Method for manufacturing a light-emitting element and method for extracting hydrogen from a light-emitting element

Abstract

The present invention provides a method for manufacturing a light-emitting element that can extract hydrogen from a p-type layer composed of a nitride semiconductor without reducing the output of the light-emitting element, and a method for extracting hydrogen from the light-emitting element. Even when the p-type layer is composed of a nitride semiconductor with a high Al composition, hydrogen can still be effectively extracted. As one aspect of the present invention, there is provided a method for manufacturing a light-emitting element 1, including the following steps: for a light-emitting element 1 with a light-emitting wavelength of 306 nm or less, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the light-emitting element 1 is applied, or in a state where no voltage is applied, ultraviolet light with a wavelength of 306 nm or less is irradiated from the outside, heat treatment is performed, and the step of extracting hydrogen in the p-type layer outside the light-emitting element 1; the step of extracting hydrogen in the p-type layer outside the light-emitting element 1 is performed in an N₂ atmosphere at 650 °C or higher or in an N₂ + O₂ atmosphere at 500 °C or higher.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a light-emitting element and a method for extracting hydrogen from a light-emitting element. Background Art

[0002] So far, a technique for removing hydrogen from a nitride semiconductor doped with a p-type impurity has been known (for example, refer to Patent Document 1). The technique described in Patent Document 1 includes: a step of irradiating a nitride semiconductor doped with a p-type impurity with an electromagnetic wave having an energy equal to or higher than the bandgap energy of the nitride semiconductor, and a step of heat-treating the nitride semiconductor in an atmosphere substantially free of active hydrogen.

[0003] According to Patent Document 1, by removing hydrogen that binds to a p-type impurity and hinders its function as a normal acceptor from the nitride semiconductor layer, the nitride semiconductor can be made to have a low resistance.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 11-238692 Summary of the Invention

[0007] However, in a light-emitting element composed of a nitride semiconductor, there is a problem that if the hydrogen removed from the p-type nitride semiconductor layer reaches the light-emitting layer, the output of the light-emitting element will be significantly reduced (for example, by 20% or more).

[0008] In particular, in a light-emitting element that emits short-wavelength light, in order to suppress self-absorption of the light emitted by the light-emitting layer, a p-type layer composed of a nitride semiconductor having a large bandgap and a high Al content can be used. However, for the p-type layer composed of a nitride semiconductor having a high Al content, since light having a high energy emitted from the light-emitting layer reaches the entire region, a large amount of hydrogen is separated from the p-type impurity and moves to the light-emitting layer. In addition, since AlN has a stronger ability to retain hydrogen or higher heat resistance than GaN, it is difficult to extract hydrogen from the p-type layer composed of a nitride semiconductor having a high Al content.

[0009] An object of the present invention is to provide a method for manufacturing a light-emitting element and a method for extracting hydrogen from a light-emitting element, which can extract hydrogen from a p-type layer composed of a nitride semiconductor without reducing the output of the light-emitting element, and can effectively extract hydrogen even when the p-type layer is composed of a nitride semiconductor having a high Al content.

[0010] To achieve the above object, one aspect of the present invention provides a method for manufacturing a light-emitting element according to the following [1] to [4] and a method for extracting hydrogen from a light-emitting element according to [5] to [8].

[0011] [1] A method for manufacturing a light-emitting element, the light-emitting element including a light-emitting layer having a light-emitting wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; the manufacturing method includes the following steps: a step of forming the above-mentioned light-emitting element having the above-mentioned light-emitting layer and the above-mentioned p-type layer, and for the above-mentioned light-emitting element, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the above-mentioned light-emitting element is applied, or in a state where no voltage is applied, irradiating ultraviolet light having a wavelength of 306 nm or less from the outside, performing heat treatment, and extracting hydrogen in the above-mentioned p-type layer outside the above-mentioned light-emitting element; performing the above-mentioned step of extracting hydrogen in the p-type layer outside the above-mentioned light-emitting element in an N2 atmosphere at 650 °C or higher or in an N2 + O2 atmosphere at 500 °C or higher.

[0012] [2] The method for manufacturing a light-emitting element according to the above [1], wherein, in the above-mentioned step of extracting hydrogen in the p-type layer outside the above-mentioned light-emitting element, a reverse voltage is applied to the above-mentioned light-emitting element.

[0013] [3] The method for manufacturing a light-emitting element according to the above [1] or [2], wherein the AlGaInN constituting the above-mentioned p-type layer is AlGaN having an Al composition of 80% or more.

[0014] [4] The method for manufacturing a light-emitting element according to any one of the above [1] to [3], wherein the above-mentioned light-emitting element has a substrate, an n-type layer on the above-mentioned substrate, the above-mentioned light-emitting layer on the above-mentioned n-type layer, the above-mentioned p-type layer on the above-mentioned light-emitting layer, and a p-contact layer on the above-mentioned p-type layer; the band gap of the above-mentioned p-contact layer is smaller than the band gaps of the above-mentioned substrate and the layer located between the above-mentioned substrate and the above-mentioned light-emitting layer; in the above-mentioned step of extracting hydrogen in the p-type layer outside the above-mentioned light-emitting element, the above-mentioned ultraviolet light having an energy lower than the band gaps of the above-mentioned substrate and the layer located between the above-mentioned substrate and the above-mentioned light-emitting layer is irradiated onto the above-mentioned light-emitting element from the above-mentioned substrate side.

[0015] [5] A method for extracting hydrogen in a light-emitting element, the light-emitting element including a light-emitting layer having a light-emitting wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; the extraction method includes the following steps: for the above-mentioned light-emitting element, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the above-mentioned light-emitting element is applied, or in a state where no voltage is applied, irradiating ultraviolet light having a wavelength of 306 nm or less from the outside, performing heat treatment, and extracting hydrogen in the above-mentioned p-type layer outside the above-mentioned light-emitting element; performing the above-mentioned step of extracting hydrogen in the p-type layer outside the above-mentioned light-emitting element in an N2 atmosphere at 650 °C or higher or in an N2 + O2 atmosphere at 500 °C or higher.

[0016] [6] The method for extracting hydrogen from the light-emitting element according to [5] above, wherein a reverse voltage is applied to the light-emitting element in the step of extracting hydrogen in the p-type layer to the outside of the light-emitting element.

[0017] [7] The method for extracting hydrogen from the light-emitting element according to [5] or [6] above, wherein the AlGaInN constituting the p-type layer is AlGaN with an Al composition of 80% or more.

[0018] [8] The method for extracting hydrogen from the light-emitting element according to any one of [5] to [7] above, wherein the light-emitting element has a substrate, an n-type layer on the substrate, a light-emitting layer on the n-type layer, a p-type layer on the light-emitting layer, and a p-contact layer on the p-type layer; the band gap of the p-contact layer is smaller than the band gaps of the substrate and the layer between the substrate and the light-emitting layer; in the step of extracting hydrogen in the p-type layer to the outside of the light-emitting element, ultraviolet light having an energy lower than the band gaps of the substrate and the layer between the substrate and the light-emitting layer is irradiated onto the light-emitting element from the substrate side.

[0019] According to the present invention, a method for manufacturing a light-emitting element and a method for extracting hydrogen from the light-emitting element can be provided. The above methods can extract hydrogen from a p-type layer made of a nitride semiconductor without reducing the output of the light-emitting element, and even when the p-type layer is made of a nitride semiconductor with a high Al composition, hydrogen can still be effectively extracted. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a vertical cross-sectional view of a light-emitting element according to an embodiment of the present invention.

[0021] Figure 2 is a graph showing the emission spectra of a light-emitting element with an emission wavelength of 280 nm and a light-emitting element with an emission wavelength of 340 nm before and after aging.

[0022] Figure 3 (a) and (b) are graphs showing the SIMS distributions of Al, Mg, Si, and H of the light-emitting element before and after aging.

[0023] Figure 4 is a bar graph showing the concentration of H read from the SIMS distribution in each of the hole supply layer, electron blocking layer, light-emitting layer to n-type contact layer of the light-emitting element Figure 3 from the SIMS distribution in (b).

[0024] Figure 5 is a graph showing the SIMS distributions of Al, Mg, Si, and H of the light-emitting element in the state just after manufacturing, the state after performing heat treatment, and the state after performing heat treatment and ultraviolet light irradiation.

[0025] Figure 6 Bar graphs showing the concentration of H read from the SIMS profiles in the hole supply layer, electron blocking layer, light-emitting layer, and n-type contact layer of the light-emitting element, respectively. Figure 5

[0026] Symbol Explanation

[0027] 1 Light-emitting element

[0028] 10 Substrate

[0029] 11 Buffer layer

[0030] 12 n-type contact layer

[0031] 13 Light-emitting layer

[0032] 14 Electron blocking layer

[0033] 15 Hole supply layer

[0034] 16 p-type contact layer

[0035] 17 p-electrode

[0036] 18 n-electrode Detailed Description of the Invention

[0037] (Configuration of the light-emitting element)

[0038] Figure 1 This is a vertical cross-sectional view of the 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).

[0039] The light-emitting element 1 includes: a substrate 10, a buffer layer 11 on the substrate 10, an n-type contact layer 12 on the buffer layer 11, a light-emitting layer 13 on the n-type contact layer 12, an electron blocking layer 14 on the light-emitting layer 13, a hole supply layer 15 on the electron blocking layer 14, a p-type contact layer 16 on the hole supply layer 15, a p-electrode 17 connected to the p-type contact layer 16, and an n-electrode 18 connected to the n-type contact layer 12.

[0040] It should be noted that "on" in the configuration of the light-emitting element 1 refers to "on" when the light-emitting element 1 is placed in the direction shown, and means the direction from the substrate 10 toward the p-electrode 17. Figure 1

[0041] The substrate 10 is a growth substrate made of sapphire. The thickness of the substrate 10 is, for example, 400 to 1000 μm. As the material of the substrate 10, in addition to sapphire, AlN, Si, SiC, ZnO, etc. can also be used.

[0042] The buffer layer 11 has, for example, a structure formed by laminating three layers, namely, a nucleation layer, a low-temperature buffer layer, and a high-temperature buffer layer, in this order. The nucleation layer is formed of undoped AlN grown at a low temperature and serves as a nucleus for crystal growth. The thickness of the nucleation layer is, for example, 10 nm. The low-temperature buffer layer is a layer formed of undoped AlN grown at a temperature higher than that of the nucleation layer. The thickness of the low-temperature buffer layer is, for example, 0.3 μm. The high-temperature buffer layer is a layer formed of undoped AlN grown at a temperature higher than that of the low-temperature buffer layer. The thickness of the high-temperature buffer layer is, for example, 2.7 μm. By providing such a buffer layer 11, it is possible to reduce the density of threading dislocations in AlN and prevent cracks.

[0043] The n-type contact layer 12 is composed of n-type AlGaInN containing a donor such as Si and is typically composed of AlGaN. In order to suppress the absorption of light emitted from the light-emitting layer 13 by the n-type contact layer 12, it is preferable that the bandgap of the n-type contact layer 12 is higher than the bandgap of the light-emitting layer 13 (the bandgap of the well layer in the case of having an MQW structure). For example, when the n-type contact layer 12 and the light-emitting layer 13 are composed of AlGaN, it is preferable that the Al composition of the n-type contact layer 12 is higher than the Al composition of the light-emitting layer 13 (the Al composition of the well layer in the case of having an MQW structure), and for example, it is preferably in the range of 50% to 75% or less. In this case, ideally, the n-type contact layer 12 has a composition represented by Al x Ga 1-x N(0.5 ≤ x ≤ 0.75). It should be noted that the percentage of the above Al composition is the ratio of the content of Al to the total value of the content of Ga and the content of Al.

[0044] Here, AlGaInN is a nitride semiconductor which is a compound of Al, Ga, or In as group IIIA elements and N. In AlGaInN, there is a tendency that the higher the Al composition, the larger the bandgap, and the higher the In composition, the smaller the bandgap.

[0045] The light-emitting layer 13 is composed of AlGaInN and preferably has a multi-quantum well (MQW) structure. The emission wavelength of the light-emitting layer 13 is 306 nm or less, and the composition of the light-emitting layer 13 (the composition of the well layer in the case of having an MQW structure) can be set according to the desired emission wavelength of 306 nm or less. For example, when the light-emitting layer 13 is composed of AlGaN and the emission wavelength is 270 to 290 nm, the Al composition is set to approximately 35 to 50%.

[0046] For example, the light-emitting layer 13 has a MQW structure with two well layers, that is, 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 sequence. The first well layer and the second well layer are composed of n-type AlGaN. The first barrier layer, the second barrier layer, and the third barrier layer are composed of n-type AlGaN with an Al composition higher than that of the first well layer and the second well layer (including the case where the Al composition is 100%, that is, AlN).

[0047] As an example, the Al composition, thickness, and concentration of Si as a dopant of the first well layer and the second well layer are 40%, 2.4 nm, and 9×10 18 cm -3 . In addition, the Al composition, thickness, and concentration of Si as a dopant of the first barrier layer and the second barrier layer are 55%, 19 nm, and 9×10 18 cm -3 . In addition, the Al composition, thickness, and concentration of Si as a dopant of the third barrier layer are 55%, 4 nm, and 5×10 18 cm -3 .

[0048] The electron blocking layer 14 is a layer for suppressing the diffusion of electrons to the p-type contact layer 16 side, and is composed of p-type AlGaInN containing Mg as an acceptor. The Mg concentration of the electron blocking layer 14 is, for example, 1×10 18 ~5×10 20 cm -3 .

[0049] In addition, in order to suppress the absorption of light emitted from the light-emitting layer 13 by the electron blocking layer 14, it is preferable that the bandgap of the electron blocking layer 14 is higher than the bandgap of the light-emitting layer 13 (the bandgap of the well layer in the case of having a MQW structure). For example, when the electron blocking layer 14 and the light-emitting layer 13 are composed of AlGaN, it is preferable that the Al composition of the electron blocking layer 14 is higher than the Al composition of the light-emitting layer 13 (the Al composition of the well layer in the case of having a MQW structure). Typically, it is preferable to have an Al composition of 80% or more (including 100%). The thickness of the electron blocking layer 14 is, for example, 1 to 50 nm.

[0050] The hole supply layer 15 is composed of p-type AlGaInN containing Mg as an acceptor. The Mg concentration of the hole supply layer 15 is, for example, 1×10 18 ~1×10 21 cm -3 . In addition, typically, the hole supply layer 15 is composed of AlGaN having an Al composition higher than that of the light-emitting layer 13 and lower than that of the electron blocking layer 14. The thickness of the hole supply layer 15 is, for example, 10 to 100 nm.

[0051] The p-type contact layer 16 is composed of p-type AlGaInN containing Mg as an acceptor. For the p-type contact layer 16, in order to improve the contact with the p-electrode 17, AlGaInN with a low Al composition (including GaInN, GaN) is sometimes used as the material. The Mg concentration in the p-type contact layer 16 is, for example, 1×10 19 ~5×10 21 cm -3 . The thickness of the p-type contact layer 16 is, for example, 5 to 30 nm.

[0052] The p-electrode 17 is composed of materials such as ITO, IZO, ZnO, Al, Rh, Ag that can make an ohmic contact with the p-type contact layer 16. In addition, the n-electrode 18 is composed of materials such as Ti / Al, V / Al that can make an ohmic contact with the n-type contact layer 12.

[0053] (Problems caused by hydrogen in the p-type layer)

[0054] In the state just after the formation of the electron blocking layer 14, hole supply layer 15, and p-type contact layer 16 as the p-type layer, hydrogen contained in nitrogen, Mg as an acceptor, and source gas in AlGaInN bonds to form Mg-N-H bonds. Mg contained in the Mg-N-H bonds hinders the function as an acceptor. Therefore, the formation of Mg-N-H bonds increases the resistance of the p-type layer and increases the initial forward voltage (V F ) of the light-emitting element 1.

[0055] In addition, when the light-emitting element 1 is operated in this state just after film formation, light with a wavelength of 306 nm or less emitted from the light-emitting layer 13 has an energy of 4.1 eV or more, which is the bond energy of the N-H bond. Therefore, the bond of N-H in the Mg-N-H bond is broken, and free hydrogen that can move to the light-emitting layer 13 is generated. Then, due to the forward voltage of a magnitude equal to or higher than the threshold voltage applied for the operation of the light-emitting element 1, the hydrogen with the N bond broken is attracted to the n-electrode 18 side, and point defects are generated through the light-emitting layer 13, causing a decrease in the output of the light-emitting element 1. In addition, heat generated by the p-type layer absorbing the light emitted from the light-emitting layer 13 also promotes the breaking of the N-H bond and the movement of the hydrogen with the bond broken.

[0056] In particular, the p-type layer composed of AlGaInN with a high Al composition easily generates a large amount of free hydrogen that can move to the light-emitting layer 13 for the following reasons, and it is difficult to extract hydrogen by heat treatment or the like.

[0057] The p-type layer composed of AlGaInN with a high Al content has a large bandgap, making it difficult to absorb the light emitted from the light-emitting layer 13. Therefore, the light reaches the entire p-type layer, cutting the N-H bonds in the Mg-N-H bonds throughout the p-type layer. As a result, there are a particularly large number of free hydrogens that can move toward the light-emitting layer 13. Additionally, Al has a stronger ability to hold H than Ga, so it is difficult to extract hydrogen from the p-type layer composed of AlGaInN with a high Al content. If the temperature of the heat treatment for hydrogen extraction is increased, hydrogen can be extracted more effectively. However, in practice, an upper limit on the heat treatment temperature is set to suppress the damage to the light-emitting element 1 caused by heat. Therefore, hydrogen tends to remain in the AlGaInN with a high Al composition.

[0058] In the light-emitting element 1 according to this embodiment, the electron blocking layer 14, the hole supply layer 15, and the p-type contact layer 16 correspond to the p-type layer, and among them, the electron blocking layer 14 has the highest Al composition. For example, when the electron blocking layer 14 is composed of AlGaN with an Al composition of 80% or more, it is particularly difficult to extract hydrogen from the p-type layer. Therefore, the method for extracting hydrogen of the present invention is particularly effective.

[0059] (Manufacturing method of light-emitting element)

[0060] Hereinafter, an example of the manufacturing method of the light-emitting element 1 according to the embodiment of the present invention will be described. In the formation of each layer of the light-emitting element 1 using the vapor growth method, for example, trimethylgallium, trimethylaluminum, and ammonia are used as the Ga source gas, Al source gas, and N source gas, respectively. Additionally, silane gas and bis(cyclopentadienyl)magnesium gas are used as the source gases for the n-type dopant Si and the p-type dopant Mg, respectively. Further, for example, hydrogen and nitrogen are used as the carrier gas.

[0061] First, a substrate 10 is prepared, and a buffer layer 11 is formed thereon. In the formation of the buffer layer 11, first, a core layer composed of AlN is formed by the MOVPE method. The growth temperature is, for example, 880°C. The core layer can also be formed by sputtering. Then, on the core layer, a low-temperature buffer layer and a high-temperature buffer layer composed of AlN are sequentially formed by the MOVPE method. The growth conditions of the low-temperature buffer layer are, for example, a growth temperature of 1090°C and a growth pressure of 50 mbar. Additionally, the growth conditions of the high-temperature buffer layer are, for example, a growth temperature of 1270°C and a growth pressure of 50 mbar.

[0062] Next, on the buffer layer 11, an n-type contact layer 12 composed of AlGaN containing Si is formed by the MOVPE method. The growth conditions of the n-type contact layer 12 are, for example, a growth temperature of 980°C and a growth pressure of 50 to 100 mbar.

[0063] Next, on the n-type contact layer 12, the light-emitting layer 13 is formed by MOVPE method. The formation of the light-emitting layer 13 is carried out by laminating the first barrier layer, the first well layer, the second barrier layer, the second well layer, and the third barrier layer in sequence. The growth conditions of the light-emitting layer 13 are, for example, a growth temperature of 975 °C and a growth pressure of 400 mbar.

[0064] Next, on the light-emitting layer 13, the electron blocking layer 14 is formed by MOVPE method. The growth conditions of the electron blocking layer 14 are, for example, a growth temperature of 975 °C and a growth pressure of 400 mbar.

[0065] Next, on the electron blocking layer 14, the hole supply layer 15 is formed by MOVPE method. The growth conditions of the hole supply layer 15 are, for example, a growth temperature of 1000 - 1100 °C and a growth pressure of 50 mbar.

[0066] Next, on the hole supply layer 15, the p-type contact layer 16 is formed by MOVPE method. The growth conditions of the p-type contact layer 16 are, for example, a growth temperature of 980 °C and a growth pressure of 50 mbar.

[0067] Next, a dry etching is performed on a specified region of the surface of the p-type contact layer 16 to form a groove with a depth reaching the n-type contact layer 12.

[0068] Next, the p electrode 17 is formed on the p-type contact layer 16, and the n electrode 18 is formed on the n-type contact layer 12 exposed on the bottom surface of the groove. The p electrode 17 and the n electrode 18 can be formed by sputtering, evaporation, etc.

[0069] Next, by the method shown below, hydrogen contained in the p-type layers, namely the electron blocking layer 14, the hole supply layer 15, and the p-type contact layer 16, is extracted outside the light-emitting element 1.

[0070] Between the p electrode 17 and the n electrode 18 of the light-emitting element 1, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the light-emitting element 1 (for example, 2 V) is applied, or in a state where no voltage is applied, ultraviolet light with a wavelength of 306 nm or less is irradiated from the outside, and heat treatment is performed to extract hydrogen in the p-type layers, namely the electron blocking layer 14, the hole supply layer 15, and the p-type contact layer 16, outside the light-emitting element 1.

[0071] The reason for extracting hydrogen in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the light-emitting element 1 is applied, or in a state where no voltage is applied, is that: if a voltage equal to or higher than the threshold voltage of the light-emitting element 1 is applied, hydrogen with the bond to N broken in the Mg-N-H bond is attracted to the n electrode 18 side and toward the light-emitting layer 13. Here, by applying a reverse voltage, hydrogen with the bond to N broken is pulled to the p electrode 17 side, and extraction can be carried out more reliably without passing through the light-emitting layer 13.

[0072] In addition, the ultraviolet light with a wavelength of 306 nm or less is irradiated because light with an energy of 4.1 eV or more, which is the bond energy of the N-H bond, will break the N-H bond in the Mg-N-H bond. In addition, if the ultraviolet light is absorbed by other layers before reaching the p-type layer, hydrogen cannot be effectively extracted. Therefore, a wavelength with a bandwidth that the ultraviolet light will not be absorbed by the layers through which it passes until it reaches the p-type layer is preferred.

[0073] For example, as described above, for the p-type contact layer 16, in order to improve the contact with the p-electrode 17, AlGaN with a low Al composition (including GaN) is sometimes used as the material. In this case, the bandgap is usually smaller than that of the substrate 10 and the layers (buffer layer 11 and n-type contact layer 12) located between the substrate 10 and the light-emitting layer 13. Therefore, in order to avoid the absorption of ultraviolet light caused by the p-type contact layer 16, it is preferred to irradiate the ultraviolet light from the substrate 10 side. In addition, in this case, in order to suppress the absorption caused by the substrate 10 and the layers located between the substrate 10 and the light-emitting layer 13, ultraviolet light with an energy lower than the bandgap of the substrate 10 and the layers located between the substrate 10 and the light-emitting layer 13 is irradiated.

[0074] In addition, the heat treatment is carried out to promote the breaking of the N-H bond in the Mg-N-H bond and the movement of the hydrogen that has broken the bond with N to the p-type layer. The reason for carrying out the hydrogen extraction process in an N2 atmosphere at 650 °C or higher, or in an N2 + O2 atmosphere at 500 °C or higher, is that hydrogen can be effectively extracted even when the p-type layer contains a layer such as the electron blocking layer 14 composed of AlGaN with an Al composition of 80% or more. By carrying out the hydrogen extraction process in an N2 atmosphere without hydrogen, hydrogen can be effectively extracted. In particular, by carrying out the process in an N2 atmosphere at 650 °C or higher, hydrogen can be extracted more effectively. In addition, if oxygen is contained in the atmosphere, the interfacial energy of the crystal surface (the surface of the p-type contact layer 16) will be reduced, and hydrogen is easily extracted. Therefore, when the hydrogen extraction process is carried out in an N2 + O2 atmosphere, hydrogen can be extracted more effectively under the temperature condition of 500 °C or higher.

[0075] It should be noted that the light-emitting element to which the method for extracting hydrogen from the p-type layer of the present invention can be applied is not limited to the light-emitting element 1 according to this embodiment, and can also be applied to light-emitting elements having other configurations. That is, according to the present invention, a method for manufacturing a light-emitting element can be provided, the light-emitting element including a light-emitting layer that emits light with a wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; including the following steps: a step of forming a light-emitting element having the above-mentioned light-emitting layer and the above-mentioned p-type layer; for the above-mentioned light-emitting element, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the above-mentioned light-emitting element is applied, or in a state where no voltage is applied, ultraviolet light with a wavelength of 306 nm or less is irradiated from the outside, heat treatment is performed, and hydrogen in the above-mentioned p-type layer is extracted outside the above-mentioned light-emitting element; the step of extracting H in the p-type layer outside the above-mentioned light-emitting element is performed in an N2 atmosphere at 650 °C or higher, or in an N2 + O2 atmosphere at 500 °C or higher.

[0076] In addition, the method for extracting hydrogen from the p-type layer of the present invention can be independently implemented for a manufactured light-emitting element without being a part of the manufacturing process. That is, according to the present invention, a method for extracting hydrogen from a light-emitting element can be provided, the light-emitting element including a light-emitting layer with a light-emitting wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; including the following steps: for the above-mentioned light-emitting element, in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the above-mentioned light-emitting element is applied, or in a state where no voltage is applied, ultraviolet light with a wavelength of 306 nm or less is irradiated from the outside, heat treatment is performed, and hydrogen in the above-mentioned p-type layer is extracted outside the above-mentioned light-emitting element; the step of extracting hydrogen in the p-type layer outside the above-mentioned light-emitting element is performed in an N2 atmosphere at 650 °C or higher, or in an N2 + O2 atmosphere at 500 °C or higher.

[0077] (Effect of the embodiment)

[0078] According to the above embodiment of the present invention, hydrogen is extracted from the p-type layer composed of a nitride semiconductor without passing through the light-emitting layer, thereby preventing a decrease in the output of the light-emitting element. In addition, even when the p-type layer is composed of a nitride semiconductor with a high Al content, hydrogen can be effectively extracted.

[0079] Examples

[0080] Hereinafter, verification results of the influence of hydrogen in the p-type layer on the output of the light-emitting element 1 in a light-emitting element 1 that emits light with a wavelength of 306 nm or less and has an N-H bond energy of 4.1 eV or more are shown. Table 1 below shows the configuration of the light-emitting element 1 used in this verification.

[0081] [Table 1]

[0082]

[0083] The light-emitting element 1 according to this embodiment having the configuration of Table 1 has a light-emitting wavelength of 280 nm included in the UVC wavelength region. In addition, in this embodiment, as a comparative example, a light-emitting element having a light-emitting wavelength of 340 nm included in the UVA wavelength region (as the light-emitting element A) was used.

[0084] Figure 2 It is a chart showing the emission spectra of the light-emitting element with a light-emitting wavelength of 280 nm and the light-emitting element A with a light-emitting wavelength of 340 nm before and after aging (applying a forward voltage of 9 V for 100 hours).

[0085] Figure 2 In, "UVC" represents the emission spectrum of the light-emitting element 1, and "UVA" represents the emission spectrum of the light-emitting element A. In addition, the spectra represented by the respective dotted lines are the spectra measured before aging, and the spectra represented by the solid lines are the spectra measured after aging.

[0086] According to Figure 2 , the intensity of the emission spectrum of the light-emitting element A hardly changes before and after aging. It is considered that this is because: the light-emitting wavelength of the light-emitting element A is 340 nm, and its energy is lower than the bond energy of N-H, which is 4.1 eV. Therefore, the N-H bond in the Mg-N-H bond is not broken, and there is almost no hydrogen moving to the light-emitting layer.

[0087] On the other hand, according to Figure 2 , the intensity of the emission spectrum of the light-emitting element 1 decreases after aging. It is considered that this is because: the light-emitting wavelength of the light-emitting element 1 is 280 nm, and its energy is higher than the bond energy of N-H, which is 4.1 eV. Therefore, the N-H bond in the Mg-N-H bond is broken, and the hydrogen with the broken bond moves to the light-emitting layer 13 due to the forward voltage applied to the light-emitting element 1 and the like.

[0088] Figure 3 (a) is a chart showing the secondary ion mass spectrometry (SIMS) distributions of Al, Mg, Si, and H of the light-emitting element A before and after aging. In addition, Figure 3 (b) is a chart showing the SIMS distributions of Al, Mg, Si, and H of the light-emitting element 1 before and after aging.

[0089] Figure 3 For each of the elements in (a) and (b), the distributions represented by the dotted lines are the distributions measured before aging, and the distributions represented by the solid lines are the distributions measured after aging.

[0090] Figure 3The ranges indicated by "12", "13", "14", and "15" in (b) respectively correspond to the ranges of the n-type contact layer 12, the light-emitting layer 13, the electron blocking layer 14, and the hole supply layer 15, and they can be confirmed by changes in the concentrations of Al, Si, and Mg. Figure 3 "12", "13", "14", and "15" in (a) respectively correspond to an AlGaN layer with an Al composition of 20 to 30% corresponding to the n-type contact layer 12, a MQW structure with an AlGaN layer having an Al composition of 7.5% as a well layer corresponding to the light-emitting layer 13, an AlGaN layer with an Al composition of 50% corresponding to the electron blocking layer 14, and an AlGaN layer with an Al composition of 20 to 30% corresponding to the hole supply layer 15.

[0091] According to Figure 3 (a), before and after aging, the concentration of H hardly changes. This means that hardly any movement of hydrogen caused by the light emission of the light-emitting element A occurs. It can be considered that this is because: the light emitted by the light-emitting element A does not break the N-H bond in the Mg-N-H bond in the p-type layer, and hydrogen does not move from the p-type layer.

[0092] On the other hand, according to Figure 3 (b), after aging, the H concentration in the electron blocking layer 14 as the p-type layer decreases, and the H concentration in the n-type contact layer 12 increases. This means that due to the light emission of the light-emitting element 1, hydrogen in the electron blocking layer 14 moves to the n-type contact layer 12 side through the light-emitting layer 13. It can be considered that this is because: the light emitted by the light-emitting element 1 breaks the N-H bond in the Mg-N-H bond in the electron blocking layer 14, and the hydrogen with the bond broken moves toward the n electrode 18 due to the forward voltage applied to the light-emitting element 1, etc.

[0093] Figure 4 To represent the concentration of H (cm Figure 3 ) read from the SIMS distribution of the hole supply layer 15, the electron blocking layer 14, the light-emitting layer 13 to the n-type contact layer 12 in the light-emitting element 1. -2 ) of a bar graph. Figure 4 "a" shown represents the concentration before aging, and "b" represents the concentration after aging.

[0094] Next, the verification results of the effect of the method for extracting hydrogen from the p-type layer according to the present invention in the light-emitting element 1 that emits light with a wavelength of 306 nm or less having an N-H bond energy of 4.1 eV or more are shown. Table 2 below shows the constitution of the light-emitting element 1 used in this verification. It should be noted that in this verification, the light-emitting element 1 in the state of the wafer before slicing is used.

[0095] [Table 2]

[0096]

[0097] Figure 5 A chart showing the SIMS distributions of Al, Mg, Si, and H of the light-emitting element 1 representing the state just after manufacturing, the state after heat treatment at 550 °C in an air atmosphere, and the state after heat treatment at 550 °C in an air atmosphere and ultraviolet light irradiation with a peak wavelength of 280 nm.

[0098] Figure 5 For each of the elements, the distribution indicated by the dotted line is the distribution measured just after manufacturing, the distribution indicated by the dashed line is the distribution measured after heat treatment, and the distribution indicated by the solid line is the distribution measured after heat treatment and ultraviolet light irradiation. It should be noted that the above heat treatment and ultraviolet light irradiation are carried out in a state where no voltage is applied to the light-emitting element 1.

[0099] Figure 5 The ranges indicated by "12", "13", "14", and "15" correspond to the n-type contact layer 12, the light-emitting layer 13, the electron blocking layer 14, and the hole supply layer 15, respectively, and they can be confirmed by changes in the concentrations of Al, Si, and Mg.

[0100] According to Figure 5 , after the heat treatment, the H concentration in the p-type layer, i.e., the electron blocking layer 14 and the hole supply layer 15, decreases, and further decreases after the heat treatment and ultraviolet light irradiation. In addition, no increase in the H concentration in the light-emitting layer 13 and the n-type contact layer 12 is observed. It is considered that this is because: through the heat treatment, the N-H bond in the Mg-N-H bond in the p-type layer is broken, and the hydrogen that is broken from the bond with N does not pass through the light-emitting layer 13 and moves toward the p-electrode 17 side, and thus is extracted. In addition, by using heat treatment and ultraviolet light irradiation in combination, hydrogen can be extracted more effectively.

[0101] It should be noted that the difference in the H concentration between only after the heat treatment and after the heat treatment and ultraviolet light irradiation is not large because: in the case of the apparatus used for the measurement of the SIMS distribution involved in Figure 5 , ultraviolet light with a sufficient light amount cannot be irradiated. If ultraviolet light with a sufficient light amount is irradiated, the H concentration in the p-type layer can be further significantly reduced. In addition, as described above, the process of extracting hydrogen is carried out in an air atmosphere. However, if it is carried out in a N2 atmosphere at 650 °C or higher, or in a N2+O2 atmosphere at 500 °C or higher, the H concentration in the p-type layer can be further significantly reduced both in the case of only heat treatment and in the case of heat treatment and ultraviolet light irradiation.

[0102] Figure 6 To show the hole supply layer 15, the electron blocking layer 14, and the light-emitting layer 13 to the n-type contact layer 12 of the light-emitting element 1, respectively, from Figure 5Concentration of H read by SIMS distribution (cm -2 ). Bar graph.

[0103] Figure 6 As shown, "c" is the concentration just after manufacturing, "d" is the concentration after heat treatment at 550 °C in an air atmosphere, and "e" is the concentration after heat treatment at 550 °C in an air atmosphere and ultraviolet light irradiation with a peak wavelength of 280 nm.

[0104] The embodiments and examples of the present invention have been described above. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made without departing from the gist of the present invention. In addition, within the scope not departing from the gist of the present invention, the constituent elements of the above embodiments and examples can be arbitrarily combined.

[0105] In addition, the above-described embodiments and examples do not limit the invention related to the scope of protection claimed. It should be noted that, for the means for solving the problems of the invention, the combination of the features described in the embodiments and examples is not necessarily required.

Claims

1. A method for manufacturing a light-emitting element, the light-emitting element including a light-emitting layer having a light-emitting wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; The manufacturing method includes the following steps: A step of forming the light-emitting element including the light-emitting layer and the p-type layer, and A step of irradiating ultraviolet light having a wavelength of 306 nm or less from the outside to the light-emitting element in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the light-emitting element is applied, or in a state where no voltage is applied, performing heat treatment, and extracting hydrogen in the p-type layer outside the light-emitting element; Performing the step of extracting hydrogen in the p-type layer outside the light-emitting element in an N2 atmosphere at 650 °C or higher or an N2+O2 atmosphere at 500 °C or higher, The light-emitting element has a substrate, an n-type layer on the substrate, the light-emitting layer on the n-type layer, the p-type layer on the light-emitting layer, and a p-contact layer on the p-type layer, The band gap of the p-contact layer is smaller than the band gaps of the substrate and the layer between the substrate and the light-emitting layer, In the step of extracting hydrogen in the p-type layer outside the light-emitting element, the ultraviolet light having an energy lower than the band gaps of the substrate and the layer between the substrate and the light-emitting layer is irradiated to the light-emitting element from the substrate side.

2. The manufacturing method of the light-emitting element according to claim 1, wherein, In the step of extracting hydrogen in the p-type layer outside the light-emitting element, a reverse voltage is applied to the light-emitting element.

3. The manufacturing method of the light-emitting element according to claim 1 or 2, wherein, The AlGaInN constituting the p-type layer is AlGaN having an Al composition of 80% or more and not containing In.

4. A method for extracting hydrogen from a light-emitting element, the light-emitting element including a light-emitting layer having a light-emitting wavelength of 306 nm or less and a p-type layer composed of AlGaInN containing Mg as an acceptor; The extraction method includes the following steps: A step of irradiating ultraviolet light having a wavelength of 306 nm or less from the outside to the light-emitting element in a state where a reverse voltage or a forward voltage lower than the threshold voltage of the light-emitting element is applied, or in a state where no voltage is applied, performing heat treatment, and extracting hydrogen in the p-type layer outside the light-emitting element; Performing the step of extracting hydrogen in the p-type layer outside the light-emitting element in an N2 atmosphere at 650 °C or higher or an N2+O2 atmosphere at 500 °C or higher, The light-emitting element has a substrate, an n-type layer on the substrate, the light-emitting layer on the n-type layer, the p-type layer on the light-emitting layer, and a p-contact layer on the p-type layer; The band gap of the p-contact layer is smaller than the band gaps of the substrate and the layer between the substrate and the light-emitting layer; In the step of extracting hydrogen in the p-type layer outside the light-emitting element, the ultraviolet light having an energy lower than the band gaps of the substrate and the layer between the substrate and the light-emitting layer is irradiated to the light-emitting element from the substrate side.

5. The method for extracting hydrogen from the light-emitting element according to claim 4, wherein, In the step of extracting hydrogen in the p-type layer outside the light-emitting element, a reverse voltage is applied to the light-emitting element.

6. The method for extracting hydrogen from the light-emitting element according to claim 4 or 5, wherein, The AlGaInN that constitutes the p-type layer is AlGaN with an Al composition of 80% or more and no In.

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