Surface emitting laser, electronic apparatus, and method for manufacturing surface emitting laser

Abstract

A surface emitting laser (1) that is provided by the present technology comprises a multilayered film reflection mirror (11) in which a plurality of types of layers (11A, 11B) with different refractive indexes are alternately layered, and has a structure in which among the plurality of types of layers, an even number of layers that have the same refractive index and have a 1 / 2 wavelength optical thickness with regard to an oscillation wavelength (λ) are positioned in at least one section.

Description

Surface-emitting laser, electronic device, and method for manufacturing a surface-emitting laser

[0001] The technology disclosed herein (hereinafter also referred to as "this technology") relates to a surface-emitting laser, an electronic device, and a method for manufacturing a surface-emitting laser.

[0002] Vertical cavity surface-emitting lasers (VCSELs) are widely used as compact yet highly efficient light sources, making them suitable for optical communication and sensor applications. However, conventional VCSELs tend to have a wide emission angle, and in particular, multimode VCSELs have higher-order modes, making it difficult to reduce the emission angle.

[0003] Conventional technologies have proposed various methods to reduce the radiation angle. For example, Patent Documents 1 and 2 employ a long resonator structure to enable stable high output in a single mode. This suppresses higher-order transverse mode oscillation.

[0004] Japanese Patent Publication No. 2014-86565 Japanese Patent Publication No. 2009-147302

[0005] However, the technology described in Patent Document 1 requires the crystal growth of thick films on the order of several micrometers, which increases the lead time in the crystal growth process and may reduce productivity. Furthermore, this method may not be applicable to certain materials because thick film growth is difficult with those materials.

[0006] Furthermore, Patent Document 2 sets the optical thickness of each layer of the spacer layer and the multilayer reflector (DBR: Distributed Bragg Reflector) to λ / 2 or λ / 4 depending on the oscillation wavelength λ. However, with this configuration, the phase is not inverted, making it difficult to reduce the radiation angle.

[0007] Therefore, the primary objective of this technology is to provide a technique that can suppress higher-order modes and effectively reduce the radiation angle.

[0008] This technology provides a surface-emitting laser comprising a multilayer reflector in which multiple types of layers with different refractive indices are alternately stacked, and at least a portion of the multiple types of layers have an even number of layers with the same refractive index and an optical thickness of half a wavelength with respect to the oscillation wavelength. In the above structure, at least a portion of the multiple types of layers, where the refractive index is higher than that of the other layers, may have an optical thickness of half a wavelength with respect to the oscillation wavelength and be arranged in an even number of layers. A first multilayer reflector, which is the multilayer reflector of a first conductivity type, an active layer, and a second multilayer reflector, which is the multilayer reflector of a second conductivity type different from the first conductivity type, are stacked in this order, and the above structure may be included in at least one of the first multilayer reflector and the second multilayer reflector. The first conductivity type may be n-type and the second conductivity type may be p-type. The multiple types of layers are semiconductor layers, and the even number of semiconductor layers with an optical thickness of half a wavelength with respect to the oscillation wavelength may be included in the first multilayer reflector. The above-mentioned multiple types of layers are semiconductor layers, and two of these semiconductor layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector. The above-mentioned multiple types of layers are semiconductor layers, and four of these semiconductor layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector and the second multilayer reflector, respectively. The above-mentioned multiple types of layers are semiconductor layers, and two of these semiconductor layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector and the second multilayer reflector, respectively. In the multilayer reflector, a high refractive index layer, an intermediate refractive index layer, and a low refractive index layer are repeatedly stacked in this order, and at least a portion of the intermediate refractive index layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, may be arranged in an even number of layers.A first multilayer reflector, which is a multilayer reflector of a first conductivity type, an active layer, and a second multilayer reflector, which is a multilayer reflector of a second conductivity type different from the first conductivity type, are stacked in this order, and an even number of intermediate refractive index layers, the optical thickness of which is half a wavelength with respect to the oscillation wavelength, may be included in at least one of the first multilayer reflector and the second multilayer reflector. The first conductivity type may be n-type and the second conductivity type may be p-type. The plurality of layers are semiconductor layers, and an even number of semiconductor layers, the optical thickness of which is half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector. The plurality of layers are semiconductor layers, and two semiconductor layers, the optical thickness of which is half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector and the second multilayer reflector, respectively. The aforementioned multiple types of layers are semiconductor layers, and two of these semiconductor layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, may be included in the first multilayer reflector and the second multilayer reflector, respectively. The aforementioned multiple types of layers are semiconductor layers and dielectric layers, and the optical thickness of the semiconductor layers is one-quarter of a wavelength with respect to the oscillation wavelength, and at least a portion of the dielectric layers may have an even number of layers with an optical thickness of half a wavelength with respect to the oscillation wavelength. Among the multiple layers included in the multilayer reflector, the layer located closest to the active layer may have an optical thickness of half a wavelength with respect to the oscillation wavelength and may have an even number of layers. Furthermore, this technology provides an electronic device equipped with the surface-emitting laser. Furthermore, this technology provides a method for manufacturing a surface-emitting laser, which includes alternately stacking multiple types of layers with different refractive indices, and at least a portion of the multiple types of layers having the same refractive index and an optical thickness of half a wavelength with respect to the oscillation wavelength, may have an even number of layers.

[0009] This is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser. This is a schematic cross-sectional view showing an enlarged view of the area near the multilayer mirror in Figure 1. This is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of this technology. This is a graph showing the reflection characteristics of the multilayer mirror. This is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of this technology manufacturing method of a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of the manufacturing method of a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of the manufacturing method of a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of the manufacturing method of a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology. This is a schematic cross-sectional view showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology. This is a diagram showing an example of the application of a surface-emitting laser according to one embodiment of this technology to a distance measuring device. This is a block diagram showing an example of the schematic configuration of a vehicle control system. This is an explanatory diagram showing an example of the installation position of the imaging unit.

[0010] Hereinafter, preferred embodiments for implementing this technology will be described with reference to the drawings. The embodiments described below are merely examples of typical embodiments of this technology and do not limit the scope of this technology. Furthermore, this technology can be implemented by combining any of the following embodiments and their modifications.

[0011] In the following description of embodiments, configurations may be described using terms with "approximately" attached, such as "approximately parallel" and "approximately orthogonal." For example, "approximately parallel" means not only that they are perfectly parallel, but also that they are substantially parallel, that is, that is, they are deviated from a perfectly parallel state by, for example, a few percent. The same applies to other terms with "approximately." Also, each figure is a schematic diagram and is not necessarily a strictly accurate representation. The scale of the drawings is exaggerated to make the technical features easier to understand. Therefore, it should be noted that the scale of the drawings and the scale of the actual device are not necessarily the same.

[0012] Unless otherwise specified, in drawings, "up" means the upper direction or upper side in the drawing, "down" means the lower direction or lower side in the drawing, "left" means the left direction or left side in the drawing, and "right" means the right direction or right side in the drawing. In addition, in drawings, the same or equivalent elements or components are denoted by the same reference numeral, and redundant explanations are omitted.

[0013] The embodiments described below represent typical embodiments of the Technology and should not be interpreted as narrowing the scope of the Technology. The effects described herein are illustrative and not limiting, and other effects may also exist.

[0014] The explanation will proceed in the following order: 1. First Embodiment of the Technology (Example 1 of a Surface-Emitting Laser) (1) Configuration of a Surface-Emitting Laser (2) Multilayer Reflecting Mirror (3) Configuration of an Embodiment of the Technology 2. Second Embodiment of the Technology (Example 2 of a Surface-Emitting Laser) 3. Third Embodiment of the Technology (Example 3 of a Surface-Emitting Laser) 4. Fourth Embodiment of the Technology (Example 4 of a Surface-Emitting Laser) 5. Fifth Embodiment of the Technology (Example 5 of a Surface-Emitting Laser) 6. Sixth Embodiment of the Technology (Example 6 of a Surface-Emitting Laser) 7. Seventh Embodiment of the Technology (Example 7 of a Surface-Emitting Laser) 8. Eighth Embodiment of the Technology (Example 8 of a Surface-Emitting Laser) 9. Ninth Embodiment of the Technology (Example 9 of a Surface-Emitting Laser) 10. Tenth Embodiment of the Technology (Example 10 of a Surface-Emitting Laser) 11. Eleventh Embodiment of the Technology (Example of a Method for Manufacturing a Surface-Emitting Laser) 12. Examples of Applications to Electronic Devices (1) Example of Application to a Distance Measuring Device (2) Example of Application to a Moving Object

[0015] [1. First Embodiment of the Technology (Example 1 of a Surface-Emitting Laser)] [(1) Configuration of the Surface-Emitting Laser] The surface-emitting laser 1 is a back-emitting laser that is suitably used as a light source for sensors that require high output and a stable light intensity distribution. Light sources for sensors are used for object detection, object recognition, night vision (non-detection imaging), distance measurement, etc., and their range of applications is wide, including automotive collision avoidance sensors, smartphone facial recognition, surveillance, security, and military.

[0016] The following describes an example of the configuration of the surface-emitting laser 1 according to the first embodiment of this technology, with reference to Figure 1. Figure 1 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser.

[0017] As shown in Figure 1, the surface-emitting laser 1 is equipped with a vertical resonator on the substrate 10. This vertical resonator is configured to oscillate at a predetermined oscillation wavelength λ using two multilayer mirrors (a first multilayer mirror 11 and a second multilayer mirror 15) that are facing each other in the direction normal to the substrate 10.

[0018] The first multilayer reflector 11 is formed, for example, in contact with the upper surface of the substrate 10. On the other hand, the second multilayer reflector 15 is formed, for example, at a position relatively farther from the substrate 10 than the first multilayer reflector 11, that is, at a position farther from the light emission surface 1S described later.

[0019] The surface-emitting laser 1 is configured to emit laser light L from the side of the first multilayer reflecting mirror 11. Therefore, the surface-emitting laser 1 is a back-side-emitting laser having a light-emitting surface 1S on its back surface.

[0020] On the substrate 10, a first multilayer reflector 11, a first spacer layer 12, an active layer 13, a second spacer layer 14, and a second multilayer reflector 15 are stacked in this order to form a semiconductor stacked structure.

[0021] The semiconductor stacked structure has a columnar mesa portion 20a on the side of the second multilayer reflecting mirror 15, which includes the second multilayer reflecting mirror 15 but does not include the active layer 13. An annular diffusion region 16 is formed on the outer edge of the mesa portion 20a. The semiconductor stacked structure has a columnar mesa portion 20b on the substrate 10 side, which has a larger diameter than the mesa portion 20a and includes the active layer 13. The mesa portion 20a is formed in contact with the upper surface of the mesa portion 20b.

[0022] The surface-emitting laser 1 includes electrode layers 17 and 18 for injecting current into a semiconductor stacked structure. The electrode layer 17 is formed, for example, on the surface of the substrate 10 on the mesa portion 20a and 20b side, and the electrode layer 18 is formed, for example, on the upper surface of the mesa portion 20a (including, for example, the second multilayer reflecting mirror 15). Furthermore, the surface-emitting laser 1 includes an insulating layer 21 that covers the mesa portion 20a and 20b, but the electrode layers 17 and 18 are not covered by the insulating layer 21 and are exposed to the outside.

[0023] The electrode layers 17 and 18 function as external terminals of the surface-emitting laser 1. The electrode layer 17 is electrically connected to the substrate 10 and is formed, for example, on the upper surface of the substrate 10 and positioned at a location corresponding to the base of the mesa portion 20b. The electrode layer 17 is constructed by stacking, for example, titanium (Ti), platinum (Pt), and gold (Au) in that order.

[0024] The electrode layer 18 is provided at a location opposite the opening of the diffusion region 16 and is formed in contact with the upper surface of the mesa portion 20a. The electrode layer 18 is, for example, circular in shape, and is made up of layers of gold (Au) and germanium (Ge), nickel (Ni), and gold (Au) stacked in sequence, and is electrically connected to the second multilayer reflecting mirror 15.

[0025] The insulating layer 21 is formed of an insulating material composed of, for example, SiN or Al2O3.

[0026] The substrate 10 is a crystal growth substrate used when epitaxial crystal growth is performed on a semiconductor stacked structure. The substrate 10 and the semiconductor stacked structure are made of, for example, a GaAs-based semiconductor. The substrate 10 is light-transmitting to light emitted from the active layer 13 and is, for example, an n-type GaAs substrate. The n-type GaAs substrate contains n-type impurities such as silicon (Si).

[0027] The active layer 13 is designed according to the oscillation wavelength λ and application, and for example, has a laminate in which well layers and barrier layers are alternately stacked. The well layer is, for example, made of In 0.05 Ga 0.95 It is composed of As, and the barrier layer is, for example, Al with a thickness of 5 nm. 0.1 Ga 0.9 It is composed of As.

[0028] The first spacer layer 12 is composed of n-type GaAs, for example. The first spacer layer 12 contains n-type impurities such as silicon (Si).

[0029] The second spacer layer 14 is formed between the active layer 13 and the second multilayer reflector 15, more specifically, between the diffusion region 16 and the active layer 13. The second spacer layer 14 is made of a semiconductor layer in which the Al composition ratio is smaller than that of the low refractive index semiconductor layer 15A described later, and is made of, for example, p-type GaAs. The second spacer layer 14 contains p-type impurities such as zinc (Zn), carbon (C), magnesium (Mg), or beryllium (Be).

[0030] The combined optical thickness of the first spacer layer 12, the active layer 13, and the second spacer layer 14 is, for example, equal to the oscillation wavelength λ. Of the active layer 13, the region facing the aperture of the diffusion region 16 becomes the light-emitting region when current is injected into the surface-emitting laser 1.

[0031] The diffusion region 16 is a region that narrows the current injected into the active layer 13, and is an impurity diffusion region with a conductivity type different from that of the second multilayer reflecting mirror 15. The diffusion region 16 is also provided with an opening for narrowing the current, and the diameter d1 of the opening is, for example, 6.6 μm, 8.8 μm, or 14.4 μm. The diffusion region 16 is formed, for example, in an annular shape.

[0032] Although not shown in this figure, an oxide layer may be laminated between the active layer 13 and the second spacer layer 14. The oxide layer primarily contributes to current confinement and optical mode control. The oxide layer is formed from a selectively oxidizable material, such as AlGaAs, and plays a role in improving the device's operational efficiency by limiting the current injection region. The thickness of the oxide layer and the size of the oxidation openings are adjusted according to the device's operational characteristics.

[0033] [(2) Multilayer Reflecting Mirror] An example of the configuration of a multilayer reflecting mirror will be described with reference to Figure 2. Figure 2 is a schematic cross-sectional view of the area around the multilayer reflecting mirror in Figure 1, magnified.

[0034] As shown in Figure 2, the first multilayer reflector 11, the first spacer layer 12, the active layer 13, the oxide layer 19, the second spacer layer 14, and the second multilayer reflector 15 are stacked in this order to form a semiconductor stacked structure.

[0035] First, let's describe the first multilayer mirror 11. This first multilayer mirror 11 is constructed by alternately stacking low-refractive-index semiconductor layers 11A and high-refractive-index semiconductor layers 11B. The low-refractive-index semiconductor layer 11A is a semiconductor layer with a relatively higher Al composition ratio than the high-refractive-index semiconductor layer 11B, and its optical thickness is, for example, λ / 4. The low-refractive-index semiconductor layer 11A is, for example, n-type Al a3 Ga 1-a3 It is composed of As (0 < a3 < 1). On the other hand, the high refractive index semiconductor layer 11B is, for example, n-type Al a4 Ga 1-a4 It is composed of As (0 ≤ a4 < a3).

[0036] The first multilayer mirror 11 contains, for example, silicon (Si) or the like as an n-type impurity. For example, when a3 is 0.9, a4 is 0.1, the number of pairs of the low refractive index semiconductor layer 11A and the high refractive index semiconductor layer 11B may be 20 pairs.

[0037] Next, the second multilayer mirror 15 will be described. This second multilayer mirror 15 is also formed by alternately laminating a low refractive index semiconductor layer 15A and a high refractive index semiconductor layer 15B. The low refractive index semiconductor layer 15A has an optical thickness of 1 / 4 wavelength of the oscillation wavelength λ (λ is, for example, about 940 nm), and is composed of p-type Al a1 Ga 1-a1 As (0 < a1 < 1). The high refractive index semiconductor layer 15B is composed of, for example, p-type Al a2 Ga 1-a2 As (0 ≤ a2 < a1), and the low refractive index semiconductor layer 15A is made of a material with a higher Al (aluminum) composition ratio than the high refractive index semiconductor layer 15B.

[0038] The second multilayer mirror 15 contains p-type impurities such as, for example, zinc (Zn), carbon (C), magnesium (Mg), or beryllium (Be). Also, for example, when a1 is 0.9, a2 is 0.1, the number of pairs of the low refractive index semiconductor layer 11A and the high refractive index semiconductor layer 11B may be 22 pairs.

[0039] The resonator has a mechanism that repeatedly reflects light by the first multilayer mirror 11 and the second multilayer mirror 15 to amplify the light. When light is repeatedly reflected in the resonator, the light as an electromagnetic wave may form different modes. A mode is a propagation pattern of light and is classified into a fundamental mode and a higher-order mode. The fundamental mode is the simplest and most efficient mode, and the light is efficiently amplified in the resonator while traveling straight. On the other hand, the higher-order mode is generated when the light is reflected at a large angle, and the confinement of light in the resonator becomes incomplete, and the energy loss tends to increase.

[0040] When the higher-order mode occurs, the radiation angle spreads and the quality of the light beam deteriorates. Also, a part of the light may be absorbed by the wall of the resonator, and the output efficiency may decrease. As a result, the performance of the device using the resonator is greatly restricted, so it is important to suppress the higher-order mode.

[0041] [(3) Configuration according to an embodiment of the present technology] Therefore, the present technology includes a multilayer mirror in which a plurality of types of layers having different refractive indices are alternately laminated, and among the plurality of types of layers, a layer having the same refractive index with an optical thickness of 1 / 2 wavelength with respect to the oscillation wavelength is arranged in an even number of layers at least in part, and a surface-emitting laser is provided.

[0042] This will be described with reference to FIG. 3. FIG. 3 is a schematic cross-sectional view showing a configuration example of a surface-emitting laser according to an embodiment of the present technology.

[0043] As shown in FIG. 3, a surface-emitting laser 1 according to an embodiment of the present technology includes multilayer mirrors 11 and 15 in which a plurality of types of layers (semiconductor layers in this configuration example) having different refractive indices are alternately laminated. This surface-emitting laser 1 has a structure in which at least a part of the layers having the same refractive index with an optical thickness of 1 / 2 wavelength with respect to the oscillation wavelength is arranged in an even number of layers among the plurality of types of layers.

[0044] In this configuration example, the first multilayer mirror 11 includes a low-refractive-index semiconductor layer 11A and a high-refractive-index semiconductor layer 11B, which are a plurality of types of semiconductor layers having different refractive indices. The second multilayer mirror 15 includes a low-refractive-index semiconductor layer 15A and a high-refractive-index semiconductor layer 15B, which are a plurality of types of semiconductor layers having different refractive indices. And at least a part of the high-refractive-index semiconductor layer 11B included in the first multilayer mirror 11 has an optical thickness of 1 / 2 wavelength with respect to the oscillation wavelength and the number is even.

[0045] With such a configuration, it is possible to suppress the high-order mode and effectively reduce the emission angle. The surface-emitting laser according to an embodiment of the present technology can reduce the emission angle by setting a part of the layers of the multilayer mirror to λ / 2 instead of the conventional optical thickness λ / 4 (λ is the oscillation wavelength).

[0046] This will be explained with reference to Figure 4. Figure 4 is a graph showing the reflection characteristics of a multilayer mirror. This graph shows the change in reflectivity of the multilayer mirror (nDBR) in the thickness direction from the edge of the active layer toward the substrate. This graph shows the reflectivity of a two-layer structure and a four-layer structure when the optical thickness of the GaAs layer is λ / 2, compared to a normal structure. The horizontal axis represents the thickness of the multilayer mirror (nm), and the vertical axis represents the reflectivity (%).

[0047] The "conventional structure" refers to a multilayer mirror composed of semiconductor layers with an optical thickness of λ / 4. In a typical multilayer mirror, layers with different refractive indices are alternately stacked with an optical thickness of λ / 4 to increase reflectivity and promote light reflection and resonance. It can be confirmed that the reflectivity gradually increases as the number of layers increases, eventually reaching a high reflectivity.

[0048] On the other hand, in structures with two and four additional λ / 2 layers of GaAs, a temporary decrease in reflectivity is observed at certain stacking counts. In particular, the addition of λ / 2 layers shows a rapid decrease in reflectivity in the initial stages, followed by a recovery in reflectivity.

[0049] This decrease in reflectivity indicates that the λ / 2 layer has the effect of suppressing higher-order modes of light. The reduced reflectivity makes it more difficult for light with large angles to return into the resonator, thus suppressing the radiation angle.

[0050] This means that the arrangement of the λ / 2 layers significantly affects the reflection characteristics of the multilayer mirror, and by selecting the optimal structure, it becomes possible to improve the efficiency of light emission and control the radiation angle.

[0051] The key feature of this technology is that it temporarily reduces reflectivity by changing the optical thickness of a specific layer to λ / 2, thereby suppressing higher-order modes of light. As a result, higher-order modes of light that cannot return to the resonator can be effectively excluded, and the radiation angle can be suppressed.

[0052] Furthermore, inserting a λ / 2 layer reverses the phase of the light, changing the reflection intensity. This structure selectively amplifies the fundamental modes of light and enhances the confinement effect of light in the longitudinal direction. As a result, the light intensity is efficiently radiated to the outside, improving the efficiency of light emission.

[0053] However, since the reflectivity temporarily decreases when a λ / 2 layer is inserted, it is necessary to insert another λ / 2 layer to invert the phase and restore the reflectivity. For this reason, the number of layers with an optical thickness of λ / 2 must be even, which ensures sufficient reflection within the resonator and improves the overall efficiency of light emission.

[0054] Let's explain again with reference to Figure 3. The first multilayer mirror 11 has a structure in which semiconductor layers with a lower refractive index (low refractive index semiconductor layer) 11A and semiconductor layers with a higher refractive index (high refractive index semiconductor layer) 11B are alternately stacked. Similarly, the second multilayer mirror 15 also has a structure in which semiconductor layers with a lower refractive index (low refractive index semiconductor layer) 15A and semiconductor layers with a higher refractive index (high refractive index semiconductor layer) 15B are alternately stacked.

[0055] The semiconductor layer (λ / 2 layer) whose optical thickness is half the wavelength of the oscillation wavelength may be any of the low refractive index semiconductor layers 11A, 15A or the high refractive index semiconductor layers 11B, 15B. However, the effect of reducing the radiation angle is greater when the high refractive index semiconductor layers 11B, 15B are used. This is not limited to semiconductor layers, but also applies to dielectric layers, which will be discussed later.

[0056] In other words, it is preferable that, among the multiple types of layers, at least a portion of the layers with a higher refractive index than the other layers have an optical thickness of half a wavelength with respect to the oscillation wavelength, and that they are arranged in an even number of layers. In the configuration example shown in Figure 3, at least a portion of the high refractive index semiconductor layer 11B has an optical thickness of half a wavelength with respect to the oscillation wavelength, and they are arranged in an even number of layers.

[0057] To further explain the configuration example shown in Figure 3, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order.

[0058] A first spacer layer 12 is positioned between the first multilayer mirror 11 and the active layer 13. A second spacer layer 14 is positioned between the second multilayer mirror 15 and the active layer 13.

[0059] It is preferable that an even number of semiconductor layers (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength are included in at least one of the first multilayer reflecting mirror 11 and the second multilayer reflecting mirror 15. In this configuration example, an even number of semiconductor layers (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength are included in the first multilayer reflecting mirror 11. More specifically, a 2-layer semiconductor layer (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength is included in the first multilayer reflecting mirror 11.

[0060] The first multilayer reflector 11 is a first-conductivity type multilayer reflector, and the second multilayer reflector 15 is a second-conductivity type multilayer reflector. It is preferable that the first conductivity type is n-type and the second conductivity type is p-type. In other words, it is preferable that an even number of semiconductor layers (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength are included in the n-type multilayer reflector.

[0061] This minimizes the effects of light absorption. Specifically, the placement of the λ / 2 layer temporarily reduces reflectivity, causing a delay in light. If this delayed light is absorbed, it negatively affects the light emission efficiency, so it is desirable to place the λ / 2 layer in a layer with low light absorption.

[0062] Since n-type materials absorb less light than p-type materials, arranging a λ / 2 layer in an n-type multilayer mirror suppresses light absorption losses and allows for more stable light emission characteristics.

[0063] In the multilayer mirrors 11 and 15, it is preferable that the layer closest to the active layer 13 has an optical thickness of half a wavelength with respect to the oscillation wavelength, and that an even number of layers are arranged. In this configuration example, among the multiple high refractive index semiconductor layers 11B included in the first multilayer mirror 11, the high refractive index semiconductor layer 11B closest to the active layer 13 has an optical thickness of half a wavelength with respect to the oscillation wavelength, and that an even number of layers are arranged.

[0064] The reason why it is preferable to place the λ / 2 layer as close to the active layer 13 as possible is to efficiently control the reflectivity of light, suppress the radiation angle, and achieve optimal light emission characteristics. Specifically, by placing the λ / 2 layer close to the active layer 13, the reflectivity can be effectively reduced, preventing higher-order mode light from returning to the active layer and reducing the radiation angle.

[0065] Furthermore, by positioning the λ / 2 layer close to the active layer 13, the necessary recovery of reflectivity after a decrease in reflectivity can be achieved with a small number of layers. This makes it possible to achieve efficient light emission without increasing the number of pairs of multilayer mirrors.

[0066] Therefore, the closer the λ / 2 layer is to the active layer 13, the better. Placing the λ / 2 layer as close to the active layer 13 as possible is most effective in improving the efficiency of light emission and suppressing the emission angle, thus contributing to improved device performance.

[0067] The above description of the surface-emitting laser according to the first embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0068] [2. Second Embodiment of the Technology (Example 2 of a Surface-Emitting Laser)] The number of semiconductor layers (λ / 2 layers) whose optical thickness is half a wavelength with respect to the oscillation wavelength can be even, and is not particularly limited.

[0069] An example of the configuration of a surface-emitting laser according to another embodiment of this technology will be described with reference to Figure 5. Figure 5 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of this technology.

[0070] As shown in Figure 5, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. The first multilayer reflector 11 contains four semiconductor layers (λ / 2 layers) 11B, the optical thickness of which is half a wavelength with respect to the oscillation wavelength.

[0071] Furthermore, the second multilayer reflecting mirror 15 may include four semiconductor layers (λ / 2 layers) whose optical thickness is half a wavelength relative to the oscillation wavelength.

[0072] The above description of the surface-emitting laser according to the second embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0073] [3. Third Embodiment of the Technology (Example 3 of a Surface-Emitting Laser)] The second multilayer reflector 15 may include an even number of semiconductor layers (λ / 2 layers) whose optical thickness is half a wavelength with respect to the oscillation wavelength. This will be explained with reference to Figure 6. Figure 6 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the Technology.

[0074] As shown in Figure 6, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. The second multilayer reflector 15 contains an even number of semiconductor layers (λ / 2 layers) 15B, the optical thickness of which is 1 / 2 wavelength with respect to the oscillation wavelength (2 layers in this example).

[0075] The above description of the surface-emitting laser according to the third embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0076] [4. Fourth Embodiment of the Technology (Example 4 of a Surface-Emitting Laser)] Semiconductor layers with an even number of layers (λ / 2 layers) whose optical thickness is half a wavelength relative to the oscillation wavelength may be included in the first multilayer reflector 11 and the second multilayer reflector 15, respectively. This will be explained with reference to Figure 7. Figure 7 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the Technology.

[0077] As shown in Figure 7, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. The first multilayer reflector 11 and the second multilayer reflector 15 each contain an even number of semiconductor layers (λ / 2 layers) whose optical thickness is half a wavelength with respect to the oscillation wavelength. More specifically, the first multilayer reflector 11 and the second multilayer reflector 15 each contain two semiconductor layers (λ / 2 layers) 11B and 15B whose optical thickness is half a wavelength with respect to the oscillation wavelength.

[0078] The number of λ / 2 layers in the first multilayer reflector 11 and the number of λ / 2 layers in the second multilayer reflector 15 may be different. For example, the first multilayer reflector 11 may contain four semiconductor layers (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength, and the second multilayer reflector 15 may contain two semiconductor layers (λ / 2 layers) with an optical thickness of half a wavelength relative to the oscillation wavelength.

[0079] The above description of the surface-emitting laser according to the fourth embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0080] [5. Fifth Embodiment of the Technology (Example 5 of a Surface-Emitting Laser)] At least a portion of the layers with a lower refractive index than the other layers may have an optical thickness of half a wavelength with respect to the oscillation wavelength, and may be arranged in an even number of layers. This will be explained with reference to Figure 8. Figure 8 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the Technology.

[0081] As shown in Figure 8, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. At least a portion of the semiconductor layer 11A, which has a lower refractive index than the other layers (low refractive index semiconductor layer), has an optical thickness of half a wavelength relative to the oscillation wavelength, and is arranged in an even number of layers (two layers in this configuration example).

[0082] The above description of the surface-emitting laser according to the fifth embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0083] [6. Sixth Embodiment of the Technology (Example 6 of a Surface-Emitting Laser)] The types of semiconductor layers included in the multilayer mirror are not limited to two types: a high-refractive-index semiconductor layer and a low-refractive-index semiconductor layer, but may be three or more types.

[0084] An example of the configuration of a surface-emitting laser according to another embodiment of this technology will be described with reference to Figure 9. Figure 9 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of this technology.

[0085] As shown in Figure 9, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order.

[0086] In this configuration example, the first multilayer reflecting mirror 11 has three types of semiconductor layers with refractive indices n1, n2, and n3 (where n1 > n2 > n3) stacked in this order: a high refractive index semiconductor layer 11B, an intermediate refractive index semiconductor layer 11C, and a low refractive index semiconductor layer 11A. Among the semiconductor layers with a refractive index of n2 (intermediate refractive index semiconductor layer 11C), at least a portion of the intermediate refractive index layers have an optical thickness of half a wavelength relative to the oscillation wavelength, and an even number of such layers are arranged.

[0087] A semiconductor layer with an even number of layers (an intermediate refractive index semiconductor layer of λ / 2 layers) having a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength may be included in at least one of the first multilayer mirror 11 and the second multilayer mirror 15. In this example configuration, the first multilayer mirror 11 includes a semiconductor layer with an even number of layers (an intermediate refractive index semiconductor layer 11C of λ / 2 layers) having a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength. More specifically, the first multilayer mirror 11 includes a semiconductor layer with two layers (an intermediate refractive index semiconductor layer 11C of λ / 2 layers) having a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength.

[0088] The first multilayer reflector 11 is a first-conductivity type multilayer reflector, and the second multilayer reflector 15 is a second-conductivity type multilayer reflector. It is preferable that the first conductivity type is n-type and the second conductivity type is p-type. In other words, it is preferable that the n-type multilayer reflector contains an even number of semiconductor layers (an intermediate refractive index semiconductor layer 11C of λ / 2 layers) with a refractive index of n² and an optical thickness of half a wavelength relative to the oscillation wavelength.

[0089] Furthermore, this is not limited to semiconductor layers, and the same may apply to dielectric layers, which will be discussed later. In other words, in a multilayer reflecting mirror, three types of dielectric layers with refractive indices n1, n2, and n3 (where n1 > n2 > n3) (high refractive index dielectric layer, intermediate refractive index dielectric layer, and low refractive index dielectric layer) may be repeatedly stacked in this order. In addition, among the dielectric layers with a refractive index of n2 (intermediate refractive index dielectric layers), at least a portion of the dielectric layers (intermediate refractive index dielectric layers) may have an even number of layers with an optical thickness of half a wavelength relative to the oscillation wavelength.

[0090] The above description of the surface-emitting laser according to the sixth embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0091] [7. Seventh Embodiment of the Technology (Example 7 of a Surface-Emitting Laser)] The number of semiconductor layers (intermediate refractive index semiconductor layers that are λ / 2 layers) with a refractive index of n2 and an optical thickness of half a wavelength with respect to the oscillation wavelength can be even, and is not particularly limited.

[0092] An example of the configuration of a surface-emitting laser according to another embodiment of this technology will be described with reference to Figure 10. Figure 10 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of this technology.

[0093] As shown in Figure 10, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order.

[0094] In this configuration example, the first multilayer mirror 11 is constructed by alternately stacking three types of semiconductor layers (high refractive index semiconductor layer 11B, intermediate refractive index semiconductor layer 11C, and low refractive index semiconductor layer 11A) with refractive indices n1, n2, and n3 (where n1 > n2 > n3). Furthermore, the first multilayer mirror 11 contains four semiconductor layers (intermediate refractive index semiconductor layer 11C, which is λ / 2 layer) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength.

[0095] The above description of the surface-emitting laser according to the seventh embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0096] [8. Eighth Embodiment of the Technology (Example 8 of a Surface-Emitting Laser)] The second multilayer reflector 15 may include four semiconductor layers (an intermediate refractive index semiconductor layer of λ / 2 layers) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength. This will be explained with reference to Figure 11. Figure 11 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the Technology.

[0097] As shown in Figure 11, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. The second multilayer reflector 15 contains an even number of semiconductor layers (two layers in this configuration example) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength (an intermediate refractive index semiconductor layer 15C of λ / 2 layers).

[0098] The above description of the surface-emitting laser according to the eighth embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0099] [9. Ninth Embodiment of the Technology (Example 9 of a Surface-Emitting Laser)] Semiconductor layers with an even number of layers (intermediate refractive index semiconductor layers of λ / 2 layers) having a refractive index of n2 and an optical thickness of 1 / 2 wavelength relative to the oscillation wavelength may be included in the first multilayer mirror 11 and the second multilayer mirror 15, respectively. This will be explained with reference to Figure 12. Figure 12 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the Technology.

[0100] As shown in Figure 12, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. The first multilayer reflector 11 and the second multilayer reflector 15 each contain an even number of semiconductor layers (intermediate refractive index semiconductor layers 11C, 15C, which are λ / 2 layers) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength. More specifically, the first multilayer reflector 11 contains two semiconductor layers (intermediate refractive index semiconductor layer 11C, which is λ / 2 layers) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength. Similarly, the second multilayer reflector 15 contains two semiconductor layers (intermediate refractive index semiconductor layer 15C, which is λ / 2 layers) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength.

[0101] The number of λ / 2 intermediate refractive index semiconductor layers 11C included in the first multilayer reflector 11 and the number of λ / 2 intermediate refractive index semiconductor layers 15C included in the second multilayer reflector 15 may be different from each other. For example, the first multilayer reflector 11 may contain four semiconductor layers (λ / 2 intermediate refractive index semiconductor layers 11C) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength, and the second multilayer reflector 15 may contain two semiconductor layers (λ / 2 intermediate refractive index semiconductor layers 15C) with a refractive index of n2 and an optical thickness of half a wavelength relative to the oscillation wavelength.

[0102] The above description of the surface-emitting laser according to the ninth embodiment of this technology can be applied to other embodiments of this technology, unless there are any particular technical inconsistencies.

[0103] [10. Tenth Embodiment of the Technology (Example 10 of a Surface-Emitting Laser)] The semiconductor layer is not limited to semiconductor layers, and at least a portion of the dielectric layer may have an even number of layers with an optical thickness of half a wavelength relative to the oscillation wavelength. In other words, the technology provides a surface-emitting laser in which the optical thickness of the semiconductor layer is one-quarter of the oscillation wavelength, and at least a portion of the dielectric layer has an even number of layers with an optical thickness of half a wavelength relative to the oscillation wavelength. This will be explained with reference to Figure 13. Figure 13 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser according to one embodiment of the technology.

[0104] As shown in Figure 13, this surface-emitting laser has a first multilayer reflector 11, which is a first conductivity type multilayer reflector, an active layer 13, and a second multilayer reflector 15, which is a second conductivity type multilayer reflector different from the first conductivity type, stacked in this order. In this example configuration, the first multilayer reflector 11 has a structure in which multiple types of dielectric layers 11D and 11E with different refractive indices are stacked alternately. Of these dielectric layers, at least a portion have an even number of layers with an optical thickness of half a wavelength with respect to the oscillation wavelength (λ / 2 layers).

[0105] In this configuration example, the first multilayer reflector 11 has a structure in which dielectric layers with a higher refractive index than other layers (high refractive index dielectric layers) 11E and dielectric layers with a lower refractive index than other layers (low refractive index dielectric layers) 11D are alternately stacked. The layer whose optical thickness is half a wavelength with respect to the oscillation wavelength may be either a high refractive index dielectric layer 11E or a low refractive index dielectric layer 11D. However, similar to semiconductor layers, the effect of reducing the radiation angle is greater when it is a high refractive index dielectric layer 11E. In other words, it is preferable that at least a portion of the dielectric layers 11E with a higher refractive index than other layers have an optical thickness of half a wavelength with respect to the oscillation wavelength and are arranged in an even number of layers.

[0106] The above description of the surface-emitting laser according to the tenth embodiment of this technology can be applied to other embodiments of this technology unless there are any particular technical inconsistencies.

[0107] [11. Eleventh Embodiment of the Technology (Example of Method for Manufacturing a Surface-Emitting Laser)] The technology provides a method for manufacturing a surface-emitting laser, which includes alternately stacking multiple types of layers with different refractive indices, wherein at least a portion of the multiple types of layers have an even number of layers with the same refractive index and an optical thickness of half a wavelength with respect to the oscillation wavelength.

[0108] A method for manufacturing a surface-emitting laser according to one embodiment of this technology will be described with reference to Figures 14 to 23. Figures 14 to 23 are schematic cross-sectional views showing an example of a method for manufacturing a surface-emitting laser according to one embodiment of this technology.

[0109] To manufacture the surface-emitting laser 1, a compound semiconductor is formed on a substrate 10 in one step by an epitaxial crystal growth method such as MOCVD (Metal Organic Chemical Vapor Deposition). In this process, methyl-based organometallic gases such as trimethylaluminum (TMAl), trimethylgallium (TMGa), and trimethylindium (TMIn), along with arsine (AsH3) gas, are used as raw materials for the compound semiconductor. Disilane (Si2H6) is used as a raw material for the donor impurity, and CBr4 is used as a raw material for the acceptor impurity.

[0110] As shown in Figure 14, first, a semiconductor stacked structure including a first multilayer reflector 11, a first spacer layer 12, an active layer 13, a second spacer layer 14, and a second multilayer reflector 15 is formed on the surface of the substrate 10 by an epitaxial crystal growth method such as MOCVD. The process of forming the multilayer reflectors 11 and 15 includes alternately stacking multiple types of layers with different refractive indices. Among the multiple types of layers, at least a portion of the stacked structure has an even number of layers with the same refractive index whose optical thickness is half a wavelength relative to the oscillation wavelength.

[0111] Next, as shown in Figure 15, for example, a circular resist layer (not shown) is formed, and then this resist layer is used as a mask to selectively etch the second multilayer reflector 15 and etch the semiconductor stacked structure to a depth that does not reach the active layer 13. At this time, it is preferable to use Reactive Ion Etching (RIE) with a Cl-based gas, for example. In this way, a mesa portion 20a is formed on the side of the semiconductor stacked structure where the second multilayer reflector 15 is located, and which includes the second multilayer reflector 15 but does not include the active layer 13. At this time, the mesa portion 20a is formed so as not to include the spacer layer 14.

[0112] Next, a circular resist layer (not shown) is formed on the surface including the surface of the mesa portion 20a. Then, using this resist layer as a mask, the multilayer reflector 11, the first spacer layer 12, the active layer 13, and the second spacer layer 14 are selectively etched. At this time, it is preferable to use RIE with a Cl-based gas, for example. In this way, the mesa portion 20b including the active layer 13 is formed.

[0113] Next, as shown in Figure 16, an electrode layer 18 is formed that is in contact with the upper surface of the mesa portion 20a (for example, the second multilayer reflecting mirror 15), and an electrode layer 17 is formed that is in contact with the upper surface of the substrate 10 and corresponds to the base of the mesa portion 20b.

[0114] Next, as shown in Figure 17, an insulating layer 21a is formed to cover the mesa portions 20a and 20b and the electrode layers 17 and 18.

[0115] Next, as shown in Figures 18 and 19, an opening 21H is formed in the insulating layer 21a by isotropic etching such as wet etching. Specifically, the opening 21H is formed on the side surface of the mesa portion 20a, which is a relatively thin portion of the insulating layer 21a. At this time, the opening 21H may be formed so that the end faces of one or more high refractive index semiconductor layers 15B closer to the active layer 13 within the second multilayer reflecting mirror 15 are not exposed into the opening 21H.

[0116] In this way, after forming an insulating layer 21a having an opening 21H on the side surface of the mesa portion 20a, an annular diffusion region 16 of a first conductivity type (e.g., n-type) different from the second conductivity type (e.g., p-type) of the second multilayer reflecting mirror 15 is formed at the outer edge of the mesa portion 20a by impurity diffusion from the side surface of the mesa portion 20a, as shown in Figures 20, 21, and 22. Specifically, the diffusion region 16 is formed by gas-phase diffusion through impurity diffusion via the opening 21H. At this time, the diffusion region 16 is formed by diffusing impurities of a first conductivity type (e.g., n-type) different from the second conductivity type (e.g., p-type) of the second multilayer reflecting mirror 15.

[0117] Here, the low refractive index semiconductor layer 15A is a semiconductor layer with a relatively higher Al composition ratio than the high refractive index semiconductor layer 15B. Therefore, of the low refractive index semiconductor layer 15A and the high refractive index semiconductor layer 15B exposed in the aperture 21H, the low refractive index semiconductor layer 15A, which has a relatively higher Al composition ratio, has a relatively faster diffusion rate than the high refractive index semiconductor layer 15B. As a result, impurities of the second conductivity type are preferentially diffused into the low refractive index semiconductor layer 15A, forming a comb-like diffusion region 16.

[0118] In this case, the second spacer layer 14 is a semiconductor layer with a relatively lower Al composition ratio than the low refractive index semiconductor layer 15A, similar to the high refractive index semiconductor layer 15B. Therefore, the second spacer layer 14 acts as a stop layer for gas-phase diffusion. In addition, among the multiple high refractive index semiconductor layers 15B contained in the second multilayer mirror 15, the layer closest to the active layer 13 also acts as a stop layer for gas-phase diffusion. Consequently, gas-phase diffusion does not reach the active layer 13.

[0119] Next, as shown in Figure 23, an insulating layer 21 is formed to fill the opening 21H. Subsequently, an opening is made in the insulating layer 21 at a location facing the electrode layers 17 and 18. In this way, the surface-emitting laser 1 is manufactured.

[0120] The above description of the method for manufacturing a surface-emitting laser according to the 11th embodiment of this technology can be applied to other embodiments of this technology unless there are any particular technical inconsistencies.

[0121] [12. Examples of Applications to Electronic Devices] The technology described herein (the Technology) can be applied to various products (electronic devices). The Technology provides electronic devices equipped with surface-emitting lasers according to the first to tenth embodiments. For example, the Technology may be implemented as a device mounted on any type of mobile vehicle such as an automobile, electric vehicle, hybrid electric vehicle, motorcycle, bicycle, personal mobility device, airplane, drone, ship, or robot.

[0122] The surface-emitting laser related to this technology can be applied, for example, as a light source for devices that form or display images using laser light (e.g., laser printers, laser copiers, projectors, head-mounted displays, head-up displays, etc.).

[0123] [(1) Examples of application to distance measuring devices] The following describes examples of applications of surface-emitting lasers according to the above embodiments.

[0124] Figure 24 shows an example of the schematic configuration of a distance measuring device 1000 equipped with a surface-emitting laser 100, as an example of an electronic device relating to this technology. The distance measuring device 1000 measures the distance to a subject S using the TOF (Time Of Flight) method. The distance measuring device 1000 is equipped with a surface-emitting laser 100 as a light source. The distance measuring device 1000 includes, for example, a surface-emitting laser 100, a light receiving device 120, lenses 119 and 130, a signal processing unit 140, a control unit 150, a display unit 160, and a storage unit 170.

[0125] The light receiving device 120 detects the light reflected from the subject S. Lens 119 is a collimating lens that aligns the light emitted from the surface-emitting laser 100. Lens 130 is a focusing lens that collects the light reflected from the subject S and guides it to the light receiving device 120.

[0126] The signal processing unit 140 is a circuit for generating a signal corresponding to the difference between the signal input from the light receiving device 120 and the reference signal input from the control unit 150. The control unit 150 is configured to include, for example, a Time to Digital Converter (TDC). The reference signal may be a signal input from the control unit 150, or it may be an output signal from a detection unit that directly detects the output of the surface-emitting laser 100. The control unit 150 is a processor that controls, for example, the surface-emitting laser 100, the light receiving device 120, the signal processing unit 140, the display unit 160, and the storage unit 170. The control unit 150 is a circuit for measuring the distance to the subject S based on the signal generated by the signal processing unit 140. The control unit 150 generates a video signal for displaying information about the distance to the subject S and outputs it to the display unit 160. The display unit 160 displays information about the distance to the subject S based on the video signal input from the control unit 150. The control unit 150 stores the information about the distance to the subject S in the storage unit 170.

[0127] [(2) Examples of application to mobile devices] The technology relating to this disclosure (this technology) can be applied to various products. For example, the technology relating to this disclosure may be realized as a device mounted on any type of mobile device such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, and robots.

[0128] Figure 25 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technology described herein may be applied.

[0129] The vehicle control system 12000 comprises a plurality of electronic control units connected via a communication network 12001. In the example shown in Figure 25, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an external information detection unit 12030, an internal information detection unit 12040, and an integrated control unit 12050. The functional configuration of the integrated control unit 12050 is shown in the figure, which includes a microcomputer 12051, an audio / image output unit 12052, and an in-vehicle network interface 12053.

[0130] The drivetrain control unit 12010 controls the operation of devices related to the vehicle's drivetrain according to various programs. For example, the drivetrain control unit 12010 functions as a control device for a drivetrain generating device that generates driving force for the vehicle, such as an internal combustion engine or a drive motor; a drivetrain transmission mechanism that transmits driving force to the wheels; a steering mechanism that adjusts the steering angle of the vehicle; and a braking device that generates braking force for the vehicle.

[0131] The body system control unit 12020 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window system, or various lamps such as headlights, reverse lights, brake lights, turn signals, or fog lights. In this case, the body system control unit 12020 may receive radio waves transmitted from a portable device that replaces a key or signals from various switches. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock system, power window system, lamps, etc.

[0132] The external information detection unit 12030 detects information from outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the external information detection unit 12030. The external information detection unit 12030 causes the imaging unit 12031 to capture images of the outside of the vehicle and receives the captured images. Based on the received images, the external information detection unit 12030 may perform object detection processing such as detecting people, cars, obstacles, signs, or characters on the road surface, or distance detection processing.

[0133] The imaging unit 12031 is a light sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0134] The in-vehicle information detection unit 12040 detects information inside the vehicle. The in-vehicle information detection unit 12040 is connected to, for example, a driver status detection unit 12041 that detects the driver's state. The driver status detection unit 12041 includes, for example, a camera that captures images of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's level of fatigue or concentration, or determine whether the driver is drowsy, based on the detection information input from the driver status detection unit 12041.

[0135] The microcomputer 12051 can calculate control target values ​​for the drive force generator, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the external information detection unit 12030 or the internal information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing ADAS (Advanced Driver Assistance System) functions, including collision avoidance or impact mitigation, following driving based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.

[0136] Furthermore, the microcomputer 12051 can perform cooperative control for purposes such as autonomous driving, where the vehicle drives autonomously without driver intervention, by controlling the drive force generating device, steering mechanism, or braking device, etc., based on information about the vehicle's surroundings acquired by the external information detection unit 12030 or the internal information detection unit 12040.

[0137] Furthermore, the microcomputer 12051 can output control commands to the body system control unit 12020 based on external information acquired by the external information detection unit 12030. For example, the microcomputer 12051 can control the headlights according to the position of a preceding or oncoming vehicle detected by the external information detection unit 12030, and perform coordinated control aimed at reducing glare, such as switching from high beams to low beams.

[0138] The audio-image output unit 12052 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying information to the vehicle's occupants or to those outside the vehicle. In the example shown in Figure 25, the output devices include an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an onboard display and a head-up display.

[0139] Figure 26 shows an example of the installation position of the imaging unit 12031.

[0140] In Figure 26, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0141] The imaging units 12101, 12102, 12103, 12104, and 12105 are installed, for example, on the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle 12100. The imaging unit 12101 installed on the front nose and the imaging unit 12105 installed on the upper part of the windshield inside the vehicle mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 installed on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 installed on the upper part of the windshield inside the vehicle is mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0142] Figure 26 shows an example of the imaging range of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 located on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 located on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 located on the rear bumper or back door. For example, by superimposing the image data captured by imaging units 12101 to 12104, an overhead view image of the vehicle 12100 can be obtained.

[0143] At least one of the imaging units 12101 to 12104 may have a function for acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera consisting of multiple image sensors, or an image sensor having pixels for phase difference detection.

[0144] For example, the microcomputer 12051, based on distance information obtained from the imaging units 12101 to 12104, can determine the distance to each object within the imaging range 12111 to 12114 and the temporal change of this distance (relative speed to the vehicle 12100). In particular, it can extract the closest object on the vehicle 12100's path that is traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or more) as the preceding vehicle. Furthermore, the microcomputer 12051 can set a predetermined distance to be maintained before the preceding vehicle and perform automatic braking control (including follow-and-stop control) and automatic acceleration control (including follow-and-start control), etc. In this way, cooperative control aimed at autonomous driving, where the vehicle drives autonomously without driver intervention, can be performed.

[0145] For example, the microcomputer 12051 can use distance information obtained from imaging units 12101 to 12104 to classify and extract three-dimensional object data related to three-dimensional objects, such as motorcycles, passenger cars, large vehicles, pedestrians, utility poles, and other three-dimensional objects, and use this data for automatic obstacle avoidance. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the degree of risk of collision with each obstacle. If the collision risk is above a set value and there is a possibility of collision, the microcomputer 12051 can provide driving assistance to avoid collisions by outputting a warning to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or evasive steering via the drive system control unit 12010.

[0146] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer 12051 can recognize pedestrians by determining whether or not pedestrians are present in the images captured by the imaging units 12101 to 12104. Such pedestrian recognition is performed, for example, by a procedure to extract feature points from the images captured by the imaging units 12101 to 12104 as infrared cameras, and a procedure to perform pattern matching on a series of feature points that indicate the contour of an object to determine whether or not it is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the imaging units 12101 to 12104 and recognizes a pedestrian, the audio-image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio-image output unit 12052 may also control the display unit 12062 to display an icon indicating a pedestrian at a desired position.

[0147] The above describes an example of a vehicle control system to which the technology described herein may be applied. The technology described herein may be applied to, for example, the imaging unit 12031 of the configuration described above.

[0148] The specific numerical values, shapes, materials (including composition), etc., described herein are examples only and are not limited to these.

[0149] Furthermore, this technology can also take the following configurations: [1] A surface-emitting laser having a structure comprising a multilayer reflector in which multiple types of layers with different refractive indices are alternately stacked, wherein at least a portion of the multiple types of layers have an optical thickness of half a wavelength with respect to the oscillation wavelength and an even number of layers are arranged. [2] The surface-emitting laser according to [1], wherein at least a portion of the multiple types of layers have an optical thickness of half a wavelength with respect to the oscillation wavelength and are arranged in an even number of layers. [3] The surface-emitting laser according to [2], wherein a first multilayer reflector which is a multilayer reflector of a first conductivity type, an active layer, and a second multilayer reflector which is a multilayer reflector of a second conductivity type different from the first conductivity type are stacked in this order, and the structure is included in at least one of the first multilayer reflector and the second multilayer reflector. [4] The surface-emitting laser according to [3], wherein the first conductivity type is n-type and the second conductivity type is p-type. [5] The surface-emitting laser according to [4], wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector. [6] The surface-emitting laser according to [4] or [5], wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector. [7] The surface-emitting laser according to any one of [4] to [6], wherein the plurality of layers are semiconductor layers, and four semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector. [8] The surface-emitting laser according to any one of [4] to [7], wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector and the second multilayer reflector, respectively. [9] The surface-emitting laser according to any one of [4] to [8], wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror and the second multilayer reflecting mirror, respectively.

[10] A surface-emitting laser according to any one of [1] to [9], wherein in the multilayer reflector, a high refractive index layer, an intermediate refractive index layer, and a low refractive index layer are repeatedly stacked in this order, and at least a portion of the intermediate refractive index layer has an even number of intermediate refractive index layers with an optical thickness of half a wavelength with respect to the oscillation wavelength.

[11] A surface-emitting laser according to

[10] , wherein a first multilayer reflector is a multilayer reflector of a first conductivity type, an active layer, and a second multilayer reflector is a multilayer reflector of a second conductivity type different from the first conductivity type are stacked in this order, and an even number of intermediate refractive index layers with an optical thickness of half a wavelength with respect to the oscillation wavelength are included in at least one of the first multilayer reflector and the second multilayer reflector.

[12] A surface-emitting laser according to

[11] , wherein the first conductivity type is n type and the second conductivity type is p type.

[13] The surface-emitting laser according to

[11] or

[12] , wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector.

[14] The surface-emitting laser according to any one of

[11] to

[13] , wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector.

[15] The surface-emitting laser according to any one of

[11] to

[14] , wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector and the second multilayer reflector, respectively.

[16] The surface-emitting laser according to any one of

[11] to

[15] , wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector and the second multilayer reflector, respectively.

[17] The surface-emitting laser according to any one of [1] to

[16] , wherein the plurality of layers are semiconductor layers and dielectric layers, the optical thickness of the semiconductor layer is 1 / 4 wavelength with respect to the oscillation wavelength, and at least a portion of the dielectric layer has an even number of layers with an optical thickness of 1 / 2 wavelength with respect to the oscillation wavelength.

[18] A surface-emitting laser according to any one of [3] to

[17] , wherein, among the plurality of layers included in the multilayer reflector, the layer located closest to the active layer has an optical thickness of half a wavelength with respect to the oscillation wavelength, and an even number of layers are arranged.

[19] An electronic device comprising the surface-emitting laser according to any one of [1] to

[18] .

[20] A method for manufacturing a surface-emitting laser, comprising alternately stacking a plurality of types of layers with different refractive indices, wherein at least a portion of the plurality of types of layers have the same refractive index and an optical thickness of half a wavelength with respect to the oscillation wavelength, and an even number of layers are arranged.

[0150] 1,100 Surface-emitting laser 1S Light-emitting surface 10 Substrate 11 First multilayer reflector 11A Low refractive index semiconductor layer 11B High refractive index semiconductor layer 11C Intermediate refractive index semiconductor layer 11D Low refractive index dielectric layer 11E High refractive index dielectric layer 12 First spacer layer 13 Active layer 14 Second spacer layer 15 Second multilayer reflector 15A Low refractive index semiconductor layer 15B High refractive index semiconductor layer 15C Intermediate refractive index semiconductor layer 16 Diffusion region 17 Electrode layer 18 Electrode layer 19 Oxide layer 20a Mesa portion 20b Mesa portion 21 Insulating layer 21a Insulating layer 21H Aperture

Claims

1. A surface-emitting laser comprising a multilayer reflecting mirror in which multiple types of layers with different refractive indices are alternately stacked, wherein at least a portion of the multiple types of layers have an even number of layers with the same refractive index whose optical thickness is half a wavelength with respect to the oscillation wavelength.

2. The surface-emitting laser according to claim 1, wherein, in the structure described above, at least a portion of the layers among the plurality of layers, the layer having a refractive index higher than the other layers, has an optical thickness of half a wavelength with respect to the oscillation wavelength, and is arranged in an even number of layers.

3. A surface-emitting laser according to claim 2, wherein a first multilayer reflector, which is a multilayer reflector of a first conductivity type; an active layer; and a second multilayer reflector, which is a multilayer reflector of a second conductivity type different from the first conductivity type, are stacked in this order, and the structure is included in at least one of the first multilayer reflector and the second multilayer reflector.

4. The surface-emitting laser according to claim 3, wherein the first conductivity type is n-type and the second conductivity type is p-type.

5. The surface-emitting laser according to claim 4, wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror.

6. The surface-emitting laser according to claim 4, wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector.

7. The surface-emitting laser according to claim 4, wherein the plurality of layers are semiconductor layers, and four of the semiconductor layers, each having an optical thickness of half a wavelength with respect to the oscillation wavelength, are included in the first multilayer reflecting mirror.

8. The surface-emitting laser according to claim 4, wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror and the second multilayer reflecting mirror, respectively.

9. The surface-emitting laser according to claim 4, wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror and the second multilayer reflecting mirror, respectively.

10. The surface-emitting laser according to claim 1, wherein in the multilayer reflecting mirror, a high refractive index layer, an intermediate refractive index layer, and a low refractive index layer are repeatedly stacked in this order, and at least a portion of the intermediate refractive index layer has an even number of intermediate refractive index layers whose optical thickness is half a wavelength with respect to the oscillation wavelength.

11. A surface-emitting laser according to claim 10, wherein a first multilayer reflector, which is a multilayer reflector of a first conductivity type; an active layer; and a second multilayer reflector, which is a multilayer reflector of a second conductivity type different from the first conductivity type, are stacked in this order, and an even number of intermediate refractive index layers, the optical thickness of which is half a wavelength with respect to the oscillation wavelength, are included in at least one of the first multilayer reflector and the second multilayer reflector.

12. The surface-emitting laser according to claim 11, wherein the first conductivity type is n-type and the second conductivity type is p-type.

13. The surface-emitting laser according to claim 11, wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflector.

14. The surface-emitting laser according to claim 11, wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror.

15. The surface-emitting laser according to claim 11, wherein the plurality of layers are semiconductor layers, and an even number of semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror and the second multilayer reflecting mirror, respectively.

16. The surface-emitting laser according to claim 11, wherein the plurality of layers are semiconductor layers, and two semiconductor layers having an optical thickness of half a wavelength with respect to the oscillation wavelength are included in the first multilayer reflecting mirror and the second multilayer reflecting mirror, respectively.

17. The surface-emitting laser according to claim 1, wherein the plurality of layers are semiconductor layers and dielectric layers, the optical thickness of the semiconductor layer is 1 / 4 wavelength with respect to the oscillation wavelength, and at least a portion of the dielectric layer has an even number of layers with an optical thickness of 1 / 2 wavelength with respect to the oscillation wavelength.

18. The surface-emitting laser according to claim 3, wherein, among the plurality of layers included in the multilayer reflecting mirror, the layer located closest to the active layer has an optical thickness of half a wavelength with respect to the oscillation wavelength, and an even number of layers are arranged.

19. An electronic device comprising the surface-emitting laser described in claim 1.

20. A method for manufacturing a surface-emitting laser, comprising alternately stacking multiple types of layers with different refractive indices, wherein at least a portion of the multiple types of layers have an even number of layers with the same refractive index and an optical thickness of half a wavelength with respect to the oscillation wavelength.

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