Group iii nitride light-emitting device

Abstract

This light-emitting device comprises: a Group III nitride semiconductor layer including Al as a constituent element; an electron blocking layer including Al as a constituent element; an active layer provided between the electron blocking layer and the Group III nitride semiconductor layer so as to generate light with a peak wavelength in a deep ultraviolet wavelength region of 240 nm to 206 nm, the active layer including an AlYGa1-YN layer (Al composition Y is greater than zero); and a base member having a main surface which includes AlXGa1-xN, and on which the Group III nitride semiconductor layer, the active layer, and the electron blocking layer are mounted, wherein X is greater than 0 and less than or equal to 1. In the active layer, the Al composition G is equal to or greater than Y but less than (Y+0.04), and the compositional difference between the maximum Al composition of the electron blocking layer and the Al composition of the active layer is 0.18 or more.

Description

Group III nitride light emitting devices

[0001] TECHNICAL FIELD This disclosure relates to Group III-nitride light emitting devices.

[0002] Non-Patent Document 1 discloses a light-emitting device using a single crystal aluminum nitride substrate. Non-Patent Documents 2 and 3 disclose light-emitting devices using an aluminum nitride template.

[0003] Hirotsugu Kobayashi et. al., "Milliwatt-power sub-230-nm AlGaN LEDs with > 1500 h lifetime on a single-crystal AlN substrate with many quantum wells for effective carrier injection", Appl. Phys. Lett. 122, 101103 (2023); doi: 10.1063 / 5.0139970Masafumi Knauer, et. al., "Strain induced power enhancement of far-UVC LEDs on high temperature annealed AlN templates"H. Amano et al., J. Phys. D: Appli. Phys. 53, 50 (2020)

[0004] Unlike the 265 nm wavelength ultraviolet light that has been used for sterilization, deep ultraviolet light with a wavelength of 230 nm or less is substantially absorbed by the stratum corneum of the epidermis of mammals such as humans. Therefore, it does not adversely affect intracellular DNA. There is a need for a new sterilization technology that does not have such adverse effects.

[0005] According to the findings of the inventors, in nitride semiconductor light-emitting devices that generate light in the deep ultraviolet region, the barrier height of the electron blocking layer is relatively low compared to that of the active layer that generates long-wave ultraviolet light. This relative reduction may not sufficiently prevent electrons from leaking out of the active layer. The maximum barrier height that can be used in nitride semiconductor light-emitting devices is aluminum nitride (AlN), and exceeding this material limit will require the emergence of a material or structure that can provide a barrier that exceeds the band gap of AlN.

[0006] What is expected is improved performance of nitride semiconductor light-emitting devices that emit light in the deep ultraviolet region, and to meet this expectation, solutions other than the emergence of new materials are required.

[0007] An object of the present disclosure is to provide a group III nitride light-emitting device that suppresses a decrease in external quantum efficiency due to a decrease in the band offset between the active layer and the electron blocking layer.

[0008] A Group III nitride light-emitting device according to one aspect of this embodiment includes a Group III nitride semiconductor layer containing Al as a constituent element, an electron blocking layer containing Al as a constituent element, and an Al blocking layer provided between the electron blocking layer and the Group III nitride semiconductor layer so as to emit light having a peak wavelength in the deep ultraviolet wavelength region of 240 nm or less and 206 nm or more. Ｙ Ga １－Ｙ an active layer including an N layer (Y is an Al composition, where Y is greater than zero); Ｘ Ga １－Ｘ a base member having a primary surface containing N and carrying the Group III nitride semiconductor layer, the active layer, and the electron blocking layer on the primary surface, where X is greater than 0 and less than 1, wherein an Al composition G in the active layer is equal to or greater than Y and less than (Y + 0.04), and a composition difference between the maximum Al composition of the electron blocking layer and the Al composition of the active layer is 0.18 or greater.

[0009] According to the above aspect, it is possible to provide a group III nitride light-emitting device that suppresses a decrease in external quantum efficiency due to a decrease in the band offset between the active layer and the electron blocking layer. Also, the above aspect solves the problem of a relative decrease in the barrier to electrons.

[0010] FIG. 1 is a schematic diagram of a light-emitting device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing the structure of an exemplary light-emitting device according to this embodiment. FIG. 3 is a diagram showing an exemplary conduction band structure and an exemplary aluminum profile of the active layer of the light-emitting device shown in FIG. 1. FIG. 4 is a diagram showing the main steps of a method for fabricating a light-emitting device according to this embodiment. FIG. 5 is a diagram showing the main steps of a method for fabricating a light-emitting device according to this embodiment. FIG. 6 is a diagram showing the main steps of a method for fabricating a light-emitting device according to this embodiment. FIG. 7 is a diagram showing the main steps of a method for fabricating a light-emitting device according to this embodiment. FIG. 8 is a diagram showing the Al composition profile in the active layer and the semiconductor region nearby the active layer of the exemplary light-emitting device shown in FIGS. 1 and 3. FIG. 9 is a flowchart showing the main steps of a method for fabricating a nitride light-emitting device according to this embodiment. FIG. 10 is a diagram showing simulation results illustrating the relationship between current injection efficiency (CIE) and emission wavelength. FIG. 11 is a diagram showing simulation results illustrating the relationship between leakage current and emission wavelength. 12 is a diagram showing an exemplary structure of a light-emitting diode (LED). FIG. 13 is a diagram showing a reciprocal lattice mapping image of the LED structure shown in FIG. 12 by an X-ray diffraction (XRD) method. FIG. 14 is a diagram showing the n-type semiconductor layer (Al ０．８６ Ga ０．１４FIG. 15 is a diagram showing diffraction peak images of the (0004) and (20-22) planes of an AlN single crystal on a sapphire support. FIG. 16 is a diagram showing electroluminescence (EL) of an LED structure. FIG. 17 is a diagram showing the external quantum efficiency (EQE) of the LED structure. FIG. 18 is a diagram showing the relationship between the emission wavelength and the external quantum efficiency (EQE) of the LED structure. FIG. 19 is a diagram showing the relationship between the injection current into the LED structure and the external quantum efficiency (EQE). FIG. 20 is a diagram showing the EL spectra of the assembled devices (DEV_A, DEV_B). FIG. 21 is a diagram showing the injection current dependence of the optical output and external quantum efficiency of the assembled device (DEV_A, emission wavelength 230 nm). FIG. 22 is a diagram showing the injection current dependence of the optical output and external quantum efficiency of the assembled device (DEV_B, emission wavelength 236 nm). FIG. 23A is a graph showing area-averaged CL spectra at room temperature. FIG. 23B is a graph showing an atomic force microscope (surface AFM) image. FIG. 23C is a graph showing a scanning electron microscope (SEM) image. FIG. 24 is a graph showing surface AFM images of light-emitting layers with a multiple quantum well structure and a bulk film. FIG. 25 is a graph showing CL images of light-emitting layers with a multiple quantum well structure and a bulk film. FIG. 26 is a graph showing CL peak energy maps of light-emitting layers with a multiple quantum well structure and a bulk film. FIG. 27 is a graph showing NBE integrated CL intensity maps and peak energy maps of a bulk film light-emitting layer measured at room temperature. FIG. 28 is a graph showing surface morphology based on AFM images. FIG. 29 is a graph showing the relationship between integrated CL intensity and photon energy. FIG. 30 is a graph showing the relationship between integrated CL intensity and photon energy measured at an absolute temperature of 79 Kelvin and room temperature.

[0011] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. Identical and similar parts will be denoted by the same or similar reference numerals, and duplicate descriptions will be omitted.

[0012] Fig. 1 is a diagram schematically illustrating a light-emitting device according to an embodiment of the present disclosure. Fig. 2 is a diagram illustrating the structure of an exemplary light-emitting device according to an embodiment of the present disclosure. Fig. 1 is a cross-section taken along line II of Fig. 2.

[0013] The light emitting device is a semiconductor element including an active layer for emitting light comprising a Group III nitride, such as a light emitting diode, a semiconductor laser, or an electron beam pumped light source. In the following description, the exemplary light emitting device 110 has the structure of a light emitting diode.

[0014] The light-emitting device 110 includes a base member 112 and an active layer 114, as well as a first nitride semiconductor layer 122 containing Al as a constituent element and an electron blocking layer 134 containing Al as a constituent element. The first nitride semiconductor layer 122 is included in a lower Group III nitride stack 113, and the electron blocking layer 134 is included in an upper Group III nitride stack 115. The first nitride semiconductor layer 122 may include a Group III nitride semiconductor layer. The active layer 114 is provided between the first nitride semiconductor layer 122 and the electron blocking layer 134, and forms, for example, a potential well. Carriers are injected into this well from the n-type semiconductor layer in the lower Group III nitride stack 113 and the p-type semiconductor layer in the upper Group III nitride stack 115. The n-type semiconductor layer and the p-type semiconductor layer may include Group III nitrides containing respective dopants.

[0015] The first nitride semiconductor layer 122, the active layer 114, and the electron blocking layer 134 are mounted on a base member 112. The base member 112 is made of, for example, Al Ｘ Ga １－Ｘ The base member 112 has a primary surface including an N-type nitride semiconductor layer 122 (X is greater than 0 and equal to or less than 1). A base member 112, a first nitride semiconductor layer 122, an active layer 114, and an electron blocking layer 134 are arranged along an axis Ax1 extending in a direction intersecting the primary surface of the base member 112. The base member 112 includes, for example, a nitride single crystal support 112b containing aluminum as a constituent element, or a template member 112c.

[0016] The single crystal support 112b is made of, for example, Al Ｘ Ga １－Ｘ The substrate has a primary surface containing N and is, for example, a bulk AlN single crystal (X=1, hexagonal system). The primary surface of the bulk AlN single crystal, for example, a bulk AlN single crystal substrate, can have, for example, a c-plane and can have an off-axis angle of 0.5 degrees in the direction of the m-axis.

[0017] 1, a template member 112c is depicted as an exemplary base member 112. The template member 112c includes a support 118 and a template layer 120. The support 118 has a major surface 118a made of a material other than a Group III nitride. The template layer 120 is made of Al Ｘ Ga １－Ｘ N (X is greater than 0 and equal to or less than 1) and covers the main surface 118a of the support 118. Ｘ Ga １－Ｘ For example, the full width at half maximum of the X-ray rocking curve of the (10-12) plane of N can be 1000 arcsec or less, and contains compressive strain. This compressive strain is the source of strain applied to the active layer 114. The template layer 120 can be, for example, 2000 nm or less and 100 nm or more, e.g., 500 nm. The Al of the template layer 120 Ｘ Ga １－Ｘ N can be AlN (X=1), providing template layer 120 with AlN containing compressive strain.

[0018] Exemplary substrates 118 include carbon, boron nitride (BN), aluminum oxide (sapphire), ceramics, silicon carbide, refractory metals, zirconia, tantalum carbide (TaC), ScAlMgO ４ The material may include at least one of the following materials:

[0019] The template member 112 c , the lower III-nitride stack 113 , the active layer 114 , and the upper III-nitride stack 115 are arranged in the direction of an axis Ax1 extending in a direction intersecting the primary surface 120 s of the template layer 120 .

[0020] The active layer 114 is provided on the base member 112, specifically the single crystal support member 112b or the template member 112c, and can be configured to generate light having a peak wavelength (maximum wavelength in terms of light intensity) in the deep ultraviolet wavelength region of 240 nm or less. The peak wavelength of the light from the active layer 114 can be 206 nm or more. The active layer 114 includes at least one Al Ｙ Ga １－ＹN layer (Y is the Al composition, where Y is greater than zero). Ｙ Ga １－Ｙ The N layer is a light-emitting layer associated with optical transitions in the active layer 114. Optical transitions generated by carrier recombination occur in at least a portion of the light-emitting layer. Specifically, the active layer 114 has a structure including a single film or a multi-layer film, and this structure can be configured to generate light having a peak wavelength in the deep ultraviolet wavelength region of 240 nm or less and 206 nm or more.

[0021] The active layer 114 may include at least one of a group III nitride containing aluminum and gallium as group III elements, such as ternary AlGaN and quaternary InAlGaN containing compressive strain. The active layer 114 may have, for example, a structure including a single film in a single well (e.g., a bulk light-emitting layer), a stacked structure including multiple films in a single well, or a multiple quantum well structure in a single well.

[0022] The upper III-nitride stack 115 includes a p-type III-nitride semiconductor region configured to supply carriers (e.g., holes) to the active layer 114. The lower III-nitride stack 113 includes an n-type III-nitride semiconductor region configured to supply carriers (e.g., electrons) to the active layer 114. Specifically, part or all of the upper III-nitride stack 115 contains a p-type dopant to form a p-type III-nitride semiconductor region. Part or all of the lower III-nitride stack 113 contains an n-type dopant to form an n-type III-nitride semiconductor region.

[0023] The upper III-nitride stack 115 may include a heterobarrier layer (e.g., electron blocking layer 134) against carriers (e.g., electrons) injected from the lower III-nitride stack 113. The electron blocking layer 134 may have a substantially constant Al composition or a compositionally graded Al composition. The lower III-nitride stack 113 may also include a heterobarrier layer (e.g., first nitride semiconductor layer 122) that provides a barrier against carriers (e.g., holes) injected from the upper III-nitride stack 115. The first nitride semiconductor layer 122 may have a substantially constant Al composition or a compositionally graded Al composition. The exemplary active layer 114 forms a junction with the first nitride semiconductor layer 122 and the electron blocking layer 134.

[0024] The active layer 114 has an Al composition G, which is represented by a profile (G). The profile (G) of the Al composition G is represented as a function of a coordinate defined in the direction of an axis Ax1, which extends from one of the first nitride semiconductor layer 122 and the electron blocking layer 134 to the other. The profile (G) may represent a substantially constant Al composition, or may represent a periodic or aperiodic variation in the Al composition from multiple semiconductor layers in the active layer 114.

[0025] The active layer 114 may satisfy the condition that the Al composition G in the active layer 114 is equal to or greater than Y and is less than (Y+0.04) (less than ΔMAX).

[0026] Setting an upper limit on the Al composition G of the active layer 114 allows the average number of Al atoms per unit volume (Al atom density) averaged throughout the active layer 114 to be reduced. Reducing this Al atom density is effective in avoiding high resistance in the active layer 114 and not reducing the relative heterobarrier for the electron level associated with optical transitions in the active layer 114. Specifically, when the thickness of the active layer 114 is fixed, the bulk light-emitting layer has a lower Al atom density than the Al atom density of the active layer 114 in a stacked structure of multilayer films in a single well and in a multiple quantum well structure. Therefore, the bulk light-emitting layer can effectively utilize the heterobarrier for electrons (the barrier of the electron blocking layer 134) while not increasing the electrical resistance to current flowing through the active layer 114.

[0027] With respect to the conditions associated with the heterobarrier layer of the upper Group III nitride stack 115, e.g., the electron blocking layer 134, and the conditions associated with the heterobarrier layer of the lower Group III nitride stack 113, e.g., the first nitride semiconductor layer 122, the active layer 114 can satisfy at least one of the following conditions (a), (b), and (c): (a) when the electron blocking layer 134 has a compositionally graded structure or a single composition structure, the minimum value (ΔAP) of the composition difference (ΔAP or ΔAP+ΔWB) between the maximum Al composition in the electron blocking layer 134 and the Al composition of the active layer 114 is 0.18 or more; (b) when the first nitride semiconductor layer 122 has a compositionally graded structure or a single composition structure, the minimum value (ΔAN) of the composition difference (ΔAN, ΔAN+ΔWB) between the maximum Al composition in the first nitride semiconductor layer 122 and the Al composition of the active layer 114 is 0.06 or more. (c) The Al composition G in the active layer 114 is equal to or greater than Y and less than (Y+0.04).

[0028] Furthermore, with respect to the conditions associated with the heterobarrier layers of the upper III-nitride stack 115 and the lower III-nitride stack 113, the bulk light-emitting layer (ΔWB=0) of the active layer 114 can satisfy at least one of the following conditions (a), (b), and (c):

[0029] (a) When the electron blocking layer 134 has a compositionally graded structure or a single composition structure, the maximum Al composition in the electron blocking layer 134 and the Al composition in the active layer 114 Ｙ Ga １－Ｙ (b) When the first nitride semiconductor layer 122 has a composition gradient structure or a single composition structure, the minimum value (ΔAP+ΔWB (where ΔWB=0)) of the composition difference between the Al composition of the N layer and the Al composition of the active layer 114 is 0.18 or more. Ｙ Ga １－Ｙ The minimum value of the composition difference (ΔAN+ΔWB (where ΔWB=0)) between the Al composition of the N layer and the Al composition of the N layer is 0.06 or more. (c) The Al composition G in the active layer 114 is equal to or greater than Y and less than (Y+0.04).

[0030] In addition, the Al of the active layer 114 Ｙ Ga １－Ｙ The difference between the Al composition of the N layer and the Al composition of the electron blocking layer 134 may be 0.18 or more. Ｙ Ga １－Ｙ The difference between the Al composition of the N layer and the Al composition of the first nitride semiconductor layer 122 can be 0.06 or more. The Al composition Y of the bulk light emitting layer can be, for example, 0.73 or more and 1 or less. The thickness of the bulk light emitting layer can be, for example, 10 nm or more and 100 nm or less.

[0031] FIG. 3 is a diagram illustrating an example conduction band structure and an example aluminum profile of the active layer of the light emitting device shown in FIG.

[0032] As shown in FIG. 3 , the active layer 114 has an Al composition G, specifically, a profile (G). In FIG. 3 , this profile (G) is represented as a function of coordinate defined in the direction of axis Ax1. The Al composition G in the active layer 114 can be equal to or greater than Y and less than (Y + 0.04). The Al composition G in the active layer 114 can be, for example, less than or equal to (Y + 0.035), less than or equal to (Y + 0.03), less than or equal to (Y + 0.02), or less than or equal to (Y + 0.01).

[0033] Setting an upper limit on the Al composition G of the active layer 114 can suppress heat generation due to increased resistance of the active layer 114, i.e., self-heating, and can separate the electron energy level associated with optical transitions in the active layer 114 from the energy level of the heterobarrier of the electron blocking layer 134. Furthermore, the upper limit on the Al composition G of the active layer 114 can relatively increase the heterobarrier of the electron blocking layer 134 against electrons in the active layer 114, without changing the material of the electron blocking layer 134 or the structure of the heterobarrier, thereby reducing the possibility of electron leakage from the active layer 114. Furthermore, the upper limit on the Al composition G of the active layer 114 can relatively increase the heterobarrier against holes in the active layer 114, without changing the material of the first nitride semiconductor layer 122 or the structure of the heterobarrier, thereby reducing hole leakage from the active layer 114.

[0034] The active layer 114 may include a stacked structure 124a, such as a multiple quantum well structure 114a. The stacked structure 124a may include multiple semiconductor layers (124b, 124c) having different Al compositions. Specifically, the stacked structure 124a includes at least one first semiconductor layer 124b and at least one second semiconductor layer 124c. The first semiconductor layer 124b has the smallest Al composition of the semiconductor layers in the stacked structure 124a, and the second semiconductor layer 124c has the largest Al composition of the semiconductor layers in the stacked structure 124a. The stacked structure 124a may include an additional semiconductor layer, such as a third semiconductor layer, having an Al composition different from the first and second semiconductor layers 124b, 124c. The multiple semiconductor layers (124b, 124c) may have different thicknesses or may have substantially the same thickness.

[0035] The first semiconductor layer 124b and the second semiconductor layer 124c are arranged in a direction from one side of the first nitride semiconductor layer 122 to the other side of the electron blocking layer 134, and form a profile of the Al composition G of the active layer 114. For example, the first semiconductor layer 124b comprises a nitride containing Ga and Al as group III constituent elements, and specifically, the Al composition G of the active layer 114. Ｙ Ga １－Ｙ The second semiconductor layer 124c includes a nitride containing Ga and Al as group III elements, for example, Al Ｚ Ga １－Ｚ It may include an N layer (Z is an Al composition, where Z is greater than Y and less than 1). The Group III nitride of the second semiconductor layer 124c has a larger bandgap than the Group III nitride of the first semiconductor layer 124b.

[0036] The difference (ΔAP) between the Al composition of the second semiconductor layer 124c and the Al composition of the electron blocking layer 134 is larger than the difference (ΔWB) between the Al composition of the first semiconductor layer 124b and the Al composition of the second semiconductor layer 124c.

[0037] In the exemplary stacked structure 124a, the Al composition of the first nitride semiconductor layer 122 is larger than the Al composition of the second semiconductor layer 124c. The composition difference (ΔAN) between the Al composition of the first nitride semiconductor layer 122 and the Al composition of the second semiconductor layer 124c is larger than the Al composition difference (ΔWB) between the Al composition of the first semiconductor layer 124b and the Al composition of the second semiconductor layer 124c.

[0038] The Al composition G in the exemplary stack structure 124a may be not less than Y (equal to or greater than Y) and may be less than (Y+0.04) (less than ΔMAX). The minimum value of the Al composition G may be the Al composition Y. Setting an upper limit on the Al composition of the stack structure 124a can reduce carrier leakage and self-heating from the active layer 114, as previously described.

[0039] Specifically, the Al composition difference (less than ΔMAX) between the Al composition of the second semiconductor layer 124c and the Al composition of the first semiconductor layer 124b can be less than 0.04. Alternatively, the Al composition difference (less than ΔMAX) between the Al composition of the second semiconductor layer 124c and the Al composition of the first semiconductor layer 124b can be 0.035 or less. Alternatively, the Al composition difference (less than ΔMAX) between the Al composition of the second semiconductor layer 124c and the Al composition of the first semiconductor layer 124b can be 0.03 or less, 0.02 or less, or 0.01 or less.

[0040] Reducing the Al composition of a semiconductor layer with a high Al composition, such as the second semiconductor layer 124c, can improve external quantum efficiency. In the stacked structure 124a of the active layer 114, the Al composition of the second semiconductor layer 124c may be less than 0.823 and greater than Y. The Al composition of the second semiconductor layer 124c may also be equal to or less than 0.801. The Al composition of the first semiconductor layer 124b may be equal to or less than 0.801.

[0041] The difference between the Al composition of the second semiconductor layer 124c and the maximum Al composition of the electron blocking layer 134 may be larger than the difference between the Al composition of the first semiconductor layer 124b and the Al composition of the second semiconductor layer 124c. Furthermore, the difference in composition between the Al composition of the first nitride semiconductor layer 122 and the Al composition of the second semiconductor layer 124c may be larger than the difference in Al composition between the Al composition of the first semiconductor layer 124b and the Al composition of the second semiconductor layer 124c.

[0042] The Al composition of the first semiconductor layer 124b and the second semiconductor layer 124c, the film thickness of the first semiconductor layer 124b and the second semiconductor layer 124c, and the arrangement of the first semiconductor layer 124b and the second semiconductor layer 124c can be specified so that a multiple quantum well structure 114a is not formed in the active layer 114.

[0043] However, the Al composition of the first semiconductor layer 124b and the second semiconductor layer 124c, the film thicknesses of the first semiconductor layer 124b and the second semiconductor layer 124c, and the arrangement of the first semiconductor layer 124b and the second semiconductor layer 124c can be specified so as to provide a multiple quantum well structure 114a in the active layer 114. In such a stacked structure 124a, the first semiconductor layer 124b serves as a well layer, and the second semiconductor layer 124c serves as a barrier layer.

[0044] Next, the multiple quantum well structure will be described with reference to the exemplary conduction band structure and aluminum profile (G) of the active layer 114 in Fig. 3. As already described, the structure of the active layer 114 is not limited to a single quantum well structure or a multiple quantum well structure.

[0045] The multiple quantum well structure 114a of the active layer 114 is provided with a plurality of well layers 114b and one or more barrier layers 114c. The barrier layer 114c is made of Al Ｚ Ga １－Ｚ Each of the well layers 114b includes an N layer (Z is an Al composition, where Z is greater than Y and less than 1). Ｙ Ga １－ＹThe barrier layer 114c includes an N layer. The Group III nitride of the barrier layer 114c has a larger bandgap than the Group III nitride of the well layer 114b. The minimum Al composition of the electron blocking layer 134 may be equal to or larger than the Al composition of the barrier layer 114c. For example, the composition difference (ΔAP) between the Al composition of the barrier layer 114c closest to the electron blocking layer 134 and the Al composition of the electron blocking layer 134 may be larger than the composition difference (ΔWB) between the Al composition of the barrier layer 114c and the Al composition of the well layer 114b.

[0046] The Al composition of the first nitride semiconductor layer 122 is larger than the Al composition of the barrier layer 114c. For example, the composition difference (ΔAN) between the Al composition of the barrier layer 114c closest to the first nitride semiconductor layer 122 and the Al composition of the first nitride semiconductor layer 122 may be larger than the Al composition difference (ΔWB) between the Al composition of the well layer 114b and the Al composition of the barrier layer 114c.

[0047] The profile (G) of the Al composition G in the exemplary multiple quantum well structure 114a can be equal to or greater than Y and less than (Y+0.04) (less than ΔMAX). Setting an upper limit on the Al composition of the multiple quantum well structure 114a can reduce carrier leakage from the active layer 114 and self-heating of the active layer 114.

[0048] Specifically, in the multiple quantum well structure 114a in which the difference in Al composition (ΔWB) between the Al composition of the barrier layer 114c and the Al composition of the well layer 114b is less than 0.04, the thicknesses of the well layer 114b and the barrier layer 114c can be in the following ranges: Thickness of the well layer 114b: 1 to 5 nm, for example, 2 nm; Thickness of the barrier layer 114c: 2 to 20 nm, for example, 3 nm.

[0049] In the multiple quantum well structure 114a in which the difference in Al composition between the barrier layer 114c and the well layer 114b is 0.035 or less, the thicknesses of the well layer 114b and the barrier layer 114c can be in the following ranges: Thickness of the well layer 114b: 0.5 to 5 nm; Thickness of the barrier layer 114c: 2 to 20 nm.

[0050] In the multiple quantum well structure 114a in which the difference in Al composition between the barrier layer 114c and the well layer 114b is 0.030 or less, the thicknesses of the well layer 114b and the barrier layer 114c can be in the following ranges: Thickness of the well layer 114b: 0.5 to 5 nm; Thickness of the barrier layer 114c: 2 to 10 nm.

[0051] In the multiple quantum well structure 114a in which the difference in Al composition between the barrier layer 114c and the well layer 114b is 0.020 or less, the thicknesses of the well layer 114b and the barrier layer 114c can be in the following ranges: Thickness of the well layer 114b: 0.5 to 5 nm; Thickness of the barrier layer 114c: 2 to 10 nm.

[0052] In the multiple quantum well structure 114a in which the difference in Al composition between the barrier layer 114c and the well layer 114b is 0.010 or less, the thicknesses of the well layer 114b and the barrier layer 114c can be in the following ranges: Thickness of the well layer 114b: 0.5 to 5 nm; Thickness of the barrier layer 114c: 2 to 5 nm.

[0053] Reducing the Al composition of a semiconductor layer with a high Al composition, such as the barrier layer 114c, in the active layer 114 can improve external quantum efficiency. In the multiple quantum well structure 114a of the active layer 114, the Al composition of the barrier layer 114c may be less than 0.823 and greater than Y. The Al composition of the barrier layer 114c may also be equal to or less than 0.801. The Al composition Y of the well layer 114b may be equal to or less than 0.801.

[0054] The average value of the Al composition in the active layer 114 is reduced to avoid high resistance of the active layer 114. In addition, the average value of the Al composition in the active layer 114 is reduced to suppress an increase in group III vacancies in the active layer 114, thereby reducing the concentration of non-radiative centers.

[0055] As described with reference to FIGS. 1, 2, and 3, when the active layer 114 has at least one of a bulk light-emitting layer, a stacked structure 124a, and a multiple quantum well structure 114a, the active layer 114 can satisfy at least one of the following conditions (a), (b), and (c) regarding its Al composition:

[0056] (a) The minimum composition difference between the maximum Al composition of the electron blocking layer 134 and the Al composition of the active layer 114 is 0.18 or more. (b) The minimum composition difference between the Al composition of the first nitride semiconductor layer 122 and the Al composition of the active layer 114 is 0.06 or more. (c) The Al composition G of the active layer 114 is equal to or greater than Y and less than (Y + 0.04).

[0057] Continuing with reference to FIG. 1, the upper group III nitride stack 115 and the lower group III nitride stack 113 will be described in detail.

[0058] The upper III-nitride stack 115 is disposed on the template member 112c such that the active layer 114 is located between the upper III-nitride stack 115 and the template member 112c. The upper III-nitride stack 115 may comprise one or more III-nitride semiconductor layers (e.g., AlN, AlGaN, GaN, InAlGaN) containing at least one of Al and Ga as a group III constituent element.

[0059] The upper III-nitride stack 115 may include an electron blocking layer 134, a p-type semiconductor layer 136, and a p-type contact layer 138. Specifically, the exemplary upper III-nitride stack 115 may include the following semiconductor layers:

[0060] Electron blocking layer 134: undoped or Mg-doped AlN, 5 nm thick. p-type semiconductor layer 136: Mg-doped compositionally graded AlGaN (Al composition gradient: 0.9 to 0.3), 12 nm thick. p-type contact layer 138: Mg-doped GaN. The p-type contact layer 138 has, for example, the following structure: p-type contact layer 138a (first layer): Mg-doped GaN, 120 nm thick. p-type contact layer 138b (second layer): heavily Mg-doped GaN, 30 nm thick. The p-side electrode 146 is connected to the p-type contact layer 138 through the opening 144a. The term "undoped" means that no dopant is intentionally added, but does not mean that the resulting dopant concentration is zero.

[0061] The lower III-nitride stack 113 is disposed between the base member 112 and the active layer 114 and may include one or more III-nitride semiconductor layers containing at least Al as a group III constituent element (e.g., AlN, AlGaN, InAlGaN).

[0062] The lower group III nitride stack 113 includes a first nitride semiconductor layer 122 (Al Ｗ Ga １－Ｗ N layer), second nitride semiconductor layer 132 (Al Ｖ Ga １－Ｖ N layer), and the third nitride semiconductor layer 130 (Al Ｕ Ga １－Ｕ N layers).

[0063] An exemplary lower III-nitride stack 113 may include the following semiconductor layers: First nitride semiconductor layer 122: Al Ｗ Ga １－Ｗ N layer (Al composition W is smaller than 1 and larger than Y. W is equal to or smaller than V) Second nitride semiconductor layer 132: Al Ｖ Ga １－Ｖ N layer (Al composition V is smaller than 1 and equal to or larger than W. V is smaller than U) Third nitride semiconductor layer 130: Al Ｕ Ga １－Ｕ N layer (Al composition U is equal to or less than X and is greater than zero)

[0064] Specifically, at least a portion of the first nitride semiconductor layer 122 may have n-conductivity. Specifically, the first nitride semiconductor layer 122 may include one or more Group III nitride semiconductor layers, such as n-type AlGaN. An n-type dopant is added to a part or all of the first nitride semiconductor layer 122, and the first nitride semiconductor layer 122 may be, for example, Si-doped AlGaN. ０．８６ Ga ０．１４ The first nitride semiconductor layer 122 may include N. The thickness of the first nitride semiconductor layer 122 is in the range of 600 nm to 1200 nm. The second nitride semiconductor layer 132 may be made of, for example, undoped AlGaN with a compositional gradient (continuous or stepwise compositional change). The thickness of the second nitride semiconductor layer 132 may be, for example, 100 nm. The third nitride semiconductor layer 130 may be made of, for example, undoped AlN. The thickness of the third nitride semiconductor layer 130 may be, for example, 200 nm.

[0065] The electron blocking layer 134 includes a heterobarrier layer that provides a heterobarrier that blocks electrons, and may further include, in addition to the heterobarrier layer, a p-side spacer layer between the heterobarrier layer and the active layer 114. The first nitride semiconductor layer 122 includes an n-type carrier supply layer that supplies electrons to the active layer 114, and may further include, in addition to the n-type carrier supply layer, an n-side spacer layer between the n-type carrier supply layer and the active layer 114.

[0066] The electron blocking layer 134 and the first nitride semiconductor layer 122 form a heterojunction with the active layer 114, providing a potential well in the active layer 114. The potential well is formed by the first nitride semiconductor layer 122 and the Al of the active layer 114. Ｙ Ga １－Ｙ The AlN layer is used as a single quantum well structure or bulk light-emitting layer formed by the arrangement of the N layer and the electron blocking layer 134. Ｙ Ga １－Ｙ Alternatively, an AlN layer can be provided as the well layer 114b in this potential well WELL. Ｙ Ga １－ＹA multiple quantum well structure including an N layer and a barrier layer 114c can be provided. Alternatively, a stacked structure 124a including an arrangement of multiple Group III nitride layers having different Al compositions can be provided within this potential well WELL. In either structure, the active layer 114 has an upper limit for its Al composition, for example, less than (Y+0.04).

[0067] When the active layer 114 is provided on the n-type Group III nitride semiconductor region with a low lattice relaxation rate that is in contact with the primary surface of the base member 112 (specifically, the primary surface 120s of the template layer 120), a compressive strain is applied to the active layer 114. Specifically, a compressive strain is applied to the bulk light-emitting layer, the well layer 114b, and the barrier layer 114c.

[0068] In the light-emitting device 110, a lower III-nitride stack 113 is located between the active layer 114 and the base member 112. An upper III-nitride stack 115 is located above the active layer 114. In this example, the lower III-nitride stack 113 forms a bond 119a with the base member 112, specifically the template layer 120 of the template member 112c in FIG. 1, to bond the Al Ｘ Ga １－Ｘ The lower III-nitride stack 113 can have compressive strain due to N. The lower III-nitride stack 113 forms a junction 119b with the active layer 114. The active layer 114 is bonded to the Al of the template layer 120 of the template member 112c. Ｘ Ga １－Ｘ The upper III-nitride stack 115 may contain compressive strain due to N. On the other hand, at least a portion of the upper III-nitride stack 115 may be lattice-relaxed. The upper III-nitride stack 115 is provided on the active layer 114 and supplies carriers to the active layer 114.

[0069] Specifically, the lower III-nitride stack 113 includes an underlayer, specifically a third nitride semiconductor layer 130 (Al Ｕ Ga １－ＵN layer, where U is equal to or less than X and greater than Y. The third nitride semiconductor layer 130 may be, for example, undoped and may be provided to cover the major surface of the template layer 120 or the single-crystal support 112b. Specifically, the third nitride semiconductor layer 130 may be made of AlN.

[0070] An exemplary third nitride semiconductor layer 130 has a thickness of, for example, 4×10 ６ cm －２ The third nitride semiconductor layer 130 may have a screw dislocation density of, for example, 9×10 ８ cm －２ The third nitride semiconductor layer 130 (undoped Al Ｕ Ga １－Ｕ The third nitride semiconductor layer 130 (N layer) can contain compressive strain. The lattice relaxation rate of the third nitride semiconductor layer 130 relative to the template layer 120 is 2% or less. The third nitride semiconductor layer 130 can inherit the dislocation density and compressive strain of the template layer 120.

[0071] The lower III-nitride stack 113 is formed by another underlayer, specifically a second nitride semiconductor layer 132 (Al Ｖ Ga １－Ｖ The second nitride semiconductor layer 132 may be, for example, undoped, and may be made of ternary AlGaN. The second nitride semiconductor layer 132 may be made of the third nitride semiconductor layer 130 (Al Ｕ Ga １－Ｕ The second nitride semiconductor layer 132 may be formed on a 4×10 ６ cm －２The second nitride semiconductor layer 132 can have a dislocation density including the following spiral component. The second nitride semiconductor layer 132 can contain compressive strain from the underlayer. When the template layer 120 is AlN, the lattice relaxation rate of the third nitride semiconductor layer 130 relative to the template layer 120 is 2% or less. According to this light-emitting device 110, the second nitride semiconductor layer 132 can have a lower Al composition toward the active layer 114 while inheriting the threading dislocation density and compressive strain of the template layer 120. Specifically, the second nitride semiconductor layer 132 (Al Ｖ Ga １－Ｖ N layer) is an Al layer with an Al composition gradient. Ｖ Ga １－Ｖ It may contain N layers (V=1 to 0.86).

[0072] In the lower Group III nitride stack 113, the lattice relaxation rate of the first nitride semiconductor layer 122 relative to the template layer 120 can be 2% or less. The n-type region of the first nitride semiconductor layer 122 is connected to an electrode (n-side electrode 148). In this case, current flows in the in-plane direction and along the axis Ax1 in the first nitride semiconductor layer 122. The thicker the n-type semiconductor region, the lower its resistance, allowing for a reduction in drive voltage. However, if the n-type semiconductor region is too thick, the lattice relaxation rate of the n-type semiconductor region increases, preventing effective transmission of compressive strain to the active layer 114. A lattice relaxation rate of 2% or less of the first nitride semiconductor layer 122 provides the n-type semiconductor with a thickness for a good current path and enables effective transmission of compressive strain to the active layer 114.

[0073] In this embodiment, the first nitride semiconductor layer 122 is a second nitride semiconductor layer 132 (Al Ｖ Ga １－Ｖ The second nitride semiconductor layer 132 forms a junction 119c with the third nitride semiconductor layer 130 (AlN layer). Ｕ Ga １－ＵA junction 119d is formed with the first nitride semiconductor layer 122 (N layer). The lower III-nitride stack 113 includes a third nitride semiconductor layer 130 and a second nitride semiconductor layer 132 in addition to the first nitride semiconductor layer 122. The third nitride semiconductor layer 130 and the second nitride semiconductor layer 132 can form an underlayer that transmits the compressive strain of the template layer 120 to the active layer 114. The first nitride semiconductor layer 122 has an Al composition smaller than the Al composition of the second nitride semiconductor layer 132, and also has an Al composition larger than the Al composition Y of the well layer 114b and the Al composition Z of the barrier layer 114c.

[0074] 1 and 2, the light emitting device 110 has a protruding region 142. The protruding region 142 may include the upper III-nitride stack 115, the active layer 114, and an upper portion of the lower III-nitride stack 113 (specifically, an upper portion of the first nitride semiconductor layer 122).

[0075] The light emitting device 110 may further include a passivation film 144, which covers the protruding region 142 and the first nitride semiconductor layer 122. The passivation film 144 has a first opening 144a located on an upper surface of the protruding region 142 and a second opening 144b located on an upper surface of the first nitride semiconductor layer 122 (specifically, on an n-type semiconductor upper surface of the first nitride semiconductor layer 122). The passivation film 144 may include, for example, a silicon-based inorganic insulator, and specifically may include silicon oxide, silicon nitride, or silicon oxynitride.

[0076] The light emitting device 110 may be provided with a p-side electrode 146 and an n-side electrode 148. The p-side electrode 146 is disposed in the first opening 144a, and the n-side electrode 148 is disposed in the second opening 144b. The p-side electrode 146 makes contact with the top surface of the p-type contact layer 138. The n-side electrode 148 makes contact with the top n-type semiconductor surface of the first nitride semiconductor layer 122.

[0077] P-side electrode 146: Ni / Au (meaning that Au is deposited on Ni) N-side electrode 148: Ti / Al / Ni / Au

[0078] The base member 112, the upper Group III nitride stack 115, the active layer 114, and the lower Group III nitride stack 113 form a nitride semiconductor structure 153. In FIG. 1 , in the nitride semiconductor structure 153, the base member 112 has a first region 120a and a second region 120b, and the first region 120a and the second region 120b are arranged along a reference plane Ref that intersects with an axis Ax1 extending from the base member 112 to the active layer 114. The n-side electrode 148 is located on the first region 120a, specifically on the lower Group III nitride stack 113, and the protruding region 142 and the p-side electrode 146 are located on the second region 120b, specifically on the upper surface of the upper Group III nitride stack 115. The p-side electrode 146 has, for example, a comb shape. The n-side electrode 148 may include a comb-shaped portion and a peripheral portion. The peripheral portion is provided along the base of the protruding region 142, specifically, so as to surround and close the protruding region 142.

[0079] Parts (a) and (b) of Figure 4, (a) and (b) of Figure 5, (a) and (b) of Figure 5, (a) and (b) of Figure 6, (a) and (b) of Figure 6, (b) of Figure 6, (a) and (b) of Figure 7, show the main steps of the method for fabricating the light-emitting device according to this embodiment. In the following description of the fabrication method, a light-emitting diode structure is fabricated as the light-emitting device.

[0080] As shown in parts (a) of Figure 4 to (b) of Figure 5, a template 162 is prepared. Preparing the template 162 includes, for example, fabricating the template 162 or obtaining the template 162 by a method other than fabrication.

[0081] Fabricating the template 162 can include the following steps.

[0082] 4A, a substrate 150 is prepared. The substrate 150 may be, for example, a 2-inch sapphire substrate. The substrate 150 is placed in a film-forming apparatus, and an Al film is formed on a main surface 150a of the substrate 150. Ｘ Ga １－Ｘ A precursor 151 for N is deposited. This deposition is performed by sputtering using, for example, a sputtering device 155a. The precursor 151 is Al Ｘ Ga１－Ｘ The AlN template layer 151 is composed of a collection of group III nitride crystal grains. The sputtering target includes AlN or AlGaN. The target is sputtered using a sputtering pressure of 0.05 Pa, and an AlN or AlGaN precursor 151 for the AlN template layer is deposited on the substrate 150. During this deposition, the surface temperature of the substrate 150 is maintained within a range of approximately 500 to 700 degrees Celsius, for example, at approximately 700 degrees Celsius. Nitrogen gas, for example, is used as the inert gas. The flow rate of the nitrogen gas is, for example, 10 to 100 sccm (standard cubic centimeters per minute).

[0083] 4(b), after the deposition of the precursor 151, the intermediate product including the substrate 150 and the precursor 151 is placed in a heat treatment device 155b. In the heat treatment device 155b, the covering member 154 and the precursor 151 are made to face each other. At this time, the covering member 154 and the precursor 151 are arranged so that the maximum distance between the main surface 152a of the precursor 151 and the main surface 154a of the covering member 154 is preferably 0.5 mm or less. Alternatively, the covering member 154 may be another intermediate product (the substrate 150 and the precursor 151).

[0084] 5A, the substrate 150 and the precursor 151 are heat-treated using a heat treatment device 155b. In the heat treatment device 155b, an inert gas and ammonia (NH ３An atmosphere 158 of either a mixed gas containing Al or an inert gas is formed. In the atmosphere 158, the substrate 150 and precursor 151 are heated to an annealing temperature. The annealing temperature can be, for example, 1600°C or higher and 1750°C or lower, e.g., 1725°C. The time for which the substrate 150 and precursor 151 are held at 1400°C or higher may be 20 minutes to 168 hours, more preferably 3 to 48 hours. In the heat treatment device 155b, the substrate 150 and precursor 151 are placed within the above temperature range and subjected to heat treatment for, for example, 20 minutes or more. This heat treatment is referred to as face-to-face annealing (FFA). This heat treatment can provide a template 162 including a template layer 160. The template layer 160 is made of Al. Ｘ Ga １－Ｘ N (where X is greater than zero and less than or equal to 1) and covers the major surface 150a of the substrate 150. The template layer 160 can be, for example, less than or equal to 2000 nm and greater than or equal to 100 nm, and in this example is 500 nm.

[0085] The covering member 154 can have a main surface 154a that is equal to or larger than the main surface 151a of the precursor 151. The main surface 154a of the covering member 154 can be made of carbon, boron nitride (BN), aluminum oxide (sapphire), ceramic, silicon carbide, high melting point metal, zirconia, tantalum carbide (TaC), ScAlMgO ４ The inert gas in the atmosphere 158 may include at least one of helium (He) gas, nitrogen (N ２ ) gas, and argon (Ar) gas.

[0086] 5B, the half-width of the (10-12) X-ray rocking curve is measured using an X-ray diffractometer 155c. The template layer 160 has a half-width of the (10-12) X-ray rocking curve of 1000 arcsec or less. Through these steps, a template 162 is fabricated from the substrate 150.

[0087] According to an exemplary process for preparing the template 162, the template layer 160 can have an X-ray rocking curve of (10-12) with a half-width of 100 arcsec or less for the (0002) plane.

[0088] The template layer 160 was formed by sputter deposition and high temperature heat treatment.

[0089] The prepared template 162 includes a substrate 150 and a template layer 160. The substrate 150 has a primary surface 150a made of a material other than a group III nitride. The template layer 160 is made of Al (10-12) with an X-ray rocking curve half-width of 1000 arcsec or less. Ｘ Ga １－Ｘ The substrate 150 contains N and covers the main surface 150 a.

[0090] Al of template layer 160 Ｘ Ga １－Ｘ Specifically, N can be AlN and / or AlGaN. ７ cm －２ The dislocation density may be less than 9×10 ８ cm －２ The threading dislocation density is as follows:

[0091] The substrate 150 may be made of carbon, boron nitride (BN), aluminum oxide (sapphire), ceramic, silicon carbide, refractory metals, zirconia, tantalum carbide (TaC), ScAlMgO ４ For example, the sapphire substrate may typically have a size of 2 inches.

[0092] Specifically, the template layer 160 can have a hexagonal crystal structure. The primary surface of the template layer 160 has an off-angle greater than 0 degrees and equal to or less than 0.5 degrees relative to the c-plane of the crystal structure. The off-angle direction is, for example, the [1-100] direction (m-axis direction) of the hexagonal crystal structure. This manufacturing method provides exemplary angle ranges and directions for the off-angle.

[0093] These steps prepare a template 162 including a template layer 160. Ｘ Ga １－Ｘ The N layer comprises AlN. A III-nitride stack 164 is then formed. The III-nitride stack 164 is formed by adding AlN to the template layer 160 or the wafer of bulk III-nitride single crystal. Ｘ Ga １－Ｘ The bulk AlN single crystal is grown on the N-primary plane. The primary surface of the wafer has an off-angle greater than 0 degrees and equal to or less than 0.5 degrees relative to the c-plane of the crystal structure. The off-angle direction is, for example, the [1-100] direction (m-axis direction) of the hexagonal crystal structure. This manufacturing method provides exemplary angle ranges and directions for the off-angle. An exemplary Group III nitride single crystal substrate can be an AlN single crystal wafer.

[0094] In the ensuing discussion, a III-nitride stack 164 is grown on the template layer 160 .

[0095] 6(a), a group III nitride stack 164 is grown on the template layer 160. This growth can be performed by, for example, metalorganic vapor phase epitaxy (MOVPE) or molecular beam epitaxy (MBE). In the following description, an MOVPE reactor 155d is employed, and trimethylgallium (TMGa) and trimethylaluminum (TMAl) are used as the gallium precursor and the aluminum precursor, respectively. NH ３ is used.

[0096] The III-nitride stack 164 includes semiconductor films for the lower III-nitride stack 113 and the active layer 114. Specifically, the III-nitride stack 164 has a nitride semiconductor region 166 and an active layer 168.

[0097] After forming template layer 160, nitride semiconductor region 166 is grown on template layer 160. Nitride semiconductor region 166 may include one or more Group III nitride semiconductor films.

[0098] According to this manufacturing method, an Al (10-12) plane X-ray rocking curve half width of 1000 arcsec or less can be obtained. Ｘ Ga １－Ｘ An n-type Group III nitride semiconductor film for nitride semiconductor region 166 is grown on N template layer 160 .

[0099] In this example, the n-type Group III nitride semiconductor film was grown using silane (SiH ４ The nitride semiconductor region 166 may be an AlGaN layer having an Al composition of 0.80 or more. In this manufacturing method, the nitride semiconductor region 166 may include an n-type dopant (e.g., silicon) from the nitride semiconductor region 166. ３ The partial pressure can be 10 kPa or greater.

[0100] After growth of the nitride semiconductor region 166, an active layer 168 is grown. Specifically, the active layer 168 may include AlGaN. By way of example and not limitation, the active layer 168 may be configured to generate light having a peak wavelength in the deep ultraviolet wavelength region of 240 nm or less. The active layer 168 may also be configured to generate light in the deep ultraviolet wavelength region, for example, up to about 206 nm. The active layer 168 includes a Group III nitride semiconductor containing compressive strain.

[0101] As previously described, the active layer 168 can have a bulk light-emitting layer in a single well, a stacked structure of multiple films in a single well, or a multiple quantum well structure in a single well. The multiple quantum well structure of the active layer 168 includes multiple well layers and one or more barrier layers. Each well layer contains compressive strain, and each barrier layer contains compressive strain. The bandgap of the compressively strained AlGaN in the well layers is smaller than the bandgap of the compressively strained AlGaN in the barrier layers. The active layer 168 is formed such that its Al composition G (see FIG. 1 ) is less than (Y+0.04). Therefore, the active layer 168 does not include a barrier layer with a high potential barrier or a well layer with a deep potential well. For example, the active layer 168 can include InAlGaN, which can generate light in the deep ultraviolet wavelength range.

[0102] According to this manufacturing method, AlＸ Ga １－Ｘ The N template layer 160 imparts compressive strain to one or more semiconductor films of the active layer 168 via a nitride semiconductor region with a low lattice relaxation rate (semiconductor region for the lower III-nitride stack 113).

[0103] In this embodiment, one or more group III nitride semiconductor layers are grown prior to the growth of the nitride semiconductor region 166 and the active layer 168. The group III nitride stack 164 includes, in addition to the nitride semiconductor region 166 and the active layer 168, undoped Al Ｕ Ga １－Ｕ N layer 170 and undoped Al Ｖ Ga １－Ｖ It may have an N layer 172 .

[0104] Specifically, Al is deposited so as to cover the template layer 160. Ｕ Ga １－Ｕ An N layer 170 (U is less than or equal to X and greater than Y) can be grown. Ｕ Ga １－Ｕ The N layer 170 has an Al composition greater than the Al composition of the nitride semiconductor region 166 .

[0105] Al Ｕ Ga １－Ｕ The N layer 170 can be, for example, undoped. Ｕ Ga １－Ｕ The screw dislocation density of the N layer 170 is, for example, 4×10 ６ cm －２ and Al Ｕ Ga １－Ｕ The threading dislocation density of the N layer 170 is, for example, 9×10 ８ cm －２ The following is true: Ｕ Ga １－Ｕ The N layer 170 can contain compressive strain. Ｕ Ga １－Ｕ The relaxation rate of the N layer is 2% or less. Ｕ Ga １－Ｕ The N layer 170 allows the threading dislocation density and compressive strain of the template layer 160 to be inherited. Ｕ Ga１－Ｕ The N layer 170 comprises AlN.

[0106] Specifically, Al Ｕ Ga １－Ｕ Another Al layer is formed on the N layer 170. Ｖ Ga １－Ｖ An N layer 172 (V is less than 1 and greater than Y, and V is less than U) can be grown. Ｖ Ga １－Ｖ The N layer 172 has an Al composition greater than the Al composition of the nitride semiconductor region 166. Ｖ Ga １－Ｖ The N layer 172 may comprise AlGaN with a constant Al composition and / or graded AlGaN, including a continuous or stepwise composition change.

[0107] Al Ｖ Ga １－Ｖ The N layer 172 can be, for example, undoped. Ｖ Ga １－Ｖ The screw dislocation density of the N layer 172 is, for example, 4×10 ６ cm －２ The following is true: Ｖ Ga １－Ｖ The N layer 172 can contain compressive strain. Ｖ Ga １－Ｖ The N layer 172 can lower the Al composition toward the active layer 168 while inheriting the threading dislocation density of the template layer 160. When the template layer 160 is made of AlN, the undoped Al Ｖ Ga １－Ｖ The lattice relaxation rate of the N layer is 2% or less.

[0108] In an embodiment, the plurality of Group III nitride semiconductor layers grown on the template layer 160 can be grown coherently with respect to the template layer 160. Here, "growing coherently" refers to a manner in which growth continues with a constant lattice constant.

[0109] Subsequently, a plurality of Group III nitride semiconductor layers (174, 176, 178) for the Group III nitride stack 164 are grown on the active layer 168. Specifically, the Group III nitride stack 164 may include an electron blocking layer 174, a p-type compositionally graded layer 176, and a p-type contact layer 178. The electron blocking layer 174, the p-type compositionally graded layer 176, and the p-type contact layer 178 may be grown on the active layer 168 in that order.

[0110] 6(b), a groove 180 that defines the outer edge of the element of the light-emitting device is formed by photolithography and etching. Etching is performed from the upper surface of the group III nitride stacked body 164 to the substrate 150, thereby forming the groove 180.

[0111] 7A, the protruding region 182 is formed by photolithography and etching. The etching is performed to form a groove 183 that extends from the upper surface of the group III nitride stack 164 to the nitride semiconductor region 166 so as to separate the active layer 168. Ｖ Ga １－Ｖ The etching does not reach the N layer 172. The upper portion of the nitride semiconductor region 166 is removed to expose the surface of the nitride semiconductor region 166 so that an n-side electrode can be formed on the etched nitride semiconductor region 166. The lower portion of the nitride semiconductor region 166 is left to provide a horizontal current path.

[0112] 7(b), a passivation film 184, a p-side electrode 186, and an n-side electrode 188 are formed. The passivation film 184 has a first opening 184a located on the top surface of the protruding region 182 and a second opening 184b located on the bottom surface of the groove 183 that defines the protruding region 182.

[0113] Next, one of the p-side electrode 186 and the n-side electrode 188, for example, the p-side electrode 186, is formed in the first opening 184a, and the other of the p-side electrode 186 and the n-side electrode 188, for example, the n-side electrode 188, is formed in the second opening 184b.

[0114] Through these steps, the light-emitting device is fabricated.

[0115] FIG. 8 shows the Al composition profile in the active layer and nearby semiconductor regions of the exemplary light emitting device shown in FIGS.

[0116] Referring to part (a) of FIG. 8 , the active layer (MQW) of the exemplary light-emitting device has a deep potential multiple quantum well structure with an Al composition of (Y+0.04) or greater. Arrows CA1, CA2, and CA3 schematically show the movement of carriers (electrons). As indicated by arrow CA1, electrons are injected into the first well layer from n-type AlGaN (e.g., the first nitride semiconductor layer 122). As indicated by arrow CA2, the electrons propagate through the active layer (MQW) by optically direct transition. Upon reaching the end of the active layer (MQW), some of the remaining electrons leak across the electron blocking layer (AlN) into the p-type semiconductor region, as indicated by arrow CA3. In the p-type semiconductor region, carrier annihilation occurs.

[0117] Referring to part (b) of FIG. 8 , the active layer of an exemplary light-emitting device has a deep potential well. The active layer of a specific light-emitting device has a shallow quantum well structure (MQW), which is contained within the deep potential well. Arrows CA4, CA5, and CA6 schematically show the movement of carriers (electrons). As indicated by arrow CA4, electrons are injected from the first nitride semiconductor layer 122 into the first well layer. As indicated by arrow CA5, the electrons propagate within the active layer (MQW) using direct optical transition. When the electrons reach the end of the active layer (MQW), they are repelled by the high barrier of the electron blocking layer (AlN), as indicated by arrow CA6. The electrons are unlikely to leak into the p-type semiconductor region.

[0118] Setting an upper limit on the Al composition of the active layer 114 reduces the Al composition difference (ΔWB) between the Al composition of the barrier layer 114c and the Al composition of the well layer 114b, weakening quantum confinement. However, a deep well potential (well) is provided in the active layer 114, which is made possible by setting an upper limit on the Al composition. The first nitride semiconductor layer 122 and the electron blocking layer 134 can tightly confine carriers to the well (well in part (b) of FIG. 8 ) provided by them. This well potential (well) fully utilizes the heterobarrier from the first nitride semiconductor layer 122 and the electron blocking layer 134, which is specified by existing materials, for carrier confinement. The well potential (well) enables carrier confinement and, in addition to the shallow potential stack structure 124a and the shallow potential multiple quantum well structure 114a within the well potential (well), enables emission at the desired wavelength from the bulk light-emitting layer.

[0119] Specifically, the active layer 114 of the well potential (WELL) is made of Al, which acts as a bulk light-emitting layer. Ｙ Ga １－Ｙ Includes N layer. Ｙ Ga １－Ｙ The N layer is provided between the first nitride semiconductor layer 122 and the electron blocking layer 134, and is configured to generate light having a peak wavelength in the deep ultraviolet wavelength region of 240 nm or less and 206 nm or more. The depth of the well potential (WELL) is determined by the ratio of the maximum Al composition of the electron blocking layer to the Al Ｙ Ga １－Ｙ The difference in composition between the Al composition Y of the N layer and the Al composition Y of the N layer is specified to be 0.18 or more. If possible, the well potential (WELL) is set to be equal to or greater than the maximum Al composition Y of the first nitride semiconductor layer 122 and the Al composition Y of the active layer 114. Ｙ Ga １－Ｙ The composition difference between the Al composition of the N layer can be specified to be 0.06 or more.

[0120] FIG. 9 is a flowchart showing the main steps in a method for fabricating a nitride light emitting device according to this embodiment.

[0121] The fabricated light-emitting diode includes a bulk AlN substrate or sapphire template, an AlN homoepitaxial layer, an AlGaN layer, an n-type electron spreader layer, an active layer, an electron blocking layer, a p-type hole injection layer, and a p-type contact layer. These semiconductor layers are stacked in this order. An n-side electrode is connected to the electron spreader layer of the n-type AlGaN layer, and a p-side electrode is connected to the p-type contact layer.

[0122] First, the formation of the template member according to the embodiment will be described.

[0123] In step S10, a substrate is prepared. This substrate can be, for example, a sapphire substrate. However, the substrate is not limited to sapphire, and can be carbon, boron nitride (BN), ceramic, silicon carbide, refractory metal, zirconia, tantalum carbide (TaC), ScAlMgO ４ The material may include at least one of the following materials:

[0124] In step S11, an AlN template layer is formed on a sapphire substrate. The AlN template layer is substantially composed of AlN. The AlN template layer is formed to grow an epitaxial layer with good crystallinity on the substrate. The primary surface of the AlN template layer substantially comprises a hexagonal c-plane. In an embodiment, AlN for the template layer provides the following advantages: The lattice constant of AlN can be well matched to the lattice constant of AlGaN used in the active layer of an ultraviolet light-emitting diode. Furthermore, AlN on a sapphire substrate exhibits high transmittance for ultraviolet light. AlN also exhibits high thermal conductivity. These advantages make it suitable as a template layer. AlGaN, in which a small number of Al atoms in AlN are substituted with Ga atoms, also exhibits similar properties.

[0125] In step S11a, a desired sputtering target is prepared. In step S11b, a precursor for the AlN template layer is deposited by sputtering, for example. In step S11c, the deposited precursor is heat-treated. Specifically, the precursor for the AlN template layer is formed by one or more depositions on the surface of a sapphire substrate by, for example, reactive sputtering, and the deposited AlN and sapphire substrate are then subjected to one or more heat treatments. This results in the formation of the template layer. The depositions and heat treatments can be performed alternately. The method for forming the template layer is not limited to reactive sputtering, and can also be performed using MOVPE, MBE, or hydride vapor phase epitaxy (HVPE).

[0126] Increasing the thickness of the template layer reduces the threading dislocation density in the AlN of the template layer. This reduction can improve the internal quantum efficiency of the active layer formed on the template layer. On the other hand, decreasing the thickness of the template layer can reduce the frequency of cracks occurring in the template layer. This reduction improves the yield of light-emitting diodes using the template layer. Specifically, the thickness of the AlN template layer may be, for example, in the range of 100 to 10,000 nm, and more preferably in the range of 500 to 1,500 nm. By performing one or more sputtering depositions and heat treatments, this thickness range results in a sufficiently low threading dislocation density and a sufficiently low frequency of cracks occurring in the template layer.

[0127] Next, a bulk single-crystal AlN substrate or a sapphire template is prepared. In the following description, an epitaxial structure for a light-emitting diode is formed on the AlN template layer of the sapphire substrate. This epitaxial structure can be formed using a deposition method such as MOVPE, HVPE, or MBE. In this example, all layers except the AlN template layer are fabricated using MOVPE.

[0128] In step S12, an AlN homoepitaxial layer is formed. Specifically, prior to forming the AlN homoepitaxial layer on the AlN template layer, if necessary, the surface of the AlN template layer is treated (surface cleaning) in the MOVPE reactor. This surface treatment is a heat treatment for about 10 minutes in a high-temperature atmosphere. The surface treatment is carried out using H ２ and N.H. ３ or in a mixed atmosphere of H ２ , N.H. ３ and N ２ The treatment is performed in a mixed atmosphere of AlN and ZnO. The treatment temperature may be, for example, 1200°C or higher, and more preferably 1300°C or higher. This treatment is performed to remove oxides and organic substances present on the surface of the AlN template layer and to suppress the introduction of defects into each layer grown on the AlN template layer, from the AlN homoepitaxial layer to the contact layer. The pressure may be, for example, 13 kPa.

[0129] (AlN homoepitaxial layer) The homoepitaxial layer is made of the same material as the surface of the template layer or bulk AlN substrate. In this embodiment, the homoepitaxial layer is made of, for example, AlN. The homoepitaxial layer has a surface with superior flatness to the surface of the AlN template layer. The homoepitaxial layer also prevents residual impurities (e.g., carbon (C), oxygen (O), and silicon (Si)) contained in the template layer from passing through the homoepitaxial layer. The thickness of the homoepitaxial layer may be, for example, in the range of 10 to 10,000 nm, and more preferably in the range of 50 to 1,000 nm. The thickness of the AlN homoepitaxial layer is, for example, 200 nm. The AlN homoepitaxial layer is made of, for example, H ２ Carrier gas of NH ３ and TMAl as raw materials, a growth pressure of 13 kPa, and a substrate temperature of 1300 degrees Celsius.

[0130] In step S13, a buffer layer such as an AlGaN buffer layer is formed on the homoepitaxial layer. The buffer layer is made of a nitride containing a group III element as a constituent element (Al ｙ１ Gaｚ１ In （１－ｚ１－ｙ１） N, 0<y1≦1, 0≦z1<1, y1+z1≦1). Specifically, the buffer layer serves to match the lattice constants of the layers formed below and above the buffer layer. The buffer layer may be made of, for example, AlGaN or AlGaInN. For example, when AlGaN (e.g., an active layer) is formed on AlN (e.g., an AlN template layer and an AlN homoepitaxial layer), the lattice constants specific to AlN and AlGaN are different, so a layer is provided between the AlN layer and the AlGaN layer to match the lattice constants specific to the crystal. The buffer layer may have a structure in which the lattice constant changes continuously or discontinuously in the stacking direction within the buffer layer. The buffer layer may be undoped, i.e., not intentionally doped with impurities, or may have n-type dopants, such as Si, Ge (germanium), Sn (tin), O (oxygen), S (sulfur), Se (selenium), or Te (tellurium), to impart n-type conductivity to the semiconductor. An exemplary buffer layer may be a compositionally graded AlGaN layer (100 nm thick).

[0131] In step S14, an electron spreader layer is formed on the buffer layer. Specifically, the electron spreader layer is made of a nitride containing a group III element as a constituent element (Al ｙ２ Ga ｚ２ In （１－ｚ２－ｙ２） N, 0<y2≦1, 0≦z2<1, y2+z2≦1). The electron spreader layer may be made of, for example, AlGaN or AlGaInN. The electron spreader layer may have an n-type dopant to impart n-type conductivity to the semiconductor. Thus, the electron spreader layer provides a conduction path for electrons to propagate to the active layer.

[0132] Providing a high Al composition in the electron spreader layer can reduce the lattice mismatch between AlN (e.g., the AlN template layer and the AlN homoepitaxial layer) and the Group III nitride (e.g., AlGaN) of the electron spreader layer. This reduction can effectively suppress the generation of misfit dislocations due to lattice relaxation. The electron spreader layer with a high Al composition can transfer compressive strain from the template layer to the active layer. This can improve the LED characteristics, and more specifically, can provide an improved internal quantum efficiency and a narrower emission spectrum of the LED.

[0133] The Al composition of the electron spreader layer may be, for example, in the range of 0.8 to 0.9. This range avoids providing an undesirable level of conductivity in the electron spreader layer due to a too high Al composition. The thickness of the electron spreader layer may be, for example, in the range of 600 to 1200 nm to provide sufficient strain to the active layer. An exemplary electron spreader layer is a 1200 nm thick n-type Al ０．８６ Ga ０．１４ There can be N layers.

[0134] Growth conditions for AlGaN for the electron spreader layer: Growth pressure: 40 kPa, Substrate temperature: 1050°C.

[0135] In step S15, an active layer is formed. Specifically, the active layer has a structure including alternating stacked AlGaN well layers and AlGaN barrier layers. The AlGaN well layers and AlGaN barrier layers contain AlGaN having respective Al compositions. Specifically, the Al composition of the AlGaN well layers is smaller than the Al composition of the AlGaN barrier layers. The number of AlGaN well layers can be, for example, seven. The uppermost layer of the active layer can be an AlGaN well layer or an AlGaN barrier layer, and thus the active layer can be in contact with an electron blocking layer. For example, the lowermost AlGaN well layer or AlGaN barrier layer of the active layer can be in contact with an electron spreader layer, and thus the active layer can be in contact with the first nitride semiconductor layer 122. Furthermore, the multiple AlGaN well layers can have the same thickness and Al composition, or can have different thicknesses and Al compositions. At least some of the multiple AlGaN well layers can have thicknesses different from the thicknesses of the remaining AlGaN well layers. The emission wavelength of the active layer can be 206 nm to 240 nm, and the Al composition of the bulk light-emitting layer can be in the range of 0.73 to 1. The thickness of the AlGaN well layer is, for example, 2 nm, and the Al composition is, for example, 0.792. The thickness of the AlGaN barrier layer is, for example, 3 nm, and the Al composition is, for example, 0.801.

[0136] Growth conditions for AlGaN active layer: Growth pressure: 40 kPa Substrate temperature: 1050 degrees Celsius

[0137] The AlGaN barrier layer may be in contact with the electron spreader layer, or the AlGaN well layer may be in contact with the electron spreader layer, or the AlGaN barrier layer may be in contact with the electron blocking layer, or the AlGaN well layer may be in contact with the electron blocking layer.

[0138] In step S16, an electron blocking layer is formed on the active layer. Specifically, the electron blocking layer is made of a nitride containing a group III element as a constituent element (Al ｙ３ Ga ｚ３ In （１－ｚ３－ｙ３）The electron blocking layer may be made of, for example, at least one of AlN, AlGaN, and AlGaInN, e.g., undoped AlN. The bandgap energy of the electron blocking layer is greater than the bandgap energy of the AlGaN barrier layer. The electron blocking layer prevents electrons from the electron spreader layer from leaking from the active layer to the hole injection layer. The film thickness of the electron blocking layer may be 1 to 20 nm, and more preferably 3 to 10 nm. The electron blocking layer may have a structure in which the bandgap energy changes continuously or stepwise in the stacking direction of the semiconductor film, i.e., a compositionally graded structure. The electron blocking layer may be undoped, i.e., not intentionally doped with impurities, or may have p-type conductivity imparted by the addition of a p-type dopant such as Mg (magnesium), Be (beryllium), C (carbon), or Zn (zinc).

[0139] Growth conditions for AlN electron blocking layer: Growth pressure: 40 kPa, Substrate temperature: 1050°C.

[0140] In step S17, a hole injection layer such as a p-type AlGaN layer is formed. Specifically, the hole injection layer is provided on the active layer and the electron blocking layer. The hole injection layer is formed of a nitride containing a group III element as a constituent element (Al ｙ４ Ga ｚ４ In （１－ｚ４－ｙ４）N, 0≦y4≦1, 0≦z4≦1, y4+z4≦1). Specifically, the hole injection layer may be made of at least one of AlN, AlGaN, or AlGaInN. The hole injection layer may have p-type conductivity imparted by the addition of a p-type dopant such as Mg (magnesium), Be (beryllium), C (carbon), or Zn (zinc). The hole injection layer provides a conduction path for providing holes to the active layer. The band gap energy of the hole injection layer is smaller than that of the electron blocking layer and larger than that of the contact layer, which will be described subsequently. The hole injection layer may have a structure in which the band gap energy changes continuously or stepwise in the direction from the active layer to the electron blocking layer, i.e., a compositionally graded structure, specifically a structure in which the band gap energy decreases. The thickness of the hole injection layer may be 1 to 50 nm.

[0141] In step S18, a contact layer is grown on the hole injection layer. Specifically, the contact layer is made of a nitride containing a group III element as a constituent element (Al ｙ５ Ga ｚ５ In （１－ｚ５－ｙ５） N, 0≦y5≦1, 0≦z5≦1, y4+z4≦1). The contact layer may be made of, for example, at least one of GaN, InGaN, AlGaN, and AlGaInN. The contact layer may have p-type conductivity imparted by adding a p-type dopant.

[0142] The contact layer may include multiple GaN layers with different dopant concentrations. In this embodiment, the contact layer may include a first contact layer and a second contact layer. The first contact layer may have a dopant concentration of, for example, 5×10 １７ ~5 x 10 １９ cm －３ The second contact layer can be GaN with a Mg dopant concentration in the range of 5×10 １９ ~1 x 10 ２１ cm －３ The GaN can be one containing an Mg dopant at a concentration in the range of 0.1 to 1.0, thereby reducing the contact resistance between the semiconductor and the metal electrode.

[0143] In step S19, an n-side electrode and a p-side electrode are formed. Specifically, the n-side electrode is in contact with the surface of the electron spreader layer. The n-side electrode may include at least one metal selected from the group consisting of Al, Ti (titanium), Ni (nickel), V (vanadium), Zr (zirconium), Mo (molybdenum), Ru (ruthenium), Rh (rhodium), Pd (palladium), Ag (silver), In, Sn (tin), Ta (tantalum), W (tungsten), Pt (platinum), and Au (gold). The n-side electrode may also be an alloy of these metals. The n-side electrode may include a conductive oxide or a conductive nitride.

[0144] The p-side electrode makes contact with the surface of the contact layer. The p-side electrode may contain at least one metal selected from the group consisting of Al, Ti, Ni, V, Zr, Mo, Ru, Rh, Pd, Ag, In, Sn, Ta, W, Pt, and Au. The p-side electrode may also be a metal alloy of these metals. The p-side electrode may contain a conductive oxide or a conductive nitride.

[0145] FIG. 10 is a diagram showing the results of a simulation showing the relationship between current injection efficiency (CIE) and emission wavelength.

[0146] Simulator: Silencer ver. 6.4

[0147] Al composition of electron blocking layer: 1. Thickness of well layer: 2 nm. Thickness of barrier layer: 3 nm. Characteristic line CIE 80. Al composition of well layer: 0.6 to 0.8. Al composition of barrier layer: 0.80. Characteristic line CIE 85. Al composition of well layer: 0.6 to 0.8. Al composition of barrier layer: 0.85.

[0148] For light emission with a wavelength of 240 nm or less, the current injection efficiency decreases as the emission wavelength shortens. By decreasing the Al composition of the barrier layer and moving the level related to optical transition away from the heterobarrier of the electron blocking layer, the injection efficiency improves.

[0149] FIG. 11 shows the results of a simulation showing the relationship between leakage current and emission wavelength. The horizontal axis represents wavelength, and the vertical axis represents leakage current ratio. The leakage current ratio (NH / NE) represents the ratio of the current from the number of electrons (NE) that reach the p-side electrode and the number of holes (NH) that reach the n-side electrode to the current applied to the light-emitting diode. While the main leakage current is electron flow, blocking electron flow is also important. Regarding hole leakage current, attention is also paid to the n-side heterobarrier.

[0150] Characteristic lines ΔBW1, ΔBW2, ΔBW3, ΔBW4, ΔBW5, and ΔBW6 show the following characteristics of the Al composition difference between the barrier layers and the well layers.

[0151] Name of characteristic line: Al composition difference Characteristic line ΔBW1: 0.30. Characteristic line ΔBW2: 0.25. Characteristic line ΔBW3: 0.20. Characteristic line ΔBW4: 0.15. Characteristic line ΔBW5: 0.10. Characteristic line ΔBW6: 0.05.

[0152] The difference in Al composition between the barrier layer and the well layer can be less than 0.07, the difference in Al composition can be less than 0.06, and further the difference in Al composition can be less than 0.05.

[0153] The results in Figure 11 show that the leakage current increases significantly when the emission wavelength is shorter than 250 nm. The increase in leakage current is particularly significant in the emission wavelength region of 240 nm or shorter. Furthermore, when the Al composition of the electron blocking layer is fixed, reducing the difference in Al composition between the barrier layer and the well layer reduces the leakage current. Therefore, if the difference in Al composition between the barrier layer and the well layer is 0.04 or less, or less than 0.04, the leakage current is further reduced.

[0154] At a certain emission wavelength, decreasing the difference in Al composition between the barrier layer and the well layer weakens quantum confinement while decreasing the leakage current ratio. A reduction in the leakage current ratio increases the external quantum efficiency. The experimental results show behavior similar to that of the simulation results. Furthermore, decreasing the difference in Al composition between the barrier layer and the well layer can move the level related to optical transition away from the heterobarrier energy level of the electron blocking layer. Furthermore, moving the level related to optical transition away from the maximum value of the heterobarrier can improve the external quantum efficiency. These advantages also apply to the level related to optical transition in the bulk light-emitting layer.

[0155] As described above, according to this embodiment, it is possible to provide a group III nitride light-emitting device that suppresses a decrease in external quantum efficiency due to a decrease in the band offset between the active layer and the electron blocking layer.

[0156] 12 shows an exemplary structure of a light emitting diode (LED), in which the anode and cathode electrodes to the p-type and n-type semiconductor regions of the LED structure are omitted.

[0157] Exemplary structure of a light-emitting diode (LED): n-type semiconductor layer: Al with a thickness of 600-1200 nm ０．８６ Ga ０．１４ N layer. Multiple quantum well structure (MQW): 7 well layers. Well layer: AlGaN with a thickness of 2 nm and an Al composition of 0.792. Barrier layer: AlGaN with a thickness of 3 nm and an Al composition of 0.823 and 0.801.

[0158] Subsequently, an evaluation of the crystalline quality of the LED structure is presented.

[0159] Fig. 13 shows an X-ray diffraction reciprocal space mapping (XRD-RSM) image of the (10-15) plane obtained by X-ray diffraction (XRD) of the LED structure shown in Fig. 12. The "-1" in the plane index indicates that a bar is drawn over the "1" in the figure.

[0160] n-type semiconductor layer (Al ０．８６ Ga ０．１４ The p-type GaN contact layer is lattice-relaxed, and the p-type GaN layer and multiple quantum well (MQW) structure are coherently grown on the AlN template layer.

[0161] FIG. 14 shows the n-type semiconductor layer (Al ０．８６ Ga ０．１４ 14 shows X-ray diffraction (XRD) images of the n-type semiconductor layer (Al ０．８６ Ga ０．１４ The diffraction peak images of the (0004) and (20-22) planes of SiO2 (N) are shown. The "-2" in the plane index indicates that a bar is drawn over the "2" in the figure. The full width at half maximum of the diffraction image of the (0004) plane: 30 degrees. The full width at half maximum of the diffraction image of the (20-22) plane: 114 degrees.

[0162] Parts (a) and (b) of Figure 15 show diffraction peak images of the (0004) and (20-22) planes of an AlN single crystal on a sapphire support. The full width at half maximum of the diffraction image of the (0004) plane is 29 degrees. The full width at half maximum of the diffraction image of the (20-22) plane is 114 degrees.

[0163] The dislocation densities of the n-type semiconductor layer and the AlN single crystal estimated from the measurements in parts (a) and (b) of FIG. 14 and parts (a) and (b) of FIG. 15 are shown below: Screw / mixed dislocation density: 1×10 ５ cm －２ Edge dislocation density: less than 1×10 ８ cm －２ less than.

[0164] Next, an evaluation of the electrical properties of the LED structure is presented.

[0165] 16 is a diagram showing the electroluminescence (EL) of the LED structure. Referring to FIG. 16, characteristic lines EL823 and LE801 are shown.

[0166] The LED structure of the characteristic line EL823 has the following multiple quantum well structure (MQW): Multiple quantum well structure (MQW): 7 well layers. Well layer: AlGaN with a thickness of 2 nm and an Al composition of 0.792. Barrier layer: AlGaN with a thickness of 3 nm and an Al composition of 0.823. EL peak wavelength: 229.5 nm.

[0167] The LED structure of characteristic curve EL801 has the following multiple quantum well structure (MQW): Multiple quantum well structure (MQW): 7 well layers. Well layer: AlGaN with a thickness of 2 nm and an Al composition of 0.792. Barrier layer: AlGaN with a thickness of 3 nm and an Al composition of 0.801. EL peak wavelength: 230.2 nm.

[0168] 17 is a graph showing the external quantum efficiency (EQE) of the LED structure, which shows characteristic line EQE 823 and characteristic line EQE 801. Decreasing the Al composition of the barrier layer increases the external quantum efficiency of the LED structure.

[0169] 18 is a graph showing the relationship between the emission wavelength and the external quantum efficiency (EQE) of an LED structure. Referring to FIG. 18, groups G801 and G823 are shown. Group G801 includes on-wafer measurement data of LED structures having a multi-quantum well structure with barrier layers having a thickness of 3 nm and an Al composition of 0.801. Group G823 includes on-wafer measurement data of LED structures having a multi-quantum well structure with barrier layers having a thickness of 3 nm and an Al composition of 0.823.

[0170] When comparing the external quantum efficiency (EQE) of on-wafer LED structures with the same emission wavelength in the emission wavelength distributions of group G801 and group G823, the LED structure of group G801 is superior to the LED structure of group G823.

[0171] The external quantum efficiency (EQE) of deep ultraviolet LEDs decreases as the wavelength decreases in the emission wavelength range from 240 nm to 206 nm.

[0172] FIG. 19 shows the relationship between the injection current into the LED structure and the external quantum efficiency (EQE). External quantum efficiencies EQE7982, EQE7980, and EQE7979 are shown in FIG. 19. "EQE7982" shows the characteristics of a multi-quantum well structure (ΔWB = 0.03) with well layers having an Al composition of 0.79 and barrier layers having an Al composition of 0.82. "EQE7980" shows the characteristics of a multi-quantum well structure (ΔWB = 0.01) with well layers having an Al composition of 0.79 and barrier layers having an Al composition of 0.80. "EQE7979" shows the characteristics of a bulk light-emitting layer in which both the well layers and barrier layers are grown with the same Al composition of 0.79. Reducing the average Al composition of the active layer increases the external quantum efficiency.

[0173] Subsequent characterization is performed using the assembled devices (DEV_A, DEV_B) which are fabricated by flip-chip bonding the LED structure to an AlN ceramic package using solder (AuSn).

[0174] DEV_A: Al composition of the barrier layer: 0.797. Al composition of the well layer: 0.785. Difference in Al composition between the barrier layer and the well layer: 0.012. Emission wavelength: 230 nm.

[0175] DEV_B: Al composition of the barrier layer: 0.743. Al composition of the well layer: 0.730. Difference in Al composition between the barrier layer and the well layer: 0.013. Emission wavelength: 236 nm.

[0176] 20 shows the EL spectra of the assembled devices (DEV_A, DEV_B). Full width at half maximum of the assembled device (DEV_A): 10 nm. Full width at half maximum of the assembled device (DEV_B): 10 nm.

[0177] Parts (a) and (b) of Figure 21 show the injection current dependence of the optical output and external quantum efficiency of the assembled device (DEV_A, emission wavelength 230 nm). Parts (a) and (b) of Figure 22 show the injection current dependence of the optical output and external quantum efficiency of the assembled device (DEV_B, emission wavelength 236 nm). The optical output and external quantum efficiency of these assembled devices (DEV_A, DEV_B) were measured by pulse driving and CW driving. The pulse width was 120 microseconds, and the pulse duty was 0.1%.

[0178] The assembled device (DEV_A) exhibited an optical output power of 3.12 mW and an external quantum efficiency (max) of 0.59% at a current of 191 mA under CW operation. Under pulse operation, the assembled device (DEV_A) exhibited an optical output power of 20.3 mW and an external quantum efficiency (max) of 0.68% at a current of 1000 mA.

[0179] The assembled device (DEV_B) exhibited an optical output power of 11.4 mW and an external quantum efficiency (max) of 1.44% at a current of 200 mA under CW driving. Under pulse driving, the assembled device (DEV_B) exhibited an optical output power of 51.0 mW and an external quantum efficiency (max) of 1.48% at a current of 1000 mA.

[0180] In the relationship between external quantum efficiency and emission wavelength shown in Non-Patent Document 4, the following values ​​are equivalent to the top level: External quantum efficiency (maximum): Emission wavelength 236 nm, 1.44% @ emission wavelength 236 nm (CW drive) External quantum efficiency (maximum): Emission wavelength 230 nm, 0.59% @ emission wavelength 236 nm (CW drive)

[0181] Furthermore, the cathodoluminescence (CL) evaluation (accelerating voltage: 2 kV) of the light-emitting layer of the LED structure is shown.

[0182] The epitaxial structure for CL evaluation is shown below: On a template including a sapphire substrate and an FFA sapphire AlN template layer (600 nm thick), an AlN film (200 nm thick), a compositionally graded AlGaN layer (100 nm thick), and an n-type AlGaN layer (100 nm thick). ０．８６ Ga ０．１４ The N layer (750 nm thick) and the light-emitting layer are grown in this order by MOVPE. The light-emitting layer has a multi-quantum well structure (seven 2 nm thick Al ０．７９ Ga ０．２１ N well layer / 3 nm thick Al ０．８６ Ga ０．１４ N barrier layer) or Al ０．７９ Ga ０．２１ It includes a N bulk film (for example, 35 nm thick).

[0183] 23A, 23B, and 23C show the area-averaged CL spectrum, atomic force microscope (surface AFM) image, and scanning electron microscope (SEM) image at room temperature, respectively. Referring to FIG. 23A, the CL spectra of the light-emitting layers with multiple quantum well structures and bulk films are shown. When the band-edge emission was analyzed by a single Gaussian fit, the peak wavelength was approximately 235 nm, and the peak intensity of the spectral image of the bulk film light-emitting layer was greater than that of the spectral image of the multiple quantum well structure light-emitting layer.

[0184] Referring to FIGS. 23B and 23C, the surface AFM image of the bulk film shows irregularities on the surface, whereas the SEM image shows no irregularities on the surface.

[0185] Figure 24 shows surface AFM images of the light-emitting layer of the multiple quantum well structure and bulk film. The arrow A, the crystal orientation system G, and the 2-micrometer-long measure G are shown in Figure 24 and are shared by parts (a) and (b) of Figure 24.

[0186] Referring to part (a) of Figure 24, steps appear in the off-direction (arrow AOFF) of the template member in the surface AFM image of the multiple quantum well structure light-emitting layer. The dashed-line box in part (a) of Figure 24 indicates the region where the surface film thickness fluctuates. The arrow AR1 indicates the recess between the steps. Referring to part (b) of Figure 24, steps appear in the off-direction (arrow AOFF) of the template member in the surface AFM image of the bulk film light-emitting layer. The dashed-line box in part (b) of Figure 24 indicates the region where the surface film thickness fluctuates. The arrow AR2 indicates the recess between the steps.

[0187] 25 shows CL images of the light-emitting layer of the multiple quantum well structure and the bulk film. The CL images are normalized to the range of the intensity measure shown on the right side of each of parts (a) and (b) of FIG.

[0188] Referring to part (a) of Figure 25, a pattern corresponding to steps appears in the CL image of the multiple quantum well structure light-emitting layer in the off-direction of the template member (arrow AOFF in Figure 24). The dashed-line box in part (a) of Figure 25 indicates an area where the CL intensity is high. The arrow AR3 indicates a dark line. Referring to part (b) of Figure 25, a pattern corresponding to steps appears in the CL image of the bulk film light-emitting layer in the off-direction of the template member (arrow AOFF). The dashed-line box in part (b) of Figure 25 indicates an area where the CL intensity is high. The arrow AR4 indicates a dark line.

[0189] Figure 26 shows CL peak energy maps of the light-emitting layer of the multiple quantum well structure and the bulk film. The crystal orientation system GOR and the 2-micrometer-long measure GMS shown in Figure 26 are shared by parts (a) and (b) of Figure 26. The CL peak energy maps are normalized to the range of the intensity measure shown on the right side of each of parts (a) and (b) of Figure 26.

[0190] Referring to part (a) of Fig. 26, the CL peak energy map of the multiple quantum well structure light-emitting layer shows a streak-like region with high peak energy in the off direction of the template member (arrow AOFF in Fig. 24). Referring to part (b) of Fig. 26, the CL peak energy map of the bulk film light-emitting layer shows a streak-like region with high peak energy in the off direction of the template member (arrow AOFF in Fig. 24).

[0191] Figure 27 shows an NBE integrated CL intensity map and a peak energy map of the bulk film light-emitting layer measured at room temperature. The crystal orientation system GOR and the 2-micrometer-long measure GMS shown in Figure 27 are shared by parts (a) and (b) of Figure 27.

[0192] The CL images in parts (a) and (b) of Figure 27 show an emission distribution that strongly reflects the off-axis orientation of the template layer surface. CL images tend to show high CL intensity at low acceleration energies. The dashed-line boxes in parts (a) and (b) of Figure 27 indicate that the CL intensity is high in the low-energy region. The CL peak energy width within the dashed-line region is approximately 80 meV. This CL peak energy width corresponds to approximately 0.03 in terms of Al composition. The AlN template layer has a step-like morphology with a width of approximately 2 to 3 micrometers in the epitaxial surface step structure associated with the off-axis orientation. Slight disturbances in this epitaxial surface step structure associated with the off-axis orientation cause a distribution of the Al composition. The light-emitting area is associated with a Ga-rich region in the light-emitting layer (e.g., a region where the Ga element is abundant by approximately 0.03). Approximately 65% ​​of the total light-emitting intensity is generated in the Ga-rich region rather than the Al-rich region. The optical transition level in the Ga-rich region differs from the energy level in the Al-rich region by approximately 30 meV at maximum.

[0193] Figure 28 shows the surface morphology based on an AFM image. The right side of Figure 28 shows a measure of the depth direction. The AFM image shows that the nanometer-order surface unevenness on the growth surface causes slight fluctuations in the composition of Group III elements.

[0194] Figure 29 shows the relationship between integrated CL intensity and photon energy. The integrated CL intensity has a peak at low photon energy, e.g., around 5.27 eV, and tails off at about 30 meV in the high photon energy region. This tailing indicates fluctuations in the Ga composition. Region SA15 indicates a region of high CL intensity (15%) at the mapping point, and region SA50 indicates a region of average CL intensity (50%) at the mapping point. This result indicates that weak, localized emission accounts for 65% of the total emission.

[0195] Figure 30 shows the relationship between integrated CL intensity and photon energy measured at an absolute temperature of 79 Kelvin and at room temperature. Part (a) of Figure 30 shows the integrated CL intensity distribution measured at 79 Kelvin. Part (b) of Figure 30 shows the integrated CL intensity distribution measured at room temperature. To the right of each integrated CL intensity distribution, a measure representing frequency is shown.

[0196] 30(a), the integrated CL peak intensity at 79 K is greater than the integrated CL peak intensity at room temperature. At low temperatures, localized light emission occurs in the Ga-rich region, and this light emission intensity is strong.

[0197] The template member 112c and the active layer 114 are arranged in the direction of the axis Ax1. Ｙ Ga １－Ｙ The layer has fluctuations in group III composition. Ｙ Ga １－Ｙ The N layer (Y is the average Al composition) includes a Ga-rich region and an Al-rich region in a reference plane intersecting the axis Ax1. The Ga-rich region contains more Ga atoms per unit volume than the Ga composition (1-Y), and the Al-rich region contains more Al atoms per unit volume than the Al composition Y. The Al-rich region contains more Al atoms than the Al composition Y. Ｙ Ga １－Ｙ The Al composition Y of the N layer has a displacement of at least 0.03. The support 118 of the template member 112c includes sapphire. The primary surface of the support 118 is off-axis in the m-axis direction, and the template layer 120 is c-axis oriented. The template layer 120 includes a hexagonal AlN layer. The surface of the template layer 120 has a step structure associated with the m-axis direction.

[0198] As described above, according to this embodiment, it is possible to provide a group III nitride light-emitting device that suppresses a decrease in external quantum efficiency due to a decrease in the band offset between the active layer and the electron blocking layer.

[0199] This embodiment has various aspects as follows.

[0200] A Group III nitride light-emitting device according to a first aspect of this embodiment includes a Group III nitride semiconductor layer containing Al as a constituent element, an electron blocking layer containing Al as a constituent element, and an Al blocking layer provided between the electron blocking layer and the Group III nitride semiconductor layer so as to emit light having a peak wavelength in the deep ultraviolet wavelength region of 240 nm or less and 206 nm or more. Ｙ Ga １－Ｙ an active layer including an N layer (Y is an Al composition, where Y is greater than zero); Ｘ Ga １－Ｘ a base member having a primary surface containing N and carrying the Group III nitride semiconductor layer, the active layer, and the electron blocking layer on the primary surface, where X is greater than 0 and less than 1, wherein an Al composition G in the active layer is equal to or greater than Y and less than (Y + 0.04), and a composition difference between the maximum Al composition in the electron blocking layer and the Al composition in the active layer is 0.18 or greater.

[0201] In a Group III nitride light-emitting device according to a second aspect of the first aspect of this embodiment, the base member includes a template member, and the template member includes a support having a primary surface made of a material different from Group III nitride, and a template layer, and the template layer includes the Al Ｘ Ga １－Ｘ Contains N, and the Al Ｘ Ga １－Ｘ N may contain compressive strain covering the main surface of the support, and the half width of the X-ray rocking curve of the (10-12) plane may be 1000 arcsec or less.

[0202] In the III-nitride light emitting device of the third aspect according to the first aspect of this embodiment, the base member can include a bulk AlN single crystal substrate.

[0203] In the group III nitride light emitting device according to any one of the first to third aspects of this embodiment, the Al composition of the group III nitride semiconductor layer and the Al Ｙ Ga １－Ｙ The maximum composition difference between the Al composition of the N layer and the Al composition of the N layer can be 0.06 or more.

[0204] In a group III nitride light emitting device according to any one of the first to fourth aspects of this embodiment, the active layer is formed of the Al as either a bulk light emitting layer or a well layer of a quantum well structure. Ｙ Ga １－Ｙ It may include N layers.

[0205] In the III-nitride light-emitting device of the sixth aspect according to the fifth aspect of this embodiment, the active layer includes the Al as the well layer of the quantum well structure. Ｙ Ga １－Ｙ The N layer may be included, and the composition difference between the maximum Al composition of the electron blocking layer and the Al composition of the barrier layer of the quantum well structure may be 0.18 or more.

[0206] In the group III nitride light emitting device according to any one of the first to sixth aspects of this embodiment, the Al Ｙ Ga １－Ｙ The N layer may be in contact with the electron blocking layer.

[0207] In the III-nitride light emitting device of the eighth aspect according to the fifth aspect of this embodiment, the Al composition G in the active layer is substantially equal to Y throughout the active layer, and the maximum Al composition of the electron blocking layer and the Al composition G are Ｙ Ga １－Ｙ The composition difference between the Al compositions of the N layers can be 0.18 or more.

[0208] In a Group III nitride light-emitting device of a ninth aspect according to any one of the first to sixth aspects of this embodiment, the active layer includes a stacked structure of a plurality of semiconductor layers having different Al compositions, the plurality of semiconductor layers including at least one first semiconductor layer having the smallest Al composition among the Al compositions of the semiconductor layers, and at least one second semiconductor layer having the largest Al composition among the Al compositions of the semiconductor layers, the first semiconductor layer and the second semiconductor layer being arranged in a direction from one to the other of the Group III nitride semiconductor layer and the electron blocking layer, and the first semiconductor layer includes at least one Al Ｙ Ga １－ＹThe semiconductor device may include an N layer, wherein a difference between the Al composition of the second semiconductor layer and the maximum Al composition of the electron blocking layer is greater than a difference between the Al composition of the first semiconductor layer and the Al composition of the second semiconductor layer, and a composition difference between the maximum Al composition of the electron blocking layer and the Al composition of the second semiconductor layer may be 0.18 or more.

[0209] In the Group III nitride light-emitting device of the tenth aspect according to the ninth aspect of this embodiment, the Al composition of the Group III nitride semiconductor layer may be larger than the Al composition of the second semiconductor layer, and a compositional difference between the Al composition of the Group III nitride semiconductor layer and the Al composition of the second semiconductor layer may be larger than a compositional difference between the Al composition of the first semiconductor layer and the Al composition of the second semiconductor layer.

[0210] In the Group III nitride light-emitting device of the eleventh aspect according to the ninth or tenth aspect of this embodiment, the difference in Al composition between the Al composition of the second semiconductor layer and the Al composition of the first semiconductor layer can be less than 0.04.

[0211] In the group III nitride light-emitting device of the twelfth aspect according to the eleventh aspect of this embodiment, the difference in Al composition between the Al composition of the second semiconductor layer and the Al composition of the first semiconductor layer can be 0.01 or less.

[0212] In the III-nitride light-emitting device of the thirteenth aspect according to any one of the ninth to twelfth aspects of this embodiment, the Al composition of the second semiconductor layer may be less than 0.823 and greater than Y.

[0213] In the III-nitride light-emitting device of the fourteenth aspect according to the thirteenth aspect of this embodiment, the Al composition of the second semiconductor layer may be equal to or less than 0.801.

[0214] In a Group III nitride light-emitting device of a fifteenth aspect according to any one of the ninth to fourteenth aspects of this embodiment, the stacked structure has a multiple quantum well structure, the multiple quantum well structure including a plurality of well layers as the first semiconductor layer and at least one barrier layer as the second semiconductor layer, and the barrier layer is Al Ｚ Ga１－Ｚ N layer (Z is an Al composition, but Z is larger than Y), and each of the well layers is Ｙ Ga １－Ｙ The barrier layer may include an N layer, the barrier layer being closest to the electron blocking layer, a difference between the Al composition of the barrier layer and the Al composition of the electron blocking layer being greater than a difference between the Al composition of the barrier layer and the Al composition of the well layer, and an Al composition difference between the maximum Al composition of the electron blocking layer and the Al composition of the barrier layer being 0.18 or more.

[0215] In the Group III nitride light-emitting device of the sixteenth aspect according to the fifteenth aspect of this embodiment, the Al composition of the Group III nitride semiconductor layer may be larger than the Al composition of the barrier layer, and the difference in Al composition between the Al composition of the Group III nitride semiconductor layer and the Al composition of the barrier layer may be larger than the difference in Al composition between the Al composition of the well layer and the Al composition of the barrier layer.

[0216] In the Group III nitride light-emitting device of the seventeenth aspect according to the fifteenth or sixteenth aspect of this embodiment, the difference in Al composition between the Al composition of the well layer and the Al composition of the barrier layer can be less than 0.04.

[0217] In the group III nitride light-emitting device of the eighteenth aspect according to the seventeenth aspect of this embodiment, the difference in Al composition between the Al composition of the well layer and the Al composition of the barrier layer can be 0.01 or less.

[0218] In the III-nitride light-emitting device of the 19th aspect according to any one of the 15th to 18th aspects of this embodiment, the Al composition G in the multiple quantum well structure can be greater than Y and less than (Y + 0.04).

[0219] In the III-nitride light-emitting device of the twentieth aspect according to any one of the fifteenth to nineteenth aspects of this embodiment, the Al composition of the barrier layer may be less than 0.823 and greater than Y.

[0220] In the III-nitride light-emitting device of the twenty-first aspect according to the twentieth aspect of this embodiment, the Al composition of the barrier layer may be equal to or less than 0.801.

[0221] In the Group III nitride light-emitting device of the twenty-second aspect according to any one of the ninth to twenty-first aspects of this embodiment, the Al composition of the first semiconductor layer, the Al composition of the second semiconductor layer, the thickness of the first semiconductor layer, the thickness of the second semiconductor layer, and the arrangement of the first semiconductor layer and the second semiconductor layer can be specified so that a quantum well structure is not formed in the active layer.

[0222] In the III-nitride light-emitting device of the twenty-third aspect according to the twenty-second aspect of this embodiment, the Al composition G in the stacked structure can be greater than Y and less than (Y+0.04).

[0223] In the III-nitride light-emitting device of the 24th aspect according to any one of the 15th to 23rd aspects of this embodiment, the Al composition of the first semiconductor layer, the Al composition of the second semiconductor layer, the thickness of the first semiconductor layer, the thickness of the second semiconductor layer, and the arrangement of the first semiconductor layer and the second semiconductor layer can be specified so as to provide a quantum well structure in the active layer.

[0224] In a Group III nitride light emitting device according to any one of the first to twenty-fourth aspects of this embodiment, the Group III nitride semiconductor layer is Ｗ Ga １－Ｗ The group III nitride semiconductor layer may include an N layer (W is 1 or less and greater than 0), and the Al composition W of the group III nitride semiconductor layer may be 0.85 or more.

[0225] In the III-nitride light-emitting device of the twenty-sixth aspect according to the second aspect of this embodiment, the template member and the active layer are arranged in a direction of a first axis, and the Al Ｙ Ga １－Ｙ The layer has a fluctuation in group III composition, and the Al Ｙ Ga １－ＹThe N layer includes a Ga-rich region and an Al-rich region in a reference plane intersecting the first axis, and the Ga-rich region contains more Ga atoms per unit volume than a Ga composition (1-Y), and the Al-rich region contains more Al atoms per unit volume than an Al composition Y.

[0226] In the III-nitride light-emitting device of the twenty-seventh aspect according to the twenty-sixth aspect of this embodiment, the Al-rich region is Ｙ Ga １－Ｙ The N layer may have a deviation of at least 0.03 with respect to the Al composition Y.

[0227] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present disclosure, all of which are included in the technical concept of the present disclosure.

[0228] This application claims priority from Japanese Patent Application No. 2023-091229, filed on June 1, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A group III nitride semiconductor layer containing Al as a constituent element, An electron blocking layer containing Al as a constituent element, Al is provided between the electron blocking layer and the group III nitride semiconductor layer to generate light having a peak wavelength in the deep ultraviolet wavelength region of 206 nm or more and less than 240 nm. Ｙ Ga １－Ｙ An active layer containing an N layer (where Y is Al composition, but Y is greater than zero), Al Ｘ Ga １－Ｘ A base member having a main surface containing N, on which the group III nitride semiconductor layer, the active layer, and the electron blocking layer are mounted, wherein X is greater than 0 and less than or equal to 1, and Equipped with, The Al composition G in the active layer is equal to or greater than Y, and less than (Y + 0.04). The compositional difference between the maximum Al composition of the electron blocking layer and the Al composition of the active layer is 0.18 or greater. The active layer comprises at least one of a stacked structure of multiple semiconductor layers having different Al compositions, and a bulk light-emitting layer, wherein the bulk light-emitting layer has a composition difference of 0.18 or more between the maximum Al composition of the electron block layer and the Al composition of the Al Y Ga 1-Y N layer, and the Al composition G in the active layer is substantially equal to Y in the Al Y Ga 1-Y N layer across the active layer. The plurality of semiconductor layers include at least one first semiconductor layer having the smallest Al composition among the Al compositions of the semiconductor layers, and at least one second semiconductor layer having the largest Al composition among the Al compositions of the semiconductor layers. The first semiconductor layer and the second semiconductor layer are arranged in a direction from one of the group III nitride semiconductor layer and the electron block layer to the other. The first semiconductor layer is made of Al Ｙ Ga １－Ｙ Including the N layer, The difference between the Al composition of the second semiconductor layer and the maximum Al composition of the electron block layer is greater than the difference between the Al composition of the first semiconductor layer and the Al composition of the second semiconductor layer. The compositional difference between the maximum Al composition of the electron blocking layer and the Al composition of the second semiconductor layer is 0.18 or more. The difference in Al composition between the Al composition of the second semiconductor layer and the Al composition of the first semiconductor layer is less than 0.

04. Group III nitride light-emitting devices.

2. The base member includes a template member, The template member includes a support having a main surface made of a material different from the group III nitride, and a template layer. The template layer is the Al Ｘ Ga １－Ｘ Including N, The above-mentioned Al Ｘ Ga １－Ｘ N includes compressive strain, covers the main surface of the support, and has a (10-12) plane X-ray rocking curve with a half-value width of 1000 arcsec or less. A group III nitride light-emitting device as described in claim 1.

3. The base member includes a bulk AlN single crystal substrate. A group III nitride light-emitting device as described in claim 1.

4. The Al composition of the group III nitride semiconductor layer and the Al Ｙ Ga １－Ｙ The maximum compositional difference between the Al composition of the N layer and the other layers is 0.06 or greater. A group III nitride light-emitting device as described in claim 1.

5. The active layer is either a bulk light-emitting layer or a well layer of a quantum well structure, and is made of Al Ｙ Ga １－Ｙ Including the N layer, A group III nitride light-emitting device as described in any one of claims 1 to 4.

6. The active layer is the well layer of the quantum well structure, and the Al Ｙ Ga １－Ｙ Including the N layer, The compositional difference between the maximum Al composition of the electron block layer and the Al composition of the barrier layer of the quantum well structure is 0.18 or greater. A group III nitride light-emitting device as described in claim 5.

7. The aforementioned Al Ｙ Ga １－Ｙ The N layer is in contact with the electron block layer. A group III nitride light-emitting device as described in any one of claims 1 to 4.

8. The Al composition G in the active layer is substantially equal to Y across the active layer. The maximum Al composition of the electron blocking layer and the Al Ｙ Ga １－Ｙ The compositional difference between the Al compositions in the N layer is 0.18 or greater. A group III nitride light-emitting device as described in claim 5.

9. The active layer comprises a stacked structure of multiple semiconductor layers having different Al compositions. The plurality of semiconductor layers include at least one first semiconductor layer having the smallest Al composition among the Al compositions of the semiconductor layers, and at least one second semiconductor layer having the largest Al composition among the Al compositions of the semiconductor layers. The first semiconductor layer and the second semiconductor layer are arranged in a direction from one of the group III nitride semiconductor layer and the electron block layer to the other. The first semiconductor layer is made of Al Ｙ Ga １－Ｙ Including the N layer, The difference between the Al composition of the second semiconductor layer and the maximum Al composition of the electron block layer is greater than the difference between the Al composition of the first semiconductor layer and the Al composition of the second semiconductor layer. The compositional difference between the maximum Al composition of the electron blocking layer and the Al composition of the second semiconductor layer is 0.18 or greater. A group III nitride light-emitting device as described in any one of claims 1 to 4.

10. The Al composition of the group III nitride semiconductor layer is greater than the Al composition of the second semiconductor layer. The difference in Al composition between the Group III nitride semiconductor layer and the second semiconductor layer is greater than the difference in Al composition between the first semiconductor layer and the second semiconductor layer. A group III nitride light-emitting device as described in claim 9.

11. The difference in Al composition between the Al composition of the second semiconductor layer and the Al composition of the first semiconductor layer is less than 0.

04. A group III nitride light-emitting device as described in claim 9.

12. The difference in Al composition between the Al composition of the second semiconductor layer and the Al composition of the first semiconductor layer is 0.01 or less. A group III nitride light-emitting device as described in claim 11.

13. The Al composition of the second semiconductor layer is less than 0.823 and greater than Y. A group III nitride light-emitting device as described in claim 9.

14. The Al composition of the second semiconductor layer is equal to or less than 0.

801. A group III nitride light-emitting device as described in claim 13.

15. The aforementioned laminated structure has a multiple quantum well structure, The multiple quantum well structure includes a plurality of well layers as the first semiconductor layer and at least one barrier layer as the second semiconductor layer. The aforementioned barrier layer is Al Ｚ Ga １－Ｚ It contains an N layer (where Z is Al composition, but Z is greater than Y), Each of the aforementioned well layers is, Ｙ Ga １－Ｙ Including the N layer, The barrier layer is closest to the electron blocking layer, The difference between the Al composition of the barrier layer and the maximum Al composition of the electron block layer is greater than the difference between the Al composition of the barrier layer and the Al composition of the well layer. The difference in Al composition between the maximum Al composition of the electron blocking layer and the Al composition of the barrier layer is 0.18 or greater. A group III nitride light-emitting device as described in claim 9.

16. The Al composition of the group III nitride semiconductor layer is greater than the Al composition of the barrier layer. The difference in Al composition between the group III nitride semiconductor layer and the barrier layer is greater than the difference in Al composition between the well layer and the barrier layer. A group III nitride light-emitting device as described in claim 15.

17. The difference in Al composition between the Al composition of the well layer and the Al composition of the barrier layer is less than 0.

04. A group III nitride light-emitting device as described in claim 15.

18. The difference in Al composition between the Al composition of the well layer and the Al composition of the barrier layer is 0.01 or less. A group III nitride light-emitting device as described in claim 17.

19. In the aforementioned multiple quantum well structure, the Al composition G in the barrier layer is greater than Y and less than (Y + 0.04). A group III nitride light-emitting device as described in claim 15.

20. The Al composition of the barrier layer is less than 0.823 and greater than Y. A group III nitride light-emitting device as described in claim 15.

21. The Al composition of the barrier layer is equal to or less than 0.

801. A group III nitride light-emitting device as described in claim 20.

22. The Al composition of the first semiconductor layer, the Al composition of the second semiconductor layer, the thickness of the first semiconductor layer, the thickness of the second semiconductor layer, and the arrangement of the first and second semiconductor layers are specified so as not to form a quantum well structure in the active layer. A group III nitride light-emitting device as described in claim 9.

23. In the aforementioned laminated structure, the Al composition G in the second semiconductor layer is greater than Y and less than (Y + 0.04). A group III nitride light-emitting device as described in claim 22.

24. The Al composition of the first semiconductor layer, the Al composition of the second semiconductor layer, the thickness of the first semiconductor layer, the thickness of the second semiconductor layer, and the arrangement of the first and second semiconductor layers are specified so as to provide a quantum well structure in the active layer. A group III nitride light-emitting device as described in claim 15.

25. The aforementioned group III nitride semiconductor layer is Al Ｗ Ga １－Ｗ It includes N layers (W is less than 1 and greater than 0), The Al composition W of the aforementioned Group III nitride semiconductor layer is 0.85 or higher. A group III nitride light-emitting device as described in any one of claims 1 to 4.

26. The template member and the active layer are arranged in the direction of the first axis, The aforementioned Al Ｙ Ga １－Ｙ The N layer has fluctuations in its group III composition. The Al of the active layer Ｙ Ga １－Ｙ The N layer includes a Ga-rich region and an Al-rich region in a reference plane intersecting the first axis. The Ga-rich region contains more Ga atoms per unit volume than the Ga composition (1-Y), The Al-rich region contains more Al atoms per unit volume than Al composition Y. A group III nitride light-emitting device as described in claim 2.

27. The Al-rich region is the Al Ｙ Ga １－Ｙ The Al composition Y of the N layer has a displacement of at least 0.

03. A group III nitride light-emitting device as described in claim 26.