SURFACE EMISSION DEVICE AND METHOD FOR MANUFACTURING A SURFACE EMISSION DEVICE

Abstract

A surface emitter device comprises a substrate, a first multilayer film reflection mirror, a semiconductor structure layer, and a second multilayer film reflection mirror. The first multilayer film reflection mirror is formed on the substrate. The semiconductor structure layer comprises a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. The first semiconductor layer is formed on the first multilayer film reflection mirror and has a first conductivity type. The light-emitting layer is formed on the first semiconductor layer. The second semiconductor layer is formed on the light-emitting layer and has a top surface in which a region at a midpoint of the top surface projects upwards with respect to a region at a circumferential edge of the top surface, and has a second conductivity type opposite to the first conductivity type.The second multilayer film reflection mirror is formed on the semiconductor structure layer and creates a resonator between the first and second multilayer film reflection mirrors. In the second semiconductor layer, the hydrogen concentration is higher in a second part along the circumferential edge region than in a first part along the top surface region.

Description

TECHNICAL AREA

[0001] The present invention relates to a surface emitter device and a method for manufacturing the surface emitter device. TECHNICAL BACKGROUND

[0002] A surface emitting laser device, or VCSEL device, is known for semiconductor lasers. This device comprises a semiconductor layer with a light-emitting layer and two multilayer film reflection mirrors or multilayer reflection mirrors positioned opposite each other across the semiconductor layer. For example, patent document 1 discloses a vertical cavity surface emitting laser (VCSEL) with two opposing multilayer film reflection mirrors, each mirror comprising an optical resonator and an n-type electrode and a p-type electrode, respectively, connected to an n-type semiconductor layer and a p-type semiconductor layer.

[0003] Patent Document 1: JP-A-2020-064994 REVELATION OF THE INVENTION: PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the surface emitter laser, or VCSEL, disclosed in patent document 1, a current flowing into 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 laser light. For example, if the surface emitter laser described above is excited for a long period of time, a misalignment that arises between an optical confinement region and a current confinement region in the optical resonator increases optical loss, potentially leading to an increased threshold current, which is the current value required to initiate laser oscillation.

[0005] For example, if such a surface emitter laser is used in a device such as a display and a headlight, which are used under a constant current driving condition, there is a problem of a reduction in the intensity of the emitted light.

[0006] The present invention was made taking into account the points described above, and it is an objective of the present invention to provide a surface emitter device which can avoid optical loss in a resonator in order to emit light with stable intensity. SOLUTIONS FOR THE PROBLEMS

[0007] A surface emitter device according to the present invention comprises a substrate, a first multilayer film reflection mirror, a semiconductor structure layer, and a second multilayer film reflection mirror. The first multilayer film reflection mirror is formed on the substrate. The semiconductor structure layer comprises a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. The first semiconductor layer is formed on the first multilayer film reflection mirror and has a first conductivity type. The light-emitting layer is formed on the first semiconductor layer. The second semiconductor layer is formed on the light-emitting layer and has a top surface in which a region at the center of the top surface projects upwards with respect to a region at a circumferential edge of the first region of the top surface. The second semiconductor layer has a conductivity type opposite to the first conductivity type.The second multilayer film reflection mirror is formed on the semiconductor structure layer and creates a resonator between the first and second multilayer film reflection mirrors. In the second semiconductor layer, the hydrogen concentration is higher in a second part of the circumferential edge region than in a first part along a first region of the top surface. BRIEF DESCRIPTION OF THE DRAWINGS Fig: 1 is a top view of a surface emitter laser or VCSEL according to an embodiment 1. Fig. Figure 2 is a cross-sectional view of the surface emitter laser according to claim 1. Fig. Figure 3 is a cross-sectional view illustrating a manufacturing process in a first manufacturing method for the surface emitter laser according to embodiment 1. Fig. Figure 4 is a cross-sectional view illustrating a manufacturing process in the first manufacturing method for the surface emitter laser according to embodiment 1. Fig. Figure 5 is a cross-sectional view illustrating a manufacturing process in the first manufacturing method for the surface emitter laser according to embodiment 1. Fig. Figure 6 is a cross-sectional view illustrating a manufacturing process in the first manufacturing method for the surface emitter laser according to embodiment 1. Fig. Figure 7 is a cross-sectional view illustrating a manufacturing process in a second manufacturing process for the surface emitter laser according to embodiment 1. Fig. Figure 8 is a cross-sectional view of a surface emitter laser according to a modification of embodiment 1. Fig. Figure 9 is a cross-sectional view of a surface emitter laser according to a modification of embodiment 1. DESCRIPTION OF PREFERRED EXECUTION EXAMPLES

[0008] The following describes specific embodiments of the present invention with reference to the drawings. In the drawings, the same components are given the same reference numerals, and an explanation of overlapping or identical components is omitted. [Example 1]

[0009] With reference to Fig. 1 and Fig. 2 describes a configuration of a surface emitter laser or VCSEL 100 (hereinafter referred to as surface emitter laser 100) according to embodiment 1. Fig. Figure 1 is a top view of the surface emitter laser 100. Fig. Figure 2 is a cross-sectional view of the surface emitter laser 100 along line 2-2 in Fig. 1. In Fig. 2 is the up-down direction in the drawing, a height direction of the surface emitter laser 100.

[0010] A substrate 11 is a transparent substrate in the form of a flat plate with a rectangular top surface. The substrate 11 is a growth substrate that allows a semiconductor crystal to grow on its surface. In this embodiment, the substrate 11 is made of a material that is transparent to light with a blue wavelength, for example, undoped gallium nitride (GaN). In the following description, an axis passing through the center of the top surface of the substrate 11 and perpendicular to it is referred to as the central axis AX.

[0011] A first multilayer film reflection mirror 12, or reflection mirror with multiple layers, is a semiconductor multilayer film reflection mirror comprising semiconductor layers grown on the substrate 11. The first multilayer film reflection mirror 12 is a so-called distributed Bragg reflector or Bragg mirror (DBR), in which semiconductor films with a high refractive index and semiconductor films with a low refractive index (lower than that of the high-refractive-index semiconductor films) are alternately stacked on the top surface of the substrate 11.

[0012] The first multilayer film reflection mirror 12, for example, has 44 pairs of layers 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 top of the substrate 11. This configuration provides the first multilayer film reflection mirror 12 with reflectivity for light in a blue wavelength range. A buffer layer (not illustrated) made of GaN is arranged between the substrate 11 and the first multilayer film reflection mirror 12.

[0013] A semiconductor structure layer EM is a stacked structure body comprising multiple semiconductor layers formed on the first multilayer film reflection mirror 12. The semiconductor structure layer EM includes an n-type semiconductor layer 13 formed on the first multilayer film reflection mirror 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] The following describes each of the structures of the n-type semiconductor layer 13, the light-emitting layer 14 and the p-type semiconductor layer 15, which form the semiconductor structure layer EM.

[0015] The n-type semiconductor layer 13, which is a first semiconductor layer with a first conductivity type, is a semiconductor layer formed on top of the first multilayer film reflection mirror 12. The n-type semiconductor layer 13 is made of GaN and is doped with silicon (Si) as n-type impurities or dopants.

[0016] The n-type semiconductor layer 13 has what is called a mesa- or plateau-shaped structure, which includes a flat plate-shaped lower part 13A and a column-shaped upper part 13B that projects from the center of the lower part 13A along the central axis AX.

[0017] The light-emitting layer 14 is a semiconductor layer formed over the upper part 13B of the n-type semiconductor layer 13 and has a quantum well structure in which a well or well layer made of InGaN and a barrier layer made of GaN are stacked against each other. The light-emitting layer 14 is shaped such that it has a light emission center aligned with the central axis AX. The light-emitting layer 14 emits, for example, blue light with a peak wavelength of 450 nm.

[0018] The p-type semiconductor layer 15, which is a second semiconductor layer having a second conductivity type, is a semiconductor layer formed over a top surface of the light-emitting layer 14. The p-type semiconductor layer 15 is made of GaN and is doped with magnesium (Mg) as an impurity or p-type doping agent.

[0019] The p-type semiconductor layer 15 has a top surface which includes a first region 15R1, which is a round or circular region and extends through the central axis AX, and a second ring-shaped region 15R2, which is a circumferential edge region of the first region 15R1 and is recessed or indented downwards relative to the first region 15R1. In other words, in the top surface of the p-type semiconductor layer 15, the first region 15R1 projects upwards relative to the second region 15R2.

[0020] In the p-type semiconductor layer 15, the second region 15R2 is a region in which the p-type impurities or dopants (Mg) doped into the p-type semiconductor layer 15 are electrically inactivated. The second region 15R2 is formed, for example, by dry etching, which leaves a circular region (first region 15R1) on the top surface of the flat, plate-like p-type semiconductor layer. In the second region 15R2, the p-type impurities are inactivated because the surface of the second region 15R2 is roughened by the dry etching process.

[0021] Specifically, the p-type impurities are located at crystal lattice positions in the p-type semiconductor layer 15, which electrically activates them when the p-type semiconductor layer is formed. From this state, the p-type impurities in the second region 15R2 are displaced from the crystal lattice positions of the p-type semiconductor layer 15, meaning they are electrically inactivated by dry etching. In other words, the second region 15R2 is a region where the p-type impurities have difficulty forming a support.

[0022] Therefore, the second region 15R2 in the top surface of the p-type semiconductor layer 15 acts as a high-resistance region with an electrical resistance higher than that of the first region 15R1. Conversely, the first region 15R1, which is a region where dry etching is not performed, i.e., a region where the p-type impurities are electrically activated, acts as a low-resistance region with a lower electrical resistance than that of the second region 15R2.

[0023] In p-type semiconductor layer 15, the hydrogen concentration in a second part 15P2, which is a surface layer part of the p-type semiconductor layer 15 along the second region 15R2, is higher than in a first part 15P1, which is a surface layer part of the p-type semiconductor layer 15 along the first region 15R1. The first part 15P1 and the second part 15P2 are located, for example, 40 nm from the top surface of the p-type semiconductor layer 15.

[0024] In particular, the hydrogen concentration in the second part 15P2 at the p-type semiconductor layer 15 is at least twice as high as the hydrogen concentration in the first part 15P1. For example, the hydrogen concentration in the first part 15P1 is 1 × 10 18 / cm 3 , and the hydrogen concentration in the second part 15P2 is 5 × 10 18 / cm 3 .

[0025] An n-type electrode NE is located on the top side of the lower part 13A of the n-type semiconductor layer 13. It is a metal electrode electrically connected to the n-type semiconductor layer 13 and has an annular top shape. The n-type electrode NE is shaped to be spaced apart from the upper part 13B of the n-type semiconductor layer 13, while surrounding the upper part 13B in a top view when looking at the surface emitter laser 100 from above. The n-type electrode NE is, for example, made of titanium (Ti) and aluminum (Al), stacked in that order on the top side of the lower part 13A.

[0026] A transparent conductive film 16 is a transparent metal oxide film electrically connected to the first region 15R1 of the p-type semiconductor layer 15 and shaped along the top surface 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 by the light-emitting layer 14, for example, indium tin oxide (ITO) and indium zinc oxide (IZO).

[0027] A p-electrode PE is a metal electrode shaped along an outer edge of the top surface of the transparent conductive film 16, is electrically connected to the transparent conductive film, and has an annular top surface. The p-electrode PE is, for example, made of gold (Au).

[0028] An insulating layer 17 is a transparent insulating layer shaped to be spaced away from the p-electrode PE, within the p-electrode PE in the top surface of the transparent conductive film 16, and has a circular top surface shape. The insulating layer 17 is shaped to cover the first region 15R1 of the p-type semiconductor layer 15 described above in a top view when looking from above the surface emitter laser 100. The p-electrode PE may be partially located beneath the insulating layer 17 instead of being spaced away from it.

[0029] The insulating layer 17 is made of a metal oxide that is transparent to blue light emitted by the light-emitting layer 14, for example tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), zinc oxide (ZrO2), titanium oxide (TiO2) and hafnium oxide (HfO2).

[0030] A second multilayer film reflection mirror 18, or multilayer reflection mirror, is a column-shaped semiconductor multilayer film reflection mirror comprising semiconductor layers grown on the top surface of the insulating layer 17. This second multilayer film reflection mirror 18 is a so-called distributed Bragg reflector (DBR Bragg mirror), in which semiconductor films with a high refractive index and semiconductor films with a lower refractive index than the high-refractive-index semiconductor films are alternately stacked on the top surface of the insulating layer 17.

[0031] The second multilayer film reflection mirror 18, for example, has 10 pairs of layers of a high-refractive-index semiconductor film made of Ta₂O₅ and a low-refractive-index semiconductor film made of aluminum oxide (Al₂O₃), stacked on top of the insulating layer 17. This configuration provides the second multilayer film reflection mirror 18 with reflectivity for the blue light emitted by the light-emitting layer 14.

[0032] In the surface emitter laser 100, the second multilayer film reflection mirror 18 has a bottom surface opposite the top surface of the first multilayer film reflection mirror 12, specifically across the insulating layer 17, the transparent conductive film 16, and the semiconductor structure layer EM. Accordingly, the first multilayer film reflection mirror 12 and the second multilayer film reflection mirror 18 form a resonator OC with a resonator length direction perpendicular to the semiconductor structure layer EM (direction perpendicular to the substrate 11) between the first multilayer film reflection mirror 12 and the second multilayer film reflection mirror 18.

[0033] In the surface emitter laser 100, the reflectivity for blue light of the first multilayer film reflection mirror 12 is slightly lower than the reflectivity for blue light of the second multilayer film reflection mirror 18. Therefore, some of the blue light that resonates in the resonator OC passes through the first multilayer film reflection mirror 12 and the substrate 11 and is extracted to the outside. That is, the light that resonates between the first multilayer film reflection mirror 12 and the second multilayer film reflection mirror 18 is extracted in Fig. 2 emitted downwards.

[0034] An anti-reflective film (not illustrated) is formed on one underside of substrate 11, in which Nb₂O₅ and silicon dioxide (SiO₂) are stacked. The anti-reflective film is a so-called AR coating, which suppresses or prevents the blue light emitted by substrate 11 from passing through the substrate 11. Fig. 2 is reflected upwards.

[0035] This describes the operation of the surface emitter laser 100. 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 shown by the thick dash-dot arrows in Fig. 2 is displayed, and when the current reaches the threshold current as a predetermined current value, the intensity of the blue light emitted by the light-emitting layer 14 increases rapidly.

[0036] The blue light, which has reached the threshold current and is emitted by the light-emitting layer 14, is repeatedly reflected between the first multilayer film reflection mirror 12 and the second multilayer film reflection mirror 18, i.e. in the resonator OC, and reaches a resonance state (i.e. performs a laser oscillation).

[0037] At this point, in the p-type semiconductor layer 15, as described above, the second region 15R2, which is a region where the impurities or dopants of the p-type are inactivated, functions as the high-resistance region, and the first region 15R1, with its lower electrical resistance than the second region 15R2, functions as the low-resistance region. Therefore, the current flowing from the p-electrode PE to the n-electrode NE across the transparent conductive film 16 flows mainly through the first part 15P1 and hardly at all through the second part 15P2.

[0038] Accordingly, in the surface emitter laser 100, the current is only supplied to the first part 15P1, since the second region 15R2 acts as the region of high resistance, and blue light is emitted only from the first part 15P1. That is, in the surface emitter laser 100, the p-type semiconductor layer 15 has a current confinement structure to limit the current supply area of ​​the light-emitting layer 14. In other words, the p-type semiconductor layer 15 in the surface emitter laser 100 confines the current in such a way that it is not allowed to propagate further.

[0039] As described above, the blue light emitted by the light-emitting layer 14 and brought to resonance in the resonator OC is partially extracted to the outside, passing through the first multilayer film reflection mirror 12 and the substrate 11, because the light reflectance of the first multilayer film reflection mirror 12 is lower than that of the second multilayer film reflection mirror 18. In other words, the underside of the substrate 11 serves as a light emission surface for the surface emitter laser 100.

[0040] The following describes optical properties of the surface emitter laser 100. In the following description, it is assumed that a central axis of light emission, passing through the light emission center (the center of the light emission region of the light-emitting layer 14), is the same as the central axis AX. The central axis of light emission corresponds to an optical axis of laser light emitted by the surface emitter laser 100.

[0041] In the resonator OC of the surface emitter laser 100, the thickness from the underside of the p-type semiconductor layer 15 to the first region 15R1 of the p-type semiconductor layer 15 is greater than the thickness from the underside of the p-type semiconductor layer 15 to the second region 15R2, by the thickness of the first part 15P1. In the resonator OC, the layer thicknesses of other semiconductor layers between the first multilayer film reflection mirror 12 and the second multilayer film reflection mirror 18, the transparent conductive film 16, and the insulating layer 17 are constant.

[0042] Therefore, the equivalent refractive index in the resonator OC of the surface emitter laser 100 differs between the columnar central region CA, which contains the first part 15P1 of the p-type semiconductor layer 15, and a cylindrical circumferential region PA around its circumference. In particular, the equivalent refractive index in the central region CA is greater than the equivalent refractive index in the circumferential region PA.

[0043] In the surface emitter laser 100 with this resonator configuration OC, the optical loss due to the emission (radiation) of a standing wave in the central region CA to the circumferential region PA is suppressed. This means that most of the light remains in the central region CA, and in this state, the laser light is extracted or directed outwards.

[0044] This means that in the surface emitter laser 100, the p-type semiconductor layer 15, which forms a current confinement structure, also forms an optical confinement structure, which keeps the light emitted by the light-emitting layer 14 in the central region CA, i.e., confines it there.

[0045] Accordingly, the laser light can be generated and emitted with high power and high density, since most of the light emitted by the light-emitting layer 14 is concentrated in the central region CA around the central axis AX of the resonator OC. This means that the configuration of the surface emitter laser 100 described above allows for the stabilization of a transverse mode (intensity distribution across the cross-section of the laser beam) of the laser light emitted from the surface emitter laser 100. [Suppression of an increase in a threshold current due to hydrogen diffusion into the p-type semiconductor layer]

[0046] Here, the suppression of an increase in the threshold current due to hydrogen diffusion into the p-type semiconductor layer 15 is described.

[0047] In an initial state, when the fabrication of the surface emitter laser 100 is complete, for example in the p-type semiconductor layer 15 the region in which the current is confined (region surrounded by the second region 15R2) is the same size as the region in which the light emitted by the light-emitting layer 14 is confined (first region 15R1).

[0048] If, for example, the surface emitter laser 100 is supplied with energy over a long period of time, the p-type impurities or dopants, which should have been electrically inactivated in the second region 15R2, transition to an electrically active state. This is because the current flows continuously at an interface between the second region 15R2, where the p-type impurities are inactivated, and the first part 15P1, where the p-type impurities are activated. That is, the electrical resistance in the second region 15R2 decreases, and the current flows easily into the second part 15P2.

[0049] If the p-type impurities in the second region 15R2 transition to an electrically active state for an extended period due to the excitation of the surface emitter laser 100, the region where the current is confined within the resonator OC—that is, the region surrounded by the second region 15R2—can gradually expand. This causes a difference in size between the region where the current is confined and the region where the light emitted by the light-emitting layer 14 is confined within the resonator. Consequently, the optical loss in the resonator OC increases, potentially resulting in a higher threshold current required for laser oscillation.

[0050] In the surface emitter laser 100 according to the embodiment described above, the hydrogen concentration in the second part 15P2 of the p-type semiconductor layer 15 is higher than the hydrogen concentration in the first part 15P1. In the surface emitter laser 100, hydrogen diffuses from the region of high concentration to the region of low concentration, that is, from the inside of the second part 15P2 to the central axis AX in the p-type semiconductor layer 15, according to the concentration gradient, since the hydrogen concentration differs between the first part 15P1 and the second part 15P2.

[0051] At this point, the hydrogen diffusion force can be reached that is sufficient to stop the activation of the p-type impurities described above, since the hydrogen concentration in the second part 15P2 is at least twice as high as the hydrogen concentration in the first part 15P1. That is, the expansion of the region in which the current is confined in the p-type semiconductor layer 15 can be suppressed.

[0052] Accordingly, in the surface emitter laser 100, it can be prevented that a size difference between the region in which the current is confined and the region in which the light is confined is caused in the resonator due to the hydrogen diffusion force according to the concentration gradient, since the hydrogen concentration in the second part 15P2 of the p-type semiconductor layer 15 is at least twice higher than the hydrogen concentration in the first part 15P1, and the increase in the threshold current of the laser oscillation can be avoided by suppressing the generation of the optical loss in the resonator OC.

[0053] Accordingly, the reduction in the intensity of the emitted light due to the increased threshold current can also be avoided when the surface emitter laser 100 is used in a device, such as a display or a headlight, that operates in a constant current state for an extended period. That is, the surface emitter laser 100 according to the exemplary embodiment can emit light with a stable intensity. [First manufacturing process for the surface emitter laser]

[0054] This refers to Fig. 2 to Fig. Section 6 describes a method for manufacturing the surface emitter laser 100 according to the exemplary embodiment. The following mainly describes steps relating to the forming of the first part 15P1 and the second part 15P2 of the p-type semiconductor layer 15.

[0055] First, a high refractive index semiconductor film made of GaN and a low refractive index semiconductor film made of AlInN are stacked on top of the substrate 11 to form the first multilayer film reflection 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 in this order so that they are formed on the first multilayer film reflection mirror 12.

[0056] Next, as in Fig. Figure 3 illustrates forming a circular mask MS with a size corresponding to the top part 13B of the n-type semiconductor layer 13 on a top side of the p-type semiconductor layer 15M, and removing an exposed portion excluding the mask region by dry etching. In particular, as shown in Fig. Figure 4 illustrates that dry etching is carried out until the lower part 13A of the n-type semiconductor layer 13 is exposed as a shaping surface for the n-electrode NE.

[0057] Next, as in Fig. Figure 5 illustrates circular masks MS with sizes corresponding to the top of the lower part 13A as the forming surface for the n-electrode NE and the first region 15R1 on the top of the p-type semiconductor layer 15M, and an exposed portion excluding the mask region is removed by dry etching. In particular, as shown in Fig. Figure 6 illustrates that dry etching is carried out until the second region 15R2 of the p-type semiconductor layer 15 is exposed. In this dry etching step, the inactivation of the p-type impurities in the second region 15R2, as described above, is performed. That is, the second region 15R2 acts as the high-resistance region.

[0058] Next, ionized hydrogen is implanted into the second region 15R2, where the p-type impurities have been inactivated, using an ion implantation device. Thus, for example, the second part 15P2 is treated with a hydrogen concentration of approximately 5 × 10⁻⁵. 18 / cm 3 receive.

[0059] In the step described above, the sequence of dry etching the p-type semiconductor layer 15M and implanting hydrogen ions into the second region 15R2 can be reversed. That is, the depth of ion implantation can be adjusted, and the implantation of hydrogen ions into the region corresponding to the second region 15R2 can be performed first, followed by dry etching to form the second region 15R2, i.e., to inactivate the p-type impurities or dopants.

[0060] Next, as in Fig. Figure 2 illustrates the formation of a transparent conductive film 16 over the top surface of a p-type semiconductor layer 15. For example, the transparent conductive film 16 is formed by sputtering at a film forming rate of 100 nm / min and at a temperature of 150°C using a sputtering device.

[0061] Then, as in Fig. Figure 2 illustrates that the insulating layer 17 and the second multilayer film reflection mirror 18 are formed on the top side of the transparent conductive film 16, the n-electrode NE is formed on the lower part 13A of the n-type semiconductor layer 13, and the p-electrode PE is formed on the top side of the transparent conductive film 16, thereby allowing the surface emitter laser 100 to be obtained according to the embodiment.

[0062] While the second region 15R2, the region in which the p-type impurities are inactivated, 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 impurities can be inactivated by slightly removing the surface of the p-type semiconductor layer 15 and then performing ion implantation, or the p-type impurities can be inactivated by an ashing process. [Second manufacturing process for the surface emitter laser]

[0063] Next, with reference to Fig. 7 a second method for manufacturing the surface emitter laser 100 is described, which differs from the first manufacturing method described above.

[0064] In this manufacturing process, the adjustment procedure for the hydrogen concentration in the second part 15P2 differs from that of the first manufacturing process, and the process up to the step of forming the p-type semiconductor layer 15, which has the second region 15R2 where the p-type impurities are inactivated by dry etching, is similar to the first manufacturing process. The main difference from the first manufacturing process is described below.

[0065] First, after forming the p-type semiconductor layer 15, which contains the second region 15R2, as shown in Fig. Figure 6 illustrates a heat treatment process for the removal of hydrogen contained in the p-type semiconductor layer 15 (hydrogen removal step). The hydrogen concentration in the p-type semiconductor layer 15 after the hydrogen removal step is, for example, 1 × 10⁻⁶. 17 / cm 3 .

[0066] Next, the transparent conductive film 16 is formed at a slower rate than the film forming rate of the first fabrication process by sputtering (conductivity film forming step). For example, the transparent conductive film 16 is formed by forming a film at a film forming rate of 2 nm / min and at a temperature of 25°C. This step results in the transparent conductive film 16 having a higher hydrogen concentration than the transparent conductive film 16 formed using the first fabrication process, because the transparent conductive film 16 is formed gradually while hydrogen from the atmosphere is trapped during sputtering.

[0067] In particular, the hydrogen concentration of the transparent conductive film 16 formed using the first manufacturing process is, for example, 1 × 10 18 / cm 3, and the hydrogen concentration of the transparent conductive film 16, which is formed using the second manufacturing process, is, for example, 1 × 10 21 / cm 3 .

[0068] Next, an electrode heat treatment process (600 °C, 5 min) is performed (electrode heat treatment step) to reduce the contact resistance between the transparent conductive film 16, acting as a transparent electrode, and the p-type semiconductor layer 15. During this step, hydrogen contained in the transparent conductive film 16 migrates into the p-type semiconductor layer 15, so that it remains in similar concentrations in the first part 15P1 and the second part 15P2 of the p-type semiconductor layer 15.

[0069] Then, as in Fig. Figure 7 illustrates how, by conducting the current between the n-electrode NE and the p-electrode PE, the current is directed into the semiconductor structure layer EM (excitation step) after the n-electrode NE and the p-electrode PE have been formed and the fabrication of the element is complete. Since the second region 15R2, as the region where the impurities of the p-type are inactivated, functions as the high-resistance region in the p-type semiconductor layer 15, as described above, at this point the current flowing from the p-electrode PE to the n-electrode NE across the transparent conductive film 16 flows mainly through the first part 15P1 and hardly flows into the second part 15P2.

[0070] Accordingly, the hydrogen, which remains in the first part 15P1, moves to the semiconductor layer 13 of the n-type together with the current flow, as shown by the dot-dash line arrows in Fig. 7 is displayed, thereby reducing the hydrogen concentration in the first part 15P1.

[0071] Incidentally, in the second part 15P2, most of the hydrogen does not move to the semiconductor layer 13 of the n-type, but remains in the second part 15P2, since the current hardly flows, as described above.

[0072] Therefore, the hydrogen concentration in the second part 15P2 can be set to be higher than the hydrogen concentration in the first part 15P1. In particular, for example, the hydrogen concentration in the first part 15P1 can be set to 1 x 10 18 / cm 3 be set, while the hydrogen concentration in the second part 15P2 is set to 5 x 10 18 / cm 3 can be determined.

[0073] After the excitation or energy supply step, as described above, the hydrogen concentration in the second part 15P2 is at least twice as high as the hydrogen concentration in the first part 15P1. To make the difference in hydrogen concentration between the second part 15P2 and the first part 15P1, for example, twice or more, it is preferred that the current be passed through the transparent conductive film 16 to move the hydrogen, in order to cause the difference in hydrogen concentration between the first part 15P1 and the second part 15P2 and the transparent conductive film 16 to become ten times or more.

[0074] In particular, as in Fig. As illustrated in Figure 7, it is preferred to conduct the current in the transparent conductive film 16 such that the hydrogen is moved in such a way that the hydrogen concentration in the second part 15P2 is at least ten times higher than the hydrogen concentration in a first part 16P1 of the transparent conductive film 16 in the first region 15R1. Alternatively, it is preferred to conduct the current in the transparent conductive film 16 such that the hydrogen is moved in such a way that the hydrogen concentration in the first part 15P1 is set at least ten times lower than the hydrogen concentration in a second part 16P2 of the transparent conductive film 16 in the second region 15R2. [Modification 1]

[0075] Next, a modification 1 of the surface emitter laser 100 according to the exemplary embodiment with reference to Fig. 8 described. Fig. Figure 8 is a cross-sectional view of a surface emitter laser 200 according to modification 1. The surface emitter laser 200 differs from embodiment 1 in that a light-transmitting insulating layer 21 is provided, and otherwise it is similar to embodiment 1.

[0076] The translucent insulating layer 21 is in contact with the second region 15R2 on the top surface of the p-type semiconductor layer 15 and the side surface of the first part 15P1, and is a transparent insulating layer with an annular surface shape. The translucent insulating layer 21 is made of a material, such as SiO2, which has a lower refractive index than the material forming the p-type semiconductor layer 15, and is transparent to blue light emitted by the light-emitting layer 14.

[0077] In the surface emitter laser 200, the transparent insulating layer 21 has the same thickness as the first part 15P1. Therefore, the first region 15R1 of the p-type semiconductor layer 15 is exposed by an opening 21O provided in the transparent insulating layer 21, so that it is positioned on the same plane as the top of the transparent insulating layer 21.

[0078] In the surface emitter laser 200, it is possible to avoid a difference in size between the region where the current is restricted and the region where the light is restricted due to a hydrogen diffusion force according to the concentration gradient in the resonator OC, even when the light-transmitting insulating layer 21 is provided as described above, and the increase in the threshold current of the laser oscillation can be avoided by suppressing the generation of an optical loss in the resonator OC. [Modification 2]

[0079] Next, a modification 2 of the surface emitter laser 100 according to the exemplary embodiment will be described with reference to Fig. 9 described. Fig.Figure 9 is a cross-sectional view of a surface emitter laser 300 according to modification 2. The surface emitter laser 300 differs from embodiment 1 with respect to the configuration of the semiconductor structure layer EM and is otherwise similar to embodiment 1. In the description, it is assumed that the surface emitter laser 300 of this modification is manufactured using the first manufacturing process.

[0080] In the surface emitter laser 300, the semiconductor structure layer EM is configured to have a tunnel contact or tunnel junction layer 23, which is formed in the first region 15R1 of the p-type semiconductor layer 15, further a n-type semiconductor layer 24, which is formed on the tunnel junction layer 23, and a n-type semiconductor layer 25, which is formed on the second region 15R2.

[0081] Tunnel junction layer 23 is a semiconductor layer formed over the first region 15R1 and has a round or circular top surface. Tunnel junction layer 23 has a heavily doped p-type semiconductor layer (not illustrated) with a higher impurity concentration than the p-type semiconductor layer 15, and a heavily doped n-type semiconductor layer (not illustrated) formed on top of the heavily doped p-type semiconductor layer, which has a higher impurity concentration than the n-type semiconductor layer 13.

[0082] The n-type semiconductor layer 24 is a third semiconductor layer of the first conductivity type and is formed above the tunnel junction layer 23, having a round or circular top surface. In the surface emitter laser 300, the n-type semiconductor layer 24 has one top surface in contact with one bottom surface of the insulating layer 17.

[0083] The n-type semiconductor layer 25 is a fourth semiconductor layer of the first conductivity type and is a semiconductor layer that is in contact with the second region 15R2 and side surfaces of the tunnel contact or tunnel junction layer 23 and the n-type semiconductor layer 24 and has a ring-shaped top surface.

[0084] The n-type semiconductor layer 25 has a thickness equal to the combined thickness of the first part 15P1, the tunnel junction layer 23, and the n-type semiconductor layer 24. Therefore, the top surface of the n-type semiconductor layer 24 is exposed by an opening 25O provided on the n-type semiconductor layer 25, so that it is on the same plane as the top surface of the n-type semiconductor layer 25.

[0085] 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, for example, with germanium (Ge) as an impurity or dopant of the n-type semiconductor.

[0086] In the surface emitter laser 300, the tunnel junction layer 23 acts as a current-limiting layer, which limits the current delivery area of ​​the light-emitting layer 14. Even if the semiconductor structure layer EM has such a configuration, the surface emitter laser 300 can provide an effect similar to that of the surface emitter laser 100 according to embodiment 1.

[0087] This means that even with the surface emitter laser 300, it is possible to avoid a size difference in the resonator OC that arises due to hydrogen diffusion force according to the concentration gradient between a region where the current is confined and the region where the light is confined, even if the semiconductor structure layer EM is designed as described above, and an increase in the threshold current of the laser oscillation can be avoided by suppressing or preventing the generation of optical loss in the resonator OC. DESCRIPTION OF REFERENCE MARKS 100, 200, 300 surface emitter lasers or VCSELs (surface emitter devices) 11 Substrat 12 first multilayer film reflection mirror 13, 24, 25 n-type semiconductor layer 14 light-emitting layer 15 p-type semiconductor layer 16 transparent conductive film 17 insulating layer 18 second semiconductor film reflection mirror 21 translucent insulating layer 23 Tunnel contact or tunnel junction layer NE n-electrode PE p-electrode QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP-A-2020-064994

[0003]

Claims

[1] Surface emitter device comprising: a substrate; a first multilayer film reflection mirror that is formed on the substrate; a semiconductor structure layer comprising a first semiconductor layer, a light-emitting layer, and a second semiconductor layer, wherein the first semiconductor layer is formed on the first multilayer film reflection mirror and has a first conductivity type, wherein the light-emitting layer is formed on the first semiconductor layer, wherein the second semiconductor layer is formed on the light-emitting layer, has a top surface in which a region at a center of the top surface projects upwards with respect to a region at a circumferential edge of the first region of the top surface, and which has a second conductivity type opposite to the first conductivity type; and a second multilayer film reflection mirror formed on the semiconductor structure layer and forming a resonator between the first multilayer film reflection mirror and the second multilayer film reflection mirror, wherein in the second semiconductor layer, the hydrogen concentration in a second part along the circumferential edge region is higher than in a first part along one region of the top surface. [2] Surface emitter device according to claim 1, wherein the second part has a hydrogen concentration at least twice as high as the hydrogen concentration of the first part. [3] Surface emitter device according to claim 2, comprising the following: a translucent conductive film formed over the top surface of the second semiconductor layer, wherein: the hydrogen concentration in the second part is at least ten times higher than the hydrogen concentration in the conductive film in one region. [4] Surface emitter device according to claim 2, comprising the following: a translucent conductive film formed over the top surface of the second semiconductor layer, wherein the hydrogen concentration in the first part is at least ten times lower than the hydrogen concentration in the conductive film at the circumferential edge region. [5] Surface emitter device according to claim 1 or 2, comprising: an insulating layer that is arranged at the circumferential edge region and has an electrically insulating property; and a translucent conductive film shaped to cover the insulating layer and the first part. [6] Surface emitter device according to claim 1 or 2, comprising the following: a tunnel junction layer formed on one region, comprising a semiconductor layer with the first conductivity type and a semiconductor layer with the second conductivity type; a third semiconductor layer formed on the tunnel junction layer and having the first conductivity type; and a fourth semiconductor layer, which is formed on the circumferential edge part and has the first conductivity type. [7] A method for manufacturing the surface emitter device according to claim 1 or 2, comprising the following: a hydrogen ion implantation step of implanting hydrogen ions into the second part of the second semiconductor layer by means of an ion implantation process. [8] Method for manufacturing the surface emitter device according to claim 1 or 2, comprising the following: a forming step for the conductive film of forming a conductive film on the second semiconductor layer with a predetermined film forming rate, such that hydrogen is provided or introduced into the conductive film with a predetermined concentration or more; a heat treatment process step of moving the hydrogen contained in the conductive film, which was formed in the forming step for the conductive film, into the second semiconductor layer by a heat treatment process; and an energy delivery step of moving the hydrogen contained in the first part of the second semiconductor layer into the first semiconductor layer by supplying energy.

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