Vertical resonance type light emitting device and method of manufacturing the same

Abstract

According to the present invention, the device comprises: 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 second semiconductor layer in which a region 1 in the center of the upper surface protrudes upward beyond a circumferential region around the region 1 of the upper surface; and a second multilayer film reflector formed on the semiconductor structure layer and forming a resonator between the first multilayer film reflector and the second multilayer film reflector. In the second semiconductor layer, a second portion along the circumferential region has a higher hydrogen concentration than a first portion of a region 1 along the upper surface.

Description

TECHNICAL FIELD

[0001] The present application relates to a vertical cavity surface emitting device and a method of manufacturing a vertical cavity surface emitting device. BACKGROUND

[0002] One of semiconductor lasers, a vertical cavity surface emitting device including a semiconductor layer including a light emitting layer and two multilayer film mirrors facing each other across the semiconductor layer, is known. For example, Patent Literature 1 discloses a vertical cavity surface emitting laser (vertical cavity surface emitting laser: VCSEL) including two multilayer film mirrors facing each other, which constitute an optical resonator and an n-electrode and a p-electrode connected to an n-type semiconductor layer and a p-type semiconductor layer, respectively.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Publication No. 2020-064994 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the vertical cavity surface emitting laser disclosed in Patent Literature 1, a current flowing in the light emitting layer via the n-electrode and the p-electrode causes light emitted from the light emitting layer to resonate in the optical resonator, thereby generating a laser. For example, when the vertical cavity surface emitting laser as described above is energized for a long period of time, misalignment generated between an optical confinement region and a current confinement region in the optical resonator increases optical loss, which can cause an increased threshold current, which is a current value at which laser oscillation starts.

[0008] For example, when such a vertical cavity surface emitting laser is applied to a device (e.g., a display and a headlamp) used under constant current driving conditions, there is a problem that the intensity of emitted light decreases.

[0009] The present application has been made in view of the above-described points, and an object thereof is to provide a vertical cavity surface emitting device capable of emitting light with stable intensity by avoiding optical loss in a resonator.

[0010] SOLUTION TO THE PROBLEM

[0011] A vertical cavity surface emitting device according to the present application includes a substrate, a first multilayer film mirror, a semiconductor structure layer, and a second multilayer film mirror. The first multilayer film mirror is formed on the substrate. The semiconductor structure layer includes a first semiconductor layer, a light emitting layer, and a second semiconductor layer. The first semiconductor layer is formed on the first multilayer film mirror and has a first conduction type. The light emitting layer is formed on the first semiconductor layer. The second semiconductor layer is formed on the light emitting layer, has an upper surface, and has a second conduction type opposite to the first conduction type, in the upper surface, one region at a center of the upper surface protrudes upward with respect to a region at a peripheral edge of one region of the upper surface. The second multilayer film mirror is formed on the semiconductor structure layer and constitutes a resonator between the first multilayer film mirror and the second multilayer film mirror. In the second semiconductor layer, a hydrogen concentration is higher in a second part along the peripheral edge region than in a first part along one region of the upper surface. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a plan view of a vertical cavity surface emitting laser according to Embodiment 1.

[0013] Figure 2 is a cross-sectional view of a vertical cavity surface emitting laser according to Embodiment 1.

[0014] Figure 3 is a cross-sectional view showing a manufacturing process in a first manufacturing method of a vertical cavity surface emitting laser according to Embodiment 1.

[0015] Figure 4 is a cross-sectional view showing a manufacturing process in a first manufacturing method of a vertical cavity surface emitting laser according to Embodiment 1.

[0016] Figure 5 is a cross-sectional view showing a manufacturing process in a first manufacturing method of a vertical cavity surface emitting laser according to Embodiment 1.

[0017] Figure 6 is a cross-sectional view showing a manufacturing process in a first manufacturing method of a vertical cavity surface emitting laser according to Embodiment 1.

[0018] Figure 7 is a cross-sectional view showing a manufacturing process in a second manufacturing method of a vertical cavity surface emitting laser according to Embodiment 1.

[0019] Figure 8 is a cross-sectional view of a modified vertical cavity surface emitting laser according to Embodiment 1.

[0020] Figure 9 is a cross-sectional view of a modified vertical cavity surface emitting laser according to Embodiment 1. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are given to the same components, and explanations of overlapping components are omitted.

[0022] Implementation Method 1

[0023] refer to Figure 1 and Figure 2 , a configuration of a vertical cavity surface emitting laser 100 (hereinafter referred to as the surface emitting laser 100 ) according to Embodiment 1 is described. Figure 1 1 is a top view of the surface emitting laser 100 . Figure 2 It is along Figure 1 A cross-sectional view of the surface emitting laser 100 along line 2-2 in FIG. Figure 2 In the figure, the up-down direction is the height direction of the surface emitting laser 100.

[0024] Substrate 11 is a flat, transparent substrate with a rectangular upper surface. Substrate 11 serves as a growth substrate, allowing semiconductor crystals to grow on its upper surface. In this embodiment, substrate 11 is made of a material transparent to light having a blue wavelength, such as undoped gallium nitride (GaN). In the following description, an axis passing through the center of the upper surface of substrate 11 and perpendicular to the upper surface is referred to as central axis AX.

[0025] The first multilayer film reflector 12 is a semiconductor multilayer film reflector including semiconductor layers grown on the substrate 11. The first multilayer film reflector 12 is a so-called distributed Bragg reflector (DBR) in which a high-refractive-index semiconductor film and a low-refractive-index semiconductor film having a lower refractive index than the high-refractive-index semiconductor film are alternately stacked on the upper surface of the substrate 11.

[0026] The first multilayer film reflector 12 comprises, for example, 44 pairs of layers, consisting of a high-refractive-index semiconductor film made of GaN and a low-refractive-index semiconductor film made of aluminum indium nitride (AlInN), stacked on the upper surface of the substrate 11. This configuration provides the first multilayer film reflector 12 with reflectivity for 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.

[0027] The semiconductor structure layer EM is a stacked structure including a plurality of semiconductor layers formed on the first multilayer film reflector 12. The semiconductor structure layer EM includes an n-type semiconductor layer 13 formed on the first multilayer film 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.

[0028] Each of the structures of the n-type semiconductor layer 13, the light emitting layer 14, and the p-type semiconductor layer 15 constituting the semiconductor structure layer EM is described below.

[0029] The n-type semiconductor layer 13, which is a first semiconductor layer having a first conductive type, is a semiconductor layer formed over the upper surface of the first multilayer film mirror 12. The n-type semiconductor layer 13 is made of GaN and doped with silicon (Si) as an n-type impurity.

[0030] The n-type semiconductor layer 13 has a so-called mesa structure including a lower portion 13A of a flat plate shape and an upper portion 13B of a columnar shape protruding upward from the center of the lower portion 13A along the central axis AX.

[0031] The light emitting layer 14 is a semiconductor layer formed over the upper portion 13B of the n-type semiconductor layer 13 and has a quantum well structure in which a well layer made of InGaN and a barrier layer made of GaN are layered with each other. The light emitting layer 14 is formed to have a light emitting center placed on the central axis AX. The light emitting layer 14 emits, for example, blue light having a peak wavelength of 450 nm.

[0032] The p-type semiconductor layer 15, which is a second semiconductor layer having a second conductive type, is a semiconductor layer formed over the upper surface of the light emitting layer 14. The p-type semiconductor layer 15 is made of GaN and doped with magnesium (Mg) as a p-type impurity.

[0033] The p-type semiconductor layer 15 has an upper surface including a first region 15R1, which is a region having a circular shape and passing through the central axis AX, and a second region 15R2, which is a peripheral edge region of the first region 15R1 and is recessed downward with respect to the first region 15R1. In other words, in the upper surface of the p-type semiconductor layer 15, the first region 15R1 protrudes upward with respect to the second region 15R2.

[0034] 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 deactivated. The second region 15R2 is formed by, for example, performing dry etching on the upper surface of the flat plate-shaped p-type semiconductor layer to leave a circular region (the first region 15R1). In the second region 15R2, the p-type impurity is deactivated due to roughening of the surface of the second region 15R2 by the dry etching.

[0035] Specifically, the p-type impurity is disposed at lattice sites of the p-type semiconductor layer 15 so as to be electrically activated at the time of forming the p-type semiconductor layer. From this state, it is understood that in the second region 15R2, the p-type impurity is displaced from the lattice sites of the p-type semiconductor layer 15, that is, electrically deactivated by the dry etching. In other words, the second region 15R2 is a region in which the p-type impurity is difficult to generate a carrier.

[0036] Thus, in the upper surface of the p-type semiconductor layer 15, the second region 15R2 functions as a high-resistance region whose resistance is higher than that of the first region 15R1. On the other hand, the first region 15R1 is a region in which dry etching is not performed, i.e., a region in which p-type impurities are electrically activated, which functions as a low-resistance region whose resistance is lower than that of the second region 15R2.

[0037] In the p-type semiconductor layer 15, the hydrogen concentration is higher in a second portion 15P2 that is a surface layer portion of the p-type semiconductor layer 15 along the second region 15R2 than in a first portion 15P1 that is a surface layer portion of the p-type semiconductor layer 15 along the first region 15R1. The first portion 15P1 and the second portion 15P2 are, for example, within a range of 40 nm from the upper surface of the p-type semiconductor layer 15.

[0038] 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 x 1018 / cm3, and the hydrogen concentration in the second portion 15P2 is 5 x 1018 / cm3. 18 3 18 3

[0039] 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 that is electrically connected to the n-type semiconductor layer 13 and has a ring-shaped upper surface shape. When the surface-emitting laser 100 is viewed from above, the n-electrode NE is formed so as to be spaced apart from the upper portion 13B of the n-type semiconductor layer 13 while surrounding the upper portion 13B in a plan view. The n-electrode NE is made of, for example, titanium (Ti) and aluminum (Al) that are sequentially layered on the upper surface of the lower portion 13A.

[0040] The transparent conductive film 16 is a transparent metal oxide film that is electrically connected to the first region 15R1 of the p-type semiconductor layer 15 and is formed on the upper surface of the p-type semiconductor layer 15 so as to be above the upper surface of the p-type semiconductor layer 15 along the upper surface shape of the p-type semiconductor layer 15. The transparent conductive film 16 is made of a metal oxide that is transparent to blue light emitted from the light-emitting layer 14, such as indium tin oxide (ITO) and indium zinc oxide (IZO).

[0041] The p-electrode PE is a metal electrode that is formed along the outer edge of the upper surface of the transparent conductive film 16, is electrically connected to the transparent conductive film 16, and has a ring-shaped upper surface shape. The p-electrode PE is made of, for example, gold (Au).

[0042] ​​​​The insulating layer 17 is a transparent insulating layer formed so as to be spaced apart from the p-electrode PE in the upper surface of the transparent conductive film 16 and have a circular upper surface shape. The insulating layer 17 is formed so as to cover the first region 15R1 of the p-type semiconductor layer 15 in a plan view when the surface-emitting laser 100 is viewed from above. The p-electrode PE can be partially under the insulating layer 17, instead of being spaced apart from the insulating layer 17.

[0043] The insulating layer 17 is made of a metal oxide that is transparent to blue light emitted from the light-emitting layer 14, such as tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), zinc oxide (ZrO2), titanium oxide (TiO2), and hafnium oxide (HfO2).

[0044] The second multilayer film mirror 18 is a columnar semiconductor multilayer film mirror including a semiconductor layer grown on the upper surface of the insulating layer 17. The second multilayer film mirror 18 is a so-called distributed Bragg reflector (DBR) in which high-refractive-index semiconductor films 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 insulating layer 17.

[0045] The second multilayer film mirror 18 includes, for example, 10 pairs of layers of high-refractive-index semiconductor films made of Ta2O5 and low-refractive-index semiconductor films made of aluminum oxide (Al2O3) laminated on the upper surface of the insulating layer 17. This configuration provides the second multilayer film mirror 18 with reflectivity to blue light emitted from the light-emitting layer 14.

[0046] In the surface-emitting laser 100, the second multilayer film mirror 18 has a lower surface opposite to the upper surface of the first multilayer film mirror 12 across the insulating layer 17, the transparent conductive film 16, and the semiconductor structure layer EM. Thus, the first multilayer film mirror 12 and the second multilayer film mirror 18 constitute an optical resonator OC between the first multilayer film mirror 12 and the second multilayer film mirror 18, which has a resonator length direction in a direction perpendicular to the semiconductor structure layer EM (a direction perpendicular to the substrate 11).

[0047] In the surface-emitting laser 100, the reflectivity of the first multilayer film mirror 12 to blue light is slightly lower than the reflectivity of the second multilayer film mirror 18 to blue light. Thus, a part of blue light resonating in the optical resonator OC passes through the first multilayer film mirror 12 and the substrate 11 and is extracted to the outside. That is, in the surface-emitting laser 100, blue light resonating between the first multilayer film mirror 12 and the second multilayer film mirror 18 is emitted downward. Figure 2

[0048] ​On the lower surface of the substrate 11, an antireflection film (not shown) in which Nb2O5and silicon dioxide (SiO2) are stacked is formed. The antireflection film is a so-called AR coating that suppresses upward reflection of blue light emitted from the substrate 11 in the Figure 2

[0049] Here, the operation of the surface-emitting laser 100 is described. When a voltage is applied to the n electrode NE and the 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 indicated by the bold double-dot chain line arrow in Figure 2

[0050] The threshold current as a predetermined current value has been reached and the blue light emitted from the light-emitting layer 14 is repeatedly reflected between the first multilayer film mirror 12 and the second multilayer film mirror 18 (i.e., in the resonator OC) and becomes a resonant state (i.e., laser oscillation is performed).

[0051] At this time, in the p-type semiconductor layer 15, as described above, the second region 15R2 that is a region in which p-type impurities are deactivated serves as a high-resistance region, and the first region 15R1 that has a smaller resistance than the second region 15R2 serves as a low-resistance region. Therefore, the current flowing from the p electrode PE to the n electrode NE via the transparent conductive film 16 flows mostly via the first portion 15P1 and hardly flows in the second portion 15P2.

[0052] Therefore, in the surface-emitting laser 100, since the second region 15R2 serves as a high-resistance region, the current is supplied only to the first portion 15P1 and blue light is emitted only from the first portion 15P1. That is, in the surface-emitting laser 100, the p-type semiconductor layer 15 has a current constriction structure to restrict the current supply range of the light-emitting layer 14. In other words, in the surface-emitting laser 100, the p-type semiconductor layer 15 restricts the current so as not to allow the current to further propagate.

[0053] As described above, since the light reflectance of the first multilayer film mirror 12 is lower than the light reflectance of the second multilayer film mirror 18, the blue light emitted from the light-emitting layer 14 and resonated in the resonator OC is partially extracted to the outside through the first multilayer film mirror 12 and the substrate 11. In other words, the lower surface of the substrate 11 serves as a light-emitting surface of the surface-emitting laser 100.

[0054] ​​The optical characteristics inside the surface-emitting laser 100 are described below. In the following description, it is assumed that a light emission center axis passing through a light emission center of the light emission region as the light emission layer 14 is the same as the central axis line AX. The light emission center axis corresponds to an optical axis of the laser light emitted from the surface-emitting laser 100.

[0055] In the resonator OC of the surface-emitting laser 100, the thickness from the lower surface of the p-type semiconductor layer 15 to the first region 15R1 of the p-type semiconductor layer 15 is thicker than the thickness from the lower surface of the p-type semiconductor layer 15 to the second region 15R2 by the thickness of the first portion 15P1. In the resonator OC, the layer thickness of the other semiconductor layers between the first multilayer mirror 12 and the second multilayer mirror 18, the transparent conductive film 16, and the insulating layer 17 is constant.

[0056] Therefore, the effective refractive index in the resonator OC of the surface-emitting laser 100 is different between the columnar central region CA including the first portion 15P1 of the p-type semiconductor layer 15 and the cylindrical peripheral region PA at the periphery thereof. Specifically, the effective refractive index in the central region CA is greater than the effective refractive index in the peripheral region PA.

[0057] In the surface-emitting laser 100, with this configuration of the resonator OC, optical loss due to emission (radiation) of the standing wave in the central region CA to the peripheral region PA is suppressed. That is, most of the light is retained in the central region CA, and in this state, the laser light is extracted to the outside.

[0058] That is, in the surface-emitting laser 100, the p-type semiconductor layer 15 that forms the current constriction structure also forms an optical confinement structure that retains, that is, confines, the light emitted from the light emission layer 14 within the central region CA.

[0059] Therefore, since most of the light emitted from the light emission layer 14 is concentrated in the central region CA around the central axis line AX of the resonator OC, a high-power and high-density laser light can be generated and emitted. That is, the above-described configuration of the surface-emitting laser 100 allows the transverse mode (intensity distribution across the laser beam cross section) of the laser light emitted from the surface-emitting laser 100 to be stabilized.

[0060] [Suppression of increase in threshold current due to hydrogen diffusion in p-type semiconductor layer]

[0061] Here, the suppression of the increase in threshold current due to hydrogen diffusion in the p-type semiconductor layer 15 is described.

[0062] For example, in an initial state at the time of completion of the manufacture of the surface-emitting laser 100, in the p-type semiconductor layer 15, the region in which the current is restricted (the region surrounded by the second region 15R2) is the same in size as the region in which the light emitted from the light-emitting layer 14 is restricted (the first region 15R1).

[0063] Here, when the surface-emitting laser 100 is energized for a long period of time, for example, since the current continuously flows in the interface between the second region 15R2, which is a region in which the p-type impurities are deactivated, and the first portion 15P1, which is a portion in which the p-type impurities are activated, the p-type impurities that should be electrically deactivated in the second region 15R2 change to an electrically activated state. That is, the electrical resistance in the second region 15R2 decreases, and the current easily flows in the second portion 15P2.

[0064] When the p-type impurities in the second region 15R2 change to an electrically activated state due to the energization of the surface-emitting laser 100 for a long period of time, the region in the resonator OC in which the current is restricted, that is, the region surrounded by the second region 15R2, can gradually expand. This causes a difference in size between the region in which the current is restricted and the region in which the light emitted from the light-emitting layer 14 is restricted in the resonator OC, and thus, the optical loss in the resonator OC increases, which can cause an increase in the threshold current required for laser oscillation.

[0065] In the surface-emitting laser 100 according to the embodiment, as described above, 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. In the surface-emitting laser 100, due to the difference in the hydrogen concentration between the first portion 15P1 and the second portion 15P2, hydrogen diffuses from the high-concentration region to the low-concentration region, that is, from the inside of the second portion 15P2 toward the central axis AX inside the p-type semiconductor layer 15, according to the concentration gradient.

[0066] At this time, since the hydrogen concentration in the second portion 15P2 is at least twice as high as the hydrogen concentration in the first portion 15P1, a hydrogen diffusion force sufficient to offset the above-described activation progress of the p-type impurities can be obtained. That is, the expansion of the region in which the current is restricted in the p-type semiconductor layer 15 can be suppressed.

[0067] Therefore, in the surface-emitting laser 100, since the hydrogen concentration in the second portion 15P2 of the p-type semiconductor layer 15 is at least twice as high as the hydrogen concentration in the first portion 15P1, a difference in size between the region in which the current is restricted and the region in which the light is restricted in the resonator OC due to the hydrogen diffusion force according to the concentration gradient can be avoided, and an increase in the threshold current for laser oscillation can be avoided by suppressing the generation of optical loss in the resonator OC.

[0068] Accordingly, for example, even when the surface-emitting laser 100 is applied to a device used under constant current driving conditions, such as a display and a headlamp, for a long period of time, a decrease in the intensity of emitted light due to an increased threshold current can be avoided. That is, the surface-emitting laser 100 according to the embodiment can emit light with a stable intensity.

[0069] [First manufacturing method of surface-emitting laser]

[0070] Here, a method for manufacturing the surface-emitting laser 100 according to the embodiment is described with reference to Figures 2 to 6 . The following mainly describes steps related to forming the first and second portions 15P1 and 15P2 of the p-type semiconductor layer 15.

[0071] First, a high-refractive-index semiconductor film made of GaN and a low-refractive-index semiconductor film made of AlInN are laminated on the upper surface of the substrate 11 to form the first multilayer film mirror 12, and an n-type semiconductor layer 13M, a light-emitting layer 14M, and a p-type semiconductor layer 15M as base materials are grown to be formed on the first multilayer film mirror 12 in this order.

[0072] Next, as shown in Figure 3 , a circular mask MS having a size corresponding to the upper portion 13B of the n-type semiconductor layer 13 is formed on the upper surface of the p-type semiconductor layer 15M, and an exposed portion excluding the mask region is removed by dry etching. Specifically, as shown in Figure 4 , dry etching is performed until the lower portion 13A of the n-type semiconductor layer 13, which forms a surface of the n-electrode NE, is exposed.

[0073] Next, as shown in Figure 5 , a circular mask MS having a size corresponding to the upper surface of the lower portion 13A, which forms a surface of the n-electrode NE, and the first region 15R1 is formed on the upper surface of the p-type semiconductor layer 15M, and an exposed portion excluding the mask region is removed by dry etching. Specifically, as shown in Figure 6 , dry etching is performed until the second region 15R2 of the p-type semiconductor layer 15 is exposed. In this dry etching step, the above-described deactivation of p-type impurities is performed in the second region 15R2. That is, the second region 15R2 functions as a high-resistance region.

[0074] Next, using an ion implantation method, ionized hydrogen is implanted into the second region 15R2 in which the p-type impurities have been deactivated using an ion implantation device. Accordingly, for example, a second portion 15P2 having a hydrogen concentration of about 5 x 1019 / cm2is obtained. 18 / cm 3

[0075] ​In the above steps, the order of dry etching of the p-type semiconductor layer 15M and implanting hydrogen ions into the second region 15R2 may be reversed. That is, the depth of the ion implantation may be adjusted, and the hydrogen ion implantation may be performed first into the region corresponding to the second region 15R2, and then dry etching may be performed to form the second region 15R2, i.e., to deactivate the p-type impurities.

[0076] Then, if Figure 2 As shown, transparent conductive film 16 is formed over the upper surface of p-type semiconductor layer 15. Transparent conductive film 16 is formed by forming a film by sputtering at a film forming rate of 100 nm / min and a temperature of 150°C using a sputtering device, for example.

[0077] Afterwards, if Figure 2 As shown, the insulating layer 17 and the second multilayer film reflecting mirror 18 are formed on the upper surface of the transparent conductive film 16, the n-electrode NE is formed on the lower portion 13A of the n-type semiconductor layer 13, and the p-electrode PE is formed on the upper surface of the transparent conductive film 16, thereby allowing the surface emitting laser 100 according to the embodiment to be obtained.

[0078] Although the second region 15R2, which is a region in which the p-type impurity is deactivated, is obtained by dry etching in this embodiment, the method for forming the second region 15R2 is not limited to dry etching. For example, in the second region 15R2 of the p-type semiconductor layer 15, the p-type impurity may be deactivated by slightly removing the surface of the p-type semiconductor layer 15 and then performing ion implantation, or the p-type impurity may be deactivated by an ashing process.

[0079] [Second Method for Manufacturing Surface Emitting Laser]

[0080] Next, refer to Figure 7 , describes a second method for manufacturing the surface emitting laser 100 that is different from the above-described first manufacturing method.

[0081] In this manufacturing method, the method for adjusting the hydrogen concentration in second portion 15P2 is different from that of the first manufacturing method, and the process up to the step of forming p-type semiconductor layer 15 including second region 15R2 in which the p-type impurity is inactivated by dry etching is similar to that of the first manufacturing method. The following mainly describes the differences from the first manufacturing method.

[0082] First, in the formation of Figure 6 After the p-type semiconductor layer 15 including the second region 15R2 is formed, an annealing process is performed to remove hydrogen contained in the p-type semiconductor layer 15 (hydrogen removal step). After the hydrogen removal step, the hydrogen concentration in the p-type semiconductor layer 15 is, for example, 1×10 17 / cm 3 .

[0083] Next, the transparent conductive film 16 is formed by sputtering at a rate slower than the film formation rate of the first manufacturing method (conductive film formation step). For example, the transparent conductive film 16 is formed by forming the film at a film formation rate of 2 nm / min and a temperature of 25°C. In this step, since the transparent conductive film 16 is gradually formed while incorporating hydrogen from the atmosphere during sputtering, the hydrogen concentration of the transparent conductive film 16 is higher than that of the transparent conductive film 16 formed using the first manufacturing method.

[0084] Specifically, the hydrogen concentration of the transparent conductive film 16 formed by the first manufacturing method is, for example, 1×10 18 / cm 3 , and the hydrogen concentration of the transparent conductive film 16 formed by the second manufacturing method is, for example, 1×10 21 / cm 3 .

[0085] Next, in order to reduce the contact resistance between transparent conductive film 16 serving as a transparent electrode and p-type semiconductor layer 15, an electrode annealing process (600°C, 5 minutes) is performed (electrode annealing step). At this time, hydrogen contained in transparent conductive film 16 moves into p-type semiconductor layer 15, remaining in first portion 15P1 and second portion 15P2 of p-type semiconductor layer 15 at similar concentrations.

[0086] Then, if Figure 7 As shown, after the n-electrode NE and the p-electrode PE are formed and device production is completed, current is caused to flow through the semiconductor structure layer EM by flowing current between the n-electrode NE and the p-electrode PE (energization step). At this time, as described above, since the second region 15R2, which is the region where the p-type impurities are inactivated, serves as a high-resistance region in the p-type semiconductor layer 15, most of the current flowing from the p-electrode PE to the n-electrode NE via the transparent conductive film 16 flows through the first portion 15P1 and almost none of the current flows through the second portion 15P2.

[0087] Therefore, the hydrogen remaining in the first portion 15P1 is Figure 7 The current flow indicated by the dashed-dotted arrow in FIG. 1 moves to the n-type semiconductor layer 13 , thereby reducing the hydrogen concentration in the first portion 15P1 .

[0088] Meanwhile, in the second portion 15P2 , since current hardly flows as described above, most of the hydrogen in the second portion 15P2 does not move to the n-type semiconductor layer 13 but remains in the second portion 15P2 .

[0089] Therefore, the hydrogen concentration in the second portion 15P2 can be set to be higher than the hydrogen concentration in the first portion 15P1. Specifically, for example, the hydrogen concentration in the first portion 15P1 can be set to 1×10 18 / cm 3 , and the hydrogen concentration in the second portion 15P2 can be set to 5x10 18 / cm 3 .

[0090] As described above, after the energization step, the hydrogen concentration in the second portion 15P2 is at least twice as high as the hydrogen concentration in the first portion 15P1. In order to make the hydrogen concentration difference between the second portion 15P2 and the first portion 15P1 two times or more, for example, it is preferable to flow a current in the transparent conductive film 16 to move hydrogen so that the hydrogen concentration difference between the first portion 15P1 and the second portion 15P2 and the transparent conductive film 16 is ten times or more.

[0091] Specifically, if Figure 7 As shown in , it is preferable to cause current to flow in the transparent conductive film 16 to move hydrogen so as to set the hydrogen concentration in the second portion 15P2 to be at least ten times higher than the hydrogen concentration in the first portion 16P1 of the transparent conductive film 16 on the first region 15R1. Alternatively, it is preferable to cause current to flow in the transparent conductive film 16 to move hydrogen so as to set the hydrogen concentration in the first portion 15P1 to be at least ten times lower than the hydrogen concentration in the second portion 16P2 of the transparent conductive film 16 on the second region 15R2.

[0092] [Variation 1]

[0093] Next, refer to Figure 8 , Modification 1 of the surface emitting laser 100 according to the embodiment will be described. Figure 8 2 is a cross-sectional view of a surface emitting laser 200 according to Modification 1. The surface emitting laser 200 is different from that of Embodiment 1 in that a light-transmitting insulating layer 21 is provided, and is similar to Embodiment 1 in other respects.

[0094] Light-transmitting insulating layer 21 is provided on the upper surface of p-type semiconductor layer 15 and the side surface of first portion 15P1 so as to contact second region 15R2, and is a transparent insulating layer having an annular upper surface shape. Light-transmitting insulating layer 21 is made of a material (such as SiO2) having a lower refractive index than the material forming p-type semiconductor layer 15 and being transparent to blue light emitted from light-emitting layer 14.

[0095] In the surface emitting laser 200, the light-transmitting insulating layer 21 has the same thickness as the first portion 15P1. Therefore, the first region 15R1 of the p-type semiconductor layer 15 is exposed from the opening 21O provided at the light-transmitting insulating layer 21 so as to be positioned on the same plane as the upper surface of the light-transmitting insulating layer 21.

[0096] In the surface-emitting laser 200, even when the light-transmissive insulating layer 21 is provided as described above, it is possible to avoid a difference in size between a region in which current is restricted due to a hydrogen diffusion force according to a concentration gradient and a region in which light is restricted in the resonator OC, and it is possible to avoid an increase in threshold current of laser oscillation by suppressing generation of optical loss in the resonator OC.

[0097] [Modified Example 2]

[0098] Next, a modified example 2 of the surface-emitting laser 100 according to the embodiment is described with reference to Figure 9 , which is a cross-sectional view of a surface-emitting laser 300 according to the modified example 2. The surface-emitting laser 300 differs from the embodiment 1 in the configuration of the semiconductor structure layer EM, and is similar to the embodiment 1 in other respects. In the description, it is assumed that the surface-emitting laser 300 of this modified example is manufactured with the first manufacturing method. Figure 9

[0099] In the surface-emitting laser 300, the semiconductor structure layer EM is configured to include the tunnel junction layer 23 formed on the first region 15R1 of the p-type semiconductor layer 15, the n-type semiconductor layer 24 formed on the tunnel junction layer 23, and the n-type semiconductor layer 25 formed on the second region 15R2.

[0100] The tunnel junction layer 23 is a semiconductor layer formed above the first region 15R1 and having a circular upper surface shape. The tunnel junction layer 23 includes a highly-doped p-type semiconductor layer (not shown) having a higher impurity concentration than the p-type semiconductor layer 15, and a highly-doped n-type semiconductor layer (not shown) formed on the highly-doped p-type semiconductor layer and having a higher impurity concentration than the n-type semiconductor layer 13.

[0101] The n-type semiconductor layer 24 is a third semiconductor layer having the first conductivity type, and is a semiconductor layer formed above the tunnel junction layer 23 and having a circular upper surface shape. In the surface-emitting laser 300, the n-type semiconductor layer 24 has an upper surface in contact with a lower surface of the insulating layer 17.

[0102] The n-type semiconductor layer 25 is a fourth semiconductor layer having the first conductivity type, and is a semiconductor layer formed in contact with the second region 15R2, and side surfaces of the tunnel junction layer 23 and the n-type semiconductor layer 24, and having a ring-shaped upper surface shape.

[0103] ​The n-type semiconductor layer 25 has the same thickness as the total thickness of the first portion 15P1, the tunnel junction layer 23, and the n-type semiconductor layer 24. Therefore, the upper surface of the n-type semiconductor layer 24 is exposed from the opening 25O provided at the n-type semiconductor layer 25 so as to be positioned on the same plane as the upper surface of the n-type semiconductor layer 25.

[0104] The n-type semiconductor layer 25 has a lower refractive index than the tunnel junction layer 23 and the n-type semiconductor layer 24. The n-type semiconductor layer 25 is doped with, for example, germanium (Ge) as an n-type impurity.

[0105] In the surface-emitting laser 300, the tunnel junction layer 23 functions as a current confinement layer that limits the current supply range of the light-emitting layer 14. Even when the semiconductor structure layer EM has such a configuration, the surface-emitting laser 300 can provide similar effects to the surface-emitting laser 100 according to Embodiment 1.

[0106] That is, in the surface-emitting laser 300, even when the semiconductor structure layer EM is provided as described above, it is possible to avoid a difference in size between the region in which the current is confined and the region in which the light is confined in the resonator OC due to the hydrogen diffusion force according to the concentration gradient, and it is possible to avoid an increase in the threshold current of the laser oscillation by suppressing the generation of optical loss in the resonator OC.

[0107] Description of Reference Numerals

[0108] 100, 200, 300, surface-emitting laser (vertical cavity surface-emitting laser)

[0109] 11, substrate

[0110] 12, first multilayer film mirror

[0111] 13, 24, 25, n-type semiconductor layer

[0112] 14, light-emitting layer

[0113] 15, p-type semiconductor layer

[0114] 16, transparent conductive film

[0115] 17, insulating layer

[0116] 18, second multilayer film mirror

[0117] 21, light-transmitting insulating layer

[0118] 23, tunnel junction layer

[0119] NE, n-electrode

[0120] PE, p-electrode

Claims

1. A vertical cavity surface light emitting device, comprising: substrate; a first multilayer film reflecting mirror, wherein the first multilayer film reflecting mirror is formed on the substrate; a semiconductor structure layer, the semiconductor structure layer including a first semiconductor layer, a light-emitting layer, and a second semiconductor layer, the first semiconductor layer being formed on the first multilayer film reflector and having a first conductivity type, the light-emitting layer being formed on the first semiconductor layer, the second semiconductor layer being formed on the light-emitting layer, and having an upper surface and having a second conductivity type opposite to the first conductivity type, wherein a region at a center of the upper surface protrudes upward relative to a region at a peripheral edge of the one region of the upper surface; as well as a second multilayer film reflecting mirror, the second multilayer film reflecting mirror being formed on the semiconductor structure layer and constituting a resonator between the first multilayer film reflecting mirror and the second multilayer film reflecting mirror, wherein In the second semiconductor layer, the hydrogen concentration is higher in a second portion along the peripheral edge region than in a first portion along the one region of the upper surface.

2. The vertical cavity surface light emitting device according to claim 1, wherein: The second portion has a hydrogen concentration that is at least two times higher than a hydrogen concentration in the first portion.

3. The vertical cavity surface light emitting device according to claim 2, comprising: a light-transmitting conductive film formed over the upper surface of the second semiconductor layer, wherein The hydrogen concentration in the second portion is at least ten times higher than the hydrogen concentration in the conductive film over the one region.

4. The vertical cavity surface emitting device according to claim 2, comprising: a light-transmitting conductive film formed over the upper surface of the second semiconductor layer, wherein The hydrogen concentration in the first portion is at least ten times lower than the hydrogen concentration in the conductive film on the peripheral edge region.

5. The vertical cavity surface light emitting device according to claim 1 or 2, comprising: an insulating layer disposed on the peripheral edge region and having electrical insulating properties; as well as A light-transmitting conductive film is formed to cover the insulating layer and the first portion.

6. The vertical cavity surface light emitting device according to claim 1 or 2, comprising: a tunnel junction layer formed on the one region and including a semiconductor layer having the first conductivity type and a semiconductor layer having the second conductivity type; a third semiconductor layer formed on the tunnel junction layer and having the first conductivity type; as well as A fourth semiconductor layer is formed on the peripheral edge region and has the first conductivity type.

7. A method for manufacturing the vertical cavity surface light emitting device according to claim 1 or 2, the method comprising the following steps: A hydrogen ion implantation step of implanting hydrogen ions into the second portion of the second semiconductor layer by an ion implantation method.

8. A method for manufacturing the vertical cavity surface light emitting device according to claim 1 or 2, the method comprising the following steps: a conductive film forming step of forming a conductive film on the second semiconductor layer at a predetermined film forming rate so as to incorporate hydrogen into the conductive film at a predetermined concentration or more; an annealing process step of moving the hydrogen contained in the conductive film formed in the conductive film forming step into the second semiconductor layer through an annealing process; as well as The step of applying electricity involves moving hydrogen contained in the first portion of the second semiconductor layer toward the first semiconductor layer by applying electricity.

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