Vertical resonator type light-emitting element and method for manufacturing the same

Abstract

To provide a long-life and highly efficient vertical resonator type light-emitting element, and a manufacturing method of the same.SOLUTION: In a vertical resonator type light-emitting element, three or more AlGaN layers including Mg as a p-type dopant and having different Al compositions are laminated. In an Al composition curve in a layer thickness direction obtained by SIMS, when a P-type AlGaN layer is divided, from an active layer side, into a first region having a 1 / 10 layer thickness of the P-type AlGaN layer, a second region having a 2 / 5 layer thickness, and a third region having a 1 / 2 layer thickness, a magnitude relationship between each region of an Al composition shown by the Al composition curve satisfies the first region<the third region<the second region. Mg concentration shown by a Mg concentration curve is less than 3×1019 atoms / cm3 throughout the layer thickness of the P-type AlGaN layer, and a magnitude relationship between each region of the Mg concentration satisfies the first region<the second region<the third region, the Mg concentration in at least some region of the second region is 3×1018 atoms / cm3 or more, and the Mg concentration curve has a peak in the second region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a vertical cavity type light-emitting element using a semiconductor multilayer mirror, and more particularly to a vertical cavity type semiconductor light-emitting element such as a vertical cavity surface-emitting laser (VCSEL). It also relates to a method for manufacturing such a vertical cavity type light-emitting element. [Background technology]

[0002] Vertical-cavity light-emitting devices are known in which distributed Bragg reflectors (DBRs) are placed above and below the active layer. Furthermore, in semiconductor light-emitting devices, it is known that an electron blocking layer with a bandgap energy higher than that of the active layer is provided to prevent electron carrier overflow.

[0003] For example, Patent Document 1 discloses a vertical resonator type light-emitting element having an AlGaN layer as an electron blocking layer between an active layer and a mesa-like structure of a p-type semiconductor, both of which are made of a GaN-based semiconductor. Furthermore, Patent Document 1 discloses increasing the bandgap energy by increasing the Al composition of the electron blocking layer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6966843 [Overview of the project] [Problems that the invention aims to solve]

[0005] For example, in a vertical-cavity light-emitting element as described above, increasing the p-type dopant concentration in the p-type AlGaN layer increases the hole carrier concentration and improves the carrier injection efficiency. However, if the p-type dopant concentration is too high, it can lead to problems such as diffusion of the p-type dopant into the active layer and a decrease in device lifetime due to the spread of defects in the active layer caused by the high p-type dopant concentration.

[0006] The present invention has been made in view of the above-mentioned points, and aims to provide a vertical resonator type light-emitting element and a method for manufacturing the same that can suppress the reduction in the lifespan of the element while ensuring high carrier injection efficiency, and that have a long lifespan and high efficiency. [Means for solving the problem]

[0007] The vertical resonator type light-emitting element according to the present invention includes a substrate, a first multilayer reflector which is a semiconductor multilayer film in which two semiconductor layers with different refractive indices are alternately stacked multiple times on the substrate, an n-type nitride semiconductor layer formed on the first multilayer reflector and consisting of a nitride semiconductor containing an n-type dopant, an active layer formed on the n-type nitride semiconductor layer, a p-type AlGaN layer formed on the active layer and having a structure in which three or more AlGaN layers with different Al compositions, each containing Mg as a p-type dopant, are stacked, a p-type nitride semiconductor layer formed on the p-type AlGaN layer and consisting of a nitride semiconductor containing a p-type dopant, and a second multilayer reflector formed on the p-type nitride semiconductor layer and provided at a position facing the first multilayer reflector, wherein the p-type AlGaN layer has secondary ions By analysis using mass spectrometry (SIMS), the p-type AlGaN layer is defined as the range of width at 50% of the peak value of the Al composition curve, which shows the change in the Al composition of the p-type AlGaN layer in the thickness direction, and the Mg concentration curve which shows the change in the Mg concentration of the p-type AlGaN layer in the thickness direction. When the p-type AlGaN layer is divided in the thickness direction from the active layer side into a first region having a thickness of 1 / 10 of the p-type AlGaN layer, a second region having a thickness of 2 / 5 of the p-type AlGaN layer, and a third region having a thickness of 1 / 2 of the p-type AlGaN layer, the relative magnitudes of the Al composition regions shown by the Al composition curve are: first region < third region < second region, and the Mg concentration shown by the Mg concentration curve is 3 × 10⁻¹⁰ over the entire thickness of the p-type AlGaN layer. 19 atoms / cm 3 The value is less than 3 × 10⁻¹⁰, and the relative magnitudes between the regions of Mg concentration are such that the first region < the second region < the third region, and the Mg concentration in at least a portion of the second region is 3 × 10⁻¹⁰. 18 atoms / cm 3 The above is characterized in that the Mg concentration curve has a peak in the second region.

[0008] Furthermore, the vertical resonator type light-emitting element according to the present invention includes a substrate, a first multilayer reflector which is a semiconductor multilayer film in which two semiconductor layers with different refractive indices are alternately stacked multiple times on the substrate, an n-type nitride semiconductor layer formed on the first multilayer reflector and consisting of a nitride semiconductor containing an n-type dopant, an active layer formed on the n-type nitride semiconductor layer, a p-type AlGaN layer formed on the active layer and having a structure in which three or more AlGaN layers containing Mg as a p-type dopant and having different Al compositions are stacked, a p-type nitride semiconductor layer formed on the p-type AlGaN layer and consisting of a nitride semiconductor containing a p-type dopant, and a second multilayer reflector formed on the p-type nitride semiconductor layer and provided at a position facing the first multilayer reflector, wherein the p-type AlGaN layer has a secondary ion Analysis by SIMS revealed that the p-type AlGaN layer is defined as the range of width at 50% of the peak value of the Al composition curve, which shows the change in the Al composition of the p-type AlGaN layer in the thickness direction, and the Mg concentration curve which shows the change in the Mg concentration of the p-type AlGaN layer in the thickness direction. The p-type AlGaN layer is then divided in the thickness direction into a first region having a thickness of 1 / 10 of the p-type AlGaN layer, a second region having a thickness of 2 / 5 of the p-type AlGaN layer, and a third region having a thickness of 1 / 2 of the p-type AlGaN layer, starting from the active layer side. The relative magnitudes of the Al compositions in each region shown by the Al composition curve are: first region < third region < second region, and the Mg concentration shown by the Mg concentration curve is 3 × 10⁻¹⁰ over the entire thickness of the p-type AlGaN layer. 19 The concentration is less than atoms / cm³, and the relative magnitudes of the Mg concentrations in each region are such that the first region < the second region < the third region, and the average value of the Mg concentration in the second region is 3 × 10⁻¹⁰ 18 atoms / cm 3 As described above, the Mg concentration curve in the second region is such that the average value of the absolute value of the slope in the portion of the second region closer to the third region is greater than the average value of the absolute value of the slope in the portion of the second region closer to the first region than the center of the second region in the thickness direction. small It is characterized by the following:

[0009] The method for manufacturing a vertical resonator type light-emitting element according to the present invention includes the steps of: forming a first multilayer reflector by alternately growing two semiconductor layers having different refractive indices on a substrate using metal-organic vapor deposition (MOCVD); growing an n-type nitride semiconductor layer on the first multilayer reflector while supplying an n-type dopant material gas; forming an active layer on the n-type nitride semiconductor layer; growing a p-type AlGaN layer, which is an AlGaN layer having a p-type conductivity, on the active layer while supplying an Mg material gas as a p-type dopant; growing a p-type nitride semiconductor layer on the p-type AlGaN layer; and forming a second multilayer reflector on the p-type nitride semiconductor layer opposite the first multilayer reflector. The p-type AlGaN layer growth step is characterized by comprising: a first growth step of growing a first p-type AlGaN layer by supplying nitrogen source gas and Ga material gas at predetermined supply amounts, supplying Al material gas at a first supply amount, and supplying Mg material gas at a second supply amount while raising the temperature from a first temperature to a second temperature; a second growth step of growing a second p-type AlGaN layer after the first growth step while maintaining the supply amounts of nitrogen source gas, Ga material gas, Al material gas, and Mg material gas in the first growth step; and a third growth step of growing a third p-type AlGaN layer after the second growth step while supplying Al material gas at a third supply amount lower than the first supply amount, and supplying Mg material gas at a fourth supply amount lower than the second supply amount.

[0010] Furthermore, the method for manufacturing a vertical resonator type light-emitting element according to the present invention includes the steps of: forming a first multilayer reflector by alternately growing two semiconductor layers having different refractive indices on a substrate using metal-organic vapor deposition (MOCVD); growing an n-type nitride semiconductor layer on the first multilayer reflector while supplying an n-type dopant material gas; forming an active layer on the n-type nitride semiconductor layer; growing a p-type AlGaN layer, which is an AlGaN layer having a p-type conductivity, on the active layer while supplying an Mg material gas as a p-type dopant; growing a p-type nitride semiconductor layer on the p-type AlGaN layer; and forming a second multilayer reflector on the p-type nitride semiconductor layer facing the semiconductor multilayer, wherein the p-type AlGaN layer growth step involves raising the temperature from a first temperature to a second temperature. The method is characterized by comprising: a pretreatment step in which a nitrogen source gas is supplied at a predetermined supply amount and the Mg material gas is supplied at a first supply amount; a first growth step in which, after the pretreatment step, the supply of the nitrogen source gas is continued while the Ga material gas is supplied at a predetermined supply amount, the Al material gas is supplied at a second supply amount, and the Mg material gas is supplied at a third supply amount to grow a first p-type AlGaN layer; a second growth step in which, after the first growth step, the supply amounts of the nitrogen source gas, the Ga material gas, the Al material gas and the Mg material gas in the first growth step are maintained while growing a second p-type AlGaN layer; and a third growth step in which, after the second growth step, the Al material gas is supplied at a fourth supply amount lower than the second supply amount and the Mg material gas is supplied at a fifth supply amount lower than the third supply amount while growing a third p-type AlGaN layer. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing the configuration of the surface-emitting laser according to Example 1. [Figure 2] This is a top view showing the configuration of the surface-emitting laser according to Example 1. [Figure 3]This is a cross-sectional view showing the configuration of a surface-emitting laser according to Example 1. [Figure 4] This figure shows the SIMS analysis results of the p-type AlGaN layer of the surface-emitting laser according to Example 1. [Figure 5] This flowchart outlines the manufacturing process of the surface-emitting laser according to Example 1. [Figure 6] This figure schematically shows the growth sequence of the p-type AlGaN layer of the surface-emitting laser according to Example 1. [Figure 7] This figure shows the SIMS analysis results of the p-type AlGaN layer of a comparative surface-emitting laser. [Figure 8] This figure shows the SIMS analysis results of the p-type AlGaN layer of a comparative surface-emitting laser. [Figure 9] This figure shows the SIMS analysis results of the p-type AlGaN layer of the surface-emitting laser according to Example 2. [Figure 10] This figure shows the SIMS analysis results of the p-type AlGaN layer of a surface-emitting laser according to a modified example of Example 2. [Figure 11] This figure schematically shows the growth sequence of the p-type AlGaN layer of a surface-emitting laser according to a modified example of Example 2. [Figure 12] This figure shows the SIMS analysis results of the p-type AlGaN layer of a surface-emitting laser relating to another modification of Example 2. [Figure 13] This figure shows the SIMS analysis results of the p-type AlGaN layer of a surface-emitting laser relating to another modification of Example 2. [Figure 14] This is a cross-sectional view showing the configuration of the surface-emitting laser according to Example 3. [Figure 15] This figure shows the SIMS analysis results of the p-type AlGaN layer of the surface-emitting laser according to Example 3. [Figure 16] This figure schematically shows the growth sequence of the p-type AlGaN layer of the surface-emitting laser according to Example 3. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described below, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially identical or equivalent parts will be denoted by the same reference numerals. [Examples]

[0013] Referring to the attached drawings, the configuration of the vertical cavity surface-emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser, hereinafter also simply referred to as a surface-emitting laser) 10 according to Embodiment 1 of the present invention will be described. The surface-emitting laser 10 of Embodiment 1 is composed of a nitride-based semiconductor layer.

[0014] Figure 1 is a perspective view showing an overview of the configuration of the surface-emitting laser 10.

[0015] The substrate 11 is a substrate for growing the nitride semiconductor layer that constitutes the surface-emitting laser 10. The substrate 11 has, for example, a rectangular top surface shape. In this embodiment, the substrate 11 is a GaN substrate. The top surface of the substrate 11, i.e., the surface on which the nitride semiconductor layer is grown, is preferably a C-plane or a surface set off within 1° from the C-plane. In addition to a GaN substrate, other substrates such as a sapphire substrate or an AlN substrate can be used as the substrate 11.

[0016] The underlayer 13 is formed on the substrate 11. The underlayer 13 is an undoped GaN layer. The underlayer 13 functions as a buffer layer to enhance the crystallinity of the nitride semiconductor layer grown on the underlayer 13.

[0017] The first multilayer reflector 15 is formed on the underlayer 13. The first multilayer reflector 15 is a semiconductor multilayer reflector in which a low refractive index semiconductor film having an AlInN composition and a high refractive index semiconductor film having a GaN composition and a higher refractive index than the low refractive index semiconductor film are alternately stacked. The first multilayer reflector 15 is a distributed flag reflector (DBR) made of nitride semiconductor material. In other words, the first multilayer reflector 15 is a nitride semiconductor multilayer reflector.

[0018] The n-type semiconductor layer 17 is an n-type GaN layer formed on the first multilayer reflecting mirror 15. The n-type semiconductor layer 17 is doped with Si as an n-type impurity.

[0019] The n-type semiconductor layer 17 has a prismatic lower portion 17A and a cylindrical upper portion 17B positioned on the lower portion 17A. In other words, the n-type semiconductor layer 17 has a cylindrical upper portion 17B that protrudes from the upper surface of the prismatic lower portion 17A. In other words, the n-type semiconductor layer 17 has a mesa-shaped structure including the upper portion 17B. The n-type semiconductor layer 17 has an exposed portion 17E where the upper surface of the lower portion 17A is partially exposed.

[0020] The active layer 19 is formed on the upper part 17B of the n-type semiconductor layer 17. The active layer 19 is a light-emitting structure layer consisting of multiple semiconductor layers forming, for example, a multi-quantum well (MQW) structure. Specifically, the active layer 19 is a layer having a quantum well structure that includes a well layer having an InGaN composition and a barrier layer having a GaN composition. When current is injected into the surface-emitting laser 10, light is generated in the active layer 19.

[0021] The intermediate layer 21 is an undoped GaN layer formed on the active layer 19. The intermediate layer 21 functions as a buffer layer that increases the distance between the active layer 19 and the p-type semiconductor layer 23 formed on the intermediate layer 21, in order to prevent impurities from diffusing from the p-type semiconductor layer 23 formed on the intermediate layer 21 to the active layer 19.

[0022] The p-type semiconductor layer 23 is formed on the intermediate layer 21 as described above and is a layer containing multiple semiconductor layers doped with p-type impurities. Mg is used as the p-type impurity.

[0023] The n-electrode 25 is a metal electrode provided on the exposed portion 17E of the n-type semiconductor layer 17. The n-electrode 25 is electrically connected to the n-type semiconductor layer 17. For example, the n-electrode 25 is formed in an annular shape so as to surround the upper part 17B of the n-type semiconductor layer 17. The shape of the n-electrode 25 is not limited to this, and for example, it may be an electrode layer formed in layers over the entire surface of the exposed portion 17E.

[0024] The insulating layer 27 is a layer formed on the p-type semiconductor layer 23, consisting of an insulator or a material with lower conductivity than the p-type semiconductor layer 23. The insulating layer 27 is made of a substance having a lower refractive index than the material constituting the p-type semiconductor layer 23, such as SiO2. The insulating layer 27 is formed in an annular shape on the p-type semiconductor layer 23 and has an opening (not shown) in its central portion that exposes the p-type semiconductor layer 23.

[0025] The translucent electrode 29 is formed on the insulating layer 27. Furthermore, the translucent electrode 29 is formed on the p-type semiconductor layer 23 via an opening in the insulating layer 27 and is electrically connected to the p-type semiconductor layer 23. The translucent electrode 29 is formed of a metal oxide that is translucent to light emitted from the active layer 19, such as ITO or IZO.

[0026] The second multilayer mirror 31 is a dielectric multilayer film provided on a light-transmitting electrode 29 above the opening of the insulating layer 27. The second multilayer mirror 31 is a dielectric multilayer mirror in which two dielectric films with different refractive indices, such as niobium oxide (Nb2O5) and silicon oxide (SiO2), are alternately stacked.

[0027] The p electrode 33 is a metal electrode provided on the translucent electrode 29. The p electrode 33 is electrically connected to the translucent electrode 29. The p electrode 33 is formed in an annular shape so as to surround the second multilayer reflecting mirror 31.

[0028] Figure 2 is a top view of the surface-emitting laser 10. As described above, the surface-emitting laser 10 is formed on a substrate 11 having a rectangular top surface shape and has an n-type semiconductor layer 17 having a mesa-shaped structure.

[0029] An annular n-electrode 25 is formed on the exposed portion 17E that is exposed from the mesa-shaped portion of the n-type semiconductor layer 17, so as to surround the mesa-shaped portion.

[0030] Furthermore, as described above, the surface-emitting laser 10 has an active layer 19, an intermediate layer 21, and a p-type semiconductor layer, which are sequentially formed on the upper part 17B, which is a mesa-shaped portion of the n-type semiconductor layer 17 and have a circular upper surface shape, and an annular insulating layer 27 (not shown in Figure 2). The insulating layer 27 has an opening OP.

[0031] The translucent electrode 29 is formed on the insulating layer 27 so as to cover the opening OP of the insulating layer 27. A second multilayer reflecting mirror 31 is provided in the region of the translucent electrode 29 that includes the center CA of the translucent electrode 29.

[0032] The second multilayer mirror 31 is formed to cover the aperture OP when viewed from above. Alternatively, the second multilayer mirror 31 may be formed to overlap with the aperture OP when viewed from above.

[0033] Furthermore, an annular p-electrode 33 is provided on the outer periphery of the translucent electrode 29.

[0034] Figure 3 is a cross-sectional view of the surface-emitting laser 10 along line 3-3 in Figure 2. As described above, the p-type semiconductor layer 23 is composed of multiple semiconductor layers containing p-type impurities. The configuration of the p-type semiconductor layer 23 will be described below.

[0035] The p-type AlGaN layer 35 is formed on the intermediate layer 21 and is doped with Mg as a p-type impurity. The p-type AlGaN layer 35 functions as an electron blocking layer.

[0036] The p-type AlGaN layer 35 is composed of three p-type AlGaN layers, each with a different distribution of Mg concentration and Al composition. In Figure 3, the three layers constituting the p-type AlGaN layer 35 are shown as the first layer 37, the second layer 39, and the third layer 41.

[0037] In a surface-emitting laser 10, it is important to efficiently inject electron carriers and hole carriers into the active layer 19 and keep them there, thereby keeping the threshold current density low. If electron carrier overflow occurs, the threshold current density increases, reducing the efficiency of current utilization. Furthermore, the device deteriorates due to the effects of heat emitted by carriers that do not contribute to light emission, thus reducing the device's lifespan.

[0038] By doping the p-type AlGaN layer 35, which acts as an electron blocking layer, with Mg, the hole carrier concentration in the p-type AlGaN layer 35 increases and the Fermi level decreases. This suppresses carrier overflow and improves carrier injection efficiency, thereby suppressing the increase in the threshold current density of the surface-emitting laser 10.

[0039] On the other hand, if the Mg concentration in the p-type AlGaN layer 35 is made too high, the device life may decrease due to the diffusion of Mg into the active layer or the spread of defects caused by Mg into the active layer.

[0040] The inventors of this invention have found that in order to suppress the decrease in device lifetime caused by Mg in the p-type AlGaN layer 35 as described above, while increasing the carrier injection efficiency, it is important to precisely control the concentration distribution of Mg in the layer thickness direction of the p-type AlGaN layer 35.

[0041] Therefore, in the present invention, the Mg concentration in the first layer 37, which is closest to the active layer 19, is controlled so as not to become too high, and the Mg concentration and Al composition in the second layer 39 adjacent to the first layer 37 and the third layer 41, which is furthest from the active layer, are controlled so as to be suitable for increasing the carrier injection efficiency.

[0042] As described above, an intermediate layer 21 is provided between the active layer 19 and the p-type semiconductor layer 23. The intermediate layer 21 has the function of increasing the distance between the p-type semiconductor layer 23 and the active layer 19, thereby suppressing the diffusion of p-type impurities into the active layer 19 and the influence of defects caused by p-type impurities. For example, the intermediate layer 21 is formed with a layer thickness of 30 to 145 nm. However, for example, in the surface-emitting laser 10, a configuration without an intermediate layer 21 may be used.

[0043] The p-type nitride semiconductor layer 43 is formed on the p-type AlGaN layer 35 and is a nitride semiconductor layer doped with p-type impurities. For example, the p-type nitride semiconductor layer 43 is a GaN layer doped with Mg as the p-type impurity.

[0044] The p-type contact layer 45 is formed on the p-type nitride semiconductor layer 43 and is a nitride semiconductor layer doped with p-type impurities at a higher concentration than the p-type nitride semiconductor layer 43. For example, the p-type contact layer 45 is a GaN layer doped with Mg as a p-type impurity at a higher concentration than the p-type nitride semiconductor layer 43.

[0045] Thus, the p-type semiconductor layer 23 is constructed by stacking a p-type AlGaN layer 35, a p-type nitride semiconductor layer 43, and a p-type contact layer 45 in this order.

[0046] The insulating layer 27 is formed on the p-type contact layer 45. As described above, the translucent electrode 29 is formed on the insulating layer 27 so as to cover the opening OP of the insulating layer 27, and the translucent electrode 29 is in contact with the p-type contact layer 45 through the opening OP.

[0047] The p electrode 33 is in electrical contact with the translucent electrode 29. Therefore, the p electrode 33 is electrically connected to the p-type semiconductor layer 23 via the translucent electrode 29.

[0048] In the surface-emitting laser 10, current is injected into the p-type semiconductor layer 23 only from the portion exposed by the aperture OP of the insulating layer 27. Therefore, the aperture OP has a current-constricting structure that limits the range of current supply to the active layer 19.

[0049] In the surface-emitting laser 10, a first multilayer reflector 15 and a second multilayer reflector 31 are arranged facing each other. The first multilayer reflector 15 has a slightly lower reflectivity than the second multilayer reflector 31. Therefore, a portion of the light emitted from the active layer 19 and resonating between the first multilayer reflector 15 and the second multilayer reflector 31 passes through the first multilayer reflector 15 and the substrate 11 and is extracted to the outside.

[0050] Figure 4 shows the SIMS analysis results of the p-type AlGaN layer 35 of the surface-emitting laser 10 according to Example 1. Figure 4 shows the Al composition and Mg concentration profiles in the depth direction, i.e., in the layer thickness direction, from the p-type nitride semiconductor layer 43, which is the upper layer of the p-type AlGaN layer 35, toward the intermediate layer 21, which is the lower layer of the p-type AlGaN layer 35 (i.e., from the surface side toward the active layer side (substrate 11 side)).

[0051] In Figure 4, the horizontal axis represents the layer thickness, or depth (nm), from the surface to the active layer, the primary axis represents the Mg concentration, and the secondary axis represents the Al composition. In Figure 4, the Al composition curve, showing the change in Al composition in the depth direction, is shown as a dashed line. Also in Figure 4, the Mg concentration curve, showing the change in Mg concentration in the depth direction, is shown as a solid line.

[0052] Regarding the Al composition curve shown in FIG. 4, the range of the full width at half maximum, which is the width at 50% of the maximum peak of the Al composition, defines the p-type AlGaN layer 35. Also, in this embodiment, the p-type AlGaN layer defined on the Al composition curve is divided into three regions in the layer thickness direction. Specifically, the p-type AlGaN layer 35 is divided in the layer thickness direction, from the active layer side towards the surface side, into a region having a layer thickness of one-tenth (10%) as the first region AR1, a region having a layer thickness of two-fifths (40%) as the second region AR2, and a region having a layer thickness of one-half (50%) as the third region AR3, and the Al composition and Mg concentration will be described.

[0053] Therefore, focusing on the horizontal axis indicating the layer thickness in the graph shown in FIG. 4, the above-mentioned full width at half maximum corresponds to the total layer thickness of the p-type AlGaN layer 35. On this horizontal axis, the first region AR1 corresponds to a layer thickness portion of one-tenth of the p-type AlGaN layer 35, the second region AR2 corresponds to a layer thickness portion of two-fifths, and the third region AR3 corresponds to a layer thickness portion of one-half.

[0054] [Mg Concentration Curve] First, the Mg concentration and the profile of the Mg concentration in the layer thickness direction shown by the Mg concentration curve will be described.

[0055] As shown in FIG. 4, the Mg concentration shown by the Mg concentration curve is less than 1×10 19 atoms / cm 3 throughout the entire layer thickness of the p-type AlGaN layer 35. By setting the Mg concentration to less than 1×10 19 atoms / cm 3 the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer are prevented. Thereby, the reduction of the device lifetime due to high-concentration Mg is prevented.

[0056] The peak concentration of Mg in the p-type AlGaN layer 35 is 3×10 19 atoms / cm 3Therefore, while the presence of a large amount of Mg improves the carrier injection efficiency, it also makes it easier for Mg to diffuse into the active layer, and defects caused by Mg are more likely to spread to the active layer, thus reducing the device lifespan.

[0057] Therefore, the Mg concentration in the p-type AlGaN layer 35 is 3 × 10⁻⁶ 19 atoms / cm 3 Less than, more preferably 1 × 10 19 atoms / cm 3 By controlling it to below a certain level, the decrease in device lifespan caused by such high concentrations of Mg can be suppressed.

[0058] In this embodiment, in order to suppress the decrease in device lifetime caused by the high concentration of Mg as described above, the Mg concentration is set to 1 × 10⁻¹⁶ over the entire thickness of the p-type AlGaN layer 35 in the Mg concentration curve. 19 atoms / cm 3 It is being controlled to be less than [a certain level].

[0059] Furthermore, in the thickness direction of the p-type AlGaN layer 35, the closer the region is to the active layer 19, the easier it is for Mg to diffuse into the active layer 19, and the easier it is for defects caused by Mg to spread to the active layer. Considering these factors, it is preferable that the Mg concentration is lowest in the first region AR1, which is closest to the active layer 19, and highest in the third region AR3, which is furthest from the active layer 19.

[0060] As shown in Figure 4, in this embodiment, when comparing the average values ​​of the Mg concentrations within each region shown by the Mg concentration curve, the third region AR3 has the highest concentration, followed by the second region AR2, and then the first region AR1 has the lowest concentration (first region AR1 < second region AR2 < third region AR3). In this way, by making the Mg concentration in the first region AR1, which is closest to the active layer 19, the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer are prevented, thereby preventing a decrease in device lifespan caused by high concentrations of Mg.

[0061] Furthermore, in order to prevent a decrease in device lifespan caused by such high concentrations of Mg, the Mg concentration in the first region is set to 2 × 10⁻⁶ 18 atoms / cm 3 It is preferable to keep it below a certain value.

[0062] Furthermore, in order to ensure sufficient carrier injection efficiency in the surface-emitting laser 10, the Mg concentration in the second region must not be too low, and at least a portion of the second region AR2 must have a concentration of 3 × 10⁻¹⁰. 18 atoms / cm 3 The above is one of the indicators. In addition, the Mg concentration profile in the second region AR2 is also important, and it was found that sufficient carrier injection efficiency can be ensured when the Mg concentration curve has a peak in the second region AR2.

[0063] As shown in Figure 4, in this embodiment, the Mg concentration shown by the Mg concentration curve is 3 × 10 in a part of the second region AR2. 18 atoms / cm 3 As described above, the Mg concentration curve has a peak in the second region. By controlling the Mg concentration in this way, sufficient carrier injection efficiency is ensured, thereby suppressing the increase in threshold current density.

[0064] [Al composition curve] The Al composition curve shown in Figure 4 has a peak in the second region, AR2. More specifically, when comparing the average values ​​of the Al composition within each region shown by the Al composition curve, the second region, AR2, is the largest, followed by the third region, AR3, and the first region, AR1, is the smallest (first region AR1 < third region AR3 < second region AR2).

[0065] In regions with low Mg concentration, increasing the Al composition raises the threshold voltage. Therefore, in the first region AR1, where the Mg concentration is low, the Al composition is also kept low to suppress the rise in the threshold voltage.

[0066] Furthermore, by making the Al composition of the second region AR2 the highest, the barrier potential can be increased, and electron carrier overflow can be suppressed.

[0067] Furthermore, instead of increasing the Al composition of the entire p-type AlGaN layer, by making the Al composition of only the second region AR2 the highest, it is possible to suppress the occurrence of cracks due to lattice mismatch between the high-Al-composition layer and the adjacent GaN layer.

[0068] As described above, the surface-emitting laser 10 of Example 1 is configured to include a first multilayer reflector laminated on a substrate, an n-type nitride semiconductor layer formed on the first multilayer reflector, an active layer formed on the n-type nitride semiconductor layer, a p-type AlGaN layer formed on the active layer and having a configuration in which three AlGaN layers with different Al compositions are laminated and contain Mg as a p-type dopant, a p-type nitride semiconductor layer formed on the p-type AlGaN layer, and a second multilayer reflector formed on the p-type semiconductor layer and provided at a position facing the first multilayer reflector.

[0069] The p-type AlGaN layer in Example 1 is defined as the range of width at 50% of the peak value of the Al composition curve, which shows the change in the Al composition in the p-type AlGaN layer in the thickness direction, and the Mg concentration curve which shows the change in the Mg concentration in the p-type AlGaN layer in the thickness direction, as determined by secondary ion mass spectrometry (SIMS) analysis of the p-type AlGaN layer. When the p-type AlGaN layer is divided in order from the active layer side into a first region having a thickness of 1 / 10 of the p-type AlGaN layer, a second region having a thickness of 2 / 5 of the p-type AlGaN layer, and a third region having a thickness of 1 / 2 of the p-type AlGaN layer, it is defined as follows.

[0070] The relative magnitudes of the Al composition regions shown by the Al composition curve are Region 1 < Region 3 < Region 2, and the Mg concentration shown by the Mg concentration curve is 3 × 10⁻¹⁰ throughout the entire thickness of the p-type AlGaN layer. 19 atoms / cm 3The value is less than 3 × 10⁻¹⁰, and the relative magnitudes between the regions of Mg concentration are 1st region < 2nd region < 3rd region, and the Mg concentration in at least a portion of the 2nd region is 3 × 10⁻¹⁰. 18 atoms / cm 3 Therefore, the Mg concentration curve has a peak in the second region.

[0071] With the above configuration, an appropriate amount of Mg is contained in an appropriate region in the thickness direction of the p-type AlGaN layer. Therefore, it is possible to ensure a sufficient hole carrier concentration in the p-type AlGaN layer while suppressing a decrease in device lifetime caused by excess Mg.

[0072] Therefore, the surface-emitting laser 10 of this embodiment can suppress the decrease in the lifespan of the element while ensuring high carrier injection efficiency, and can provide a long-life, highly efficient vertical-cavity type light-emitting element.

[0073] An example of a manufacturing method for the surface-emitting laser 10 will be described with reference to Figures 5 and 6. Figure 5 is a flowchart outlining the manufacturing process of the surface-emitting laser 10. Each semiconductor layer was formed by metal-organic chemical vapor deposition (MOCVD).

[0074] First, a base layer 13 was formed on the substrate 11, and a first multilayer reflecting mirror 15 was formed on the base layer 13 (step S11).

[0075] A C-plane GaN substrate was used for the growth substrate, substrate 11. Although not shown in the figures, in the semiconductor layer growth apparatus, substrate 11 is placed on a susceptor. A thermocouple is placed below the susceptor, and the temperature of this thermocouple is referred to as the "substrate temperature" in this specification. Furthermore, in this specification, "growth temperature" refers to the substrate temperature.

[0076] In step S11, the temperature of the substrate 11 was first raised to 1200°C, and a 100 nm thick underlayer 13 made of undoped GaN was grown in a hydrogen carrier gas (atmosphere gas) by supplying trimethylgallium (hereinafter referred to as TMG) ​​and ammonia (NH3) gas. In the case of homoepitaxial growth, it is not necessary to stack the underlayer 13 and it is optional.

[0077] Next, the first multilayer reflector 15 was formed. A semiconductor DBR (Distributed Bragg reflector) made of an InAlN / GaN laminate was grown on the underlayer 13.

[0078] First, an InAlN layer was grown on the substrate layer 13. The substrate temperature was set to 950°C, nitrogen (N2) gas was used as the carrier gas, and trimethylindium (hereinafter referred to as TMI), the material gas for indium, trimethylaluminum (hereinafter referred to as TMA), the material gas for aluminum, and ammonia gas were supplied to grow the InAlN layer.

[0079] Next, a GaN layer was grown on the InAlN layer. The substrate temperature was raised to 1100°C, the carrier gas was changed to hydrogen gas, and trimethylgallium (hereinafter referred to as TMG), a material gas for gallium, and ammonia gas were supplied to form the GaN layer on the InAlN layer.

[0080] Subsequently, the process of growing the InAlN layer and the process of growing the GaN layer were repeated 40 more times, resulting in a total of 41 pairs of InAlN and GaN layers being stacked. The AlInN and GaN were formed in layers on the (0001) crystal plane of the substrate 11, with each layer thickness being 1 / 4 of the optical layer thickness for the desired wavelength.

[0081] Subsequently, an n-type semiconductor layer 17 was formed on the first multilayer reflecting mirror 15 (step S12). In step S12, the substrate temperature was 1200°C, hydrogen gas was used as the carrier gas, TMG was supplied as the material gas for gallium, ammonia gas as the nitrogen source gas, and disilane (Si2H6), which is the material gas for the n-type dopant and contains silicon, was supplied, and 3 × 10⁻¹⁶ Si was formed on the first multilayer reflecting mirror 15. 18 atoms / cm 3 A doped n-type GaN layer (high-temperature n-GaN layer) was formed at a wavelength of 1500 nm.

[0082] After the formation of the n-type semiconductor layer 17, an active layer 19 was stacked on the n-type semiconductor layer 17 (step S13).

[0083] In step S13, a multi-quantum well (MQW) layer was formed on the n-type semiconductor layer 17. The barrier layer and the well layer were made of In x Al y Ga 1-x-y It consists of N. In this example, a 3nm undoped InGaN (y=0) layer was used as the well layer, and a 4nm undoped GaN (x=y=0) layer was used as the barrier layer. These layers were stacked five times to form an MQW consisting of five pairs.

[0084] After the formation of the active layer 19, a p-type semiconductor layer 23 was formed on the active layer 19 (step S14). In step 14, a GaN layer with a thickness of 130 nm was formed on the active layer 19 as an intermediate layer 21, and the p-type semiconductor layer 23 was formed on the intermediate layer 21.

[0085] Figure 6 schematically shows the growth sequence (p-type AlGaN layer growth steps) of the p-type AlGaN layer 35 of the surface-emitting laser 10. In Figure 6, the horizontal axis represents time T. The vertical axis in Figure 6 represents the substrate temperature Ts. In Figure 6, along with the change in substrate temperature Ts over time, the ON or OFF state, indicating whether or not the gas is being supplied, is shown for each type of supply gas. Furthermore, for the Al material gas (TMA) and the Mg material gas (biscyclopentadienylmagnesium (hereinafter, Cp2Mg)), the ON state is indicated as ON (High) when a large supply amount is being supplied and ON (Low) when a small supply amount is being supplied.

[0086] As shown in Figure 6, the p-type AlGaN layer 35 was grown in three steps. First, in the first growth step (STEP 1 in the figure), the substrate temperature was increased from TP1 (950°C, first temperature) to TP2 (1000°C, second temperature) over 30 seconds (time T=T1~T2), while nitrogen gas and ammonia gas were used as carrier gases. TMA, the material gas for Al, was supplied at 9.4 sccm (Standard Cubic Centimeter per Minute) (first supply amount, ON (high) in the figure), TMG, the material gas for Ga, was supplied at 1.6 sccm, and then Mg material gas (Cp2Mg) was supplied at 37.2 sccm (second supply amount, ON (high) in the figure) to grow the first p-type AlGaN layer (first layer 37 in Figure 3). The ammonia gas served as the nitrogen source gas for the p-type AlGaN layer 35. The design value for the thickness of the first p-type AlGaN layer is 0.8 nm. The design value for the Al composition of the first p-type AlGaN layer is 25%.

[0087] In the second growth step (STEP2 in the figure), the substrate temperature was maintained at TP2, and the supply of TMG, nitrogen gas, ammonia gas, TMA, and Cp2Mg was continued at the same supply levels as in the first growth step to grow the second p-type AlGaN layer (second layer 39 in Figure 3) (T=T2~T3). In the second growth step, the supply of TMA was maintained at the first supply level, and the supply of Cp2Mg was maintained at the second supply level. The design value for the thickness of the second p-type AlGaN layer is 2.2 nm. The design value for the Al composition of the second p-type AlGaN layer is 42%.

[0088] In the third growth step (STEP3 in the figure), the substrate temperature was maintained at TP2, and while maintaining the supply amounts of TMG, nitrogen gas, and ammonia gas, the third p-type AlGaN layer (third layer 41 in Figure 3) was grown by supplying TMA at a smaller amount than the first supply amount (4.9 sccm, third supply amount, ON(Low) in the figure) and Cp2Mg at a smaller amount than the second supply amount (2.5 sccm, fourth supply amount, ON(Low) in the figure) (T=T3~T4). The design value for the thickness of the third p-type AlGaN layer is 7 nm. The design value for the Al composition of the third p-type AlGaN layer is 28%.

[0089] As described above, a p-type AlGaN layer 35 with a design value of 10 nm was formed. The amount of Mg material gas supplied in the above p-type AlGaN layer growth steps does not correspond to the SIMS profile described above. Specifically, as described above, the amount of Mg material gas supplied in the third growth step is significantly lower than in the first and second growth steps, to less than one-tenth. In contrast, the SIMS analysis results shown in Figure 4 show that the Mg concentration indicated by the Mg concentration curve is highest in the third region.

[0090] This is thought to be due to the fact that the decomposition efficiency of CP2Mg increases with higher substrate temperatures, making it easier for Mg to be incorporated into the growth layer, in addition to the influence of the Mg memory effect. In the MOCVD method, it is known that a phenomenon called the memory effect occurs, in which Mg dopant solid-phase thermal diffusion and Mg raw materials remaining in the chamber are unintentionally mixed into the film. For example, if too much Cp2Mg is supplied in the third growth step, the influence of Mg components supplied and remaining in the first and second growth steps is added, resulting in an excessive Mg concentration in the p-type AlGaN layer 35, for example, 3 × 10⁻⁶. 19 atoms / cm 3 If it exceeds this limit, it will lead to a decrease in the lifespan of the element.

[0091] The growth sequence described above adjusts the supply amount to obtain the desired SIMS profile, taking into account these Mg characteristics. Specifically, by setting the supply amount of Cp2Mg in the third growth step (fourth supply amount) to less than one-tenth of the supply amount of Cp2Mg in the second growth step (second supply amount), the Mg concentration is reduced to 3 × 10⁻⁶ due to the memory effect. 19 atoms / cm 3 The goal is to ensure that the value does not exceed this limit. Furthermore, in this embodiment, nitrogen gas is used as the carrier gas instead of hydrogen gas, which is more readily incorporated into the layer with Mg.

[0092] In this embodiment, by employing the growth method described above, a p-type AlGaN layer 35 with a SIMS profile as shown in Figure 4 can be formed. This suppresses the increase in the threshold current density of the surface-emitting laser 10 and also suppresses the reduction in its lifetime.

[0093] After forming the p-type AlGaN layer 35, Mg was added as the p-type nitride semiconductor layer 43, with a total weight of 5 × 10⁻¹⁴. 18 atoms / cm 3 A doped p-type GaN layer was formed. Subsequently, 5 × 10⁻¹⁶ Mg was added as a p-type contact layer 45 on the p-type nitride semiconductor layer 43. 20 atoms / cm 3 The doped p-type GaN contact layer was formed as described above, completing the formation of the p-type semiconductor layer 23.

[0094] [Element manufacturing process] After forming the p-type semiconductor layer, Mg was activated by heat treatment using a Rapid Thermal Annealing (RTA) apparatus. Subsequently, a mesa pattern was formed using photoresist, and a mesa structure was formed by dry etching, while an exposed area 17E (see Figure 1) was formed around this mesa structure in which the n-type semiconductor layer 17 was partially exposed. After that, the photoresist was removed.

[0095] A 150 nm thick layer of silicon oxide (SiO2) was formed as an insulating layer 27 on the mesa structure and exposed area 17E by sputtering. A pattern was formed with photoresist, and etching was performed with buffered hydrofluoric acid (BHF) to form an aperture OP as a light emission aperture in the insulating layer 27 on the mesa structure. Subsequently, the photoresist was removed.

[0096] Approximately 17 nm of indium tin oxide (ITO) was formed as a translucent electrode 29 by sputtering. A pattern was formed with photoresist, and the ITO was etched with mixed acid to form the translucent electrode 29 on the insulating layer 27 on the mesa structure and on the p-type contact layer 45 exposed by the opening OP of the insulating layer 27. Subsequently, the photoresist was removed, and heat treatment was performed with RTA to improve the transparency and conductivity of the ITO.

[0097] A p-side metal layer (p-electrode 33) that does not cover the aperture was formed on the translucent electrode 29 by electron beam (EB) deposition, with a thickness of approximately 300 nm. A laminate of platinum (Pt), gold (Au), and titanium (Ti) was used for the p-side metal layer. Next, after lift-off with chemicals, the photoresist was removed.

[0098] After forming a pattern with photoresist, an n-electrode 25, electrically connected to the exposed portion 17E of the n-type semiconductor layer 17, was formed by EB deposition, with a wavelength of approximately 700 nm. A laminate of Ti, Al, Pt, and Au was used for the n-electrode. The photoresist was removed by lift-off using chemicals.

[0099] By EB deposition, 10.5 pairs (approximately 1300 nm) of dielectric multilayer films (dielectric multilayer mirrors, dielectric DBRs) were formed on the translucent electrode 29 as a second multilayer reflecting mirror 31. The dielectric DBRs consist of niobium oxide (hereinafter referred to as Nb2O) 5、 A laminate of approximately 45 nm thick film and SiO2 (approximately 76 nm thick film) was used. Next, a dielectric DBR pattern was formed using photoresist, and unwanted portions of the dielectric DBR (on the p electrode and n electrode) were etched off using a dry etching apparatus. Finally, the photoresist was removed using chemicals.

[0100] A pattern was formed using photoresist, and an additional p-side metal layer (not shown) electrically connected to the p-electrode was formed at approximately 2200 nm using EB deposition. A laminate of Ti, Pt, and Au was used for the p-electrode (p-pad layer). Next, the photoresist was removed by lift-off using chemicals. In this way, the device was fabricated (step S15).

[0101] The surface-emitting laser 10 was manufactured through the above process.

[0102] Referring to Figure 7, the p-type AlGaN layer of the surface-emitting laser of Comparative Example 1 will be described. The surface-emitting laser of Comparative Example 1 differs from Example 1 in that, instead of the p-type AlGaN layer 35, it has a p-type AlGaN layer grown with a design thickness of 10 nm and a design Al composition of 30%, by keeping the supply amount of Al material gas (TMA) constant at 4.9 sccm and the supply amount of Mg material gas (Cp2Mg) constant at 37.2 sccm. In other respects, it is configured the same as Example 1. In other words, the p-type AlGaN layer of Comparative Example 1 was grown in one step, which is different from the growth method of Example 1, which involves three steps.

[0103] Figure 7 shows the SIMS analysis results of the p-type AlGaN layer of the surface-emitting laser in Comparative Example 1. Similar to the graph in Figure 4, in Figure 7, the Al composition curve showing the change in Al composition in the depth direction is shown as a dashed line, and the Mg concentration curve showing the change in Mg concentration in the depth direction is shown as a solid line. Also, similar to the case of Example 1 shown in Figure 4, the width at 50% of the maximum peak of the Al composition is defined as the p-type AlGaN layer, and the p-type AlGaN layer 35 is divided sequentially from the active layer side toward the surface side into a first region AR1 with a layer thickness of 10%, a second region AR2 with a layer thickness of 40%, and a third region AR3 with a layer thickness of 50%.

[0104] As shown in Figure 7, the Mg concentration curve has a peak in the second region AR2, and in most of the second region AR2 and the third region AR3, the peak is 3 × 10⁻⁶. 19 atoms / cm 3 It exceeds 3 × 10⁻⁶. Thus, in the second region, the Mg concentration is 3 × 10⁻⁶. 19 atoms / cm 3 When the concentration exceeds a certain level, the carrier injection efficiency increases, but the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer also become more likely, which reduces the device lifespan.

[0105] Referring to Figure 8, the p-type AlGaN layer of the surface-emitting laser of Comparative Example 2 will be described. The surface-emitting laser of Comparative Example 2 differs from Example 1 and Comparative Example 1 in that it has a p-type AlGaN layer grown in a different way than the p-type AlGaN layer 35 of Example 1 and the p-type AlGaN layer of Comparative Example 1, but is otherwise configured in the same way as Example 1.

[0106] In Comparative Example 2, the p-type AlGaN layer had a Mg concentration of 3 × 10⁻¹⁶ throughout the entire thickness of the layer. 19 atoms / cm 3 These were grown to be less than 0.9 × 10⁶. In Comparative Example 2, the maximum concentration of Mg was 0.9 × 10⁶ each. 19 atoms / cm 3 , 2.0×10 19 atoms / cm 3 , 2.6×10 19 atoms / cm3 Three samples were prepared.

[0107] Maximum Mg concentration 0.9×10 19 atoms / cm 3 The sample (hereinafter also referred to as Sample 1) was grown with a constant supply of Al material gas (TMA) at 6.0 sccm and a constant supply of Mg material gas (Cp2Mg) at 37.2 sccm, with a design thickness of 10 nm and an Al composition of 30%.

[0108] Mg maximum concentration 2.0×10 19 atoms / cm 3 The first sample (hereinafter also referred to as Sample 2) was grown with a constant supply of Al material gas (TMA) at 6.0 sccm, and a supply of Mg material gas (Cp2Mg) at 37.2 sccm until 5 nm of growth, and then at 2.5 sccm for the remaining 5 nm growth. The layer was grown to a design thickness of 10 nm and an Al composition of 30% of the design value.

[0109] Mg maximum concentration 2.6×10 19 atoms / cm 3 The sample (hereinafter also referred to as Sample 3) was grown with a constant supply of Al material gas (TMA) at 4.9 sccm, and a supply of Mg material gas (Cp2Mg) at 37.2 sccm until 5 nm of growth, and then at 2.5 sccm for the remaining 5 nm growth. The layer was grown to a design thickness of 10 nm and an Al composition of 30% of the design value.

[0110] Figure 8 shows the SIMS analysis results of the p-type AlGaN layer of the surface-emitting laser in Comparative Example 2. In Figure 8, the Al composition curve showing the change in Al composition in the depth direction is shown as a dashed line, and the Mg concentration curve showing the change in Mg concentration in the depth direction is shown as a solid line. Furthermore, the Al composition curve and the Mg concentration curve are shown as 2.0 × 10⁻⁶. 19 atoms / cm 3 Regarding sample (sample 2), the lines are thicker than in sample 1, and the dimensions are 2.6 × 10 19 atoms / cm 3 The sample (Sample 3) is shown with a thicker line than Sample 2.

[0111] In Figure 8, the Mg concentration curve for sample 3 shows that the maximum Mg concentration is 3 × 10⁻⁶. 19 atoms / cm 3 The Mg concentration is less than 1, and the Mg concentration in the first region AR1 is low, with a peak in the third region AR3, which is furthest from the active layer. Thus, the low Mg peak concentration and the presence of the peak in a region far from the active layer are desirable because they make it less likely for Mg to diffuse into the active layer or for Mg-induced defects to affect the active layer.

[0112] On the other hand, the Mg concentration curve of sample 3 shows a monotonically decreasing curve toward the active layer in the second region AR2. In such cases, 3 × 10⁻¹⁰ is one of the indicators for obtaining a sufficient hole carrier concentration in almost the entire second region AR2. 18 atoms / cm 3 Despite exceeding a certain threshold, it was found that the hole carrier concentration was insufficient, the electron carrier overflow could not be suppressed, the carrier injection efficiency decreased, and the threshold current density increased.

[0113] For sample 2, 3 × 10 19 atoms / cm 3 It was less than 1 × 10⁻⁶, and for Sample 1, the maximum Mg concentration was even lower at 1 × 10⁻⁶. 19 atoms / cm 3 Since it is less than this, it is preferable because it is less likely for Mg to diffuse into the active layer or for Mg-induced defects to affect the active layer.

[0114] However, in Sample 2 and Sample 1, the Mg concentration in the second region AR2 is even lower than in Sample 3, resulting in insufficient hole carrier concentration and reduced carrier injection efficiency.

[0115] As explained with reference to Figures 7 and 8, in Comparative Example 1, the peak concentration of Mg was 3 × 10⁻⁶ 19 atoms / cm 3 In Comparative Example 2, the peak concentration of Mg was 3 × 10⁻⁶. 19 atoms / cm 3Although samples were prepared at levels below a certain threshold, in all cases, the Mg concentration profile could not be adequately controlled.

[0116] Specifically, in Comparative Example 1, the peak concentration of Mg was set to 3 × 10⁻⁶. 19 atoms / cm 3 As a result, a peak with a high Mg concentration appears in the region close to the active layer 19, indicating increased diffusion of Mg into the active layer and greater influence on the active layer due to Mg-induced defects. This leads to a decrease in the device's lifespan.

[0117] Furthermore, in Comparative Example 2, the peak concentration of Mg was set to 3 × 10⁻⁶. 19 atoms / cm 3 Under the following conditions, the peak of the Mg concentration curve appears in the third region, AR3. The Mg concentration in the second region decreases monotonically towards the active layer, leading to a decrease in hole carriers, which reduces carrier injection efficiency and increases the threshold current density. This increase in threshold current density also reduces the device lifetime.

[0118] In contrast, in Example 1, the Mg concentration shown by the Mg concentration curve is 1 × 10⁻⁶ across the entire thickness of the p-type AlGaN layer 35. 19 atoms / cm 3 It is less than 3 × 10⁻¹⁰, and the Mg concentration curve in the second region AR2 is 3 × 10⁻¹⁰. 19 atoms / cm 3 It has a peak exceeding [a certain value]. A p-type AlGaN layer 35 exhibiting such an Mg profile can provide a sufficient hole carrier concentration in the p-type AlGaN layer while suppressing the reduction in device lifetime caused by excess Mg. A p-type AlGaN layer 35 exhibiting such an Mg profile can be realized by growing it using a method that includes three steps as shown in Figure 6.

[0119] In this embodiment, the thickness of the first p-type AlGaN layer is preferably 0.4 nm or more and 1 nm or less. If it is less than 0.4 nm, the effect of preventing the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer is poor, and if it exceeds 1 nm, it may lead to an increase in the device voltage.

[0120] In this embodiment, it is preferable that the design value for the Al composition of the first p-type AlGaN layer be 25% or less. This is because if the Al composition exceeds 25%, the device voltage may increase.

[0121] Furthermore, in this embodiment, the design value of the Al composition of the second p-type AlGaN layer is preferably 33% or more and 50% or less. If the Al composition is less than 33%, electron carrier overflow is more likely to occur, and the threshold current density tends to increase. If the Al composition exceeds 50%, the effects of decreased crystallinity of the p-type AlGaN layer, crack formation, and increased operating voltage become more pronounced.

[0122] Furthermore, in this embodiment, the thickness of the second p-type AlGaN layer is preferably 2 nm or more and 6 nm or less. If it is less than 2 nm, the Mg concentration in the second region should be 3 × 10⁻⁶ 18 atoms / cm 3 It is difficult to maintain this level, and the device voltage may increase significantly beyond 6nm.

[0123] Furthermore, in this embodiment, it is preferable that the design value of the Al composition of the third p-type AlGaN layer be 20% or more and 30% or less. By setting the Al composition of the third p-type AlGaN layer within this range, it is possible to suppress electron carrier overflow together with the second p-type AlGaN layer, while also suppressing crack occurrence and an increase in operating voltage.

[0124] Furthermore, in this embodiment, it is preferable that the thickness of the third p-type AlGaN layer is greater than the thickness of the second p-type AlGaN layer. By making the thickness of the third p-type AlGaN layer greater than that of the second p-type AlGaN layer, the average Al composition of the entire p-type AlGaN layer 35 can be reduced, thereby suppressing the occurrence of cracks. [Examples]

[0125] While referring to FIG. 9, the configuration of the surface-emitting laser 50 according to Example 2 will be described. The surface-emitting laser 50 is configured in the same manner as the surface-emitting laser 10 of Example 1 described with reference to FIGS. 1 to 3, except that only the configuration of the p-type AlGaN layer 35 is different from that of the surface-emitting laser 10. Specifically, the p-type AlGaN layer 35 of Example 2 has a different profile of the Al composition and Mg concentration in the layer thickness direction obtained by SIMS analysis from that in the case of Example 1.

[0126] FIG. 9 is a diagram showing the results of performing the same SIMS analysis as in Example 1 on the p-type AlGaN layer 35 of the surface-emitting laser 50. In FIG. 9, similar to Example 1, the range of the full width at half maximum of the Al composition (%) is defined as the p-type AlGaN layer 35, and the p-type AlGaN layer 35 is sequentially divided into the first region AR1 to the third region AR3 in the layer thickness direction. Also, in FIG. 9, the Al composition curve is shown by a broken line, and the Mg concentration curve is shown by a solid line.

[0127] As shown in FIG. 9, it is common to Example 1 in that the Mg concentration indicated by the Mg concentration curve is less than 1×10 19 atoms / cm 3 over the entire layer thickness of the p-type AlGaN layer 35. Also, when comparing the average values within each region of the Mg concentration indicated by the Mg concentration curve between the regions, the third region AR3 is the largest, the second region AR2 is the second largest, and the first region AR1 is the smallest (first region AR1 < second region AR2 < third region AR3), which is also common to Example 1. By controlling the Mg concentration over the entire layer thickness of the p-type AlGaN layer 35 and the Mg concentration in each region in this way, the reduction in device lifetime due to the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer is prevented.

[0128] In the Mg concentration curve shown in FIG. 9, the average value of the Mg concentration in the second region is 3×10 19 atoms / cm 3That concludes the explanation. Furthermore, as shown in Figure 9, the Mg concentration curve has a peak in the third region, and has a flatter (approximately flat) portion centered near the boundary between the second region AR2 and the third region AR3, extending into a part of the second region AR2 and a part of the third region AR3.

[0129] More specifically, in Figure 9, when the Mg concentration curve in the second region is divided into a portion on the first region side and a portion on the third region side, with the center of the second region's thickness direction as the dividing line, the slope of the portion on the third region side is gentler than the slope of the portion on the first region side.

[0130] In the example graph shown in Figure 9, the absolute value of the slope of the approximation formula for the portion on the first region side (hereafter, the slope will be expressed as an absolute value) is approximately 2 × 10⁻⁶. 18 Therefore, the slope of the approximation formula for the third region is approximately 2 × 10⁻⁶. 17 Yes, that is. In other words, the Mg concentration curve in the second region has a smaller average slope in the portion closer to the third region than in the portion closer to the first region than in the center of the second region's thickness direction.

[0131] It was found that even when the Mg concentration was controlled to the profile described above, it was possible to prevent the Mg concentration in the second region from becoming too low and to ensure sufficient carrier injection efficiency. In the surface-emitting laser 50 of Example 2, the average value of the Mg concentration in the second region was 3 × 10⁻⁶. 18 atoms / cm 3 In summary, by controlling the Mg concentration in the second region such that the average slope in the portion closer to the third region is smaller than the average slope in the portion closer to the first region than the center of the second region in the thickness direction, sufficient carrier injection efficiency can be ensured, thereby suppressing an increase in threshold current density.

[0132] In addition, in this actual example, when comparing the average values within each region of the Al composition indicated by the Al composition curve among the regions, the second region AR2 is the largest, the third region AR3 is the second largest, and the first region AR1 is the smallest (the first region AR1 < the third region AR3 < the second region AR2), which is common to Example 1.

[0133] [Manufacturing Method of Example 2] The p-type AlGaN layer 35 of Example 2 was grown in three steps, similar to the sequence shown in FIG. 6. In Example 2, for Steps 1 and 2, the supply amount of TMA, which is the source gas for Al, the designed layer thickness, and the designed Al composition value are different from those in Example 1. For other conditions, the p-type AlGaN layer 35 was grown in the same manner as in Example 2.

[0134] Specifically, it is different from Example 1 in that the first supply amount of TMA was set to 6.2 sccm, the designed layer thickness of the first p-type AlGaN layer was 0.6 nm, the designed Al composition value was 23%, the designed layer thickness of the second p-type AlGaN layer was 2.4 nm, and the designed Al composition value was 33%, which is lower than that in Example 1. The supply amounts of nitrogen gas and ammonia gas, which are the ambient gases, and the supply amount of TMG, which is the source gas for gallium, are the same as those in Example 1.

[0135] Thus, by adjusting the composition ratio of Al by the supply amount of TMA, the way Mg is incorporated into the film can also be adjusted. As a result, when performing SIMS analysis on the grown p-type AlGaN layer 35, a profile as shown in FIG. 9 is obtained. Specifically, the average value of the Mg concentration in the second region is 3×10 18 atoms / cm 3 or more, and a Mg concentration curve is obtained in which the average value of the slope in the portion on the third region side is smaller than the average value of the slope in the portion on the first region side from the center in the layer thickness direction of the second region.

[0136] Therefore, according to the method for manufacturing a surface-emitting laser 50, including the method for growing the p-type AlGaN layer 35 of Example 2, it is possible to form a p-type AlGaN layer in which an appropriate amount of Mg is contained in an appropriate region in the thickness direction of the p-type AlGaN layer, thereby ensuring a sufficient hole carrier concentration while suppressing a decrease in device lifetime caused by excess Mg.

[0137] Therefore, the surface-emitting laser 50 of this embodiment can suppress the decrease in the lifespan of the element while ensuring high carrier injection efficiency, and can provide a long-life, highly efficient vertical-cavity type light-emitting element.

[0138] [Differentiation] Referring to Figures 10-14, the configuration of the surface-emitting laser 60 according to a modified example of Example 2 will be described. The surface-emitting laser 60 is configured similarly to the surface-emitting laser 50 of Example 2, with only a part of the method for growing the p-type AlGaN layer 35 being different.

[0139] Figure 10 shows the Al composition curve (Al-A) and Mg concentration curve (Mg-A) obtained by SIMS analysis of sample A of the p-type AlGaN layer 35 of the surface-emitting laser 60. Similar to Example 2, the range of the full width at half maximum of the Al composition curve (Al-A) is defined as the p-type AlGaN layer 35, and the p-type AlGaN layer 35 is divided into first region AR1 to third region AR3 in the thickness direction. In Figure 10, the Al composition curve of Example 2 is shown as Al-EX2 and the Mg concentration curve as Mg-EX2.

[0140] As shown in Figure 10, the Mg concentration curve of the p-type AlGaN layer 35 of the surface-emitting laser 60 has similar characteristics to the Mg concentration curve of Example 2. Specifically, the modified Mg concentration curve Mg-A, like Mg-EX2 of Example 2, shows that in the second region, the average slope in the portion on the third region side is smaller than the average slope in the portion on the first region side of the center in the thickness direction of the second region.

[0141] However, as shown in Figure 10, the Mg concentration curve of the p-type AlGaN layer 35 of the surface-emitting laser 60 is shifted to a higher concentration side compared to the Mg concentration curve of Example 2. This shift to a higher concentration side is particularly pronounced in the region from the second region to the third region, especially in the region including the substantially flat portion that forms the shoulder of the peak of the third region, centered on the boundary between the second and third regions. An increase in the Mg concentration in this flat portion is desirable because it increases the hole carrier concentration and improves carrier injection efficiency.

[0142] The shift in the Mg concentration profile towards higher concentrations, as described above, is due to the addition of a step to supply Mg material gas before the start of growth of the p-type AlGaN layer 35. The method for manufacturing the p-type AlGaN layer 35 of the surface-emitting laser 60 will be described below.

[0143] Figure 11 shows the growth sequence for sample A of the p-type AlGaN layer 35 of the surface-emitting laser 60. The figure schematically shows the p-type AlGaN layer growth steps. As shown in Figure 11, in this modified example, the p-type AlGaN layer was grown in three steps after performing a heating step as a pretreatment step.

[0144] In the heating step, the substrate temperature was increased from TP1 (950°C, first temperature) to TP2 (1000°C, second temperature) over 30 seconds (time T=T1~T2), while nitrogen gas and ammonia gas were used as carrier gases, and Mg material gas (Cp2Mg) was supplied at a rate of 37.2 sccm (first supply amount, ON (high) in the figure). Al material gas (TMA) and Ga material gas (TMG) were not supplied during the heating step. Therefore, the p-type AlGaN layer did not grow during the heating step.

[0145] After the heating step, in the first growth step (STEP 1 in the figure), the substrate temperature was maintained at TP2 (1000°C, the second substrate temperature), and the carrier gases continued to be nitrogen gas and ammonia gas as the nitrogen source gas. In the first growth step, 6.2 sccm of TMA, the material gas for Al, was supplied (second supply amount, ON (high) in the figure), and 1.6 sccm of TMG, the material gas for Ga, was supplied (ON) in the figure. Furthermore, 37.2 sccm of Mg material gas (Cp2Mg) was supplied (third supply amount, ON (high) in the figure). Under these conditions, the first p-type AlGaN layer (first layer 37 in Figure 3) was grown (T2-T3). The design value for the thickness of the first p-type AlGaN layer is 0.6 nm. The design value for the Al composition of the first p-type AlGaN layer is 25%.

[0146] Following the first growth step, the second growth step (STEP2 in the figure) and the third growth step (STEP3 in the figure) proceeded in the same manner as the second and third growth steps in Example 2.

[0147] In the second growth step, the substrate temperature was maintained at TP2, and TMG, nitrogen gas, ammonia gas, TMA, and Cp2Mg were supplied at the same rates as in the first growth step to grow the second p-type AlGaN layer (second layer 39 in Figure 3) (T=T3~T4). In the second growth step, TMA was supplied at the second supply rate and Cp2Mg at the third supply rate. The design value for the thickness of the second p-type AlGaN layer is 2.4 nm. The design value for the Al composition of the second p-type AlGaN layer is 33%.

[0148] Following the second growth step, in the third growth step, the substrate temperature was maintained at TP2, and while maintaining the supply rates of TMG, nitrogen gas, and ammonia gas, the third p-type AlGaN layer (third layer 41 in Figure 3) was grown by supplying TMA at a lower rate than the second supply rate of 4.9 sccm (fourth supply rate, ON (Low) in the figure) and Cp2Mg at a lower rate than the third supply rate of 2.5 sccm (fifth supply rate, ON (Low) in the figure) (T=T4~T5). The design value for the thickness of the third p-type AlGaN layer is 7 nm. The design value for the Al composition of the third p-type AlGaN layer is 28%.

[0149] As described above, a modified p-type AlGaN layer 35 was formed with a design value of 10 nm.

[0150] In the above explanation, we described an example where the processing time (T1~T2) (i.e., heating time) in the heating step was 30 seconds, and the supply amount of Mg material gas (first supply amount) was 37.2 sccm. In this modified example, it was found that the Mg concentration in the second region can be adjusted by further adjusting the heating time and the supply amount of Mg material gas.

[0151] Figure 12 shows the Al composition curve and Mg concentration curve for sample B of the p-type AlGaN layer 35 grown under the conditions described in Figure 11, with a Mg material gas supply rate (first supply rate) of 75 sccm and a heating time of 15 seconds during the heating step, along with the results from Example 2.

[0152] In the region including the nearly flat area that forms the shoulder of the peak in the third region, centered on the boundary between the second and third regions, the Mg concentration curve is shifted towards higher concentrations compared to Example 2. The increase in Mg concentration for Sample B compared to Example 2 is about the same as the increase for Sample A shown in Figure 10.

[0153] Figure 13 shows the Al composition curve and Mg concentration curve for sample C of a p-type AlGaN layer 35 grown using the method described in Figure 11, with a Mg material gas supply rate (first supply rate) of 37.5 sccm and a heating time of 15 seconds, for all other conditions. The increase in Mg concentration is smaller than that of sample A shown in Figure 10, but sample C shows a concentration of 1 × 10⁻¹⁶ across the entire thickness of the p-type AlGaN layer 35. 19 atoms / cm 3 It is less than 1 × 10⁻⁶. According to the conditions for sample C, the entire thickness of the layer is 1 × 10⁻⁶. 19 atoms / cm 3 It can be said that the Mg concentration in the second region can be shifted towards higher concentrations within the range of less than [value missing].

[0154] From the above, it was found that the Mg concentration in the flat portion of the Mg concentration profile in the second region, that is, the portion of the second region closer to the third region than to the center in the thickness direction, increases in accordance with the heating time in the heating step, i.e., the supply time and amount of Mg material gas supplied. Furthermore, it was found that the magnitude of the increase in Mg concentration in this flat portion is roughly correlated with the product of the supply time and amount of Mg material gas supplied.

[0155] As described above, when growing a p-type AlGaN layer, the Mg memory effect is likely to occur, and Cp2Mg is more easily decomposed into Mg at higher substrate temperatures. In this modified example, considering the effects of the memory effect and substrate temperature, the Mg concentration profile can be reliably controlled by supplying the Mg material gas in advance during the heating step.

[0156] As explained above, according to the p-type AlGaN layer growth step of this modified example, the Mg concentration in the p-type AlGaN layer is 3 × 10⁻⁶ 19 atoms / cm 3 Less than 1 × 10 19 atoms / cm 3 It is less than , and the average value of the Mg concentration in the second region is 3 × 10⁻⁶. 18 atoms / cm 3Thus, the Mg concentration curve in the second region can be reliably controlled such that the average slope in the portion closer to the third region is smaller than the average slope in the portion closer to the first region than the center of the second region in the thickness direction. [Examples]

[0157] The surface-emitting laser 70 according to Example 3 will be described with reference to Figures 14-17. Figure 14 is a cross-sectional view showing the configuration of the surface-emitting laser 70. The surface-emitting laser 70 is basically configured in the same way as the surface-emitting laser 10 of Example 1 and the surface-emitting laser 50 of Example 2.

[0158] The surface-emitting laser 70 differs from the surface-emitting lasers 10 and 50 in that it has a p-type AlGaN layer 71 with a five-layer structure instead of the p-type AlGaN layer 35 with a three-layer structure.

[0159] The p-type AlGaN layer 71, like the p-type AlGaN layer 35, is formed on the intermediate layer 21 and is an AlGaN layer doped with Mg as a p-type impurity, functioning as an electron blocking layer.

[0160] The p-type AlGaN layer 71 is composed of five p-type AlGaN layers, each with a different distribution of Mg concentration and Al composition. In Figure 14, the five layers constituting the p-type AlGaN layer 71 are shown as the first layer 72, the second layer 73, the third layer 74, the fourth layer 75, and the fifth layer 76.

[0161] Figure 15 shows the results of SIMS analysis performed on the p-type AlGaN layer 71 of the surface-emitting laser 70, similar to that in Example 2. In Figure 15, as in Example 2, the range of the full width at half maximum of the Al composition (%) is defined as the p-type AlGaN layer 71, and the p-type AlGaN layer 71 is divided into three regions in the thickness direction: the first region AR1 to the third region AR3. In Figure 15, the Al composition curve is shown as a dashed line, and the Mg concentration curve is shown as a solid line.

[0162] As shown in Figure 15, the Al composition curve and Mg concentration curve of the p-type AlGaN layer 71 have the same characteristics as in Example 2.

[0163] Specifically, the Mg concentration shown by the Mg concentration curve of the p-type AlGaN layer 71 is 1 × 10⁻⁶ across the entire thickness of the p-type AlGaN layer 71. 19 atoms / cm 3 The fact that the values ​​are less than the threshold is consistent with the analysis results of Example 2 shown in Figure 9. Furthermore, when comparing the average values ​​of Mg concentrations within each region shown by the Mg concentration curve, the third region AR3 is the largest, followed by the second region AR2, and then the first region AR1 is the smallest (first region AR1 < second region AR2 < third region AR3), which is also consistent with the analysis results of Example 2.

[0164] Furthermore, the average value of Mg concentration in the second region of the p-type AlGaN layer 71 is 3 × 10⁻⁶. 18 atoms / cm 3 In this respect, it is also common with the analysis results of Example 2.

[0165] Furthermore, compared to Example 2, in the Mg concentration curve of the p-type AlGaN layer 71, when the region closer to the first region is considered the lower layer and the region closer to the third region is considered the upper layer, the slope is smaller in the upper layer region, relative to the center of the layer thickness direction of the second region. In other words, the shoulder portion of the peak in the third region is flatter. Also, in the upper layer region, the Mg concentration is 5 × 10⁻⁶. 18 atoms / cm 3 That's all.

[0166] As described above, when a flat region appears in the Mg concentration curve of the p-type AlGaN layer, extending from the center of the second region in the thickness direction to the region close to the third region, a sufficient hole carrier concentration is obtained, the carrier injection efficiency increases, and the threshold current density is kept low. Therefore, in this embodiment as well, a high hole carrier concentration is obtained in the p-type AlGaN layer 71. Thus, the surface-emitting laser 70 can be said to have high carrier injection efficiency, low threshold current density, and long device lifetime.

[0167] Figure 16 schematically shows the growth sequence (p-type AlGaN layer growth steps) of the p-type AlGaN layer 71 of the surface-emitting laser 70.

[0168] As shown in Figure 16, the p-type AlGaN layer 71 was grown in five steps. The growth sequence shown in Figure 16 proceeds similarly to the growth sequence of Example 1 shown in Figure 6 up to step 3, but in this example, the design film thickness in step 3 is smaller than in Example 1. In this example, after step 3, steps 4 and 5 are different from Example 1 in that the steps corresponding to steps 2 and 3 of Example 1 are repeated with a smaller design layer thickness. Table 1 shows an example of the growth conditions, including the supply amount of each material gas and the design layer thickness, when growing the p-type AlGaN layer 71.

[0169] [Table 1]

[0170] As shown in Figure 16 and Table 1, in steps 1 to 5, the carrier gas was nitrogen gas and ammonia (NH3) gas as the nitrogen source gas, and TMG, the material gas for Ga, was supplied at a constant rate of 1.6 sccm.

[0171] The first growth step (STEP 1 in the figure) proceeded in the same manner as in Example 1. In the first growth step, the substrate temperature was increased from TP1 (950°C, first temperature) to TP2 (1000°C, second temperature) over 30 seconds (time T=T1~T2), while supplying 9.4 sccm of TMA, the Al material gas (first supply amount, ON(high) in the figure), and 37.2 sccm of Mg material gas (Cp2Mg) (second supply amount, ON(high) in the figure), to grow the first p-type AlGaN layer (first layer 72 in Figure 14) with a design layer thickness of 0.8 nm and an Al composition of the design value of 25%.

[0172] In the second growth step (STEP2 in the figure), the substrate temperature was maintained at TP2 (1000°C), and the supply amounts of TMA and Cp2Mg were not changed. A second p-type AlGaN layer (second layer 73 in Figure 14) was grown with a design layer thickness of 2.2 nm and an Al composition of the design value of 42% (T2-T3).

[0173] In the third growth step (STEP3 in the figure), the supply amount of TMA was set to 4.9 sccm (third supply amount, ON(Low) in the figure), and the supply amount of Cp2Mg was set to 2.5 sccm (fourth supply amount, ON(Low) in the figure), which is less than one-tenth of the second supply amount. The third p-type AlGaN layer (third layer 74 in Figure 14) was grown with a design layer thickness of 2.0 nm and an Al composition of the design value of 28% (T3~T4).

[0174] In the fourth growth step (STEP4 in the figure), the supply of TMA was again set to 9.4 sccm (first supply amount, ON(high) in the figure), and the supply of Cp2Mg was maintained at 2.5 sccm (fourth supply amount, ON(Low) in the figure), and the fourth p-type AlGaN layer (fourth layer 75 in Figure 14) was grown with a design layer thickness of 3.0 nm and an Al composition of the design value of 42% (T4~T5).

[0175] In the fifth growth step (STEP 5 in the figure), the supply of TMA was reduced to 4.9 sccm (third supply, ON (Low) in the figure), and the supply of Cp2Mg was maintained at 2.5 sccm (fourth supply, ON (Low) in the figure), and the fifth p-type AlGaN layer (fifth layer 76 in Figure 14) was grown with a design layer thickness of 2.0 nm and an Al composition of the design value of 28% (T5~T6).

[0176] As described above, a p-type AlGaN layer 71 with a design value of 10 nm was formed. From step 3 onward, more Mg than expected is incorporated into the layer due to the memory effect of Mg. As described above, from step 3 onward, the supply amount of CP2Mg is reduced to less than one-tenth of the first supply amount up to step 2, thereby reducing the Mg concentration throughout the entire p-type AlGaN layer to 3 × 10⁻¹⁶. 19 atoms / cm 3 It can be less than.

[0177] In Example 3, the thickness of the first p-type AlGaN layer is preferably 0.4 nm or more and 1 nm or less. If it is less than 0.4 nm, the effect of preventing the diffusion of Mg into the active layer and the spread of defects caused by Mg into the active layer is poor, and if it exceeds 1 nm, it may lead to an increase in the device voltage.

[0178] Furthermore, in this embodiment, it is preferable that the design value of the Al composition of the first p-type AlGaN layer be 25% or less. This is because if the Al composition exceeds 25%, the device voltage may increase.

[0179] Furthermore, in this embodiment, the design value of the Al composition of the second p-type AlGaN layer and the fourth p-type AlGaN layer is preferably 33% or more and 50% or less. If the Al composition is less than 33%, electron carrier overflow is more likely to occur, and the threshold current density tends to increase. If the Al composition exceeds 50%, the effects of decreased crystallinity of the p-type AlGaN layer, crack formation, and increased operating voltage become more pronounced.

[0180] Furthermore, in this embodiment, the thickness of the second p-type AlGaN layer is preferably 2 nm or more and 3 nm or less. If it is less than 2 nm, the Mg concentration in the second region should be 3 × 10⁻⁶ 18 atoms / cm 3 It is difficult to keep the thickness above this level, as exceeding 3 nm raises concerns about an increase in the device voltage due to its interaction with the fourth p-type AlGaN layer. Similarly, it is preferable that the thickness of the fourth p-type AlGaN layer be between 2 nm and 3 nm.

[0181] Furthermore, in this embodiment, it is preferable that the design value of the Al composition of the third p-type AlGaN layer and the fifth p-type AlGaN layer be 20% or more and 30% or less. By setting the Al composition of the third p-type AlGaN layer and the fifth p-type AlGaN layer within this range, it is possible to suppress the occurrence of cracks and the rise in operating voltage while suppressing electron carrier overflow in combination with the second p-type AlGaN layer and the fourth p-type AlGaN layer.

[0182] As explained above, according to the p-type AlGaN layer growth step of this embodiment, by growing the p-type AlGaN layer in the five steps described above, the Mg concentration in the p-type AlGaN layer is 3 × 10⁻⁶. 19 atoms / cm 3 Less than 1 × 10 19 atoms / cm 3 It is less than , and the average value of the Mg concentration in the second region is 3 × 10⁻⁶. 18 atoms / cm 3 In summary, the Mg concentration curve in the second region is such that the average slope in the portion closer to the third region is greater than the average slope in the portion closer to the first region than the average slope in the portion closer to the center of the second region in the thickness direction. small It can be reliably controlled to prevent it from cracking.

[0183] In the above examples, an example was described in which the thickness of the p-type AlGaN layer was 10 nm, but this is not the only example. The thickness of the p-type AlGaN layer is preferably 8 nm or more and 15 nm or less. If the layer thickness is less than 8 nm, electron carrier overflow is more likely to occur, and the threshold current density tends to increase. If the layer thickness exceeds 15 nm, it may lead to crack formation and an increase in operating voltage.

[0184] In the above examples, it is preferable that the difference between the Al composition in the second region and the Al composition in the third region, as shown by the Al composition curve, is between 3% and 18%. For example, it is preferable that the difference between the maximum value of the Al composition in the second region and the maximum value of the Al composition in the third region (hereinafter simply referred to as the difference in Al composition) is 3% or more, as in Examples 2 and 3, where a flat portion appears in the second region of the Mg concentration curve, and that when the difference in Al composition exceeds 8%, a peak appears in the second region of the Mg concentration curve, as in Example 1. However, it is undesirable when the difference in Al composition exceeds 18%, as this is where a decrease in the crystallinity of the p-type AlGaN layer begins to occur.

[0185] In the above embodiment, a nitride semiconductor multilayer film is used as the lower reflector. Since nitride semiconductor multilayer films containing AlInN have low thermal conductivity, and given the increased resonator length, surface-emitting lasers using a nitride semiconductor multilayer film as a reflector tend to have particularly high threshold current densities, which in turn makes them prone to carrier overflow. Therefore, applying the present invention to a vertical-cavity type light-emitting element using a nitride semiconductor containing AlInN as a reflector is effective.

[0186] The configurations in the above-described examples and manufacturing methods are merely illustrative and can be modified as appropriate depending on the application. [Explanation of symbols]

[0187] 10, 50, 60, 70-face emitting lasers 11 circuit boards 15. First multilayer reflecting mirror 17 n-type semiconductor layer 19 Active layer 21 Middle Class 23 p-type semiconductor layer 25n electrode 27 Insulating layer 29 Translucent electrode 31. Second multilayer reflecting mirror 33p electrode

Claims

1. circuit board and A first multilayer reflecting mirror is a semiconductor multilayer film in which two semiconductor layers with different refractive indices are alternately stacked multiple times on the substrate, An n-type nitride semiconductor layer is formed on the first multilayer reflecting mirror and consists of a nitride semiconductor containing an n-type dopant, An active layer formed on the n-type nitride semiconductor layer, A p-type AlGaN layer formed on the active layer, containing Mg as a p-type dopant, and having a structure in which three or more AlGaN layers with different Al compositions are stacked, A p-type nitride semiconductor layer is formed on the aforementioned p-type AlGaN layer and is a semiconductor layer made of a nitride semiconductor containing a p-type dopant, It includes a second multilayer reflecting mirror formed on the p-type nitride semiconductor layer and positioned opposite the first multilayer reflecting mirror, Analysis of the p-type AlGaN layer by secondary ion mass spectrometry (SIMS) revealed the following: an Al composition curve showing the change in the Al composition of the p-type AlGaN layer in the thickness direction and an Mg concentration curve showing the change in the Mg concentration of the p-type AlGaN layer in the thickness direction. The width range at 50% of the peak value of the Al composition curve is defined as the p-type AlGaN layer, and the p-type AlGaN layer is divided in the thickness direction into a first region having a thickness of 1 / 10 of the p-type AlGaN layer, a second region having a thickness of 2 / 5 of the p-type AlGaN layer, and a third region having a thickness of 1 / 2 of the p-type AlGaN layer, The relationship between the average values ​​of each region of Al composition shown by the Al composition curve is such that the first region < the third region < the second region. The Mg concentration shown by the aforementioned Mg concentration curve is 3 × 10⁻¹⁰ over the entire thickness of the p-type AlGaN layer. １９ atoms / cm ３ It is less than and the relative magnitudes of the average values ​​between each region of Mg concentration are such that the first region < the second region < the third region. The Mg concentration in at least a portion of the second region is 3 × 10 １８ atoms / cm ３ That's all. The vertical resonator type light-emitting element is characterized in that the Mg concentration curve has a peak in the second region.

2. circuit board and A first multilayer reflecting mirror is a semiconductor multilayer film in which two semiconductor layers with different refractive indices are alternately stacked multiple times on the substrate, An n-type nitride semiconductor layer is formed on the first multilayer reflecting mirror and consists of a nitride semiconductor containing an n-type dopant, An active layer formed on the n-type nitride semiconductor layer, A p-type AlGaN layer formed on the active layer, containing Mg as a p-type dopant, and having a structure in which three or more AlGaN layers with different Al compositions are stacked, A p-type nitride semiconductor layer is formed on the aforementioned p-type AlGaN layer and is a semiconductor layer made of a nitride semiconductor containing a p-type dopant, It includes a second multilayer reflecting mirror formed on the p-type nitride semiconductor layer and positioned opposite the first multilayer reflecting mirror, Analysis of the p-type AlGaN layer by secondary ion mass spectrometry (SIMS) revealed the following: an Al composition curve showing the change in the Al composition of the p-type AlGaN layer in the thickness direction and an Mg concentration curve showing the change in the Mg concentration of the p-type AlGaN layer in the thickness direction. The width range at 50% of the peak value of the Al composition curve is defined as the p-type AlGaN layer, and when the p-type AlGaN layer is divided in the thickness direction from the active layer side into a first region having a thickness of 1 / 10 of the p-type AlGaN layer, a second region having a thickness of 2 / 5 of the p-type AlGaN layer, and a third region having a thickness of 1 / 2 of the p-type AlGaN layer, the magnitude relationship of the average values ​​of the Al composition between each region shown by the Al composition curve is the first region < the third region < the second region. The Mg concentration shown by the aforementioned Mg concentration curve is 3 × 10⁻¹⁰ over the entire thickness of the p-type AlGaN layer. １９ atoms / cm ３ It is less than and the relative magnitudes of the average values ​​between each region of Mg concentration are such that the first region < the second region < the third region. The average value of the Mg concentration in the second region is 3 × 10⁻⁶ １８ atoms / cm ３ That's all. A vertical-cavity light-emitting element characterized in that the Mg concentration curve in the second region has a smaller average value of the absolute values ​​of the slope in the portion of the second region closer to the third region than the average value of the absolute values ​​of the slope in the portion of the second region closer to the first region than to the center of the second region in the thickness direction.

3. The Mg concentration in the p-type AlGaN layer indicated by the Mg concentration curve is 1×10 １９ atoms / cm ３ less than throughout the entire layer thickness, and the vertical cavity surface emitting device according to claim 1 or 2, characterized in that.

4. The Mg concentration in the first region shown by the Mg concentration curve is 2 × 10 １８ atoms / cm ３ The vertical resonator type light-emitting element according to claim 1, characterized in that it is less than .

5. The vertical resonator type light-emitting element according to claim 1, characterized in that the difference between the Al composition in the second region and the Al composition in the third region, as shown by the Al composition curve, is 3% or more and 18% or less.

6. The vertical resonator type light-emitting element according to claim 1, characterized in that the thickness of the p-type AlGaN layer is 8 nm or more and 15 nm or less.

7. A method for manufacturing a vertical resonator type light-emitting element according to claim 1 or 2, By metal-organic vapor deposition (MOCVD), The steps include forming the first multilayer reflecting mirror by alternately growing two semiconductor layers having different refractive indices on the substrate, An n-type nitride semiconductor layer growth step in which the n-type nitride semiconductor layer is grown on the first multilayer reflecting mirror while supplying the n-type dopant material gas, The steps include forming the active layer on the n-type nitride semiconductor layer, A p-type AlGaN layer growth step involves growing the p-type AlGaN layer, which is an AlGaN layer having a p-type conductivity, on the active layer while supplying a material gas of Mg as a p-type dopant. A step of growing a p-type nitride semiconductor layer on the p-type AlGaN layer, The step includes forming a second multilayer mirror on the p-type nitride semiconductor layer that faces the first multilayer mirror, The aforementioned p-type AlGaN layer growth step is, A first growth step involves raising the temperature from a first temperature to a second temperature while supplying nitrogen source gas and Ga material gas at predetermined supply amounts, supplying Al material gas at a first supply amount, and supplying Mg material gas at a second supply amount to grow a first p-type AlGaN layer. Following the first growth step, a second growth step is performed in which a second p-type AlGaN layer is grown while maintaining the supply amounts of the nitrogen source gas, the Ga material gas, the Al material gas, and the Mg material gas in the first growth step, A method for manufacturing a vertical resonator type light-emitting element according to claim 1 or 2, characterized by comprising: a third growth step, after the second growth step, of growing a third p-type AlGaN layer while supplying the Al material gas at a third supply amount lower than the first supply amount, and supplying the Mg material gas at a fourth supply amount lower than the second supply amount.

8. The method for manufacturing a vertical resonator type light-emitting element according to claim 7, further comprising the step of performing the second growth step and the third growth step after performing the third growth step.

9. The method for manufacturing a vertical resonator type light-emitting element according to claim 8, characterized in that the fourth supply amount is one-tenth or less of the second supply amount.

10. A method for manufacturing a vertical resonator type light-emitting element according to Claim 2, By metal-organic vapor deposition (MOCVD), The steps include forming the first multilayer reflecting mirror by alternately growing two semiconductor layers having different refractive indices on the substrate, An n-type nitride semiconductor layer growth step in which the n-type nitride semiconductor layer is grown on the first multilayer reflecting mirror while supplying the n-type dopant material gas, The steps include forming the active layer on the n-type nitride semiconductor layer, A p-type AlGaN layer growth step involves growing the p-type AlGaN layer, which is an AlGaN layer having a p-type conductivity, on the active layer while supplying a material gas of Mg as a p-type dopant. A step of growing a p-type nitride semiconductor layer on the p-type AlGaN layer, The step includes forming a second multilayer mirror on the p-type nitride semiconductor layer that faces the first multilayer mirror, The aforementioned p-type AlGaN layer growth step is, A pretreatment step in which the temperature is raised from a first temperature to a second temperature while supplying a nitrogen source gas at a predetermined supply rate and supplying the Mg material gas at a first supply rate, After the aforementioned pretreatment step, a first growth step is performed in which, while continuing to supply the nitrogen source gas, a Ga material gas is supplied at a predetermined supply amount, an Al material gas is supplied at a second supply amount, and the Mg material gas is supplied at a third supply amount to grow a first p-type AlGaN layer. Following the first growth step, a second growth step is performed in which a second p-type AlGaN layer is grown while maintaining the supply amounts of the nitrogen source gas, the Ga material gas, the Al material gas, and the Mg material gas in the first growth step, A third growth step is performed after the second growth step, in which a third p-type AlGaN layer is grown while supplying the Al material gas at a fourth supply amount lower than the second supply amount, and supplying the Mg material gas at a fifth supply amount lower than the third supply amount. A method for manufacturing a vertical resonator type light-emitting element according to claim 2, characterized by including the above.

11. The method for manufacturing a vertical resonator type light-emitting element according to claim 10, characterized in that the atmospheric gas in the p-type AlGaN layer growth step is nitrogen gas.

12. The method for manufacturing a vertical resonator type light-emitting element according to claim 10, characterized in that the third supply amount is less than or equal to the first supply amount.

13. The method for manufacturing a vertical resonator type light-emitting element according to claim 10, characterized in that the fifth supply amount is one-tenth or less of the third supply amount.

14. The method for manufacturing a vertical resonator type light-emitting element according to claim 7, characterized in that the atmospheric gas in the p-type AlGaN layer growth step is nitrogen gas.

Images