Surface-emitting laser, projection device, head-up display, mobile device, head-mounted display, and optometry device.

Abstract

To provide a surface-emitting laser capable of improving uniformity of a density of a current injected to a resonator, a projection device, a head-up display, a mobile, a head-mounted display and an optometric device.SOLUTION: A surface-emitting laser comprises: a first reflector; a second reflector; a resonator which is provided between the first reflector and the second reflector and includes an active layer; and a conductive layer which injects a current to the resonator. The surface-emitting laser comprises a semiconductor multilayer structure including the resonator. The semiconductor multilayer structure includes: a first layer including a first p-type semiconductor layer and a second layer which is provided between the first layer and the active layer and includes a second p-type semiconductor layer. The second p-type semiconductor layer is in contact with the first layer and comprises a band gap which is larger than a band gap of the first p-type semiconductor layer. A partial or entire top face of the first layer and an interface of the first layer and the second layer are in contact with the conductive layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a surface-emitting laser, a projection device, a head-up display, a mobile device, a head-mounted display, and an ophthalmography device. [Background technology]

[0002] A vertical cavity surface-emitting laser (VCSEL) is a laser in which a thin active layer is sandwiched between a pair of mirrors, forming a resonator perpendicular to the substrate. Therefore, the mirrors are sometimes required to have a reflectivity of 99% or higher.

[0003] In GaN-based materials, it is more difficult to form semiconductor mirrors with low resistance compared to GaAs-based materials. Therefore, when fabricating surface-emitting lasers with GaN-based materials, an intracavity contact structure is often used, where the mirror is not energized and contact is made in the resonator to inject current into the active layer. In this case, the p-side contact is often created as a current-constricting structure by using a high-resistance layer such as a dielectric on a highly doped p-GaN to form a limited aperture, and current is injected using a conductive transparent film such as indium tin oxide (ITO). [Overview of the project] [Problems that the invention aims to solve]

[0004] In VCSELs with current injection structures using ITO, the light absorption of ITO becomes a problem. Typically, ITO has several thousand cm² of light absorption in the 400 nm band to the visible light range, which is developed for GaN-based VCSELs. -1 It has light absorption properties. Therefore, the effect of absorption is reduced by placing a thin layer of ITO at the nodal points of the electric field strength in the resonator. The thickness of the ITO is almost always 50 nm or less, and often 20 nm or less.

[0005] The resistivity of ITO is typically 1 × 10⁻⁶. -4With resistances in the Ωcm range, the lateral resistance of the ITO is inevitably high. Furthermore, because the resistivity of the p-GaN being injected is in the single-digit Ωcm range, the current injected from the ITO does not spread much laterally but flows vertically through the resonator towards the active layer. In this case, the thin ITO makes it difficult to make the current density uniform between the outer and central parts of the aperture, resulting in a current injection density into the active layer that tends to be dense at the outer edge and sparse in the center. This effect is particularly pronounced with larger aperture diameters. This makes it difficult for the active layer inside the aperture to obtain a uniform gain, and in particular, it becomes difficult to obtain a stable single-mode diode.

[0006] Furthermore, Non-Patent Document 1 describes an attempt to equalize current injection into the aperture by making the n-side distributed Bragg reflector (DBR) conductive. However, even with the configuration described in Non-Patent Document 1, the non-uniformity of current injection density caused by the high electrical resistance of ITO remains unresolved.

[0007] The present invention aims to provide a surface-emitting laser, projection device, head-up display, mobile device, head-mounted display, and ophthalmoscopic device that can improve the uniformity of the density of the current injected into the resonator. [Means for solving the problem]

[0008] According to one aspect of the disclosed technology, a surface-emitting laser comprises a first reflector, a second reflector, a resonator provided between the first reflector and the second reflector and including an active layer, and a conductive layer for injecting current into the resonator, and comprises a semiconductor stacked structure including the resonator, the semiconductor stacked structure comprising a first layer including a first p-type semiconductor layer, and a second layer provided between the first layer and the active layer and including a second p-type semiconductor layer, the second p-type semiconductor layer being in contact with the first layer and having a band gap larger than the band gap of the first p-type semiconductor layer, and part or all of the upper surface of the first layer and the interface between the first layer and the second layer being in contact with the conductive layer. Effects of the Invention

[0009] According to the disclosed technique, the uniformity of the density of current injected into a resonator can be improved. Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a surface-emitting laser according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating the vicinity of a ridge of the surface-emitting laser according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view illustrating the vicinity of a ridge of a surface-emitting laser according to a second embodiment. [Figure 4] FIG. 4 is a cross-sectional view illustrating the vicinity of a ridge of a surface-emitting laser according to a third embodiment. [Figure 5] FIG. 5 is a cross-sectional view illustrating the vicinity of a ridge of a surface-emitting laser according to a fourth embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating the vicinity of a ridge of a surface-emitting laser according to a fifth embodiment. [Figure 7] FIG. 7 is a schematic diagram illustrating a head-up display, which is an example of a projection apparatus according to a sixth embodiment. [Figure 8] FIG. 8 is a schematic diagram illustrating a vehicle equipped with the head-up display according to the sixth embodiment. [Figure 9] FIG. 9 is a perspective view exemplifying an appearance of a head-mounted display according to a seventh embodiment. [Figure 10] FIG. 10 is a diagram partially exemplifying the configuration of the head-mounted display according to the seventh embodiment. [Figure 11] FIG. 11 is a block diagram illustrating an optometry apparatus according to an eighth embodiment. Mode for Carrying Out the Invention

[0011] Embodiments of this disclosure will be described below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configuration will be denoted by the same reference numerals to avoid redundant descriptions.

[0012] (First Embodiment) First, the first embodiment will be described. The first embodiment relates to a surface-emitting laser. Figure 1 is a cross-sectional view showing a surface-emitting laser according to the first embodiment. Figure 2 is a cross-sectional view showing the vicinity of the ridge structure of the surface-emitting laser according to the first embodiment. Figure 2(a) is an enlarged cross-sectional view of a part of Figure 1, and Figure 2(b) is a cross-sectional view showing the current in the vicinity of the region indicated by the dashed circle in Figure 2(a) with arrows.

[0013] As shown in Figure 1, the surface-emitting laser 1 according to the first embodiment includes a substrate 50, a lower reflector 10, a resonator 20, a conductive layer 40, and an upper reflector 30. The lower reflector 10 is on the substrate 50, the resonator 20 is on the lower reflector 10, the conductive layer 40 is on the resonator 20, and the upper reflector 30 is on the conductive layer 40. The surface-emitting laser 1 is configured to output light with a wavelength of 450 nm.

[0014] The substrate 50 is, for example, a GaN substrate with a c-plane on its top surface. The lower reflector 10 is, for example, a DBR made of semiconductor material.

[0015] The resonator 20 comprises a lower spacer layer 100, an active layer 200, and an upper spacer layer 300. The lower spacer layer 100 is located on the lower mirror 10, the active layer 200 is located on the lower spacer layer 100, and the upper spacer layer 300 is located on the active layer 200. Although not essential, an electron blocking layer 250 with a thickness of approximately 20 nm may be present between the active layer 200 and the upper spacer layer 300. The resonator 20 is an example of a semiconductor multilayer structure.

[0016] For example, the lower spacer layer 100 is made of, for example, Si, 3 × 10 18 / cm 3is an n-type GaN layer doped at the concentration. The active layer 200 has a multiple quantum well layer including a plurality of InGaN layers and GaN layers, and emits light at 450 nm. The electron blocking layer 250 has, for example, 2×10 Mg 19 / cm 3 Al doped at the concentration 0.2 Ga 0.8 is an N layer.

[0017] The upper spacer layer 300 includes a first layer 310, a second layer 320, and a third layer 330, as shown in FIG. 2(a). The second layer 320 is provided on the third layer 330, and the first layer 310 is provided on the second layer 320. The third layer 330 is the layer closest to the active layer 200 side among the upper spacer layer 300. The third layer 330 has, for example, 2×10 Mg 19 / cm 3 is a p-type GaN layer doped at the concentration. The second layer 320 has, for example, 2×10 Mg 19 / cm 3 p-type Al doped at the concentration 0.05 Ga 0.95 is an N layer. The thickness of the second layer 320 is, for example, 10 nm. The first layer 310 has, for example, 2×10 Mg 19 / cm 3 p-type In doped at the concentration 0.07 Ga 0.93 is an N layer. The thickness of the first layer 310 is, for example, 15 nm. However, the outermost layer portion from the upper surface of the first layer 310 to a depth of 10 nm is doped with Mg at a higher concentration, for example, 3×10 20 / cm 3 Mg is doped at the concentration. The band gap of the second layer 320 is larger than the band gap of the first layer 310. In the present embodiment, the second layer 320 is an example of the second p-type semiconductor layer, and the first layer 310 is an example of the first p-type semiconductor layer.

[0018] A mesa structure 340 is formed in the upper spacer layer 300, the active layer 200, and the lower spacer layer 100. The mesa structure 340 is formed at a height such that the lower spacer layer 100 is exposed around the mesa structure 340. The mesa structure 340 is formed in a cylindrical shape with a diameter of 25 μm.

[0019] A ridge structure 350 is formed on the upper spacer layer 300. The ridge structure 350 is formed to a height such that the second layer 320 is exposed around the ridge structure 350. For example, the height of the ridge structure 350 is 20 nm. The ridge structure 350 is formed in a cylindrical shape with a diameter of 10 μm. A dielectric layer 60 is formed on the second layer 320 that is exposed from the ridge structure 350. The dielectric layer 60 is in contact with the side surface of the portion of the second layer 320 that constitutes the ridge structure 350. The upper surface of the dielectric layer 60 is on the active layer 200 side of the interface between the first layer 310 and the second layer 320. The dielectric layer 60 is, for example, an SiO2 layer.

[0020] The conductive layer 40 is provided on the dielectric layer 60 and the ridge structure 350. The conductive layer 40 is in contact with the entire upper surface of the first layer 310 and the interface between the first layer 310 and the second layer 320. The conductive layer 40 is a transparent conductive layer, such as an ITO layer.

[0021] The upper reflector 30 is positioned so as to overlap with the ridge structure 350 in a plan view. The upper reflector 30 is, for example, a dielectric DBR.

[0022] An n-side electrode 71 is formed on an n-type lower spacer layer 100 exposed from the mesa structure 340, and is in ohmic contact with the lower spacer layer 100. The n-side electrode 71 has a laminated film in which, for example, a Ti film, an Al film, a Pt film, and an Au film are stacked in that order from bottom to top. A dielectric layer 80 is formed on the portion of the n-type lower spacer layer 100 excluding the portion on which the n-side electrode 71 is formed, and on the side surface of the mesa structure 340. The dielectric layer 80 is, for example, a SiN layer.

[0023] Around the upper reflector 30, a p-side electrode 72 is formed on the conductive layer 40. The p-side electrode 72 has a laminated film in which a Ti film and an Au film are stacked in that order from bottom to top.

[0024] Furthermore, it is preferable that the electric field strength nodes be located near the highly doped portion of the first layer 310 or near the conductive layer 40.

[0025] Next, a method for manufacturing a surface-emitting laser according to the first embodiment will be described.

[0026] First, a lower reflector 10, a lower spacer layer 100, an active layer 200, and an upper spacer layer 300 are formed on the substrate 50 by metal-organic chemical vapor deposition (MOCVD).

[0027] Next, a mesa structure 340 is formed on the laminate of the upper spacer layer 300, the active layer, and the lower spacer layer 100. In forming the mesa structure 340, an etching mask is formed on the upper spacer layer 300 using photolithography with photoresist or metal, and dry etching is performed on the laminate of the upper spacer layer 300, the active layer, and the lower spacer layer 100. At this time, the dry etching is stopped midway through the thickness direction of the lower spacer layer 100.

[0028] Next, near the mesa structure 340, an n-side electrode 71 is formed on the lower spacer layer 100 exposed from the mesa structure 340. The n-side electrode 71 can be formed using lift-off. After forming the metal film constituting the n-side electrode 71, the n-side electrode 71 can be brought into ohmic contact with the lower spacer layer 100 by annealing in an N2 atmosphere at 550°C.

[0029] Next, a dielectric layer 80 covering the mesa structure 340 and the n-side electrode 71 is formed on the lower spacer layer 100. Then, for example, using photolithography, a resist mask is formed that exposes only the upper surface of the mesa structure 340, and the dielectric layer 80 is removed by wet etching. Next, a ridge structure 350 is formed on the upper spacer layer 300. In forming the ridge structure 350, a resist mask is formed on the upper spacer layer 300 using photolithography, and the upper spacer layer 300 is dry-etched.

[0030] Next, a dielectric layer 60 is formed on the upper spacer layer 300 exposed from the ridge structure 350. The thickness of the dielectric layer 60 is such that the upper surface of the dielectric layer 60 is located on the active layer 200 side of the interface between the first layer 310 and the second layer 320 (see Figure 2(a)). Next, a conductive layer 40 is formed on the dielectric layer 60 and the ridge structure 350. In forming the dielectric layer 60 and the conductive layer 40, first, the SiO2 layer and the ITO layer are formed by sputtering or the like while leaving the resist mask used to form the ridge structure 350, and then the resist mask is removed. In other words, lift-off is performed. At this time, the thickness of the ITO layer is such that the upper surface of the ITO layer is approximately flush with the upper surface of the ridge structure 350. After lift-off, another ITO layer is formed so that it is in contact with the upper surface of the ridge structure 350. After that, the excess ITO layer formed on the dielectric layer 80 is removed, for example, by wet etching.

[0031] Next, an upper reflector 30 is formed on the conductive layer 40. The upper reflector 30 can be formed, for example, by lift-off. Next, a p-side electrode 72 is formed on the conductive layer 40 around the upper reflector 30. The p-side electrode 72 can be formed, for example, by lift-off. Next, the portion of the dielectric layer 80 on the n-side electrode 71 is removed by dry etching or the like.

[0032] In this way, the surface-emitting laser 1 according to the first embodiment can be manufactured.

[0033] In the surface-emitting laser 1 according to the first embodiment, the first layer 310 (for example, In 0.07 Ga 0.93 Below the N layer is a second layer 320 (e.g., Al 0.05 Ga 0.95There is an N layer, and the band gap of the second layer 320 is larger than that of the first layer 310. As a result, a two-dimensional hole gas (2DHG) is formed near the interface between the first layer 310 and the second layer 320. The 2DHG contains a high concentration of carriers formed two-dimensionally in a narrow region with a thickness of about 1 nm. Furthermore, the conductive layer 40 is in contact with the entire upper surface of the first layer 310 and the interface between the first layer 310 and the second layer 320.

[0034] Therefore, as shown in Figure 2(b), current is injected from the conductive layer 40 to the resonator 20 not only from the top surface of the first layer 310, but also from the interface between the first layer 310 and the second layer 320. In other words, current is injected from the conductive layer 40 to the resonator 20 via the top surface and side walls of the ridge structure 350. Furthermore, since the electrical resistance of 2DHG is lower than that of the first layer 310 and the second layer 320, carriers tend to spread laterally. Consequently, the current injected from the top surface of the ridge structure 350 spreads laterally in 2DHG, and the current injection density tends to become uniform inside the aperture. In other words, variations in the current injection density inside the ridge structure 350 are suppressed.

[0035] Thus, with the surface-emitting laser 1, the density of the current flowing inside the aperture can be made more uniform, and electrical resistance can be reduced. In the surface-emitting laser 1, the phase difference with respect to the resonant wavelength is shifted between the inside and outside of the ridge structure 350, resulting in an effective refractive index difference, which can be used to confine light in the lateral direction. By improving light confinement in the lateral direction, the lateral single-mode capability can be improved. Furthermore, by utilizing the refractive index difference for light confinement in the lateral direction, the loss due to diffraction can be reduced, making it easier to obtain a single mode at a low threshold.

[0036] Furthermore, if the conductive layer 40 is in contact with the interface between the first layer 310 and the second layer 320, the second layer 320 does not need to be etched when the ridge structure 350 is formed. In other words, if the second layer 320 is exposed by etching the first layer 310, the second layer 320 does not need to be etched. However, if the second layer 320 is also etched, the interface between the first layer 310 and the second layer 320 clearly appears on the side wall surface of the ridge structure 350, making it easier to bring the conductive layer 40 into contact with this interface. Therefore, it is more preferable to etch not only the first layer 310 but also the second layer 320.

[0037] Further, the material of the first layer 310 is not limited to InGaN, and the first layer 310 may be a p-type GaN layer. Generalizing, for example, the first layer 310 is In a Ga 1-a N layer (0≦a<1), and the second layer 320 is Al b Ga 1-b N layer (0<b<1). When the material of the first layer 310 is GaN, crystal defects at the interface between the first layer 310 and the second layer 320 are easily suppressed, and it is easy to obtain effectively high mobility for 2DHG. Further, when the material of the first layer 310 is InGaN, it is easy to obtain high-concentration 2DHG. The material of the dielectric layer 60 is not limited to SiO₂, and the dielectric layer 60 may be a SiNₓ layer, a TaOₓ layer, or the like.

[0038] Further, in the first embodiment, the first layer 310 and the second layer 320 are provided in the resonator 20. However, part or all of the upper reflecting mirror may be a semiconductor DBR, and the thicknesses of the first layer and the second layer are adjusted so that the semiconductor DBR functions as a part thereof, whereby the first layer and the second p-layer may be included in the reflecting mirror.

[0039] (Second Embodiment) The second embodiment will be described. The second embodiment differs from the first embodiment mainly in the configuration of the ridge structure. Figure 3 is a cross-sectional view showing the vicinity of the ridge structure of the surface-emitting laser according to the second embodiment. Figure 3(b) is a cross-sectional view showing current with arrows in the vicinity of the region indicated by the broken-line circle in Figure 3(a).

[0040] As shown in Figure 3, in the surface-emitting laser according to the second embodiment, the first layer 310 includes a first p-type semiconductor layer 311 and an undoped semiconductor layer 312. The undoped semiconductor layer 312 is located on the second layer 320, and the first p-type semiconductor layer 311 is located on the undoped semiconductor layer 312. The undoped semiconductor layer 312 is made of, for example, In 0.07 Ga 0.93 It is an N-type layer. The thickness of the undoped semiconductor layer 312 is, for example, 2.5 nm. The first p-type semiconductor layer 311 is, for example, made of Mg with a content of 2 × 10⁻¹⁶ 19 / cm 3 p-type In doped at the following concentration 0.07 Ga 0.93 It is an N layer. The thickness of the first p-type semiconductor layer 311 is, for example, 12.5 nm. However, the outermost layer of the first p-type semiconductor layer 311, from the top surface to a depth of 10 nm, has a higher density, for example, 3 × 10⁻¹⁶. 20 / cm 3 The material is doped with Mg at a certain concentration. The band gap of the second layer 320 is larger than that of the first layer 310.

[0041] The other configurations are the same as in the first embodiment.

[0042] In the surface-emitting laser according to the second embodiment, the first p-type semiconductor layer 311 (for example, In 0.07 Ga 0.93 An undoped semiconductor layer 312 (for example, In) is located beneath the N layer. 0.07 Ga 0.93 There is an N layer, and below the undoped semiconductor layer 312 is a second layer 320 (e.g., Al 0.05 Ga 0.95 There is an N layer. Also, the band gap of the second layer 320 is larger than the band gap of the first layer 310. As a result, 2DHG is formed near the interface between the undoped semiconductor layer 312 and the second layer 320. The 2DHG contains a high concentration of carriers formed two-dimensionally in a narrow region of about 1 nm thickness within the undoped semiconductor layer 312. Furthermore, the conductive layer 40 is in contact with the entire upper surface of the first layer 310 and the interface between the first layer 310 and the second layer 320.

[0043] Therefore, as shown in Figure 3(b), current is injected from the conductive layer 40 to the resonator 20 not only from the upper surface of the first layer 310, but also from the interface between the first layer 310 and the second layer 320. In other words, current is injected from the conductive layer 40 to the resonator 20 via the upper surface and side walls of the ridge structure 350. Furthermore, the electrical resistance of 2DHG is lower than the electrical resistance of the first layer 310 and the second layer 320, for example, the carrier mobility in the undoped semiconductor layer 312 (unit: m 2 The value of / (V·s)) is expected to be around two orders of magnitude. Therefore, the concentration of 2DHG is 1 × 10⁻¹⁰ 19 / cm 3 If the above is true, then the p-GaN layer (usually with a carrier concentration of 1 × 10) 17 A region is formed where the resistance is three orders of magnitude lower than the mobility (one order of magnitude lower) at the base. As a result, the current injected from the top surface of the ridge structure 350 spreads laterally in 2DHG, and the current injection density tends to become uniform inside the aperture. In other words, variations in current injection density inside the ridge structure 350 are suppressed.

[0044] Thus, the same effects as the first embodiment can be obtained with the second embodiment as well.

[0045] Furthermore, if the conductive layer 40 is in contact with the interface between the undoped semiconductor layer 312 and the second layer 320, the second layer 320 does not need to be etched during the formation of the ridge structure 350. In other words, if the second layer 320 is exposed by etching of the undoped semiconductor layer 312, the second layer 320 does not need to be etched. However, if the second layer 320 is also etched, the interface between the undoped semiconductor layer 312 and the second layer 320 becomes clearly visible on the sidewall surface of the ridge structure 350, making it easier to bring the conductive layer 40 into contact with this interface. Therefore, it is more preferable to etch not only the first layer 310 but also the second layer 320.

[0046] Furthermore, the material of the first p-type semiconductor layer 311 is not limited to InGaN; the first p-type semiconductor layer 311 may be a p-type GaN layer. In this case, the undoped semiconductor layer 312 is In 0.08 Ga0.92 It is preferable that the layer is N. By making the band gap of the undoped semiconductor layer 312 smaller than the band gap of the first p-type semiconductor layer 311, 2DHG is more easily formed. Thus, it is preferable that the band gap of the second layer 320 is larger than the band gap of the first layer 310, and that the band gap of the first p-type semiconductor layer 311 is greater than or equal to the band gap of the undoped semiconductor layer 312. In general, for example, the first p-type semiconductor layer 311 and the undoped semiconductor layer 312 are In a Ga 1-a It has N layers (0≦a<1), and the second layer 320 is Al b Ga 1-b N layer(0 <b<1)である。

[0047] (Third embodiment) A third embodiment will now be described. The third embodiment differs from the second embodiment mainly in the configuration of the insulating region. Figure 4 is a cross-sectional view showing the vicinity of the ridge structure of the surface-emitting laser according to the third embodiment.

[0048] As shown in Figure 4, the surface-emitting laser according to the third embodiment has an inert semiconductor layer 321 instead of a dielectric layer 60. The inert semiconductor layer 321 contains impurity elements that deactivate acceptors and is an electrically insulating layer.

[0049] The inert semiconductor layer 321 is formed, for example, by injecting impurity elements that deactivate acceptors into the surface layer of the second layer 320 after the formation of the ridge structure 350, while leaving the resist mask used to form the ridge structure 350 in place. The impurity elements used to deactivate acceptors are those that deactivate acceptors by binding to p-type dopants or by forming deep energy levels. Examples of such elements include B, H, and Fe.

[0050] The other configurations are the same as in the second embodiment.

[0051] The same effects as those of the second embodiment can be obtained with the third embodiment. Furthermore, the formation of the dielectric layer 60 can be omitted.

[0052] (Fourth Embodiment) A fourth embodiment will now be described. The fourth embodiment differs from the second embodiment mainly in the configuration of the conductive layer. Figure 5 is a cross-sectional view showing the vicinity of the ridge structure of the surface-emitting laser according to the fourth embodiment.

[0053] As shown in Figure 5, in the surface-emitting laser according to the fourth embodiment, the conductive layer 40 includes a transparent conductive layer 41 and a metal layer 42. The metal layer 42 is on top of the dielectric layer 60, and the transparent conductive layer 41 is on top of the metal layer 42. The metal layer 42 is in direct contact with the interface between the first layer 310 and the second layer 320. The metal layer 42 is, for example, an Au layer. The transparent conductive layer 41 is, for example, an ITO layer. For example, the upper surface of the metal layer 42 and the upper surface of the first layer 310 are substantially flush. The transparent conductive layer 41 is an example of a first conductive layer, and the metal layer 42 is an example of a second conductive layer.

[0054] In manufacturing the surface-emitting laser according to the fourth embodiment, for example, after forming the dielectric layer 60, a metal layer 42 is formed on the dielectric layer 60 while leaving the resist mask used to form the ridge structure 350 in place, and then the resist mask is removed. At this time, the thickness of the metal layer 42 is such that the upper surface of the metal layer 42 is substantially flush with the upper surface of the ridge structure 350. Then, after lift-off, a transparent conductive layer 41 is formed so as to be in contact with the upper surface of the ridge structure 350.

[0055] The other configurations are the same as in the second embodiment.

[0056] The same effects as the second embodiment can be obtained with the fourth embodiment. Furthermore, since the electrical resistance of the metal layer 42 is lower than that of the transparent conductive layer, the overall electrical resistance of the surface-emitting laser can be further reduced. In addition, since light is blocked outside the ridge structure 350 covered by the metal layer 42, it is easier to confine light in the lateral direction.

[0057] (Fifth embodiment) A fifth embodiment will now be described. The fifth embodiment differs from the fourth embodiment mainly in the configuration of the conductive layer. Figure 6 is a cross-sectional view showing the vicinity of the ridge structure of the surface-emitting laser according to the fifth embodiment. Figure 6(b) is a cross-sectional view showing the current in the vicinity of the region indicated by the dashed circle in Figure 6(a), indicated by arrows.

[0058] As shown in Figure 6(a), in the surface-emitting laser according to the fifth embodiment, the conductive layer 40 includes a first transparent conductive layer 43 and a second transparent conductive layer 44. The second transparent conductive layer 44 is located on the dielectric layer 60, and the first transparent conductive layer 43 is located on the second transparent conductive layer 44. The second transparent conductive layer 44 is in direct contact with the interface between the first layer 310 and the second layer 320. The first transparent conductive layer 43 and the second transparent conductive layer 44 are, for example, ITO layers. The electrical resistance of the second transparent conductive layer 44 is lower than that of the first transparent conductive layer 43. For example, the upper surface of the second transparent conductive layer 44 and the upper surface of the first layer 310 are substantially flush. The first transparent conductive layer 43 is an example of a first conductive layer, and the second transparent conductive layer 44 is an example of a second conductive layer.

[0059] In manufacturing the surface-emitting laser according to the fifth embodiment, for example, after forming the dielectric layer 60, a second transparent conductive layer 44 is formed on the dielectric layer 60 while leaving the resist mask used to form the ridge structure 350 in place, and then the resist mask is removed. At this time, the thickness of the second transparent conductive layer 44 is such that the upper surface of the second transparent conductive layer 44 is substantially flush with the upper surface of the ridge structure 350. Then, after lift-off, the first transparent conductive layer 43 is formed so as to be in contact with the upper surface of the ridge structure 350.

[0060] The other configurations are the same as in the fourth embodiment.

[0061] The same effects as the fourth embodiment can be obtained with the fifth embodiment. Furthermore, while using a material such as ITO that does not easily absorb light and easily achieves good flatness for the first transparent conductive layer 43, a material such as ITO that absorbs light more easily than the first transparent conductive layer 43 or has lower flatness but still has low electrical resistance can be used for the second transparent conductive layer 44. As a result, the electrical resistance of the second transparent conductive layer 44 is lower than that of the first transparent conductive layer 43, and as shown in Figure 6(b), current is easily injected from the conductive layer 40 to the resonator 20 from the interface between the first layer 310 and the second layer 320. Consequently, the overall electrical resistance of the surface-emitting laser can be further reduced.

[0062] Furthermore, compared to the fourth embodiment, the loss due to diffraction can be reduced, making it easier to obtain a single mode at a low threshold.

[0063] (Sixth Embodiment) A sixth embodiment will now be described. The sixth embodiment relates to a head-up display (HUD), which is an example of a projection device. Figure 7 is a schematic diagram showing a HUD, which is an example of a projection device according to the sixth embodiment. Figure 8 is a schematic diagram showing an automobile equipped with a HUD according to the sixth embodiment.

[0064] A projection device is a device that projects images by scanning light, such as a HUD (Head-Up Display).

[0065] The HUD 500 according to the sixth embodiment is installed, for example, near the windshield (windshield 401, etc.) of an automobile 400, as shown in Figure 8. The projected light L emitted from the HUD 500 is reflected by the windshield 401 and directed towards the user, the observer (driver 402). As a result, the driver 402 can see the image projected by the HUD 500 as a virtual image. Alternatively, a combiner may be installed on the inner wall surface of the windshield, and the virtual image may be seen by the user by the projected light reflected by the combiner. The automobile 400 is an example of a moving object.

[0066] As shown in Figure 7, the HUD 500 emits laser light from red, green, and blue laser light sources 501R, 501G, and 501B. The emitted laser light passes through an incident optical system consisting of collimating lenses 502, 503, and 504 provided for each laser light source, two dichroic mirrors 505 and 506, and a light intensity adjustment unit 507, and is then deflected by a movable device 513 having a reflective surface 514. The deflected laser light then passes through a projection optical system consisting of a free-form mirror 509, an intermediate screen 510, and a projection mirror 511, and is projected onto a screen. In the HUD 500, the laser light sources 501R, 501G, and 501B, the collimating lenses 502, 503, and 504, and the dichroic mirrors 505 and 506 are unitized as a light source unit 530 by an optical housing. The laser light sources 501R, 501G, and 501B include a surface-emitting laser according to any of the first to fifth embodiments. The laser light sources 501R, 501G, and 501B may also include a surface-emitting laser array comprising a plurality of surface-emitting lasers according to any of the first to fifth embodiments.

[0067] The HUD 500 projects the intermediate image displayed on the intermediate screen 510 onto the windshield 401 of the car 400, allowing the driver 402 to perceive the intermediate image as a virtual image.

[0068] The laser light of each color emitted from the laser light sources 501R, 501G, and 501B is made into approximately parallel light by collimating lenses 502, 503, and 504, respectively, and then combined by two dichroic mirrors 505 and 506, which form a combining section. After the combined laser light is adjusted in intensity by an intensity adjustment section 507, it is scanned in two dimensions by a movable device 513 having a reflective surface 514. The projected light L scanned in two dimensions by the movable device 513 is reflected by a free-form mirror 509 to correct distortion, and then focused onto an intermediate screen 510 to display an intermediate image. The intermediate screen 510 is composed of a microlens array in which microlenses are arranged in two dimensions, and magnifies the projected light L incident on the intermediate screen 510 in units of microlenses.

[0069] The movable device 513 reciprocates the reflective surface 514 in two axial directions, scanning the projected light L incident on the reflective surface 514 in two dimensions. The drive control of this movable device 513 is synchronized with the light emission timing of the laser light sources 501R, 501G, and 501B.

[0070] The light source unit 530 and the movable device 513 are controlled by the control device 515.

[0071] The above describes the HUD500 as an example of a projection device, but the projection device can be any device that projects an image by performing a light scan using a movable device 513 having a reflective surface 514. For example, it can be similarly applied to projectors that are placed on a desk or the like and project an image onto a display screen, or to head-mounted displays that are mounted on a wearable member attached to the observer's head and project an image onto a reflective-transmitting screen on the wearable member, or onto the eyeballs as a screen.

[0072] Furthermore, the projection device may be mounted not only on vehicles and mounting components, but also on mobile objects such as aircraft, ships, and mobile robots, or on non-mobile objects such as work robots that operate driven objects such as manipulators without moving from their location.

[0073] (Seventh Embodiment) Next, a seventh embodiment will be described. The seventh embodiment relates to a head-mounted display (HMD). Figure 9 is a perspective view illustrating the appearance of the HMD according to the seventh embodiment.

[0074] An HMD is a head-mounted display that can be worn on a person's head, and can take the form of, for example, eyeglasses.

[0075] As shown in Figure 9, the HMD600 according to the seventh embodiment consists of a front 600a and temples 600b, each provided in a substantially symmetrical arrangement on the left and right sides. The front 600a can be made of, for example, a light guide plate 610, and the optical system, control device, etc., can be built into the temples 600b.

[0076] Figure 10 is a diagram illustrating a partial configuration of the HMD600. While Figure 10 illustrates the configuration for the left eye, the HMD600 has a similar configuration for the right eye.

[0077] The HMD600 includes a control device 515, a light source unit 530, a light intensity adjustment unit 507, a movable device 513 having a reflective surface 514, a light guide plate 610, and a half mirror 620.

[0078] As described above, the light source unit 530 is a unit comprising laser light sources 501R, 501G, and 501B, collimating lenses 502, 503, and 504, and dichroic mirrors 505 and 506, all enclosed in an optical housing. In the light source unit 530, the three colors of laser light from the laser light sources 501R, 501G, and 501B are combined by the dichroic mirrors 505 and 506, which act as the combining section. The combined parallel light is emitted from the light source unit 530.

[0079] Light from the light source unit 530 is adjusted in intensity by the light intensity adjustment unit 507 before being incident on the movable device 513. Based on a signal from the control device 515, the movable device 513 moves the reflective surface 514 in the XY direction and scans the light from the light source unit 530 in two dimensions. The drive control of this movable device 513 is synchronized with the light emission timing of the laser light sources 501R, 501G, and 501B, and a color image is formed by the scanning light.

[0080] The scanning light from the movable device 513 enters the light guide plate 610. The light guide plate 610 guides the scanning light to the half mirror 620 while reflecting it off its inner wall surface. The light guide plate 610 is made of a resin or the like that is transparent to the wavelength of the scanning light.

[0081] The half-mirror 620 reflects light from the light guide plate 610 to the back side of the HMD 600 and emits it towards the eyes of the wearer 630. The half-mirror 620 has, for example, a free-form surface shape. The image formed by the scanning light is projected onto the wearer's retina by reflection from the half-mirror 620. Alternatively, it is projected onto the wearer's retina by reflection from the half-mirror 620 and the lens effect of the crystalline lens in the eyeball. Furthermore, spatial distortion of the image is corrected by reflection from the half-mirror 620. The wearer 630 can observe the image formed by light scanned in the XY direction.

[0082] Since a half-mirror 620 is provided on the front 600a, the wearer 630 observes an image superimposed between the image from light from the outside and the image from the scanning light. Alternatively, a mirror can be provided instead of the half-mirror 620 to eliminate light from the outside and allow observation of only the image from the scanning light.

[0083] (Eighth embodiment) Next, an eighth embodiment will be described. The eighth embodiment relates to an ophthalmoscopic device. Figure 11 is a block diagram showing an ophthalmoscopic device according to the eighth embodiment.

[0084] The ophthalmological examination device 800 according to the eighth embodiment is a device capable of performing various examinations such as visual acuity testing, refractive power testing, intraocular pressure testing, and axial length testing. The ophthalmological examination device 800 is a device capable of non-contact examination of the eyeball 830 and includes a light source unit 810, a control unit 821, an input unit 822, a storage unit 823, and a display unit 824. The light source unit 810 includes a light source 811 and a projection optical system 812. During ophthalmological examination, the control unit 821 controls the light source 811, and the projection optical system 812 projects the light emitted by the light source 811 onto the subject's eyeball 830. In other words, light is irradiated from the light source unit 810 onto the subject's eyeball 830 as examination information. The input unit 822 is a device into which the subject or operator inputs information to be used for ophthalmological examination. The information input to the input unit 822 is transmitted to the control unit 821. The storage unit 823 stores the information output by the control unit 821. The display unit 824 displays the information output by the control unit 821. The subject fixes their face to the support unit that supports the subject's face and stares at the examination information projected by the projection optical system 812 through the eye examination window. A surface-emitting laser according to any of the first to fifth embodiments can be used as the light source 811 for projecting the examination information of the light source unit 810. A surface-emitting laser array equipped with multiple surface-emitting lasers according to any of the first to fifth embodiments may also be used as the light source 811 for projecting the examination information. Furthermore, the eye examination device may be a glasses-type eye examination device. A glasses-type eye examination device eliminates the need for space and large eye examination devices required for the examination, making it possible to perform the examination in a simple configuration regardless of location.

[0085] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0086] The aspects of this disclosure are, for example, as follows: <1> The first reflecting mirror, The second reflector, A resonator including an active layer is provided between the first reflector and the second reflector, A conductive layer for injecting current into the resonator, It has, The semiconductor stacked structure includes the aforementioned resonator, The aforementioned semiconductor stacked structure is A first layer including a first p-type semiconductor layer, A second layer is provided between the first layer and the active layer, and includes a second p-type semiconductor layer. It has, The second p-type semiconductor layer is in contact with the first layer and has a band gap larger than the band gap of the first p-type semiconductor layer. A surface-emitting laser characterized in that a part or all of the upper surface of the first layer and the interface between the first layer and the second layer are in contact with the conductive layer. <2> The first layer further includes an undoped semiconductor layer having a band gap less than or equal to the band gap of the first p-type semiconductor layer. The undoped semiconductor layer is in contact with the second layer, characterized in that <1> The surface-emitting laser described above. <3> The laminate of the first layer and the second layer has a ridge structure, The above is characterized in that, in a plan view from a direction perpendicular to the upper surface of the first layer, the outer periphery of the first layer is inward from the outer periphery of the active layer. <1> or <2> The surface-emitting laser described above. <4> The laminate is characterized by having an insulating region that electrically insulates the portion located outside the ridge structure in a plan view from the conductive layer. <3> The surface-emitting laser described above. <5> The aforementioned ridge structure is in the thickness direction, The entirety of the aforementioned first layer, A part or all of the second p-type semiconductor layer, Includes, The insulating region is characterized by having a dielectric layer whose upper surface is on the active layer side of the interface between the first layer and the second layer. <4> The surface-emitting laser described above. <6> In the thickness direction, the ridge structure includes the entirety of said first layer, The surface-emitting laser according to <4>, wherein said insulating region has an upper surface located closer to said active layer side than an interface between said first layer and said second layer, and includes an inactive semiconductor layer containing an impurity element that inactivates acceptors. <7> Said conductive layer includes: a first conductive layer in contact with an upper surface of said first layer and transmitting at least a part of oscillated light; and a second conductive layer in contact with the interface between said first layer and said second layer, wherein the electrical resistance of said second conductive layer is lower than the electrical resistance of said first conductive layer, which is the surface-emitting laser according to any one of <1> to <6>. <8> The surface-emitting laser according to <7>, wherein said second conductive layer is a metal layer. <9> Said first p-type semiconductor layer is In a Ga 1-a N layer (0≦a<1), Said second p-type semiconductor layer is Al b Ga 1-b N layer (0<b<1), which is the surface-emitting laser according to any one of <1> to <8>. <10> the surface-emitting laser according to any one of <1> to <9>, and an optical deflector that deflects light emitted by said surface-emitting laser, comprising: a projection apparatus that deflects and projects said light. <11> A head-up display, comprising the surface-emitting laser according to any one of <1> to <9>. <12> A moving body, comprising the head-up display according to <11>. <13> A head-mounted display, comprising the surface-emitting laser according to any one of <1> to <9>. <14> The aforementioned <1> from <9> An ophthalmic device comprising a surface-emitting laser as described in any of the following. [Explanation of symbols]

[0087] Single-sided emitting laser 20 resonator 40 Conductive layer 41 Transparent conductive layer 42 Metal layer 43. First transparent conductive layer 44 Second transparent conductive layer 310 First layer 311 First p-type semiconductor layer 312 Undoped semiconductor layer 320 Second layer 321 Inert semiconductor layer 330 The third layer [Prior art documents] [Non-patent literature]

[0088] [Non-Patent Document 1] Japanese Journal of Applied Physics 59, SGGE08 (2020)

Claims

1. The first reflecting mirror, The second reflecting mirror, A resonator including an active layer is provided between the first reflector and the second reflector, A conductive layer for injecting current into the resonator, It has, The semiconductor stacked structure includes the aforementioned resonator, The aforementioned semiconductor stacked structure is A first layer including a first p-type semiconductor layer, A second layer is provided between the first layer and the active layer, and includes a second p-type semiconductor layer, It has, The second p-type semiconductor layer is in contact with the first layer and has a band gap larger than the band gap of the first p-type semiconductor layer. A surface-emitting laser characterized in that a part or all of the upper surface of the first layer and the interface between the first layer and the second layer are in contact with the conductive layer.

2. The first layer further includes an undoped semiconductor layer having a band gap less than or equal to the band gap of the first p-type semiconductor layer. The surface-emitting laser according to claim 1, characterized in that the undoped semiconductor layer is in contact with the second layer.

3. The laminate of the first layer and the second layer has a ridge structure, The surface-emitting laser according to claim 1 or 2, characterized in that, in a plan view from a direction perpendicular to the upper surface of the first layer, the outer periphery of the first layer is inward from the outer periphery of the active layer.

4. The surface-emitting laser according to claim 3, characterized in that it has an insulating region that electrically insulates the portion of the laminate located outside the ridge structure in a plan view from the conductive layer.

5. The aforementioned ridge structure is in the thickness direction, The entirety of the first layer, A part or all of the second p-type semiconductor layer, Includes, The surface-emitting laser according to claim 4, characterized in that the insulating region has a dielectric layer whose upper surface is on the active layer side of the interface between the first layer and the second layer.

6. The ridge structure includes the entirety of the first layer in the thickness direction. The surface-emitting laser according to claim 4, characterized in that the insulating region has an upper surface located on the active layer side of the interface between the first layer and the second layer, and has an inert semiconductor layer containing impurity elements that deactivate the acceptor.

7. The conductive layer is A first conductive layer in contact with the upper surface of the first layer and transmitting at least a portion of the emitted light, A second conductive layer in contact with the interface between the first layer and the second layer, Includes, The surface-emitting laser according to claim 1 or 2, characterized in that the electrical resistance of the second conductive layer is lower than the electrical resistance of the first conductive layer.

8. The surface-emitting laser according to claim 7, characterized in that the second conductive layer is a metal layer.

9. The first p-type semiconductor layer is In ａ Ga １－a It is an N-layer (0 ≤ a < 1), The second p-type semiconductor layer is Al ｂ Ga １－ｂ The surface-emitting laser according to claim 1 or 2, characterized in that it has an N layer (0 < b < 1).

10. A surface-emitting laser according to claim 1 or 2, A light deflection device that deflects the light emitted by the surface-emitting laser, Equipped with, A projection device that projects the aforementioned light with deflection.

11. A head-up display comprising the surface-emitting laser according to claim 1 or 2.

12. A mobile device comprising the head-up display described in claim 11.

13. A head-mounted display comprising the surface-emitting laser described in claim 1 or 2.

14. An ophthalmic device comprising the surface-emitting laser described in claim 1 or 2.

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