having insulating properties (such as Ta2O5, Nb2O5, ZrO2, TiO2, and HfO2). The insulating layer 18 has light-transmitting properties for light emitted from the light-emitting layer 14.

[0035] The surface emitting laser 10 includes a second multilayer film reflector (hereinafter referred to as the second reflector) 19 formed on the insulating layer 18. The second reflector 19 is arranged at a position facing the first reflector 12, with the light emitting structure layer EM1 interposed therebetween. A resonator OC1 having a direction perpendicular to the light emitting structure layer EM1 (a direction perpendicular to the substrate 11) as a resonator length direction is formed between the second reflector 19 and the first reflector 12.

[0036] In this embodiment, the second reflecting mirror 19 has a structure in which a first dielectric film (hereinafter referred to as a high refractive index dielectric film) H2 and a second dielectric film (hereinafter referred to as a low refractive index dielectric film) L2 having a lower refractive index than the high refractive index dielectric film H2 are alternately stacked.

[0037] That is, in this embodiment, the second reflecting mirror 19 constitutes a distributed Bragg reflector (DBR) made of a dielectric material. For example, in this embodiment, the high refractive index dielectric film H2 is made of a Nb2O5 film, and the low refractive index dielectric film L2 is made of a SiO2 film.

[0038] In this embodiment, the second reflecting mirror 19 has a first and a second dielectric multilayer film (hereinafter referred to as the first and second multilayer film) 19A and 19B, each including a plurality of high refractive index dielectric films H2 and low refractive index dielectric films L2, and an intermediate dielectric film (intermediate film) 19C, which is formed between the first multilayer film 19A and the second multilayer film 19B and has an etching rate smaller than, for example, the high refractive index dielectric film H2 and the low refractive index dielectric film L2.

[0039] The intermediate dielectric film 19C is made of, for example, an Al2O3 film, and has a dry etching rate of 1 / 10 or less of that of a Nb2O5 film and a SiO2 film. Another example of the intermediate dielectric film 19C includes an AlN film.

[0040] In this embodiment, the intermediate dielectric film 19C is formed between the high refractive index dielectric films H2 in the second reflecting mirror 19. Specifically, in this embodiment, the first multilayer film 19A has a high refractive index dielectric film (hereinafter referred to as a first thin film high refractive index dielectric film) H21 having a film thickness half the film thickness of the high refractive index dielectric film H2 on its upper surface. The intermediate dielectric film 19C is formed on the first thin film high refractive index dielectric film H21. The second multilayer film 19B has a high refractive index dielectric film (second thin film high refractive index dielectric film) H21 on the interface with the intermediate dielectric film 19C.

[0041] The second multilayer film 19B is disposed inside the intermediate dielectric film 19C in the in-plane direction of the intermediate dielectric film 19C. In the present embodiment, the first multilayer film 19A and the intermediate dielectric film 19C have the same width. In the present embodiment, the first multilayer film 19A and the intermediate dielectric film 19C have a cylindrical shape with the same diameter.

[0042] The width of the second multilayer film 19B is smaller than that of the intermediate dielectric film 19C. In the present embodiment, the second multilayer film 19B is formed coaxially with the first multilayer film 19A and the intermediate dielectric film 19C and has a cylindrical shape having a smaller diameter than those of the first multilayer film 19A and the intermediate dielectric film 19C.

[0043] In this embodiment, if Figure 1 As shown, the surface emitting laser 10 has a resonator OC1 having a cross-sectional shape corresponding to the shape of the first multilayer film 19A of the second reflecting mirror 19, and in this embodiment, a cylindrical shape.

[0044] The surface emitting laser 10 has a metal film 20 formed on the second reflecting mirror 19. In the present embodiment, the metal film 20 has reflectivity to the light emitted from the light emitting layer 14. The metal film 20 includes a first metal film 21 covering the upper surface of the second multilayer film 19B and a second metal film 22 covering the upper surface region of the intermediate dielectric film 19C exposed from the second multilayer film 19B. For example, the metal film 20 is made of a metal material such as Ti, Cr, Ni, Pt, Au, and Sn.

[0045] The surface emitting laser 10 includes a first electrode E1 and a second electrode E2 for applying current to the light emitting structure layer EM1. The first electrode E1 is formed on the n-type semiconductor layer 13. The second electrode E2 is formed on the light-transmitting electrode layer 17.

[0046] Applying a voltage between the first electrode E1 and the second electrode E2 causes light to be emitted from the light emitting layer 14 in the light emitting structure layer EM1. The light emitted from the light emitting layer 14 repeatedly reflects between the first reflector 12 and the second reflector 19, thereby entering a resonant state (laser oscillation).

[0047] In this embodiment, the reflectivity of the first reflector 12 is slightly lower than the reflectivity of the second reflector 19. Therefore, a portion of the light resonating between the first reflector 12 and the second reflector 19 is transmitted through the first reflector 12 and the substrate 11 and taken out to the outside. Therefore, the surface emitting laser 10 emits light in a direction perpendicular to the substrate 11 and the light emitting structure layer EM1.

[0048] The convex portion 15A of the p-type semiconductor layer 15 as the current limiting portion in the light emitting structure layer EM1 defines the light emitting region in the light emitting layer 14, and defines the central axis (light emitting central axis) CA of the resonator OC1 as an axis passing through the center of the light emitting region. For example, the central axis CA of the resonator OC1 passes through the center of the convex portion 15A of the p-type semiconductor layer 15 and extends in a direction perpendicular to the p-type semiconductor layer 15 (light emitting structure layer EM1).

[0049] The light emitting region of the light emitting layer 14 is, for example, a region having a predetermined width, from which light having a predetermined intensity or more is emitted in the light emitting layer 14, and the center of the region is the light emitting center. For example, the light emitting region of the light emitting layer 14 is a region in which a current having a predetermined density or more is injected into the light emitting layer 14, and the center thereof is the light emitting center. A straight line passing through the light emitting center and perpendicular to the substrate 11 is the central axis CA. The central axis CA is a straight line extending in the resonator length direction of the resonator OC1 constituted by the first reflector 12 and the second reflector 19. The central axis CA corresponds to the optical axis of the laser beam emitted from the surface emitting laser 10.

[0050] Here, an exemplary configuration of each layer in the surface emitting laser 10 will be described. In the present embodiment, the first reflector 12 is formed of 44 pairs of GaN layers and AlInN layers. The n-type semiconductor layer 13 has a layer thickness of 650 nm. The light emitting layer 14 is formed of an active layer having a multi-quantum well structure in which a 4 nm InGaN layer and a 5 nm GaN layer are stacked three times. The second reflector 19 is formed of 10.5 pairs of Nb2O5 layers and SiO2 layers.

[0051] The p-type semiconductor layer 15 has a layer thickness of 50 nm in the region of the convex portion 15A. The p-type semiconductor layer 15 has a layer thickness of 30 nm in the region other than the convex portion 15A. The outer diameter of the convex portion 15A is 8 μm. The insulating layer 16 has a layer thickness of 20 nm. The upper surface of the insulating layer 16 is formed to be arranged at the same height position as the upper end surface of the convex portion 15A of the p-type semiconductor layer 15. Note that these are just examples.

[0052] Figure 3 is a side view of the second reflector 19. Figure 3 , the detailed construction of the second reflecting mirror 19 will be described. First, the first multilayer film 19A has the following structure: a low refractive index dielectric film L2 and a high refractive index dielectric film H2 are sequentially stacked four times on the insulating layer 18, and a first thin film high refractive index dielectric film H21 is formed on the uppermost low refractive index dielectric film L2.

[0053] The second multilayer film 19B has the following structure: the second thin film high refractive index dielectric film H21 is formed on the intermediate dielectric film 19C, the low refractive index dielectric film L2 and the high refractive index dielectric film H2 are stacked five times thereon in sequence, and the low refractive index dielectric film L2 is formed on the uppermost high refractive index dielectric film H2.

[0054] like Figure 3 As shown in FIG. 1 , in the present embodiment, the second reflecting mirror 19 is made of 10 high refractive index dielectric films H2 and 11 low refractive index dielectric films L2. The first and second thin film high refractive index dielectric films H21 (6) have a configuration equivalent to when the layer thickness of the sixth high refractive index dielectric film H2 (6) from the uppermost surface side (metal film 20 side) is halved and divided into two. An intermediate dielectric film 19C is formed between these first and second thin film high refractive index dielectric films H21 (6).

[0055] In the present embodiment, the film thickness of each low-refractive-index dielectric film L2 and each high-refractive-index dielectric film H2 corresponds to 1 / 4 of the wavelength in each dielectric film of light emitted from the light-emitting layer 14. For example, when the refractive index of each dielectric film is set to the refractive index n (which is different between the low-refractive-index dielectric film L2 and the high-refractive-index dielectric film H2 in practice), and the wavelength of light emitted from the light-emitting layer 14 is the wavelength λ, the film thickness of each dielectric film is λ / 4n.

[0056] On the other hand, in this embodiment, the film thickness of the first and second thin film high refractive index dielectric films H21(6) is half that, ie, λ / 8n. In this embodiment, the film thickness of the intermediate dielectric film 19C is λ / 2n.

[0057] Figure 4A and Figure 4B FIG. 1 is a diagram showing a part of a method for manufacturing the surface emitting laser 10. Figure 4A and Figure 4B , a method for manufacturing the surface emitting laser 10 will be described. First, Figure 4A 1 is a cross-sectional view showing a portion of a semiconductor wafer on which the first multilayer film 19A and the second multilayer film 19BP as multilayer films serving as the second reflecting mirror 19 and the intermediate dielectric film 19C are formed.

[0058] First, on a semiconductor wafer used as a substrate 11, a first reflector 12, a light emitting structure layer EM1, an insulating layer 16, a light-transmitting electrode layer 17, and an insulating layer 18 are formed. On the insulating layer 18, a low-refractive-index dielectric film L2 and a high-refractive-index dielectric film H2 are stacked multiple times (five pairs in this embodiment), and a first thin-film high-refractive-index dielectric film H21 is formed, thereby forming a first multilayer film 19A (step 1).

[0059] On the first multilayer film 19A, a dielectric film serving as the intermediate dielectric film 19C and having an etching rate lower than that of the high refractive index dielectric film H2 and the low refractive index dielectric film L2 is formed (step 2). On the intermediate dielectric film 19C, a second thin film high refractive index dielectric film H21 is formed, five pairs of low refractive index dielectric films L2 and high refractive index dielectric films H2 are stacked, and a low refractive index dielectric film L2 is formed, thereby forming a second multilayer film 19BP (step 3).

[0060] then, Figure 4B 1 is a cross-sectional view showing a portion of a semiconductor wafer after etching is performed on the second multilayer film 19BP. After forming the second multilayer film 19BP, etching is performed on the second multilayer film 19BP to partially remove the second multilayer film 19BP and partially expose the intermediate dielectric film 19C. In the present embodiment, dry etching is performed on the second multilayer film 19BP. This forms the second multilayer film 19B, thereby forming the second reflecting mirror 19 (step 4).

[0061] Here, the etching rate of the intermediate dielectric film 19C is lower than the etching rate of other dielectric films in the second reflecting mirror 19. Therefore, when etching of the second multilayer film 19BP is performed, etching can be reliably stopped in the middle of the intermediate dielectric film 19C. That is, for example, in the case where the dielectric film at the bottom of the second multilayer film 19BP or a part of the first multilayer film 19A that does not partially remain in the etched portion is etched, only the second multilayer film 19BP can be stably etched.

[0062] Therefore, the etching accuracy is basically stable. Therefore, the multilayer film can be processed so that the etching stops at the designed depth position or the designed film position. In this embodiment, the reflection characteristics as the second reflection mirror 19 can be stably adjusted.

[0063] In this embodiment, after forming the second reflector 19, the metal film 20 is formed on the intermediate dielectric film 19C and the second multilayer film 19B (step 5). Next, the first and second electrodes E1 and E2 are formed on the n-type semiconductor layer 13 and the p-type semiconductor layer 15 of the light emitting structure layer EM1, respectively (step 6). Thus, the surface emitting laser 10 can be manufactured.

[0064] Figure 5 1 is a diagram showing the relationship between the etching depth (position) based on the upper surface of the second multilayer film 19BP and the mirror loss in the second reflecting mirror 19. Figure 5 As shown, it can be seen that when etching is performed halfway through the sixth pair of high refractive index dielectric films H2 from the upper surface side (for example, the center in the film thickness direction), a significantly larger mirror loss will result compared to the case where etching is performed at other positions.

[0065] Therefore, like the second reflecting mirror 19 in this embodiment, the sixth pair of high refractive index dielectric films H2 is divided into first and second thin film high refractive index dielectric films H21 (6), and an intermediate dielectric film 19C is arranged therebetween to stop etching on the way, thereby stably removing the second multilayer film 19B, thereby ensuring that a larger mirror loss is caused in the removed part.

[0066] In the present embodiment, the second multilayer film 19B is formed in the central portion of the first multilayer film 19A within the plane of the first multilayer film 19A. That is, in the peripheral portion of the first multilayer film 19A, the second multilayer film 19B is removed. The first multilayer film 19A and the second multilayer film 19B are arranged on the central axis CA of the resonator OC1. This stably ensures that the mirror loss in the region of the peripheral portion including the region of the central axis CA is higher than the mirror loss in the region including the central axis CA of the resonator OC1.

[0067] This results in a stable transverse mode of the surface emitting laser 10. Specifically, when the difference in mirror loss between the region on the central axis CA and the region of the surrounding portion thereof is small, the oscillation mode of the surface emitting laser 10 becomes unstable, and sometimes laser oscillation is performed in a higher-order mode. This is caused by the failure to stably form the difference in mirror loss.

[0068] For example, in the present embodiment, when the dielectric multilayer film forms the second reflector 19, the difference in mirror loss between the central axis CA and its surrounding portion is generally formed by partially removing the multilayer film. However, when the amount of removal of the multilayer film becomes unstable, such as Figure 5 As shown, the mirror loss is hardly caused depending on the depth position of the residual multilayer film. This causes the oscillation mode to become multimode or unstable.

[0069] In contrast, in the present embodiment, as in the intermediate dielectric film 19C, a film that is extremely slow to etch is formed at a preferred position in the multilayer film serving as the second reflecting mirror 19, and the second multilayer film 19BP is partially removed by etching thereon. Therefore, etching can be reliably stopped at a preferred position, and the second reflecting mirror 19 having preferred mirror characteristics can be formed. This can provide a surface emitting laser 10 having a stable transverse mode.

[0070] In the present embodiment, the case where the second reflecting mirror 19 is a DBR made of a dielectric material has been described. However, the second reflecting mirror 19 only needs to be a multilayer reflecting mirror, and the material is not limited to a dielectric material.

[0071] The construction of the first multilayer film 19A and the second multilayer film 19B is also not limited to the above case. For example, the first multilayer film 19A only needs to have a structure in which a low refractive index film (low refractive index dielectric film L2) made of a low refractive index material (e.g., a low refractive index dielectric material) and a high refractive index film (high refractive index dielectric film H2) made of a high refractive index material having a refractive index greater than that of the low refractive index material are alternately stacked.

[0072] The second multilayer film 19B only needs to be formed to partially cover the upper surface of the intermediate dielectric film 19C, and have a structure in which a low refractive index film made of a low refractive index material (low refractive index dielectric film L2) and a high refractive index film made of a high refractive index material (high refractive index dielectric film H2) are alternately stacked.

[0073] The film thickness of the intermediate dielectric film 19C is not limited to the above. For example, the intermediate dielectric film 19C only needs to have a film thickness that does not destroy the DBR condition in the second reflector 19, that is, a film thickness that the light emitted from the light emitting layer 14 passes through without being reversed at the interface with other layers in the intermediate dielectric film 19C. For example, the intermediate dielectric film 19C only needs to have a film thickness based on 1 / 2 of the wavelength of the light emitted from the light emitting layer 14 in the intermediate dielectric film 19C, for example, the film thickness satisfies λx / 2n (x is a natural number).

[0074] As for the position of the intermediate dielectric film 19C, it is only necessary to set the intermediate dielectric film 19C at any preferred position in the second reflector 19. For example, when the metal film 20 covers the upper surface of the second reflector 19, it is preferably set between the first and second thin-film high refractive index films H21 provided in each of the first multilayer film 19A and the second multilayer film 19B.

[0075] More specifically, for example, it is preferred that the low refractive index dielectric film L2 is disposed on the side of the first multilayer film 19A closest to the substrate 11. It is preferred that a thin film high refractive index dielectric film H21 made of a high refractive index material and having a film thickness less than the film thickness of the high refractive index dielectric film H2 is disposed on the side of the first multilayer film 19A closest to the intermediate dielectric film 19C. It is preferred that the low refractive index dielectric film L2 is disposed on the side of the second multilayer film 19B closest to the upper surface. It is preferred that a thin film high refractive index dielectric film H21 made of a high refractive index material and having a film thickness less than the film thickness of the high refractive index dielectric film H2 is disposed on the side of the second multilayer film 19B closest to the intermediate dielectric film 19C.

[0076] For example, Figure 3As shown, the second multilayer film 19B preferably has 5 low-refractive index dielectric films L2 and 5 high-refractive index dielectric films H2 and a thin film high-refractive index film H21. Preferably, the film thickness of the low-refractive index dielectric film L2 and the high-refractive index dielectric film H2 in the first multilayer film 19A and the second multilayer film 19B is based on 1 / 4 of the wavelength of the light emitted from the light-emitting layer 14 in the low-refractive index dielectric film L2 and the high-refractive index dielectric film H2 respectively (for example, the film thickness satisfies λx / 4n (x is a natural number)). Preferably, the film thickness of the thin film high-refractive index film H21 is based on 1 / 8 of the wavelength of the light emitted from the light-emitting layer 14 in the thin film high-refractive index film (for example, the film thickness satisfies λx / 8n (x is a natural number)).

[0077] The present embodiment has described the case where the etching rate of the intermediate dielectric film 19C is lower than the etching rates of the high refractive index dielectric film H2 and the low refractive index dielectric film L2. However, the intermediate dielectric film 19C only needs to be a light-transmitting film having a film thickness (e.g., the above-mentioned film thickness) sufficient to reliably stop etching. The intermediate dielectric film 19C is not limited to the case where the etching rate of the film is lower than the etching rate of other layers. The intermediate dielectric film 19C only needs to cover the upper surface of the first multilayer film 19A.

[0078] As described above, in the present embodiment, the surface emitting laser 10 has a substrate 11, a first multilayer film reflector 12 formed on the substrate 11, a light emitting structure layer EM1 formed on the first multilayer film reflector 12 and including a light emitting layer 14, and a second multilayer film reflector 19 formed on the light emitting structure layer EM1 and constituting a resonator OC1 between the first multilayer film reflector 12 and the second multilayer film reflector 19.

[0079] The second multilayer film reflector 19 includes: a first multilayer film 19A, in which a low refractive index film L2 made of a low refractive index material and a high refractive index film H2 made of a high refractive index material having a refractive index greater than that of the low refractive index material are alternately stacked; an intermediate dielectric film 19C, which covers the upper surface of the first multilayer film 19A and is translucent to the light emitted from the light-emitting layer 14; and a second multilayer film 19B, which is formed to partially cover the upper surface of the intermediate dielectric film 19C, and in which a low refractive index film L2 made of a low refractive index material and a high refractive index film H2 made of a high refractive index material are alternately stacked.

[0080] The film thickness of the intermediate dielectric film 19C is based on 1 / 2 of the wavelength in the intermediate dielectric film 19C of the light emitted from the light emitting layer 14. Therefore, the surface emitting laser 10 (vertical cavity surface emitting device) capable of emitting light in a stable lateral mode can be provided.

[0081] Example 2

[0082] Figure 6 is a top view of the surface emitting laser 30 of Embodiment 2. Figure 7is a cross-sectional view of the surface emitting laser 30 . Figure 7 is along Figure 6 The surface emitting laser 30 has a configuration similar to that of the surface emitting laser 10 except for the configurations of the second reflecting mirror 31 and the metal film 32 .

[0083] In this embodiment, the second reflector 31 has a second multilayer film 31A formed in an annular shape on the upper surface of the intermediate dielectric film 19C instead of the second reflector 19B of the second reflector 19. In this embodiment, the second multilayer film 31A has a high refractive index dielectric film H2 and a low refractive index dielectric film L2 formed in an annular shape.

[0084] The metal film 32 is formed on the intermediate dielectric film 19C and the second multilayer film 31A including the upper surface of the intermediate dielectric film 31A exposed from the second multilayer film 31 on the inner side of the second multilayer film 31 .

[0085] In this embodiment, similarly to the second multilayer film 19B, the second multilayer film 31A has a second thin film high refractive index dielectric film H21 at the interface with the intermediate dielectric film 19C. The intermediate dielectric film 19C is formed between the first and second thin film high refractive index dielectric films H21.

[0086] This embodiment can provide a surface emitting laser 30 that performs laser oscillation in a more stable transverse mode. Specifically, in this embodiment, a high mirror loss region is formed even in the region of the central axis CA of the resonator OC1. That is, in the resonator OC1, a region having high reflection characteristics is formed in a ring shape around the central axis CA.

[0087] This can allow laser oscillation while confining the light in the annular region. Thus, for example, adjusting the width of the annular region ensures that a plurality of eigenmodes are formed in the annular region.

[0088] For example, the second multilayer film 31A has an outer diameter W1 of 7.5 μm and an inner diameter W2 of 2.5 μm. For example, the second multilayer film 31A formed in such a ring shape can ensure that a near-field pattern with intensity peaks is generated at multiple positions. Light having a near-field pattern of such a pattern is emitted while being narrowed as a whole due to interference with each other. That is, for example, a stable single-peak laser beam can be emitted.

[0089] Therefore, the present embodiment ensures that the second reflecting mirror 31 having the second multilayer film 31A in a ring shape is formed using the intermediate dielectric film 19C. Therefore, the region having a small mirror loss can be stably formed in a ring shape, and thus the surface emitting laser 30 having a stable transverse mode can be provided.

[0090] Example 3

[0091] Figure 81 is a top view of a surface emitting laser 40 of Embodiment 3. Fig. 9 : is a cross-sectional view of the surface emitting laser 40. The surface emitting laser 40 has a configuration similar to that of the surface emitting laser 10 except for the configuration of the second reflecting mirror 41. In the surface emitting laser 40, the second reflecting mirror 41 is optically exposed in the upper surface.

[0092] In the present embodiment, the second reflecting mirror 41 has a first multilayer film 41A having a low refractive index layer L2 on the uppermost surface, an intermediate dielectric film 41C formed on the low refractive index layer L2 of the first multilayer film 41A, and a second multilayer film 41B formed on the intermediate dielectric film 41C and having a high refractive index layer H2 at the interface with the intermediate dielectric film 41C. The upper surfaces of the second multilayer film 41B and the intermediate dielectric film 41C have no metal film and are optically exposed.

[0093] Fig.10 : is a side view of the second reflecting mirror 41. In this embodiment, the first multilayer film 41A has a structure in which five pairs of low-refractive-index dielectric films L2 and high-refractive-index dielectric films H2 and a fifth low-refractive-index dielectric film L2 are stacked. The second multilayer film 41B has a structure in which five pairs of high-refractive-index dielectric films H2 and low-refractive-index dielectric films L2 are stacked.

[0094] like Fig.10 As shown, in this embodiment, in the second reflecting mirror 41, an intermediate dielectric film 41C is formed between the fifth pair of high refractive index dielectric films H2 (5) and the sixth pair of low refractive index dielectric films L2 (6) from the upper surface of the second multilayer film 41B.

[0095] In this embodiment, the upper surface of the second reflecting mirror 41 is optically exposed, which is different from the case where the metal film is provided on the end surface in a light reflecting state. In this case, the intermediate dielectric film 41C is provided at the position as described above and is etched to ensure that a large mirror loss is caused. Therefore, for example, a single peak laser beam can be stably emitted.

[0096] Note that in the present embodiment, for example, the second multilayer film 41B may be formed into a ring shape (tube shape) as shown in Embodiment 2. In this case, similarly to Embodiment 2, a laser beam can be generated in a more stable transverse mode. For example, when the second multilayer film 41B is formed into a ring shape, examples of its size include an outer diameter W1 of 9 μm and an inner diameter W2 of 3 μm.

[0097] Furthermore, in the present embodiment, the configurations of the first multilayer film 41A and the second multilayer film 41B and the configuration of the intermediate dielectric film 41C are also not limited to the above. For example, when the upper surface of the second reflector 41 is optically exposed, it is preferred that the low-refractive-index dielectric film L2 is provided on the side of the first multilayer film 41A closest to the substrate 11, and the low-refractive-index dielectric film L2 is provided on the side of the first multilayer film 41A closest to the intermediate dielectric film 41C. It is preferred that the low-refractive-index dielectric film L2 is provided on the side of the second multilayer film 41B closest to the upper surface, and the high-refractive-index dielectric film H2 is provided on the side of the second multilayer film 41B closest to the intermediate dielectric film 41C.

[0098] For example, Fig.10 As shown, it is preferred that the second multilayer film 41B has 5 low-refractive index dielectric films L2 and 5 high-refractive index dielectric films H2. It is preferred that the film thickness of the low-refractive index dielectric film L2 and the high-refractive index dielectric film H2 is based on 1 / 4 of the wavelength of light emitted from the light emitting layer 14 in each of the low-refractive index dielectric film L2 and the high-refractive index dielectric film H2 (for example, the film thickness satisfies λx / 4n (x is a natural number)).

[0099] As in the above-mentioned embodiments, forming a layer having a smaller etching rate than other layers in the second reflector 19, 31 and 41 can ensure the formation of a reflector having preferred reflection characteristics, thereby ensuring the provision of, for example, surface emitting lasers 10, 30 and 40 (vertical cavity surface emitting devices) having stable lateral modes.

[0100] Description of Reference Numerals

[0101] 10, 30 and 40: Surface-emitting lasers (vertical cavity surface-emitting devices)

[0102] EM1: Luminous structure layer

[0103] 14: Luminous layer

[0104] 19, 31 and 41: Second multilayer mirror

Claims

1. A vertical cavity surface light emitting device, comprising: substrate; a first multilayer film reflector formed on the substrate; A light emitting structure layer formed on the first multilayer film reflector, wherein the light emitting structure layer comprises a light emitting layer; A second multilayer film reflector is formed on the light emitting structure layer, and a resonator is formed between the first multilayer film reflector and the second multilayer film reflector, wherein: The second multilayer film reflector includes a first multilayer film, an intermediate film, and a second multilayer film, wherein the first multilayer film includes a low refractive index film made of a low refractive index material and a high refractive index film made of a high refractive index material having a higher refractive index than the low refractive index material, the low refractive index films and the high refractive index films are alternately stacked, the intermediate film covers the upper surface of the first multilayer film, the intermediate film is light-transmissive to light emitted from the light-emitting layer, the second multilayer film is formed to partially cover the upper surface of the intermediate film, the second multilayer film includes a low refractive index film made of the low refractive index material and a high refractive index film made of the high refractive index material, the low refractive index films and the high refractive index films are alternately stacked, The film thickness of the intermediate film is a natural number multiple of 1 / 2 of the wavelength of the light emitted by the light-emitting layer in the intermediate film. In a plan view viewed from a direction along the central axis of the resonator, an outer edge of the second multilayer film is located inside an outer edge of the intermediate film, and the central axis is located inside an outer edge of the second multilayer film, A low refractive index film is disposed on the side of the first multilayer film closest to the substrate, and a first thin-film high refractive index film made of the high refractive index material is disposed on the side of the first multilayer film closest to the intermediate film, the film thickness of the first thin-film high refractive index film being smaller than the film thickness of the high refractive index film, and A low refractive index film is arranged on the side of the second multilayer film closest to its upper surface, and a second thin film high refractive index film made of the high refractive index material is arranged on the side of the second multilayer film closest to the intermediate film, and the film thickness of the second thin film high refractive index film is smaller than the film thickness of the high refractive index film.

2. The vertical cavity surface light emitting device according to claim 1, wherein: The second multi-layer film and the intermediate film have upper surfaces covered with a metal film.

3. The vertical cavity surface light emitting device according to claim 2, wherein: The second multilayer film has five low-refractive index films and five high-refractive index films and the second thin-film high-refractive index film, The film thicknesses of the low refractive index film and the high refractive index film in the first multilayer film and the second multilayer film are based on 1 / 4 of the wavelength of light emitted from the light emitting layer in each of the low refractive index film and the high refractive index film, and The film thicknesses of the first thin-film high refractive index film and the second thin-film high refractive index film in the first and second multi-layer films are based on 1 / 8 of the wavelength of light emitted from the light emitting layer within the first and second thin-film high refractive index films.

4. The vertical cavity surface light emitting device according to claim 1, wherein: The low refractive index film is disposed on a side of the first multilayer film closest to the substrate, and the low refractive index film is disposed on a side of the first multilayer film closest to the intermediate film. The second multilayer film has the low refractive index film disposed on a side closest to the upper surface thereof, and the second multilayer film has the high refractive index film disposed on a side closest to the intermediate film, and The second multilayer film and the intermediate film have optically exposed upper surfaces.

5. The vertical cavity surface light emitting device according to claim 4, wherein: The second multilayer film has five low-refractive index films and five high-refractive index films. The film thicknesses of the low refractive index film and the high refractive index film in the first and second multilayer films are based on 1 / 4 of the wavelength of light emitted from the light emitting layer in each of the low refractive index film and the high refractive index film.

6. The vertical cavity surface light emitting device according to claim 1, wherein: The second multi-layer film is formed in a ring shape on the upper surface of the intermediate film.

7. The vertical cavity surface light emitting device according to any one of claims 1 to 6, wherein: The etching rate of the intermediate film is lower than the etching rates of the low refractive index film and the high refractive index film of the second multilayer film.

8. The vertical cavity surface light emitting device according to claim 1, wherein: The high refractive index film, the low refractive index film, and the intermediate film are made of dielectric films.

9. The vertical cavity surface light emitting device according to claim 8, wherein: The intermediate film is made of an Al2O3 film or an AlN film.

Images