Vertical resonator-type light emitting element

Abstract

To provide a vertical resonator-type light emitting element capable of preventing a decrease in light emitting area while preventing a deterioration in optical output.SOLUTION: A vertical resonator-type light emitting element includes: a substrate; a first multilayer film reflecting mirror formed on the substrate; a semiconductor structure layer including a first semiconductor layer that is formed on the first multilayer film reflecting mirror and that has a first conductivity type, a light emitting layer that is formed on the first semiconductor layer, and a second semiconductor layer that is formed on the light emitting layer and that has a second conductivity type opposite to the first conductivity type; a translucent metal oxide film that is formed on the second semiconductor layer, that is electrically connected to the second semiconductor layer in one region at the center of the upper surface of the second semiconductor layer while covering the one region, and that is partially formed on a peripheral region around the one region and insulated from the surface of the second semiconductor layer in the peripheral region; and a second multilayer film reflecting mirror that is formed so as to cover the one region on the semiconductor structure layer and that constitutes a resonator together with the first multilayer film reflecting mirror.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vertical cavity light emitting device. [Background technology]

[0002] A vertical cavity light emitting device is known as one type of semiconductor laser. For example, Patent Document 1 discloses a vertical cavity surface emitting laser (VCSEL) including a semiconductor structure layer including an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer, with a protrusion formed on the upper surface of the p-type semiconductor layer, an insulating layer formed on the upper surface of the p-type semiconductor layer, and a light-transmitting electrode layer including the insulating layer and formed on the upper surface of the p-type semiconductor layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-197437 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vertical cavity surface emitting laser disclosed in Patent Document 1, for example, the threshold current increases with long-term current application, and the output of emitted light may decrease. As a countermeasure to this, for example, hydrogen is injected into the p-type semiconductor layer to suppress the increase in threshold current, but depending on the hydrogen concentration in the p-type semiconductor layer, the flow of current may be suppressed too much, resulting in a problem of a reduced light-emitting area of ​​the vertical cavity surface emitting laser.

[0005] The present invention has been made in consideration of the above-mentioned points, and aims to provide a vertical cavity light emitting device that can prevent a decrease in light output while preventing a reduction in the light emitting area. [Means for solving the problem]

[0006] A vertical cavity light emitting device according to the present invention is characterized by comprising: a substrate; a first multilayer film reflector formed on the substrate; a semiconductor structure layer including a first semiconductor layer having a first conductivity type formed on the first multilayer film reflector, a light emitting layer formed on the first semiconductor layer, and a second semiconductor layer formed on the light emitting layer and having a second conductivity type opposite to the first conductivity type; a light-transmitting metal oxide film formed on the second semiconductor layer, covering a central region of an upper surface of the second semiconductor layer and electrically connected to the second semiconductor layer in the first region, partially formed on a peripheral region on the periphery of the first region and insulated from a surface of the second semiconductor layer in the peripheral region; and a second multilayer film reflector formed on the semiconductor structure layer so as to cover the first region and constituting a resonator between itself and the first multilayer film reflector. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view of a vertical cavity surface emitting laser in accordance with a first embodiment. [Diagram 2] 1 is a top view of a vertical cavity surface emitting laser in accordance with a first embodiment. [Diagram 3] 1 is a cross-sectional view of a vertical cavity surface emitting laser in accordance with a first embodiment. [Figure 4] FIG. 1 is a cross-sectional view of a vertical cavity surface emitting laser as a conventional example. [Diagram 5] FIG. 4 is a top view of a vertical cavity surface emitting laser according to a modified example of the first embodiment. [Figure 6] FIG. 4 is a top view of a vertical cavity surface emitting laser according to a modified example of the first embodiment. [Figure 7] FIG. 4 is a top view of a vertical cavity surface emitting laser according to a modified example of the first embodiment. [Figure 8] FIG. 11 is a cross-sectional view of a vertical cavity surface emitting laser according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and the description of the same components will be omitted. EXAMPLES

[0009] The configuration of a vertical cavity surface emitting laser 100 (hereinafter referred to as surface emitting laser 100) according to Example 1 will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view of the surface emitting laser 100. Fig. 2 is a top view of the surface emitting laser 100, and Fig. 3 is a cross-sectional view taken along line 3-3 of the surface emitting laser 100 shown in Fig. 2. In Fig. 3, the up-down direction corresponds to the height direction of the surface emitting laser 100.

[0010] The substrate 11 is a flat, transparent substrate with a rectangular upper surface. The substrate 11 is a growth substrate on which a semiconductor crystal can be grown. The substrate 11 is made of a material that is transparent to light having a blue wavelength, such as undoped gallium nitride (GaN). In the following description, an axis that passes through the center of the upper surface of the substrate 11 and is perpendicular to the upper surface is defined as a central axis AX.

[0011] The first multilayer film reflector 12 is a semiconductor multilayer film reflector made of semiconductor layers grown on the substrate 11. The first multilayer film reflector 12 is a so-called distributed Bragg reflector (DBR) in which high-refractive index semiconductor films having a relatively high refractive index and low-refractive index semiconductor films having a refractive index lower than that of the high-refractive index semiconductor films are alternately laminated on the upper surface of the substrate 11.

[0012] The first multilayer film reflector 12 is formed by, for example, stacking 42 pairs of a high refractive index semiconductor film made of GaN and a low refractive index semiconductor film made of aluminum indium nitride (AlInN) on the upper surface of the substrate 11. The first multilayer film reflector 12 has such a configuration and is reflective to light in the blue wavelength range. A buffer layer (not shown) made of GaN is provided between the substrate 11 and the first multilayer film reflector 12.

[0013] The semiconductor structure layer EM is a laminated structure made up of a plurality of semiconductor layers formed on the first multilayer reflector 12. The semiconductor structure layer EM has an n-type semiconductor layer 13 formed on the first multilayer reflector 12, a light emitting layer 14 formed on the n-type semiconductor layer 13, and a p-type semiconductor layer 15 formed on the light emitting layer 14.

[0014] Hereinafter, the structures of the n-type semiconductor layer 13, the light emitting layer 14, and the p-type semiconductor layer 15 that constitute the semiconductor structure layer EM will be described.

[0015] N-type semiconductor layer 13 as a first semiconductor layer having a first conductivity type is a semiconductor layer formed over the upper surface of first multilayer film reflector 12. N-type semiconductor layer 13 is made of GaN and is doped with silicon (Si) as an n-type impurity.

[0016] The n-type semiconductor layer 13 has a so-called mesa-shaped structure composed of a flat lower portion 13A and a cylindrical upper portion 13B protruding upward from the center of the lower portion 13A along the central axis AX (see FIGS. 1 and 3).

[0017] The light emitting layer 14 is formed over the upper portion 13B of the n-type semiconductor layer 13, and is a semiconductor layer having a quantum well structure in which a well layer made of InGaN and a barrier layer made of GaN are stacked on each other. The light emitting layer 14 is formed so that its light emitting center is brought onto the central axis AX. The light emitting layer 14 emits blue light having a peak wavelength of, for example, 450 nm.

[0018] P-type semiconductor layer 15 as a second semiconductor layer having a second conductivity type is a semiconductor layer formed over the upper surface of light emitting layer 14. P-type semiconductor layer 15 is made of GaN and is doped with magnesium (Mg) as a p-type impurity.

[0019] The p-type semiconductor layer 15 has, on its upper surface, a first region 15R1 that has a circular shape and is a region passing through the central axis AX, and a second region 15R2 that is a peripheral region of the first region 15R1 and is annular and recessed downward from the first region 15R1 (see FIG. 3). In other words, the p-type semiconductor layer 15 has a protruding portion that protrudes upward in the center of the upper surface.

[0020] Furthermore, the p-type semiconductor layer 15 has, on its upper surface, a third region 15R3 that is a peripheral region of the second region 15R2 and protrudes upward from the second region 15R2. That is, the p-type semiconductor layer 15 has, on its upper surface, a recess whose bottom surface is the second region 15R2.

[0021] In the p-type semiconductor layer 15, the second region 15R2 is a region in which the p-type impurity (Mg) doped in the p-type semiconductor layer 15 is electrically inactivated. The second region 15R2 is formed, for example, by performing dry etching on the upper surface of the flat p-type semiconductor layer so as to leave regions corresponding to the first region 15R1 and the third region 15R3.

[0022] In the second region 15R2, the p-type impurity is inactivated by being damaged by dry etching. Specifically, the p-type impurity is placed at the lattice position of the crystal of the p-type semiconductor layer 15 during the formation of the p-type semiconductor layer, and is thus in an electrically activated state.

[0023] However, in the second region 15R2, the p-type impurities are in a state where they are displaced from the lattice positions of the crystals of the p-type semiconductor layer 15 through dry etching or where they no longer function as acceptor ions due to defects generated by dry etching, i.e., they are in an electrically inactive state. In other words, the second region 15R2 is a region where the p-type impurities are unlikely to generate carriers.

[0024] Therefore, the second region 15R2 functions as a high-resistance region having a higher electrical resistance than the first region 15R1 on the upper surface of the p-type semiconductor layer 15. On the other hand, the regions not subjected to dry etching, i.e., the first region 15R1 and the third region 15R3 which are regions in which the p-type impurities are electrically activated, function as low-resistance regions having a lower electrical resistance than the second region 15R2.

[0025] Furthermore, in the surface-emitting laser 100, the second portion 15P2, which is the peripheral portion of the first portion 15P1 and also the portion along the second region 15R2 and the third region 15R3, has a higher hydrogen concentration than the first portion 15P1, which is the portion along the first region 15R1 of the p-type semiconductor layer 15.

[0026] Specifically, in the p-type semiconductor layer 15, the hydrogen concentration in the second portion 15P2 is at least twice as high as the hydrogen concentration in the first portion 15P1. For example, the hydrogen concentration in the first portion 15P1 is 1×10 18 / cm 3 and the hydrogen concentration in the second portion 15P2 is 2×10 18 / cm 3 It is.

[0027] The insulating layer 19 is a transparent coating layer having electrical insulation properties that is formed continuously to cover the second region 15R2 and the third region 15R3 on the upper surface of the p-type semiconductor layer 15. In other words, the insulating layer 19 is formed on the upper surface of the p-type semiconductor layer 15 so as to expose only the first region 15R1 of the upper surface of the p-type semiconductor layer 15.

[0028] Moreover, the insulating layer 19 is formed to have an inclined surface that slopes downward from the third region 15R3 to the second region 15R2 on the upper surface of the p-type semiconductor layer 15. The insulating layer 19 is made of a material having a lower refractive index than the p-type semiconductor layer 15, such as silicon dioxide (SiO2).

[0029] The conductive film 21 is a transparent metal oxide film formed to extend from the first region 15R1 to partway through the second region 15R2 while covering the above-mentioned first region 15R1 in a plan view of the p-type semiconductor layer 15. In other words, the conductive film 21 is formed in a manner that covers the first region 15R1 but does not reach the outer edge of the upper surface of the p-type semiconductor layer 15.

[0030] The conductive film 21 is electrically connected to the p-type semiconductor layer 15 in the first region 15R1, and is electrically insulated from the second region 15R2 and the third region 15R3 by the insulating layer 19. That is, when a current flows through the conductive film 21, most of the current flows into the p-type semiconductor layer 15 via the first region 15R1.

[0031] The conductive film 21 is made of a metal oxide, such as indium tin oxide (ITO) or indium zinc oxide (IZO), that is transparent to the blue light emitted from the light-emitting layer 14. The thickness of the conductive film 21 depends on the absorptivity of the light emitted from the light-emitting layer 14, but is preferably 10 nm to 100 nm, and more preferably 10 nm to 50 nm.

[0032] When manufacturing the surface-emitting laser 100, the conductive film 21 is formed, for example, by forming a metal oxide film made of ITO over the upper surface of the p-type semiconductor layer 15, and then removing the formed metal oxide film from the outer edge of the third region 15R3 to halfway through the second region by etching or plasma cleaning.

[0033] The p-electrode PE is formed on the insulating layer 19 along the outer edge of the upper surface of the p-type semiconductor layer 15 so as to cover the outer edge of the conductive film 21, and is a metal electrode with a ring-shaped upper surface that is electrically connected to the conductive film 21. The p-electrode PE is formed, for example, by forming nickel (Ni) and gold (Au) in this order.

[0034] The n-electrode NE is provided on the upper surface of the lower portion 13A of the n-type semiconductor layer 13, and is a metal electrode with a ring-shaped upper surface shape that is electrically connected to the n-type semiconductor layer 13. In a plan view of the surface-emitting laser 100 seen from above, the n-electrode NE is formed to surround the upper portion 13B of the n-type semiconductor layer 13 while being spaced apart from the upper portion 13B. The n-electrode NE is formed, for example, by laminating titanium (Ti) and aluminum (Al) in this order on the upper surface of the lower portion 13A.

[0035] The second multilayer film reflector 23 is a cylindrical dielectric multilayer film reflector made of dielectric layers formed on the upper surface of the conductive film 21. The second multilayer film reflector 23 is formed to cover the first region 15R1 and to be spaced apart from the p-electrode PE in a plan view of the surface-emitting laser 100 seen from above.

[0036] The second multilayer film reflector 23 is a so-called distributed Bragg reflector (DBR) in which a high refractive index dielectric film having a relatively high refractive index and a low refractive index dielectric film having a lower refractive index than the high refractive index dielectric film are alternately stacked on the upper surface of the conductive film 21.

[0037] The second multilayer film reflector 23 is formed, for example, by laminating 10.5 pairs of a high refractive index dielectric film made of niobium pentoxide (Nb2O5) and a low refractive index dielectric film made of SiO2 on the upper surface of the conductive film 21. The second multilayer film reflector 23 has reflectivity for the blue light emitted from the light emitting layer 14 by having such a configuration.

[0038] A transparent dielectric layer (not shown) having a circular upper surface shape is formed between the second multilayer film reflector 23 and the conductive film 21. The dielectric layer is made of, for example, Nb2O5, tantalum pentoxide (Ta2O5), zinc oxide (ZrO2), titanium oxide (TiO2), hafnium oxide (HfO2), or the like.

[0039] In the surface-emitting laser 100, the lower surface of the second multilayer film reflector 23 faces the upper surface of the first multilayer film reflector 12, with the above-mentioned dielectric layer, conductive film 21, and semiconductor structure layer EM sandwiched between them. As a result, the first multilayer film reflector 12 and the second multilayer film reflector 23 form a resonator OC between the first multilayer film reflector 12 and the second multilayer film reflector 23, with the resonator length direction being in a direction perpendicular to the semiconductor structure layer EM (direction perpendicular to the substrate 11).

[0040] In the surface-emitting laser 100, the reflectance of the first multilayer film reflector 12 for blue light is slightly lower than the reflectance of the second multilayer film reflector 23 for blue light. Therefore, part of the blue light resonated in the resonator OC passes through the first multilayer film reflector 12 and the substrate 11 and is extracted to the outside. That is, the light resonated between the first multilayer film reflector 12 and the second multilayer film reflector 23 is emitted downward in FIG.

[0041] An antireflection film (not shown) made of a laminate of Nb2O5 and SiO2 is formed on the lower surface of the substrate 11. The antireflection film is a so-called AR coat that suppresses the blue light emitted from the substrate 11 from being reflected upward in FIG. 3 by the interface between the substrate 11 and the outside.

[0042] Here, we will explain the operation and optical characteristics of the surface-emitting laser 100. When a voltage is applied to the above-mentioned n-electrode NE and p-electrode PE and a current flows between the n-electrode NE and the p-electrode PE, the current flows in the light-emitting layer 14 of the semiconductor structure layer EM as shown by the thick dashed-dotted arrow in Fig. 3, and when the current reaches a threshold current, which is a predetermined current value, the intensity of the blue light emitted from the light-emitting layer 14 increases rapidly.

[0043] The blue light emitted from the light-emitting layer 14 when the threshold current is reached is repeatedly reflected between the first multilayer film reflector 12 and the second multilayer film reflector 23, i.e., in the resonator OC, and reaches a resonant state (i.e., laser oscillation occurs).

[0044] At this time, in the p-type semiconductor layer 15, most of the current flowing from the p-electrode PE to the conductive film 21 flows to the n-electrode NE via the first region 15R1 which is a low-resistance region. Therefore, in the surface-emitting laser 100, a current is supplied to the light-emitting layer 14 via the first region 15R1, and blue light is emitted from the first region 15R1 along the central axis AX.

[0045] That is, in the surface-emitting laser 100, the central protruding portion of the p-type semiconductor layer 15 formed by the first region 15R1 and the second region 15R2 and the insulating layer 19 formed on the second region 15R2 function as a current constriction portion that limits the current supply range so that the current does not spread any further.

[0046] Therefore, when a current is passed from the p-electrode PE to the n-electrode NE, most of the current flowing through the conductive film 21 flows to the n-type semiconductor layer 13 via the first portion 15P1 of the p-type semiconductor layer 15, and almost no current flows to the second portion 15P2.

[0047] In the surface-emitting laser 100, the equivalent refractive index, which is the average refractive index in the thickness direction between the first multilayer reflector 12 and the second multilayer reflector 23, is different between a cylindrical central region CA including the first region 15R1 of the p-type semiconductor layer 15 and a cylindrical peripheral region PA therearound.

[0048] Specifically, since the refractive index of the insulating layer 19 in the peripheral region PA is lower than the refractive index of the protruding portion (p-type semiconductor layer 15) in the central region CA, the equivalent refractive index in the central region CA is higher than the equivalent refractive index in the peripheral region PA.

[0049] The surface-emitting laser 100 has such a configuration, which suppresses optical loss caused by the standing wave in the central area CA diverging (radiating) to the peripheral area PA. In other words, most of the light remains in the central area CA, and the laser light is extracted to the outside in this state.

[0050] Therefore, a large amount of light emitted from the light emitting layer 14 is concentrated in the central area CA, so that high-output and high-density laser light can be generated and emitted. That is, the transverse mode (intensity distribution in the transverse cross section of the laser beam) of the laser light emitted from the surface emitting laser 100 can be stabilized.

[0051] [Suppression of the reduction in the light-emitting area of ​​surface-emitting lasers] 3 and 4, the suppression of the reduction in the light-emitting area in the surface-emitting laser 100 of this embodiment will be described below. Fig. 4 is a cross-sectional view of a surface-emitting laser 110 as a conventional example. The surface-emitting laser 110 differs from the surface-emitting laser 100 in that the conductive film 21 is formed across the upper surface of the p-type semiconductor layer 15, but is the same in other respects.

[0052] As described above, in the surface-emitting laser 100, the hydrogen concentration in the second portion 15P2 of the p-type semiconductor layer 15 is higher than the hydrogen concentration in the first portion 15P1. Here, an example of a method for generating a hydrogen concentration difference between the first portion 15P1 and the second portion 15P2 of the p-type semiconductor layer 15 during fabrication of the surface-emitting laser 100 will be described.

[0053] During the manufacture of the surface-emitting laser 100, the conductive film 21 is formed on the p-type semiconductor layer 15 by sputtering at a deposition rate of 2 nm / min at a temperature of 25° C., so that the conductive film 21 is formed gradually while containing hydrogen from the atmosphere. As a result, the hydrogen concentration in the conductive film 21 becomes, for example, 1×10 21 / cm 3 It will be about that amount.

[0054] Thereafter, an electrode annealing treatment (600°C, 5 minutes) is performed to reduce the contact resistance between the conductive film 21 and the surface of the p-type semiconductor layer 15, whereby the hydrogen contained in the conductive film 21 migrates into the p-type semiconductor layer 15 so that it remains at approximately the same concentration in the first portion 15P1 and the second portion 15P2 of the p-type semiconductor layer 15.

[0055] Although it seems that the movement of hydrogen contained in the conductive film 21 is prevented by the insulating layer 19 between the conductive film 21 and the second portion 15P2, in fact the hydrogen moves to the second portion 15P2 through the insulating layer 19. The reason for this is not entirely clear, but it is presumed to be related to the fact that the insulating layer 19 is polycrystalline or amorphous and does not have a dense solid structure like a single crystal, or to tiny pinholes present in the insulating layer 19.

[0056] Thereafter, a current is passed between the n-electrode NE and the p-electrode PE after completing the fabrication of the surface-emitting laser 100. At this time, since the insulating layer 19 is formed in the second region 15R2 and the third region 15R3, most of the current flowing from the p-electrode PE to the n-electrode NE through the conductive film 21 flows through the first portion 15P1, and almost none flows through the second portion 15P2.

[0057] Therefore, hydrogen remaining in the first portion 15P1 escapes to the n-type semiconductor layer 13 as current is applied, whereas most of the hydrogen remaining in the second portion 15P2 does not escape even when current is applied and remains in the second portion 15P2 in large amounts. Therefore, the hydrogen concentration in the second portion 15P2 is higher than the hydrogen concentration in the first portion 15P1.

[0058] By making the hydrogen concentration in the second portion 15P2 higher than the hydrogen concentration in the first portion 15P1 in this manner, hydrogen in the p-type semiconductor layer 15 diffuses from the region of higher concentration to the region of lower concentration according to the concentration gradient, i.e., from the second portion 15P2 toward the first portion 15P1.

[0059] For example, when the surface-emitting laser 100 is energized for a long period of time, a phenomenon may occur in which the current that mostly flows only through the first portion 15P1 when the surface-emitting laser 100 starts to operate flows through the first portion 15P1 and also through the second portion 15P2. That is, a phenomenon may occur in which the current path of the current flowing through the p-type semiconductor layer 15 widens due to the energization for a long period of time. When such a phenomenon occurs, the optical loss in the resonator OC increases, and the threshold current required for laser oscillation may increase.

[0060] In this case, when the hydrogen concentration in the second portion 15P2 is higher than the hydrogen concentration in the first portion 15P1, the diffusion force of hydrogen diffusing from the second portion 15P2 toward the first portion 15P1 can suppress the phenomenon of the current path widening within the p-type semiconductor layer 15 described above.

[0061] Therefore, for example, even when the surface-emitting laser 100 is applied for a long period of time to a device such as a display or a headlamp that is used under a constant current driving condition, it is possible to prevent a decrease in the intensity of the emitted light due to an increase in the threshold current.

[0062] However, when the above-mentioned electrode annealing and current application are performed in a state where the conductive film 21 is formed over the upper surface of the p-type semiconductor layer 15 during fabrication of the surface-emitting laser, a phenomenon may occur in which the difference between the hydrogen concentration in the first portion 15P1 and the hydrogen concentration in the second portion 15P2 becomes too large. For example, in the case of the conventional surface-emitting laser 110 shown in FIG. 4, the hydrogen concentration in the second portion 15P2 may be five or more times the hydrogen concentration in the first portion 15P1.

[0063] In this manner, if the difference in hydrogen concentration between the first portion 15P1 and the second portion 15P2 is too large, hydrogen in the second portion 15P2 will diffuse excessively into the first portion 15P1, causing the diameter of the current passing through the first portion 15P1 (shown in the thick wavy line in FIG. 4) to become narrower than the diameter of the first region 15R1.

[0064] When the diameter of the current flowing through the first portion 15P1 is narrowed, the diameter of the current injected into the light emitting layer 14 is also narrowed, which may result in a phenomenon in which the area of ​​the light emitted from the surface emitting laser 110, that is, the light emitting area, becomes smaller.

[0065] 3, in the surface-emitting laser 100 of this embodiment, the conductive film 21 is formed so as not to reach the outer edge of the upper surface of the p-type semiconductor layer 15. That is, the volume of the conductive film 21 on the second portion 15P2 in the surface-emitting laser 100 of this embodiment is smaller than the volume of the conductive film 21 on the second portion 15P2 in the surface-emitting laser 110 of the conventional example.

[0066] Therefore, according to the surface-emitting laser 100 of this embodiment, when electrode annealing of the conductive film 21 is performed during the fabrication of the surface-emitting laser 100 as described above, only hydrogen contained in the conductive film 21 formed on the second portion 15P2 flows into the second portion 15P2. Therefore, the average hydrogen concentration in the second portion 15P2 in the surface-emitting laser 100 is smaller than the average hydrogen concentration in the second portion 15P2 in the surface-emitting laser 110.

[0067] That is, according to the surface-emitting laser 100 of this embodiment, by forming the conductive film 21 in a manner that does not reach the outer edge of the upper surface of the p-type semiconductor layer 15, the hydrogen concentration in the second portion 15P2 can be reduced, thereby controlling the hydrogen concentration between the first portion 15P1 and the second portion 15P2 so that it does not become too high.

[0068] In order to prevent a decrease in the intensity of the emitted light due to an increase in the threshold current as described above, it is preferable that the hydrogen concentration in the second portion 15P2 is at least twice as high as the hydrogen concentration in the first portion 15P1.

[0069] In order to prevent the diameter of the current flowing through the first portion 15P1 from narrowing, the hydrogen concentration in the second portion 15P2 is preferably less than five times the hydrogen concentration in the first portion 15P1. Therefore, the hydrogen concentration in the second portion 15P2 is preferably at least two times and less than five times the hydrogen concentration in the first portion 15P1.

[0070] Therefore, according to the surface-emitting laser 100 of this embodiment, by forming the conductive film 21 so as not to reach the outer edge of the upper surface of the p-type semiconductor layer 15, it is possible to prevent a decrease in the light output while preventing a decrease in the light-emitting area.

[0071] [Variation 1] Next, a first modified example of the surface-emitting laser 100 in the first embodiment will be described with reference to Fig. 5. Fig. 5 is a top view of a surface-emitting laser 200 according to the first modified example. The surface-emitting laser 200 is similar to the first embodiment except for the formation of the conductive film 21, which is different from that of the first embodiment. In Fig. 5, the p-electrode PE and the second multilayer film reflector 23 are omitted to avoid complication of the drawing.

[0072] 5, in the surface-emitting laser 200, the conductive film 21 is composed of a central portion 21A formed to cover the first region 15R1 on the upper surface of the p-type semiconductor layer 15, and extended portions 21B extending radially from the central portion 21A and reaching the outer edge of the third region 15R3. That is, in the surface-emitting laser 200 of this modification, the conductive film 21 is formed so that the insulating layer 19 is exposed between the adjacent extended portions 21B.

[0073] Even when the conductive film 21 is formed in this manner, the volume of the conductive film 21 formed on the second portion 15P2 is smaller than when the conductive film 21 is formed across the upper surface of the p-type semiconductor layer 15. Therefore, when fabricating the surface-emitting laser 200, it is possible to control the hydrogen concentration between the first portion 15P1 and the second portion 15P2 so as not to become too high.

[0074] Therefore, according to the surface-emitting laser 200 of this modified example, by partially forming the conductive film 21 on the second portion 15P2 of the p-type semiconductor layer 15, it is possible to prevent a decrease in the light output while preventing a decrease in the light-emitting area.

[0075] In this modification, the conductive film 21 is formed to have an inclined surface that follows the inclined surface of the insulating layer 19. By forming the conductive film 21 in this manner, it is expected that the durability against cracks and the like during long-term use will be improved compared to the case where the conductive film 21 is simply formed in a flat plate shape.

[0076] [Variation 2] Next, a second modified example of the surface-emitting laser 100 in the first embodiment will be described with reference to Fig. 6. Fig. 6 is a top view of a surface-emitting laser 300 according to the second modified example. The surface-emitting laser 300 is similar to the first embodiment in other respects, except for the formation of the conductive film 21, which is different from that of the first embodiment. Note that, in Fig. 6 as well, the p-electrode PE and the second multilayer film reflector 23 are omitted to avoid complication of the drawing.

[0077] In the surface-emitting laser 300, the conductive film 21 is composed of a first conductive film 25 as a first metal oxide film formed to cover a first region 15R1 on the upper surface of the p-type semiconductor layer 15, and a second conductive film 26 as a second metal oxide film formed on the second region 15R2 and spaced apart from the first conductive film 25, as shown in FIG. 6.

[0078] Even when the conductive film 21 is formed in this manner, the volume of the conductive film 21 formed on the second portion 15P2 is smaller than when the conductive film 21 is formed across the upper surface of the p-type semiconductor layer 15. Therefore, when fabricating the surface-emitting laser 300, it is possible to control the hydrogen concentration between the first portion 15P1 and the second portion 15P2 so as not to become too high.

[0079] Therefore, according to the surface-emitting laser 300 of this modified example, by partially forming the conductive film 21 on the second portion 15P2 of the p-type semiconductor layer 15, it is possible to prevent a decrease in the light output while preventing a decrease in the light-emitting area.

[0080] [Variation 3] Next, a third modification of the surface-emitting laser 100 in the first embodiment will be described with reference to Fig. 7. Fig. 7 is a top view of a surface-emitting laser 400 according to the third modification. The surface-emitting laser 400 is similar to the first embodiment in other respects, except for the formation of the conductive film 21, which is different from that of the first embodiment. Note that, in Fig. 7 as well, the p-electrode PE and the second multilayer film reflector 23 are omitted to avoid complication of the drawing.

[0081] In the surface-emitting laser 400, as shown in FIG. 7, the conductive film 21 is composed of a central portion 21C formed to cover the first region 15R1 on the upper surface of the p-type semiconductor layer 15, a ring-shaped peripheral portion 21D surrounding the central portion 21C and formed along the outer edge of the third region 15R3, and a connecting portion 21E extending radially from the central portion 21C and connecting the central portion 21C and the peripheral portion 21D,

[0082] Even when the conductive film 21 is formed in this manner, the volume of the conductive film 21 formed on the second portion 15P2 is smaller than when the conductive film 21 is formed across the upper surface of the p-type semiconductor layer 15. Therefore, when fabricating the surface-emitting laser 400, it is possible to control the hydrogen concentration between the first portion 15P1 and the second portion 15P2 so as not to become too high.

[0083] Therefore, according to the surface-emitting laser 400 of this modified example, by partially forming the conductive film 21 on the second portion 15P2 of the p-type semiconductor layer 15, it is possible to prevent a decrease in the light output while preventing a decrease in the light-emitting area. EXAMPLES

[0084] Next, a surface-emitting laser 500 according to Example 2 will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the surface-emitting laser 500. The surface-emitting laser 500 is different from Example 1 in the shape of the p-type semiconductor layer 15 and the formation of the insulating layer 19 and the conductive film 21, but is otherwise similar to Example 1.

[0085] In the surface emitting laser 500, the p-type semiconductor layer 15 has only a first region 15R1 on the upper surface and a second region 15R2 recessed downward from the first region 15R1 around the periphery of the first region 15R1.

[0086] That is, in a plan view of the surface-emitting laser 500 seen from above, the second region 15R2 is formed from the outer edge of the first region 15R1 to the outer edge of the p-type semiconductor layer 15. Therefore, the p-type semiconductor layer 15 is composed of a first portion 15P1 along the first region 15R1 and a second portion 15P2 along the second region 15R2.

[0087] In the surface-emitting laser 500, the insulating layer 19 is formed from the outer edge of the p-type semiconductor layer 15 to the middle of the second region 15R2. The insulating layer 19 is formed on the second region 15R2 and separated from the conductive film 21. In other words, in the surface-emitting laser 500, a part of the second region 15R2 is exposed between the insulating layer 19 and the conductive film 21.

[0088] In the surface-emitting laser 500, the p-electrode PE is formed so as to contact the conductive film 21 and a part of the second region 15R2 exposed between the insulating layer 19 and the conductive film 21. As described above, since the second region 15R2 functions as a high-resistance region, when a current flows from the p-electrode PE to the n-electrode NE, the current flows only through the conductive film 21 and then into the p-type semiconductor layer 15 via the first region 15R1.

[0089] Even when the p-type semiconductor layer 15 and the conductive film 21 are formed in this manner, the volume of the conductive film 21 formed on the second portion 15P2 is smaller than when the conductive film 21 is formed across the upper surface of the p-type semiconductor layer 15. Therefore, when the surface-emitting laser 500 is fabricated, it is possible to control the hydrogen concentration between the first portion 15P1 and the second portion 15P2 so as not to become too high.

[0090] Therefore, according to the surface-emitting laser 500 of this embodiment, by partially forming the conductive film 21 on the second portion 15P2 of the p-type semiconductor layer 15, it is possible to prevent a decrease in the light output while preventing a decrease in the light-emitting area. [Explanation of symbols]

[0091] 100, 200, 300, 400, 500 Surface Emitting Laser 11 Substrate 12 First multilayer mirror 13 n-type semiconductor layer 14 Emitting layer 15 p-type semiconductor layer 19 Insulating layer 21 Conductive film 23 Second multilayer mirror NE n electrode PE p electrode

Claims

1. circuit board and A first multilayer reflecting mirror formed on the substrate, A semiconductor structural layer comprising a first semiconductor layer having a first conductivity type formed on the first multilayer reflecting mirror, a light-emitting layer formed on the first semiconductor layer, and a second semiconductor layer formed on the light-emitting layer having a second conductivity type opposite to the first conductivity type, A translucent metal oxide film formed on the second semiconductor layer, covering a central region 1 on the upper surface of the second semiconductor layer and electrically connected to the second semiconductor layer in the region 1, partially formed on the peripheral region of the periphery of the region 1 and insulated from the surface of the second semiconductor layer in the peripheral region, The semiconductor structure layer includes a second multilayer reflector formed to cover the region 1 and to form a resonator with the first multilayer reflector, A vertical resonator type light-emitting element characterized in that, in the second semiconductor layer, the hydrogen concentration is higher in the second portion along the peripheral region than in the first portion along the first region on the upper surface.

2. The vertical resonator type light-emitting element according to claim 1, characterized in that the hydrogen concentration in the second portion is 2 times or more but less than 5 times the hydrogen concentration in the first portion.

3. The vertical resonator type light-emitting element according to claim 1 or 2, characterized in that the metal oxide film is formed in such a manner that it does not extend to the outer edge of the peripheral region when viewed in a plan view from a direction perpendicular to the upper surface of the second semiconductor layer.

4. The vertical resonator type light-emitting element according to claim 1 or 2, characterized in that the metal oxide film, in a plan view taken from a direction perpendicular to the upper surface of the second semiconductor layer, consists of a central portion covering the region 1 and an extending portion extending radially from the central portion.

5. The vertical resonator type light-emitting element according to claim 1 or 2, characterized in that the metal oxide film comprises, in a plan view taken from a direction perpendicular to the upper surface of the second semiconductor layer, a first metal oxide film covering the region 1 and a second metal oxide film formed on the peripheral region at a distance from the first metal oxide film.

6. The vertical resonator type light-emitting element according to claim 5, characterized in that it has connecting portions that extend radially from the first metal oxide film and connect the first metal oxide film and the second metal oxide film.

7. The vertical resonator type light-emitting element according to claim 1 or 2, characterized in that it has an electrically insulating insulating layer formed on the peripheral region of the second semiconductor layer.

8. The vertical resonator type light-emitting element according to claim 1 or 2, characterized in that the thickness of the metal oxide film is 10 nm to 100 nm.

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