Method for manufacturing light-emitting element

Abstract

To provide a manufacturing method of a light emitting element including a light emitting functional portion made of a group III nitride semiconductor, and capable of forming a base layer with excellent transmittance and surface flatness on PSS.SOLUTION: A manufacturing method of a light emitting element 1 according to the present invention includes the steps of forming a base layer 12 made of AlN on a PSS 10 via a buffer layer 11 made of AlN, and epitaxially growing a group III nitride semiconductor on the base layer 12 to form a light emitting function unit 13 including a light emitting layer 132, and in the step of forming the base layer 12, the base layer 12 is formed by epitaxially growing AlN using an MOVPE method with the V / III ratio of the source gas being in the range of 1.0 or more and 2.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a light-emitting device. [Background technology]

[0002] Conventionally, there has been known a method for manufacturing a light-emitting element in which an AlGaN underlayer having a flat surface is formed on a sapphire substrate (PSS) having a concave-convex pattern formed on its surface via an AlN layer as a buffer layer, and a Group III nitride semiconductor is epitaxially grown on the AlGaN underlayer to form a light-emitting functional section including a light-emitting layer (see Patent Document 1).

[0003] According to the method for manufacturing a light-emitting element described in Patent Document 1, an AlN layer is formed on PSS by sputtering, and then a heat treatment is performed at a temperature of 1150°C or higher. This reduces the amount of AlGaN with a high Al composition growing from the slopes of the protrusions of the uneven pattern of the PSS, making it possible to flatten the surface of the AlGaN underlayer without leaving any grooves resulting from the uneven pattern of the PSS. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-56551 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the AlGaN grown from the slopes of the protrusions of the PSS has non-uniform Ga and Al composition. This is because GaN tends to grow in a direction perpendicular to the substrate (it tends to grow on the C-plane), whereas AlN does not migrate as easily, so it grows preferentially from the slopes of the protrusions. Therefore, according to the method for manufacturing a light-emitting device described in Patent Document 1, although the surface of the AlGaN underlayer becomes flat by reducing the amount of AlGaN grown from the protrusions, the non-uniform Ga and Al composition reduces the transmittance of the AlGaN underlayer, which may reduce the light extraction efficiency of the light-emitting device.

[0006] An object of the present invention is to provide a method for manufacturing a light-emitting device having a light-emitting functional unit made of a Group III nitride semiconductor, which is capable of forming an underlayer having excellent transmittance and surface flatness on PSS. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention provides the following methods for producing a light-emitting device [1] to [5].

[0008] [1] A method for manufacturing a light-emitting element, comprising: a step of forming an underlayer made of AlN on PSS via a buffer layer made of AlN; and a step of epitaxially growing a Group III nitride semiconductor on the underlayer to form a light-emitting functional unit including a light-emitting layer, wherein in the step of forming the underlayer, AlN is epitaxially grown by MOVPE with a V / III ratio of a source gas within a range of 1.0 or more and 2.0 or less to form the underlayer. [2] The method for manufacturing a light-emitting element according to the above [1], wherein in the step of forming the underlayer, the V / III ratio of the source gas is set within a range of 1.5 or more and 2.0 or less. [3] The method for manufacturing a light-emitting element according to the above [1] or [2], wherein in the step of forming the underlayer, the buffer layer is formed by sputtering. [4] The method for manufacturing a light-emitting element according to [1] or [2] above, wherein the step of forming the light-emitting function portion includes the steps of forming a first AlGaN layer on the base layer and forming a second AlGaN layer on the first AlGaN layer, wherein the first AlGaN layer is formed by epitaxially growing n-type AlGaN at a growth temperature in the range of 800° C. or more and 1100° C. or less, and after forming the first AlGaN layer, an annealing treatment is performed for 30 seconds or more at a temperature in the range of 800° C. or more and 1100° C. or less with the supply of Ga raw material gas for the n-type AlGaN stopped, and then the second AlGaN layer is formed. [5] The method for producing a light-emitting device according to [4] above, wherein the Al composition of the first AlGaN layer is in the range of 0.6 to 0.7. Effect of the Invention

[0009] According to the present invention, there is provided a method for manufacturing a light-emitting device having a light-emitting functional unit made of a Group III nitride semiconductor, which is capable of forming an underlayer excellent in transmittance and surface flatness on PSS. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a vertical cross-sectional view of a light-emitting device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a table showing the relationship between the V / III ratio of the source gas in forming the underlayer and the surface flatness of the underlayer. [Diagram 3] FIG. 3 is a table showing the relationship between the V / III ratio of the source gas in forming the underlayer and the surface flatness of the underlayer. [Figure 4] FIG. 4 is a table showing the relationship between the V / III ratio of the source gas in forming the underlayer and the surface flatness of the underlayer. [Diagram 5] FIG. 5 is a graph showing the transmittance of the nine wafers shown in FIGS. [Figure 6] FIG. 6 is a table showing the relationship between the method of forming the buffer layer and the surface flatness of the underlayer. [Figure 7]Fig. 7(a) is a table showing the relationship between the formation conditions of the n-type contact layer and the reverse leakage characteristics of the light-emitting device, and Fig. 7(b) is a table showing the relationship between the formation conditions of the n-type contact layer and the forward leakage characteristics of the light-emitting device. [Figure 8] 8(a) and (b) are graphs showing the change over time in output of a light-emitting device that has been subjected to n-annealing after the formation of an n-type contact layer. [Figure 9] FIG. 9 is a graph showing the relationship between the half-width of the (102) plane diffraction peak obtained by X-ray rocking curve measurement of the n-type contact layer and the output of the light-emitting device. [Figure 10] FIG. 10 is a graph showing the relationship between the Al composition of the n-type contact layer and the change in output of the light-emitting device over time. [Figure 11] FIG. 11 is a table showing the relationship between the Al composition of the n-type contact layer and the surface state of the underlayer. [Figure 12] Fig. 12(a) is a graph showing the relationship between the Al composition of the n-type contact layer and the half-width of the (105) diffraction peak obtained by X-ray rocking curve measurement of the n-type contact layer, and Fig. 12(b) is a graph showing the relationship between the Al composition of the n-type contact layer and the relaxation rate of the n-type contact layer. [Figure 13] FIG. 13 is a graph showing the relationship between the Al composition of the n-type contact layer and the operating voltage when a current of 63 A / cm −2 is applied to the light emitting element 1. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Configuration of light-emitting element) 1 is a vertical cross-sectional view of a light-emitting element 1 according to an embodiment of the present invention. The light-emitting element 1 is a flip-chip mounted light-emitting diode (LED) and includes a sapphire substrate (PSS) 10 having a concave-convex pattern formed on its surface, a buffer layer 11 made of AlN on the PSS 10, an underlayer 12 made of AlN on the buffer layer 11, and a light-emitting functional unit 13 made of a Group III nitride semiconductor including a light-emitting layer on the underlayer 12.

[0012] In addition, the term "upper" in the configuration of the light-emitting element 1 refers to the "upper" when the light-emitting element 1 is placed in the orientation shown in FIG.

[0013] The PSS 10 has an uneven pattern on its upper surface that is made up of a number of protrusions 101. This uneven pattern diffuses light and reduces the confinement of light inside the light-emitting element 1, thereby improving the light extraction efficiency. The uneven pattern of the PSS 10 is formed by, for example, photolithography and etching.

[0014] The shape of the protrusions 101 is a shape having an inclined surface on which N and Al are arranged, and is typically a circular cone or a polygonal pyramid. The planar arrangement pattern of the protrusions 101 is, for example, a polygonal lattice pattern such as a triangular lattice, a square lattice, or a hexagonal lattice. The main surface of the PSS 10 is, for example, a c-plane, and in this case, the inclined surface of the protrusions 101 is a plane different from the c-plane.

[0015] The buffer layer 11 is formed so as to cover the upper surface of the PSS 10, and buffers the difference in lattice constant between the PSS 10 and the underlayer 12 for the epitaxial growth of the underlayer 12. Since the thickness of the buffer layer 11 is small (e.g., 20 nm) compared to the size of the protrusions 101, the surface of the buffer layer 11 has an uneven pattern resulting from the uneven pattern of the PSS 10. The buffer layer 11 can be formed by sputtering, metalorganic vapor phase epitaxy (MOVPE), or the like, but it is preferable to use sputtering for the following reasons.

[0016] Forming the buffer layer 11 by sputtering can reduce crystal defects. In particular, it is effective in reducing screw dislocations and mixed dislocations including screw dislocations. By forming the buffer layer 11 by sputtering to reduce the dislocation density, the dislocation density of the layer epitaxially grown on the buffer layer 11 can be reduced, so that the decrease in output caused by dislocations near the light-emitting layer of the light-emitting element 1 can be suppressed. In addition, by reducing the dislocation density of the layer epitaxially grown on the buffer layer 11, the leakage current can also be reduced. In addition, the buffer layer 11 formed by sputtering according to this embodiment has a lower C concentration than the nucleation layer formed by the MOVPE method, so that the absorption of light by C can be suppressed.

[0017] The underlayer 12 is a layer that serves as a base for the growth of the light-emitting functional section 13, and has a highly flat surface with reduced irregularities resulting from the unevenness pattern of the PSS 10. The underlayer 12 is formed so as to reduce the irregularities resulting from the unevenness pattern of the PSS 10, and therefore the entire surface of the underlayer 12 is located higher than the protrusions 101 of the PSS 10. The thickness of the underlayer 12 is, for example, 500 nm. The underlayer 12 is formed by MOVPE.

[0018] 1, the light-emitting function section 13 includes, for example, an n-type contact layer 131, an emission layer 132 on the n-type contact layer 131, an electron blocking layer 133 on the emission layer 132, a p-type cladding layer 134 on the electron blocking layer 133, and a p-type contact layer 135 on the p-type cladding layer 134. An n-electrode 15 is connected to the n-type contact layer 131, and a p-electrode 16 is connected to the p-type contact layer 135 via a transparent electrode 14 formed on the p-type contact layer 135.

[0019] The light emitting function section 13 is mainly composed of a group III nitride semiconductor and is formed by, for example, MOVPE. When the light emitting function section 13 is formed by MOVPE, the base layer 12 and the light emitting function section 13 can be formed consecutively in the chamber of the same device. Since the surface of the base layer 12 has high flatness, the group III nitride semiconductor grown on the base layer 12 constituting the light emitting function section 13 has excellent crystal quality.

[0020] The light emitting layer 132 is a layer laminated on the n-type contact layer 131. The light emitting layer 132 is made of AlGaN, and preferably has a multiple quantum well (MQWs) structure. The Al composition x of the light emitting layer 132 (the Al composition x of the well layer in the case of an MQWs structure) is set according to the desired emission wavelength, and is set to 0.35 to 0.45 when the emission wavelength is about 280 nm, for example. Here, the above Al composition x is the ratio of the Al content when the sum of the Ga content and the Al content is set to 1, and in the ideal composition of AlGaN, the Al composition x is 0.35 to 0.45. x Ga 1-x It is expressed as N(0≦x≦1).

[0021] For example, the light emitting layer 132 has an MQWs structure with two well layers, i.e., a structure in which a first barrier layer, a first well layer, a second barrier layer, a second well layer, and a third barrier layer are stacked in this order. The first well layer and the second well layer are made of n-type AlGaN. The first barrier layer, the second barrier layer, and the third barrier layer are made of n-type AlGaN (Al composition x is 1, i.e., including AlN) having a higher Al composition than the first well layer and the second well layer.

[0022] As an example, the Al composition x, thickness, and concentration of Si as a dopant of the first and second well layers are 0.4, 1.8 nm, and 9.0×10 18 / cm 3 The Al composition x, thickness, and Si concentration as a dopant of the first and second barrier layers are 0.5, 11 nm, and 9.0×10 18 / cm 3 The Al composition x, thickness, and Si concentration as a dopant of the third barrier layer are 0.5, 5.5 nm, 5.0 × 1018 / cm 3 It is.

[0023] The n-type contact layer 131 is made of n-type AlGaN containing a group IV element such as Si or Ge as a donor. The lower limit of the Al composition x of the n-type contact layer 131 is set as the lower limit of the range in which the absorption of light emitted from the light emitting layer 132 can be suppressed. If the Al composition x of the n-type contact layer 131 is 0.1 or more larger than the Al composition x of the AlGaN constituting the light emitting layer 132 (the Al composition x of the well layer when the light emitting layer 132 has an MQWs structure), the absorption of light emitted from the light emitting layer 132 by the n-type contact layer 131 can be effectively suppressed, and if it is 0.15 or more larger, the absorption can be more effectively suppressed. Therefore, the Al composition x of the n-type contact layer 131 is preferably 0.1 or more larger than the Al composition x of the light emitting layer 132, and more preferably 0.15 or more larger.

[0024] For example, when the Al composition x of the light emitting layer 132 is 0.35 to 0.45, light having a wavelength of approximately 280 nm is emitted, and when the Al composition x of the n-type contact layer 131 is 0.5 or more, absorption can be effectively suppressed, and when it is 0.55 or more, absorption can be even more effectively suppressed.

[0025] The upper limit of the Al composition x of the n-type contact layer 131 can be set as the upper limit of a range that can suppress an increase in electrical resistance with an increase in the Al composition x. When the Al composition x is increased, the electrical resistance of AlGaN is almost constant up to 0.7, but begins to increase when the Al composition x exceeds 0.7. For this reason, it is preferable that the Al composition x of the n-type contact layer 131 is set to 0.7 or less.

[0026] Furthermore, by setting the Al composition x of the n-type contact layer 131 within the range of 0.6 to 0.7, the crystallinity of the n-type contact layer 131 can be improved, and the device characteristics and life of the light emitting element 1 can be improved. In this case, ideally, the n-type contact layer 131 should be Al x Ga 1-xN (0.6≦x≦0.7). As an example, the Al composition x, thickness, and concentration of Si as a dopant of the n-type contact layer 131 are 0.6, 1.3 μm, and 2.0×10 19 / cm 3 It is.

[0027] The electron blocking layer 133 is made of p-type AlGaN having a higher Al composition x than the third barrier layer. The electron blocking layer 133 suppresses the diffusion of electrons from the light emitting layer 132 to the p-type contact layer 135. The Al composition x, thickness, and Mg concentration as a dopant of the electron blocking layer 133 are, for example, 0.85, 25 nm, and 1.0×10, respectively. 20 / cm 3 It is.

[0028] The p-type cladding layer 134 has a structure in which a first p-type cladding layer and a second p-type cladding layer are laminated in this order. The first p-type cladding layer and the second p-type cladding layer are made of p-type GaN. The thickness of the first p-type cladding layer and the concentration of Mg as a dopant are, for example, 50 nm and 4.0×10 19 / cm 3 The thickness of the second p-type cladding layer and the concentration of Mg as a dopant are, for example, 400 nm and 1.0×10 19 / cm 3 It is.

[0029] The p-type contact layer 135 is made of p-type GaN. The thickness of the p-type contact layer 135 and the Mg concentration as a dopant are, for example, 18 nm and 1.5×10 20 / cm 3 It is.

[0030] A groove is provided in a partial region of the surface of p-type contact layer 135. The groove penetrates p-type contact layer 135, p-type cladding layer 134, electron blocking layer 133, and light emitting layer 132 to reach n-type contact layer 131, and an n-electrode 15 is connected to the surface of n-type contact layer 131 exposed by this groove.

[0031] The transparent electrode 14 is made of a conductive oxide such as IZO, ITO, ICO, or ZnO. The p-electrode 16 is made of Ni / Au. The n-electrode 15 is made of Ti / Al / Ni, V / Al / Ni, or V / Al / Ru.

[0032] (Method of manufacturing light-emitting element) An example of a method for manufacturing the light-emitting element 1 according to the embodiment of the present invention will be described below. In forming each layer of the light-emitting element 1 by MOVPE, for example, trimethylgallium, trimethylaluminum, and ammonia are used as the Ga source gas, Al source gas, and N source gas, respectively. For example, silane gas, which is a source gas for Si, and bis(cyclopentadienyl)magnesium gas, which is a source gas for Mg, are used as the source gas for the n-type dopant and the p-type dopant, respectively. For example, hydrogen gas or nitrogen gas is used as the carrier gas. In the present embodiment, the growth temperature of each layer is the temperature of a heater in a film-forming apparatus, and the surface temperature of the PSS10 is approximately 100° C. lower than the temperature of the heater.

[0033] First, PSS10 is mixed with Ar and N 2 A pretreatment step is performed in which the PSS 10 is exposed to a plasma to remove organic matter and oxides adhering to the surface of the PSS 10.

[0034] Next, a buffer layer 11 made of AlN is formed on the PSS 10 by sputtering or MOVPE. When the buffer layer 11 is formed by sputtering, the growth temperature is, for example, 600° C., and when the buffer layer 11 having a single crystal structure is formed, the flow rate of the N raw material gas is 50% to 100%, preferably 50%, of the total flow rate of the N raw material gas and the inert gas. When the buffer layer 11 is formed by MOVPE, the growth temperature is, for example, 900° C., and the V / III ratio of the raw material gas of the buffer layer 11 is, for example, 56. Here, the V / III ratio means the ratio of the number of atoms in the raw material gas of Al, which is a group III element, and N, which is a group V element.

[0035] Next, an underlayer 12 made of AlN is formed by MOVPE on the buffer layer 11. At this time, by setting the V / III ratio of the source gas within the range of 1.0 to 2.0, the crystallinity of the AlN growing from the slopes of the protrusions 101 on the surface of the PSS 10 is improved, and as a result, an underlayer 12 with excellent crystallinity and surface flatness is obtained.

[0036] This is believed to be because Al and N are alternately arranged in a 1:1 ratio on the inclined surfaces of protrusions 101, and the Al:N ratio in the source gas is somewhat close to 1, which is suitable for the growth of AlN. That is, by using AlN instead of AlGaN as the material for base layer 12 and setting the V / III ratio of the source gas within the range of 1.0 to 2.0, base layer 12 with excellent crystallinity and surface flatness can be formed by MOVPE.

[0037] Furthermore, by setting the V / III ratio of the source gas within the range of 1.5 to 2.0, the crystallinity of the underlayer 12 can be further increased, thereby improving the transmittance.

[0038] The growth temperature of the underlayer 12 is, for example, within a range of 1000° C. to 1450° C. The growth pressure of the underlayer 12 is, for example, within a range of 20 mbar to 500 mbar.

[0039] In order to further improve the crystallinity of underlayer 12, a method of performing an annealing treatment at 1150° C. or higher and 1450° C. or lower, which is the decomposition temperature of PSS 10, before forming underlayer 12 after forming buffer layer 11, or a method of performing a high-temperature heat treatment at 1000 to 1300° C. with the upper surface of underlayer 12 covered with a GaN cap layer may be used. The GaN cap layer is used to suppress evaporation of underlayer 12 during the high-temperature heat treatment, and evaporates and disappears during the high-temperature heat treatment.

[0040] Next, an n-type contact layer 131 made of AlGaN containing a group IV element such as Si is formed on the underlayer 12 by MOVPE. In forming the n-type contact layer 131, the V / III ratio of the source gas for the n-type contact layer 131 is set within the range of 1000 to 3200 inclusive in order to reduce the electrical resistance of the n-type contact layer 131. This V / III ratio refers to the ratio of the number of atoms in the source gas of the group III elements Ga and Al and the group V element N.

[0041] In addition, in forming the n-type contact layer 131, it is preferable to set the growth temperature of the n-type contact layer 131 to 1100° C. or less. By setting the growth temperature to 1100° C. or less, it is possible to suppress an increase in electrical resistance that accompanies an increase in the growth temperature. By setting the growth temperature to 1100° C. or less, evaporation of group III elements, particularly Ga which is easily evaporated, is suppressed, and excessive generation of group III vacancies is suppressed. This is believed to suppress an increase in electrical resistance caused by the influence of complex defects of group III vacancies and group IV elements.

[0042] In addition, in forming the n-type contact layer 131, it is preferable to set the growth temperature of the n-type contact layer 131 to 800° C. or higher. If the growth temperature is lower than 800° C., ammonia, which is a raw material for the group V element N, is difficult to decompose, and therefore the amount of ammonia supplied must be increased, and the V / III ratio must be set abnormally high. In addition, if the growth temperature is low, a problem of C being mixed in from the group III raw material may occur, so it is preferable to set the growth temperature to a temperature at which this problem can be avoided, for example, 800° C. or higher.

[0043] The growth pressure of the n-type contact layer 131 is set to, for example, 20 to 200 mbar.

[0044] After forming the n-type contact layer 131 on the underlayer 12, it is preferable to perform an annealing treatment at a temperature in the range of 800° C. to 1100° C. for 30 seconds or more, for example 180 seconds, in a state where the supply of the Ga source gas of AlGaN constituting the n-type contact layer 131 is stopped and only an N source gas such as ammonia gas and a carrier gas are supplied. This makes it possible to suppress a decrease in output of the light-emitting element 1 caused by the desorption of Ga on the surface of the n-type contact layer 131 and a decrease in crystallinity.

[0045] Next, the light emitting layer 132 is formed by MOVPE on the n-type contact layer 131. The light emitting layer 132 is formed by stacking the first barrier layer, the first well layer, the second barrier layer, the second well layer, and the third barrier layer in this order. The growth conditions for the light emitting layer 132 are, for example, a growth temperature of 975° C. and a growth pressure of 400 mbar.

[0046] Next, the electron blocking layer 133 is formed by MOVPE on the light emitting layer 132. The growth conditions for the electron blocking layer 133 are, for example, a growth temperature of 1025° C. and a growth pressure of 50 mbar.

[0047] Next, the p-type cladding layer 134 is formed on the electron blocking layer 133 by MOVPE. The p-type cladding layer 134 is formed by stacking the first p-type cladding layer and the second p-type cladding layer in this order. The growth conditions for the first p-type cladding layer and the second p-type cladding layer are, for example, a growth temperature of 1050° C. and a growth pressure of 200 mbar.

[0048] Next, the p-type contact layer 135 is formed by MOVPE on the p-type cladding layer 134. The growth conditions for the p-type contact layer 135 are, for example, a growth temperature of 1050° C. and a growth pressure of 100 mbar.

[0049] Next, a predetermined region on the surface of the p-type contact layer 135 is dry etched to form a groove deep enough to reach the n-type contact layer 131 .

[0050] Next, transparent electrode 14 is formed on p-type contact layer 135. Next, p-electrode 16 is formed on transparent electrode 14, and n-electrode 15 is formed on n-type contact layer 131 exposed on the bottom surface of the groove. Transparent electrode 14, p-electrode 16, and n-electrode 15 are formed by sputtering, vapor deposition, or the like.

[0051] (Evaluation experiment) 2 to 4 are tables showing the relationship between the V / III ratio of the source gas in forming the underlayer 12 and the surface flatness of the underlayer 12. Figures 2 to 4 include atomic force microscope (AFM) images of the top surface and cross section of a wafer in which the underlayer 12 is formed on the PSS 10 via the buffer layer 11, as well as external appearance photographs. Figures 2 to 4 also include the growth temperature, V / III ratio of the source gas, and film formation rate in forming the underlayer 12 for each wafer.

[0052] 2 to 4 show that when the V / III ratio of the raw material gas is within the range of approximately 1.0 or more and 2.0 or less, the flatness of the surface of the underlayer 12 is improved and discoloration observed in an external photograph is suppressed.

[0053] Fig. 5 is a graph showing the transmittance of the nine wafers shown in Figs. 2 to 4. The "V / III ratio" value included in Fig. 5 is the V / III ratio value of the source gas in forming the underlayer 12.

[0054] Figure 5 shows that when the V / III ratio of the raw material gas is 1.0 or more, the crystallinity of the underlayer 12 increases and the transmittance increases, and when the V / III ratio of the raw material gas is 1.5 or more, the crystallinity of the underlayer 12 further increases and the transmittance increases.

[0055] Fig. 6 is a table showing the relationship between the deposition method of the buffer layer 11 and the surface flatness of the underlayer 12. Like Figs. 2 to 4, Fig. 6 includes atomic force microscope (AFM) images of the top surface and cross section of a wafer in which the underlayer 12 is formed on the PSS 10 via the buffer layer 11, as well as an external photograph. Fig. 6 also includes the growth temperature, V / III ratio of the source gas, and deposition rate in forming the underlayer 12 for each wafer.

[0056] The wafer on the left side of Fig. 6 has a buffer layer 11 formed by MOVPE. The formation of the buffer layer 11 by MOVPE was performed under conditions of a growth temperature of 900°C and a V / III ratio of the source gas of the buffer layer 11 of 56. The wafer on the right side of Fig. 6 has a buffer layer 11 formed by sputtering. The formation of the buffer layer 11 by sputtering was performed under conditions of a growth temperature of 600°C, a film formation pressure of 1.8 Pa, and a flow rate of the N source gas of 50% of the total flow rate of the N source gas and the inert gas.

[0057] FIG. 6 shows that whether the buffer layer 11 is formed by MOVPE or by sputtering, the underlayer 12 has a high surface flatness.

[0058] Fig. 7(a) is a table showing the relationship between the formation conditions of the n-type contact layer 131 and the reverse leakage characteristics of the light-emitting element 1. Fig. 7(a) shows the magnitude of the leakage current that flows when a reverse voltage of -5V is applied to the light-emitting element 1. Fig. 7(b) is a table showing the relationship between the formation conditions of the n-type contact layer 131 and the forward leakage characteristics of the light-emitting element 1. Fig. 7(b) shows the magnitude of the forward voltage when a leakage current of 1 μA flows in the light-emitting element 1.

[0059] 7(a) and (b) is an annealing process at 980° C. for 180 seconds, performed in a state where only ammonia gas and carrier gas as N source gas are supplied into the chamber after the n-type contact layer 131 is formed. Figures 7(a) and (b) show that when n-annealing is performed after the n-type contact layer 131 is formed, the occurrence of reverse and forward leakage currents is suppressed.

[0060] 8(a) and (b) are graphs showing the change over time in output (peak intensity of electroluminescence spectrum) of two light-emitting elements 1 that were subjected to n-annealing after the formation of the n-type contact layer 131. Figs. 8(a) and (b) show that the lifetime of the light-emitting element 1 is extended by performing n-annealing after the formation of the n-type contact layer 131.

[0061] Fig. 9 is a graph showing the relationship between the half-width of the (102) plane diffraction peak obtained by X-ray rocking curve measurement of the n-type contact layer 131 and the output of the light-emitting element 1. Fig. 9 shows that the narrower the half-width of the X-ray rocking curve of the n-type contact layer 131, that is, the higher the crystallinity of the n-type contact layer 131, the greater the output of the light-emitting element 1.

[0062] Fig. 10 is a graph showing the relationship between the Al composition of the n-type contact layer 131 and the change in output over time of the light-emitting element 1. "Al:0.58", "Al:0.68", "Al:0.73", and "Al:0.78" in Fig. 10 respectively indicate the Al composition of the n-type contact layer 131. Fig. 10 shows that the life of the light-emitting element 1 is extended when the Al composition x of the n-type contact layer 131 is 0.68 to 0.73.

[0063] Fig. 11 is a table showing the relationship between the Al composition of the n-type contact layer 131 and the surface state of the underlayer 12. Fig. 11 includes an atomic force microscope (AFM) image of the surface of the n-type contact layer 131. Fig. 11 shows that the crystallinity of the n-type contact layer 131 changes depending on the Al composition of the n-type contact layer 131, and that the crystallinity of the n-type contact layer 131 is high when the Al composition x is 0.60 to 0.80.

[0064] Fig. 12(a) is a graph showing the relationship between the Al composition of the n-type contact layer 131 and the half-width of the (105) plane diffraction peak obtained by X-ray rocking curve measurement of the n-type contact layer 131. Fig. 12(b) is a graph showing the relationship between the Al composition of the n-type contact layer 131 and the relaxation rate of the n-type contact layer 131. Figs. 12(a) and (b) show that within the range of Al composition x of 0.55 to 0.8, the smaller the Al composition x, the more the crystallinity deteriorates (the larger the half-width).

[0065] FIG. 13 shows the relationship between the Al composition of the n-type contact layer 131 and the 63 A cm -2 13 is a graph showing the relationship between the operating voltage and the current flowing through the n-type contact layer 131. Fig. 13 shows that the operating voltage of the light-emitting element 1 can be suppressed when the Al composition of the n-type contact layer 131 is within a range of approximately 0.6 to 0.7.

[0066] (Effects of the embodiment) According to the above embodiment of the present invention, by growing AlN by MOVPE with the V / III ratio of the source gas in the range of 1.0 or more and 2.0 or less, a base layer having excellent transmittance and surface flatness can be formed on PSS.

[0067] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the light-emitting element 1 may be a face-up mounting type. Furthermore, the features of the present invention, such as the conditions for forming the underlayer 12 of the light-emitting element 1, can also be applied to a manufacturing method for light-emitting elements other than LEDs, such as laser diodes. Furthermore, the components of the above-mentioned embodiments can be combined in any manner without departing from the spirit of the invention.

[0068] In addition, the above-described embodiments do not limit the scope of the invention according to the claims. Also, it should be noted that not all of the combinations of features described in the embodiments are essential to the means for solving the problems of the invention. [Explanation of symbols]

[0069] 1 Light emitting element 10 PSS 11 Buffer layer 12 Base layer 13 Light-emitting function part 131 n-type contact layer 132 Light-emitting layer 133 Electron Block Layer 134 p-type cladding layer 135 p-type contact layer 14 Transparent electrode 15n electrode 16p electrode

Claims

1. forming an underlayer made of AlN on the PSS via a buffer layer made of AlN; forming a light emitting functional portion including a light emitting layer by epitaxially growing a Group III nitride semiconductor on the underlayer; Including, In the step of forming the underlayer, a V / III ratio of a source gas is set within a range of 1.0 or more and 2.0 or less, and AlN is epitaxially grown by MOVPE to form the underlayer; the step of forming the light emitting function portion includes a step of forming a first AlGaN layer on the base layer, and a step of forming a second AlGaN layer on the first AlGaN layer; The formation of the first AlGaN layer is carried out by epitaxially growing n-type AlGaN at a growth temperature in the range of 800° C. or more and 1100° C. or less; The formation of the second AlGaN layer is performed after the formation of the first AlGaN layer, and then an annealing treatment is performed for 30 seconds or more at a temperature in the range of 800° C. or more and 1100° C. or less in a state where the supply of the Ga source gas for the n-type AlGaN is stopped. A method for manufacturing a light-emitting device.

2. In the step of forming the underlayer, the V / III ratio of the source gas is set within a range of 1.5 or more and 2.0 or less. The method for producing the light-emitting device according to claim 1 .

3. In the step of forming the underlayer, the buffer layer is formed by sputtering. The method for producing the light-emitting device according to claim 1 .

4. The Al composition of the first AlGaN layer is in the range of 0.6 to 0.

7. The method for producing the light-emitting device according to claim 1 .

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