Nitride semiconductor light emitting element

Abstract

To provide a nitride semiconductor light emitting element that can be driven at a low current and has a reduced forward voltage.SOLUTION: A semiconductor device includes: a first n-type semiconductor layer containing an n-type impurity; a first p-type semiconductor layer disposed on the first n-type semiconductor layer and containing a p-type impurity; an active layer disposed on the first p-type semiconductor layer and having a hole; an intermediate layer disposed on the active layer and made of a semiconductor containing substantially no n-type impurities; a second n-type semiconductor layer disposed on the intermediate layer and containing an n-type impurity; a first electrode electrically connected to the first n-type semiconductor layer; and a second electrode electrically connected to the second n-type semiconductor layer. The intermediate layer covers at least an inner lateral surface of the hole.

Description

[Technical Field]

[0001] The present disclosure relates to nitride semiconductor light emitting devices. [Background technology]

[0002] As the applications of nitride semiconductor light-emitting devices expand, improvements in light-emitting efficiency are being demanded, and the light-emitting device disclosed in Patent Document 1 is said to be capable of being driven with a low current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2020-501345 Summary of the Invention [Problem to be solved by the invention]

[0004] However, nitride semiconductor light emitting devices are required to be driven at low current and have a reduced forward voltage.

[0005] Therefore, an object of the present disclosure is to provide a nitride semiconductor light emitting device that can be driven at a low current and has a reduced forward voltage. [Means for solving the problem]

[0006] In order to achieve the above object, the nitride semiconductor light emitting device according to the present disclosure comprises: a first n-type semiconductor layer containing n-type impurities; a first p-type semiconductor layer disposed on the first n-type semiconductor layer and containing p-type impurities; an active layer disposed on the first p-type semiconductor layer and having a hole; an intermediate layer disposed on the active layer and made of a semiconductor containing substantially no n-type impurities; a second n-type semiconductor layer disposed on the intermediate layer and containing n-type impurities; a first electrode electrically connected to the first n-type semiconductor layer; a second electrode electrically connected to the second n-type semiconductor layer; Including, The intermediate layer covers at least the inner surface of the hole. [Effects of the Invention]

[0007] According to the nitride semiconductor light emitting device configured as described above, it is possible to provide a nitride semiconductor light emitting device that can be driven at a low current and that can reduce the forward voltage. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a nitride semiconductor light-emitting element according to a first embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a part of FIG. [Figure 3] 2 is an enlarged cross-sectional view showing another part of FIG. 1. FIG. [Figure 4] FIG. 4 is a cross-sectional view of the nitride semiconductor light-emitting element of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments and examples for carrying out the present disclosure will be described with reference to the drawings. Note that the nitride semiconductor light-emitting device and the method for manufacturing the nitride semiconductor light-emitting device described below are intended to embody the technical concept of the present disclosure, and unless otherwise specified, the present disclosure is not limited to the following. In each drawing, components having the same function may be assigned the same symbol. For convenience, the embodiments and examples may be shown separately to facilitate explanation or understanding of the main points, but partial substitution or combination of the configurations shown in different embodiments and examples is possible. In the embodiments and examples described below, descriptions of matters common to the above may be omitted, and only the differences may be described. In particular, similar effects due to similar configurations may not be mentioned sequentially in each embodiment or example. The size and positional relationship of components shown in each drawing may be exaggerated to clarify the explanation.

[0010] As shown in FIG. 1 and other figures, the nitride semiconductor light emitting device of the embodiment according to the present disclosure includes: a first n-type semiconductor layer 20 containing n-type impurities; a first p-type semiconductor layer 30 disposed on the first n-type semiconductor layer 20 and containing p-type impurities; an active layer 60 disposed on the first p-type semiconductor layer 30 and having a hole 65; an intermediate layer 70 disposed on the active layer 60 and made of a semiconductor containing substantially no n-type impurities; a second n-type semiconductor layer 80 disposed on the intermediate layer 70 and containing n-type impurities; a first electrode 11 electrically connected to the first n-type semiconductor layer 20; a second electrode 12 electrically connected to the second n-type semiconductor layer 80; Includes. The intermediate layer 70 covers at least the inner surface of the hole 65 as shown in FIG. The nitride semiconductor light-emitting element configured as described above can be driven with a low current and can reduce the forward voltage because the intermediate layer 70 made of a semiconductor that does not substantially contain n-type impurities covers the inner surface of the hole 65. Here, the nitride semiconductor in this specification refers to a binary to quaternary semiconductor containing at least one of aluminum (Al), gallium (Ga), and indium (In) and nitrogen (N), and In x Al y Ga 1-x-y It may include semiconductors of all compositions in which the composition ratios x and y in the chemical formula N (0≦x≦1, 0≦y≦1, x+y≦1) are varied within their respective ranges. Hereinafter, nitride semiconductor light emitting devices according to embodiments of the present disclosure will be described in detail.

[0011] [Embodiment 1] Fig. 1 is a cross-sectional view of the nitride semiconductor light-emitting device of Embodiment 1. Fig. 2 is an enlarged cross-sectional view of a portion of Fig. 1, and Fig. 3 is an enlarged cross-sectional view of another portion of Fig. 1. As shown in FIG. 1, the semiconductor light-emitting element of embodiment 1 includes a substrate 10, and a first n-type semiconductor layer 20, a first p-type semiconductor layer 30, an active layer 60, an intermediate layer 70, and a second n-type semiconductor layer 80 arranged on the substrate 10. Furthermore, the nitride semiconductor light-emitting element of embodiment 1 includes a first electrode 11 electrically connected to the first n-type semiconductor layer 20, for example, by making ohmic contact with the first n-type semiconductor layer 20, and a second electrode 12 electrically connected to the second n-type semiconductor layer 80, for example, by making ohmic contact with the second n-type semiconductor layer 80. In the nitride semiconductor light-emitting device of Embodiment 1 configured as above, a current injected from the first electrode 11 disposed on the first n-type semiconductor layer 20 is injected into the active layer 60 via the first n-type semiconductor layer 20 and the first p-type semiconductor layer 30, causing the active layer 60 to emit light. That is, in the nitride semiconductor light-emitting device of Embodiment 1, the first electrode 11 disposed on the first n-type semiconductor layer 20 is a positive electrode, and the second electrode 12 is a negative electrode. Here, in a preferred embodiment, the semiconductor light-emitting device of embodiment 1 further includes an underlayer 15 arranged between the substrate 10 and the first n-type semiconductor layer 20, and a second intermediate layer 40 and a superlattice layer 50 arranged between the first p-type semiconductor layer 30 and the active layer 60. The first n-type semiconductor layer 20 includes an n-type semiconductor layer 21 having a low concentration of n-type impurities (hereinafter also referred to as low-concentration n-type semiconductor layer 21), and an n-type semiconductor layer 22 (hereinafter also referred to as high-concentration n-type semiconductor layer 22) having a higher concentration of n-type impurities than the low-concentration n-type semiconductor layer 21. The second n-type semiconductor layer 80 includes a third n-type semiconductor layer 81 and a fourth n-type semiconductor layer 82.

[0012] The nitride semiconductor light-emitting device configured as above is manufactured, for example, by growing nitride semiconductor layers on the substrate 10 while appropriately changing the composition, thereby forming the above-mentioned layers. When growing the nitride semiconductor layers in the nitride semiconductor light-emitting device, a starting point is formed inside any layer between the first n-type semiconductor layer 20 and the active layer 60, and a hole 65 is formed from this starting point so as to penetrate the active layer 60. The hole here is, for example, a pit that is V-shaped (conical) in cross section. In the nitride semiconductor light-emitting device shown in FIG. 1 , the holes 65 are formed, for example, as shown in FIG. 3 , starting near the boundary between the second intermediate layer 40 and the superlattice layer 50 and penetrating the active layer 60. As described above, in the nitride semiconductor light-emitting device shown in FIG. 1 , the second electrode 12 is a negative electrode. In a nitride semiconductor light-emitting device configured in this manner, a nitride semiconductor layer having n-type conductivity is usually disposed between the active layer 60 and the second electrode 12, and the inner surfaces of the holes are covered with the nitride semiconductor layer having n-type conductivity. However, the present inventors, through repeated intensive studies to reduce the forward voltage, have discovered that if the inner surfaces of the holes are covered with a nitride semiconductor layer substantially free of n-type impurities, it becomes possible to drive the device with a low current and reduce the forward voltage. The nitride semiconductor element of the embodiment of the present disclosure was made based on the findings uniquely obtained by the inventors of the present application described above, and includes an intermediate layer 70 (hereinafter also referred to as the first intermediate layer) made of a semiconductor that does not substantially contain n-type impurities between the active layer 60 and the second n-type semiconductor layer 80, and the first intermediate layer 70 covers the inner surface of the hole portion 65. The nitride semiconductor element of the embodiment configured as described above can be driven with a low current and can reduce the forward voltage because the first intermediate layer 70 made of a semiconductor that does not substantially contain n-type impurities covers the inner surface of the hole 65.

[0013] The reason why such an effect is obtained is thought to be that the recombination of holes and electrons that do not contribute to light emission in the hole 65 (V pit) and its vicinity can be suppressed, thereby reducing the forward voltage Vf. In other words, if a layer containing n-type impurities is formed on the surface (inner surface) of the hole 65 (V pit) and its vicinity, recombination of holes and electrons that do not contribute to light emission occurs, which is thought to increase the forward voltage Vf. In contrast, if the first intermediate layer 70, which is a layer that does not substantially contain n-type impurities, is formed on the surface (inner surface) of the hole 65 (V pit) and its vicinity, it is believed that the recombination of holes and electrons that do not contribute to light emission can be suppressed. Furthermore, as shown in FIG. 3, holes can be injected into the active layer 60 through the first intermediate layer 70 formed on the surface (inner surface) of the hole 65 (V pit) and its vicinity, contributing to light emission, and it is believed that the forward voltage Vf can be reduced. Such functions and effects can be obtained as long as the first intermediate layer 70 is formed on at least a part of the surface (inner surface) of the hole 65 (V pit). Furthermore, such functions and effects can be obtained even if the first intermediate layer 70 contains p-type impurities. Here, in this specification, "substantially free of n-type impurities" means that the 17 less than the power of 1×10, preferably 1×10 16 In other words, "substantially free of n-type impurities" refers to a layer formed by growing the layer using a source gas that does not contain n-type impurities, and may contain n-type impurities from an adjacent n-type layer due to diffusion or the like. Each layer constituting the nitride semiconductor light emitting device of the first embodiment will be described in detail below.

[0014] <Substrate> The material of the substrate 10 is, for example, sapphire, Si, SiC, GaN, etc. The substrate 10 can be a growth substrate for growing a nitride semiconductor layer.

[0015] <Underlayer> Underlayer 15 is a buffer layer for alleviating lattice mismatch when a nitride semiconductor layer is formed on substrate 10, and is composed of, for example, a GaN layer, an AlGaN layer, an AlN layer, or the like that is substantially free of n-type impurities and p-type impurities. Underlayer 15 may also be composed of a buffer layer for alleviating lattice mismatch when a nitride semiconductor layer is formed on substrate 10, and an undoped GaN layer, an AlGaN layer, an AlN layer, or the like that reduces threading dislocations and pits. The thickness of the underlayer is preferably, for example, 0.5 μm to 8 μm, and more preferably 4 μm to 6 μm.

[0016] <First n-type semiconductor layer 20> The first n-type semiconductor layer 20 can be composed of, for example, a nitride semiconductor layer containing n-type impurities such as silicon (Si) or germanium (Ge). For example, when the active layer 60 is composed of a nitride semiconductor layer containing In, the nitride semiconductor constituting the first n-type semiconductor layer 20 may be, for example, an n-type GaN layer and may contain In, Al, etc. Furthermore, when the active layer 60 is composed of a nitride semiconductor containing Al, the nitride semiconductor constituting the first n-type semiconductor layer 20 may be, for example, an n-type AlGaN layer and may further contain In. The first n-type semiconductor layer 20 may include one or more n-type nitride semiconductor layers. In the nitride semiconductor light-emitting device of the first embodiment, the first n-type semiconductor layer 20 includes a low-concentration n-type semiconductor layer 21 and a high-concentration n-type semiconductor layer 22. The high-concentration n-type semiconductor layer 22 may include, for example, 8×10 Si as an n-type impurity. 19 Over 8 x 10 20 / cm 3 The heavily doped n-type semiconductor layer 22 is a nitride semiconductor layer doped at a relatively high concentration of, for example, 8×10 Si. 19 Over 8 x 10 20 / cm 3 It is made of n-type GaN doped at a relatively high concentration as follows, for example, with a thickness of 1 nm to 10 nm. The low-concentration n-type semiconductor layer 21 is, for example, a layer on which the first electrode 11 is formed. In order to enable good ohmic contact with the first electrode 11, for example, Si, which is an n-type impurity, is doped at a concentration of 1×10 18 cm -3 5x10 or more 19 cm -3 The low concentration n-type semiconductor layer 21 preferably contains, for example, 1×10 Si, which is an n-type impurity. 18 cm -3 5x10 or more 19 cm -3 It can be composed of an n-type GaN layer including: The first n-type semiconductor layer 20 may include a portion of an undoped semiconductor layer. Here, an undoped semiconductor layer refers to a layer to which n-type impurities and p-type impurities are not intentionally added. The total thickness of the first n-type semiconductor layer 20 is, for example, 5 μm or more and 15 μm or less.

[0017] <First p-type semiconductor layer 30> The first p-type semiconductor layer 30 can be composed of, for example, a nitride semiconductor layer containing p-type impurities such as magnesium (Mg) or zinc (Zn). For example, when the active layer 60 is composed of a nitride semiconductor layer containing In, the nitride semiconductor constituting the first p-type semiconductor layer 30 may be, for example, a p-type GaN layer and may contain In, Al, etc. Furthermore, when the active layer 60 is composed of a nitride semiconductor containing Al, the nitride semiconductor constituting the first p-type semiconductor layer 30 may be, for example, a p-type AlGaN layer and may further contain In. The first p-type semiconductor layer 30 may include one or more p-type nitride semiconductor layers. For example, the first p-type semiconductor layer 30 may include 8×10 19 Over 8 x 10 20 / cm 3 It is preferable that the first n-type semiconductor layer 20 includes a nitride semiconductor layer doped at a relatively high concentration as follows: the uppermost layer of the first n-type semiconductor layer 20, for example, a layer that forms a tunnel junction with the high-concentration n-type semiconductor layer 22. The layer that forms a tunnel junction in the first p-type semiconductor layer 30 has a Mg content of 8×10 19 Over 8 x 10 20 / cm 3The first p-type semiconductor layer 30 is preferably made of p-type GaN having a thickness of, for example, 10 nm to 25 nm, doped at a relatively high concentration of 1×10 or less. The first p-type semiconductor layer 30 preferably includes a nitride semiconductor layer containing p-type impurities other than the tunnel junction layer, and the p-type impurity concentration of the nitride semiconductor layer containing p-type impurities other than the tunnel junction layer is, for example, 1×10 18 cm -3 Over 2×10 20 cm -3 For example, the p-type impurity Mg is preferably 1×10 18 cm -3 Over 2×10 20 cm -3 The first p-type semiconductor layer 30 may be composed of a p-type GaN layer including the following. The first p-type semiconductor layer 30 may include an undoped semiconductor layer in part. The total thickness of the first p-type semiconductor layer 30 may be, for example, 0.04 μm or more and 0.2 μm or less.

[0018] <Second intermediate layer 40> The second intermediate layer 40 can be composed of a nitride semiconductor layer that is substantially free of n-type impurities and p-type impurities, for example, undoped GaN. This second intermediate layer 40 has the function of repairing deterioration in crystallinity and surface flatness caused by forming a tunnel junction between the first n-type semiconductor layer 20 and the first p-type semiconductor layer 30, and can improve the crystallinity of layers formed on the second intermediate layer 40. The thickness of the second intermediate layer 40 can be, for example, 0.01 μm or more and 0.30 μm or less.

[0019] <Superlattice layer 50> The superlattice layer 50 includes a first layer and a second layer, which are alternately stacked. For example, the lattice constant of the second layer is different from that of the first layer. By disposing the superlattice layer 50 in addition to the second intermediate layer between the first p-type semiconductor layer 30 and the active layer 60, it is possible to reduce the crystal distortion of the active layer 60 due to the difference in lattice constant between the first p-type semiconductor layer 30 and the active layer 60. By reducing the crystal distortion of the active layer 60, it is possible to increase the internal quantum efficiency of the active layer 60. As a result, it is possible to improve the light-emitting efficiency. The compositions of the first and second layers are preferably set in consideration of, for example, the composition or band gap of the active layer 60, or the composition or band gap of the well layer if the active layer 60 has a quantum well structure. For example, if the well layer is composed of an InGaN layer, it is preferable that the first and second layers have a lower In composition ratio than the well layer.

[0020] The first layer and the second layer have different lattice constants, for example, due to different In composition ratios. At least one of the first layer and the second layer is a layer doped with p-type impurities. As described above, doping at least one of the first layer and the second layer with p-type impurities can reduce the forward voltage Vf. The p-type impurity concentration of at least one of the first layer and the second layer is 1×10 18 cm -3 3x10 or more 19 cm -3 Preferably, the concentration of the p-type impurity doped into at least one of the first layer and the second layer is lower than the p-type impurity concentration of the first p-type semiconductor layer 30.

[0021] For example, the In composition ratio of the first layer can be made higher than the In composition ratio of the second layer. In this case, by making the p-type impurity concentration of the first layer higher than the p-type impurity concentration of the second layer, it is easy to reduce the forward voltage Vf. This is thought to be because the tendency for In to be distributed near the top surface of the first layer makes it easy to reduce the surface roughness of the top surface of the first layer, and even if the first layer is doped with p-type impurities, the crystallinity of the superlattice layer 50 is unlikely to deteriorate. When the In composition ratio of the first layer is made larger than that of the second layer and the p-type impurity concentration of the first layer is made larger than that of the second layer, the p-type impurity concentration of the first layer is set to 1×10 18 cm -3 3x10 or more 19 cm -3It is preferable that the p-type impurity concentration of the first layer is within this range. By setting the p-type impurity concentration of the first layer within this range, it is possible to increase the efficiency of supplying holes to the active layer 60 while reducing deterioration in the crystallinity of the superlattice layer 50. In this case, it is preferable that the second layer is an undoped layer. Furthermore, when the In composition ratio of the first layer is made higher than that of the second layer and the p-type impurity concentration of the first layer is made higher than that of the second layer, it is preferable that the thickness of the first layer is thinner than that of the second layer. By making the first layer, which has a relatively high p-type impurity concentration, thinner, deterioration of the crystallinity of the superlattice layer 50 can be reduced. In particular, when the first n-type semiconductor layer 20 and the first p-type semiconductor layer 30 are tunnel junctioned, as will be described later, the impurity concentration at the junction between the first n-type semiconductor layer 20 and the first p-type semiconductor layer 30 becomes high. However, by disposing the superlattice layer 50, the diffusion of impurities into the active layer 60 can be reduced, and the decrease in light-emitting efficiency due to the diffusion of impurities into the active layer 60 can be effectively reduced.

[0022] The nitride semiconductor light-emitting device of embodiment 1 having the superlattice layer 50 configured as described above can reduce the forward voltage Vf and increase the emission intensity relative to the applied voltage by disposing the superlattice layer 50 containing p-type impurities between the first p-type semiconductor layer 30 containing p-type impurities and having p-type conductivity and the active layer 60. Furthermore, the holes 65, which are formed starting from inside the superlattice layer 50, in other words, have their bottoms located in the superlattice layer 50, penetrate the active layer 60 with an appropriate size that allows holes to be efficiently injected into the active layer 60 and contribute to light emission, thereby effectively reducing the forward voltage Vf. The size of the holes 65 in the active layer 60 can be adjusted appropriately by the thickness of the superlattice layer 50, and it is preferable that the overall thickness of the superlattice layer 50 be 45 nm or more and 200 nm or less, for example.

[0023] <Active layer 60> The active layer 60 is, for example, a nitride semiconductor layer that emits light with an emission peak wavelength in the range of 200 nm to 760 nm. The active layer 60 may be, for example, a multiple quantum well structure having multiple well layers and multiple barrier layers, or a single quantum well structure including one well layer and barrier layers on both sides of it. When the active layer 60 is a single or multiple quantum well, the well layers are, for example, GaN, InGaN, or AlGaN, and the barrier layers are, for example, AlGaN or GaN.

[0024] <Intermediate layer 70 (first intermediate layer)> The first intermediate layer 70 is a layer disposed on the active layer 60 so as to cover at least a part of the inner surface of the hole 65 . The first intermediate layer 70 can be composed of, for example, a nitride semiconductor layer that is substantially free of n-type impurities such as silicon (Si) and germanium (Ge). For example, when the active layer 60 is composed of a nitride semiconductor layer containing In, the nitride semiconductor that constitutes the first intermediate layer 70 may be, for example, an i-type GaN layer that contains In and Al. For example, when the active layer 60 is composed of a nitride semiconductor containing Al, the nitride semiconductor that constitutes the first intermediate layer 70 may be, for example, an i-type AlGaN layer that may further contain In. The first intermediate layer 70 may also contain p-type impurities. The first intermediate layer 70 is formed on at least a portion of the inner surface of the hole portion 65 (V pit) and in its vicinity, thereby suppressing the recombination of holes and electrons that do not contribute to light emission, and injecting holes into the active layer 60 through the first intermediate layer 70 to allow them to contribute to light emission, thereby lowering the forward voltage Vf. It is preferable that the first intermediate layer 70 covers the entire inner surface of the hole 65, which more effectively suppresses the recombination of holes and electrons that do not contribute to light emission in the hole 65 and its vicinity, thereby further reducing the forward voltage Vf. The thickness of the first intermediate layer 70 is, for example, 2 nm to 150 nm, preferably 10 nm to 120 nm, and more preferably 40 nm to 80 nm. With such a thickness, holes are supplied from the holes 65 (V pits) into the active layer 60 through the first intermediate layer 70, and the distance between the active layer 60 and the n-type semiconductor layer 80 is also shortened, so that electrons can be supplied efficiently and the forward voltage Vf can be reduced.

[0025] <Second n-type semiconductor layer 80> The second n-type semiconductor layer 80 includes, for example, a nitride semiconductor layer containing an n-type impurity such as silicon (Si). For example, when the active layer 60 is composed of a nitride semiconductor layer containing In, the nitride semiconductor that forms the second n-type semiconductor layer 80 may be, for example, an n-type GaN layer and may contain In, Al, and the like. Furthermore, when the active layer 60 is composed of a nitride semiconductor containing Al, the nitride semiconductor that forms the second n-type semiconductor layer 80 may be, for example, an n-type AlGaN layer and may further contain In. The thickness of the second n-type semiconductor layer 80 can be, for example, 100 nm to 1500 nm, preferably 200 nm to 800 nm, and more preferably 300 nm to 500 nm. When the second n-type semiconductor layer 80 contains Si as an n-type impurity, the impurity concentration of the second n-type semiconductor layer 80 can be, for example, 1×10 18 cm -3 5x10 or more 19 cm -3 It can be as follows:

[0026] The second n-type semiconductor layer 80 may include one or more n-type nitride semiconductor layers, or may partially include an undoped semiconductor layer. Furthermore, as shown in FIG. 1, the second n-type semiconductor layer 80 preferably includes a third n-type semiconductor layer 81 and a fourth n-type semiconductor layer 82 on which the second electrode 12 is disposed. The third n-type semiconductor layer 81 and the fourth n-type semiconductor layer 82 may have the same composition. For example, the third n-type semiconductor layer 81 and the fourth n-type semiconductor layer 82 may be grown using different carrier gases so as to have the same composition. For example, the third n-type semiconductor layer 81 may be grown by metalorganic chemical vapor deposition (MOCVD) using nitrogen gas (N) as a carrier gas, and the fourth n-type semiconductor layer 82 may be grown using hydrogen gas (H) as a carrier gas so as to have the same composition as the third n-type semiconductor layer 81. By growing the third n-type semiconductor layer 81 by metalorganic chemical vapor deposition (MOCVD) using nitrogen gas as a carrier gas, it is possible to easily fill the holes 65 whose inner surfaces are partially or entirely covered with the first intermediate layer 70, and to easily form the third n-type semiconductor layer 81 having a flat surface. By growing the fourth n-type semiconductor layer 82 using hydrogen gas as a carrier gas on the third n-type semiconductor layer 81 grown using nitrogen gas as a carrier gas, it is possible to grow the fourth n-type semiconductor layer 82 having a flatter surface than the third n-type semiconductor layer 81. In other words, the surface roughness of the upper surface of the fourth n-type semiconductor layer 82 can be made smaller than the surface roughness of the upper surface of the third n-type semiconductor layer 81.

[0027] Furthermore, the n-type impurity concentration of fourth n-type semiconductor layer 82 is preferably higher than the n-type impurity concentration of third n-type semiconductor layer 81, which can reduce the contact resistance between fourth n-type semiconductor layer 82 and second electrode 12 and increase the light-emitting efficiency. Furthermore, because the semiconductor layer located near the surface is likely to become p-type due to thermal diffusion of Mg remaining in the furnace and Mg in the semiconductor layer, for example, by making the n-type impurity concentration of fourth n-type semiconductor layer 82 higher than the n-type impurity concentration of third n-type semiconductor layer 81, it can be easily made n-type for fourth n-type semiconductor layer 82.

[0028] <First and second electrodes> The first electrode 11 and the second electrode 12 are electrodes electrically connected to the first n-type semiconductor layer 20 and the second n-type semiconductor layer 60, i.e., the n-type semiconductor layers, and can be made of, for example, a metal such as Au, Pt, Pd, Rh, Ni, W, Mo, Cr, Ti, Al, or Cu, or an alloy containing these metals. The first electrode 11 and the second electrode 12 may have a single-layer structure or a multilayer structure in which multiple layers are stacked. The first electrode 11 and the second electrode 12 can have, for example, a multilayer structure in which a Ti layer, an Al-Si-Cu alloy layer, a Ti layer, a Pt layer, an Au layer, and a Ti layer are stacked in this order.

[0029] [Embodiment 2] FIG. 4 is a cross-sectional view of the nitride semiconductor light-emitting device of the second embodiment. As shown in FIG. 4 , the nitride semiconductor light-emitting device of Embodiment 2 further comprises a second active layer 160 in addition to the nitride semiconductor light-emitting device of Embodiment 1. The second active layer 160 is disposed on the second n-type semiconductor layer 80, and a second p-type semiconductor layer 130 is further disposed on the second active layer 160. The nitride semiconductor light-emitting device of Embodiment 2 also comprises a third electrode 110 electrically connected to the second p-type semiconductor layer 130. Here, the third electrode 110 may include a pad electrode 110b and an electrode layer 110a disposed in contact with the second p-type semiconductor layer 130. In the nitride semiconductor light-emitting device of Embodiment 2, the second electrode 120 is disposed on the second n-type semiconductor layer 80 exposed by removing the second active layer 160 and the second p-type semiconductor layer 130, for example. In addition, the first electrode 11 is disposed on the low-concentration n-type semiconductor layer 21, similar to the nitride semiconductor light-emitting device of Embodiment 1.

[0030] In the nitride semiconductor light-emitting device of Embodiment 2 configured as above, the first electrode 11 functions as a positive electrode for the active layer 60. The third electrode 110 functions as a positive electrode for the second active layer 160. The second electrode 120 functions as a negative electrode for the active layer 60 (hereinafter also referred to as the first active layer 60) and the second active layer 160. In the nitride semiconductor light-emitting device of Embodiment 2, the first active layer 60 can be made to emit light by applying a voltage between the first electrode 11 and the second electrode 120. Furthermore, the second active layer 160 can be made to emit light by applying a voltage between the third electrode 110 and the second electrode 120. In this way, the first active layer 60 and the second active layer 160 can be made to emit light independently. Furthermore, even when the first active layer 60 and the second active layer 160 are caused to emit light simultaneously, the emission intensities of the first active layer 60 and the second active layer 160 can be controlled individually by adjusting the voltage applied between the first electrode 11 and the second electrode 120 and the voltage applied between the third electrode 110 and the second electrode 120. The nitride semiconductor light emitting device of the second embodiment configured as described above can reduce the forward voltage Vf and increase the light emission intensity relative to the applied voltage, similar to the nitride semiconductor light emitting device of the first embodiment.

[0031] In the nitride semiconductor light-emitting device of Embodiment 2 configured as described above, the first active layer 60 and the second active layer 160 may have the same or different peak emission wavelengths. Furthermore, in the nitride semiconductor light-emitting device of Embodiment 2, the second active layer 160 is located above the first active layer 60. Therefore, when the peak emission wavelengths of the first active layer 60 and the second active layer 160 are different, color mixing can be improved. The peak emission wavelength of the first active layer 60 can be made different from the peak emission wavelength of the second active layer 160 by making the composition of the first active layer 60 different from the composition of the second active layer 160. For example, the peak emission wavelength of the first active layer 60 can be made different from the peak emission wavelength of the second active layer 160 by making the In composition ratio of the first active layer 60 different from the In composition ratio of the second active layer 160. Furthermore, for example, in nitride semiconductor light-emitting devices, the luminous efficiency may vary depending on the emission peak wavelength. In the nitride semiconductor light-emitting device of Embodiment 2, as described above, even when the first active layer 60 and the second active layer 160 are simultaneously turned on, the emission intensities of the first active layer 60 and the second active layer 160 can be individually controlled by adjusting the voltage applied between the first electrode 11 and the second electrode 120 and the voltage applied between the third electrode 110 and the second electrode 120. Therefore, in the nitride semiconductor light-emitting device of Embodiment 2, even when the emission peak wavelengths of the first active layer 60 and the second active layer 160 are different, it is possible to emit light of different colors by adjusting the voltage applied between the first electrode 11 and the second electrode 120 and the voltage applied between the third electrode 110 and the second electrode 120.

[0032] Example Hereinafter, examples of the present disclosure will be described. In the following examples, the nitride semiconductor light emitting device of the first embodiment shown in FIG. 1 was fabricated, and the forward voltage Vf was measured to confirm the effect of including the intermediate layer 70. Specifically, a nitride semiconductor light-emitting device according to the embodiment including the intermediate layer 70 and a nitride semiconductor light-emitting device according to the comparative example not including the intermediate layer 70 were fabricated, and the forward voltage Vf of each was measured to confirm the effect of including the intermediate layer 70. Furthermore, in the nitride semiconductor light-emitting device of the example including the intermediate layer 70, the film thicknesses of the intermediate layer 70, the third n-type semiconductor layer 81, and the fourth n-type semiconductor layer 82 were changed, and the forward voltage Vf was measured for each, to confirm the film thickness dependency of the effect.

[0033] In the following examples and comparative examples, the compositions and film thicknesses of the semiconductor layers excluding the intermediate layer 70, the third n-type semiconductor layer 81, and the fourth n-type semiconductor layer 82 are shown in Table 1 below, and the compositions and film thicknesses of the intermediate layer 70, the third n-type semiconductor layer 81, and the fourth n-type semiconductor layer 82 in Examples 1 to 4 are shown in Table 2. Table 2 also shows the measured forward voltage Vf.

[0034] [Table 1]

[0035] [Table 2]

[0036] Here, in Table 2, the (N2) in the intermediate layer 70 (N2) and the third n-type semiconductor layer 81 (N2) indicates that the intermediate layer 70 and the third n-type semiconductor layer 81 were grown using nitrogen gas (N2) as a carrier gas, and the (H2) in the fourth n-type semiconductor layer 82 (H2) indicates that the layer was grown using hydrogen gas (H2) as a carrier gas.

[0037] As shown in Table 2 above, it was confirmed that Examples 1 to 4, which included the intermediate layer 70, all had a lower forward voltage Vf than the comparative example, which did not include the intermediate layer 70.

[0038] The nitride semiconductor light emitting device according to the embodiment of the present disclosure includes, for example, the following aspects. [Section 1] a first n-type semiconductor layer containing n-type impurities; a first p-type semiconductor layer disposed on the first n-type semiconductor layer and containing p-type impurities; an active layer disposed on the first p-type semiconductor layer and having a hole; an intermediate layer disposed on the active layer and made of a semiconductor containing substantially no n-type impurities; a second n-type semiconductor layer disposed on the intermediate layer and containing n-type impurities; a first electrode electrically connected to the first n-type semiconductor layer; a second electrode electrically connected to the second n-type semiconductor layer; Including, The intermediate layer covers at least the inner side surface of the hole. [Section 2] Item 2. The nitride semiconductor light emitting device according to item 1, wherein the intermediate layer covers the entire inner side surface of the hole. [Section 3] Item 3. The nitride semiconductor light emitting device according to item 1 or 2, wherein the intermediate layer contains a p-type impurity. [Section 4] a superlattice layer including p-type impurities and disposed between the first p-type semiconductor layer and the active layer; 4. The nitride semiconductor light emitting device according to any one of items 1 to 3, wherein the holes penetrate through the superlattice layer. [Section 5] a superlattice layer including p-type impurities and disposed between the first p-type semiconductor layer and the active layer; 5. The nitride semiconductor light emitting device according to any one of items 1 to 4, wherein the bottom of the hole is located in the superlattice layer. [Section 6] the second n-type semiconductor layer includes a third n-type semiconductor layer and a fourth n-type semiconductor layer, 6. The nitride semiconductor light emitting device according to any one of items 1 to 5, wherein the second electrode is disposed on the fourth n-type semiconductor layer. [Section 7] 7. The nitride semiconductor light emitting device according to item 6, wherein the surface roughness of the upper surface of the fourth n-type semiconductor layer is smaller than the surface roughness of the upper surface of the third n-type semiconductor layer. [Section 8] Item 8. The nitride semiconductor light emitting device according to item 6 or 7, wherein the n-type impurity concentration of the fourth n-type semiconductor layer is higher than the n-type impurity concentration of the third n-type semiconductor layer. [Section 9] Item 4, Item 5, Item 6 reciting Item 4 or 5, and Item 7 reciting Item 4 or 5. The nitride semiconductor light-emitting device according to any one of Items 4, 5, Item 6 reciting Item 4 or 5, further comprising a second intermediate layer disposed between the first p-type semiconductor layer and the superlattice layer and substantially not containing n-type impurities. [Explanation of symbols]

[0039] 10 Substrate 11 1st electrode 12, 120 2nd electrode 15 Base layer 20 First n-type semiconductor layer 21 Low concentration n-type semiconductor layer 22 Highly doped n-type semiconductor layer 30 First p-type semiconductor layer 40 Second Middle Class 50 super grid layers 60 active layer, first active layer 65 hole 70 Middle layer, 1st middle layer 80 2nd n-type semiconductor layer 81 3rd n-type semiconductor layer 82 4th n-type semiconductor layer 110 3rd electrode 110a electrode layer 130 2nd p-type semiconductor layer 160 2nd active layer

Claims

1. a first n-type semiconductor layer containing n-type impurities; a first p-type semiconductor layer disposed on the first n-type semiconductor layer and containing p-type impurities; an active layer disposed on the first p-type semiconductor layer and having a hole; an intermediate layer disposed on the active layer and made of a semiconductor containing substantially no n-type impurities; a second n-type semiconductor layer disposed on the intermediate layer and containing n-type impurities; a first electrode electrically connected to the first n-type semiconductor layer; a second electrode electrically connected to the second n-type semiconductor layer; Including, The intermediate layer covers at least the inner side surface of the hole.

2. The nitride semiconductor light emitting device according to claim 1 , wherein the intermediate layer covers the entire inner surface of the hole.

3. The nitride semiconductor light emitting device according to claim 1 , wherein the intermediate layer contains a p-type impurity.

4. a superlattice layer including p-type impurities and disposed between the first p-type semiconductor layer and the active layer; The nitride semiconductor light emitting device according to claim 1 , wherein the holes penetrate through the superlattice layer.

5. a superlattice layer including p-type impurities and disposed between the first p-type semiconductor layer and the active layer; The nitride semiconductor light emitting device according to claim 1 , wherein the bottom of the hole is located in the superlattice layer.

6. the second n-type semiconductor layer includes a third n-type semiconductor layer and a fourth n-type semiconductor layer, The nitride semiconductor light emitting device according to claim 1 , wherein the second electrode is disposed on the fourth n-type semiconductor layer.

7. The nitride semiconductor light-emitting device according to claim 6 , wherein the surface roughness of the upper surface of the fourth n-type semiconductor layer is smaller than the surface roughness of the upper surface of the third n-type semiconductor layer.

8. The nitride semiconductor light-emitting device according to claim 6 , wherein the n-type impurity concentration of the fourth n-type semiconductor layer is higher than the n-type impurity concentration of the third n-type semiconductor layer.

9. 6. The nitride semiconductor light-emitting device according to claim 4, further comprising a second intermediate layer disposed between the first p-type semiconductor layer and the superlattice layer and containing substantially no n-type impurities.

Images