Light-emitting element and light-emitting device

Abstract

To provide a light-emitting element and a light-emitting device capable of improving the extraction efficiency of light in an oblique direction.SOLUTION: A light-emitting element includes a single-crystal substrate including a first region and a second region at a position different from the first region, a first semiconductor layer of a first conductivity disposed on the single-crystal substrate, a light-emitting layer disposed on the first semiconductor layer in the first region, a second semiconductor layer of a second conductivity type disposed on the light-emitting layer, a first electrode disposed on the first semiconductor layer in the second region, a second electrode disposed on the second semiconductor layer, a side surface absorption region that is provided on a side surface of at least one of the single-crystal substrate and the first semiconductor layer and absorbs light emitted from the light-emitting layer, and a low-refractive-index region that is provided on the inside of at least one of the single-crystal substrate and the first semiconductor layer in the second region and has a lower refractive index than its periphery.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a light-emitting element and a light-emitting device.

Background Art

[0002] Ultraviolet light-emitting elements are applied in various fields by taking advantage of their characteristics of being small and having low power consumption. As disclosed in Patent Document 1, generally, an ultraviolet light-emitting element includes a stacked portion having an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer. In this ultraviolet light-emitting element, ultraviolet light is emitted from the light-emitting layer by electric power supplied through one electrode portion on the n-type nitride semiconductor layer and the other electrode portion on the p-type nitride semiconductor layer.

[0003] Generally, the semiconductor material used in an ultraviolet light-emitting element has a high refractive index. For this reason, the ultraviolet light generated from the light-emitting layer is totally reflected at the interface between the extraction surface and air due to the refractive index difference between the surface for extracting light and air, and is absorbed on the side surface or inside of the ultraviolet light-emitting element. The ultraviolet light generated from the light-emitting layer has an angle with respect to the extraction surface, and since a lot of light with an angle equal to or less than the total reflection critical angle is reflected, there is a problem of low light extraction efficiency.

[0004] To solve this problem, a method of processing the front or back surface of the element is widely used. For example, Patent Document 2 describes a method of forming an uneven structure on the semiconductor surface by forming a nitride semiconductor layer so as to provide a hexagonal pyramid cavity.

[0005] In addition, a method of forming a film having a refractive index smaller than that of the substrate on the back surface of the substrate is also used. For example, Patent Document 3 describes a method of increasing the light extraction efficiency by coating a thin film on the back surface of the substrate of an ultraviolet light-emitting element.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] When an uneven structure is formed on a semiconductor light-emitting element to improve the light extraction efficiency to the outside of the light-emitting element, while the light obliquely incident on the light extraction surface is easily extracted, the light perpendicular to the light extraction surface is difficult to emit, and the effect of the light extraction efficiency may not be sufficiently obtained.

[0008] Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a light-emitting element and a light-emitting device capable of improving the light extraction efficiency in an oblique direction. [Means for Solving the Problems]

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following light-emitting element and light-emitting device, and have completed the present disclosure.

[0010] The light-emitting element according to the first aspect of the present disclosure includes a single-crystalline substrate having a first region and a second region different in position from the first region, a first semiconductor layer of a first conductivity type disposed on the single-crystalline substrate, a light-emitting layer disposed on the first semiconductor layer in the first region, a second semiconductor layer of a second conductivity type disposed on the light-emitting layer, a first electrode disposed on the first semiconductor layer in the second region, a second electrode disposed on the second semiconductor layer, a side absorption region provided on at least one side surface of the single-crystalline substrate and the first semiconductor layer, for absorbing light emitted from the light-emitting layer, and a low refractive index region provided inside at least one of the single-crystalline substrate and the first semiconductor layer in the second region, having a lower refractive index than the surroundings.

[0011] The light-emitting device according to the second aspect of the present disclosure includes a light-emitting element and a submount electrically connected to the light-emitting element. The light-emitting element includes a single-crystalline substrate having a first region and a second region different in position from the first region, a first semiconductor layer of a first conductivity type disposed on the single-crystalline substrate, a light-emitting layer disposed on the first semiconductor layer in the first region, a second semiconductor layer of a second conductivity type disposed on the light-emitting layer, a first electrode disposed on the first semiconductor layer in the second region, a second electrode disposed on the second semiconductor layer, a side absorption region provided on at least one side surface of the single-crystalline substrate and the first semiconductor layer and absorbing light emitted from the light-emitting layer, and a low refractive index region provided inside at least one of the single-crystalline substrate and the first semiconductor layer in the second region and having a refractive index lower than that of the surroundings.

Effects of the Invention

[0012] According to one aspect of the present disclosure, it is possible to improve the extraction efficiency of light in an oblique direction by effectively reflecting the light in the oblique direction among the light emitted from the light-emitting layer.

Brief Description of the Drawings

[0013]

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[0014] Hereinafter, the present disclosure will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thicknesses of the respective devices and members, etc. are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Also, it goes without saying that there are portions where the dimensional relationships and ratios are different between the drawings. The definitions of the up-down and other directions in the following description are merely for convenience of explanation and do not limit the technical idea of the present disclosure. For example, if the object is rotated by 90° and observed, the up-down becomes left-right and is read accordingly, and if it is rotated by 180° and observed, the up-down is inverted and read, of course.

[0015] In the following description, the directions may be described using the terms of the X-axis direction, the Y-axis direction, and the Z-axis direction. For example, the Z-axis direction is the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6. The Z-axis direction is also the normal direction of the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction and the Y-axis direction are directions parallel to the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. The definitions of the up-down and other directions in the following description are merely for convenience of explanation and do not limit the technical idea of the present disclosure. For example, if the object is rotated by 90° and observed, the up-down becomes left-right and is read accordingly, and if it is rotated by 180° and observed, the up-down is inverted and read, of course. In the following description, the directions may be described using the terms of the X-axis direction, the Y-axis direction, and the Z-axis direction. For example, the Z-axis direction is the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6. The Z-axis direction is also the normal direction of the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction and the Y-axis direction are directions parallel to the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. The definitions of the up-down and other directions in the following description are merely for convenience of explanation and do not limit the technical idea of the present disclosure. For example, if the object is rotated by 90° and observed, the up-down becomes left-right and is read accordingly, and if it is rotated by 180° and observed, the up-down is inverted and read, of course. The definitions of the up-down and other directions in the following description are merely for convenience of explanation and do not limit the technical idea of the present disclosure. For example, if the object is rotated by 90° and observed, the up-down becomes left-right and is read accordingly, and if it is rotated by 180° and observed, the up-down is inverted and read, of course.

[0016] In the following description, the directions may be described using the terms of the X-axis direction, the Y-axis direction, and the Z-axis direction. For example, the Z-axis direction is the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6. The Z-axis direction is also the normal direction of the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction and the Y-axis direction are directions parallel to the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other.

[0017] In the following description, the directions may be described using the terms of the X-axis direction, the Y-axis direction, and the Z-axis direction. For example, the Z-axis direction is the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6. The Z-axis direction is also the normal direction of the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction and the Y-axis direction are directions parallel to the first main surface and the second main surface of the single crystal substrate 7. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other.

[0018] In the following description, the case where the first conductivity type is n-type and the second conductivity type is p-type will be exemplarily described. However, the conductivity types may be selected in the reverse relationship, with the first conductivity type being p-type and the second conductivity type being n-type.

[0019] <Light-emitting element> FIG. 1 is a cross-sectional view schematically showing Configuration Example 1 of an ultraviolet light-emitting element 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the ultraviolet light-emitting element 1 (an example of the “light-emitting element” of the present disclosure) includes a single-crystalline substrate 7 having a first region AR1 and a second region AR2 whose position is different from that of the first region AR1, and an n-type semiconductor layer 6 (an example of the “first semiconductor layer of the first conductivity type” of the present disclosure) disposed on the single-crystalline substrate 7.

[0020] Further, the ultraviolet light-emitting element 1 includes a light-emitting layer 4 disposed on the n-type semiconductor layer 6 in the first region AR1, a p-type semiconductor layer 12 (an example of the “second semiconductor layer of the second conductivity type” of the present disclosure) disposed on the light-emitting layer 4, an n-type electrode 5 (an example of the “first electrode” of the present disclosure) disposed on the n-type semiconductor layer 6 in the second region AR2, and a p-type electrode 2 (an example of the “second electrode” of the present disclosure) disposed on the p-type semiconductor layer 12.

[0021] Furthermore, the ultraviolet light-emitting element 1 includes a side absorption region 9 provided on at least one side surface of the single-crystalline substrate 7 and the n-type semiconductor layer 6 and configured to absorb light emitted from the light-emitting layer 4, and a low refractive index region 8 provided inside at least one of the single-crystalline substrate 7 and the n-type semiconductor layer 6 in the second region AR2 and having a refractive index lower than that of the surroundings.

[0022] The boundary BL between the first region AR1 and the second region AR2 is, for example, the boundary between a region located directly below the light-emitting layer 4 and a region not located directly below the light-emitting layer 4.

[0023] In this specification, the single-crystalline substrate 7 and the n-type semiconductor layer 6 are collectively referred to as the base 10. The side absorption region 9 is provided on at least a part of the side surface of the base 10. The low refractive index region 8 is provided inside the base 10 in the second region AR2. The low refractive index region 8 has a lower refractive index than the base 10.

[0024] Hereinafter, each part constituting the ultraviolet light-emitting element 1 will be described in more detail. <Single-crystalline substrate> The single-crystalline substrate 7 is not particularly limited as long as a first semiconductor layer of a first conductivity type (for example, a first nitride semiconductor layer of a first conductivity type) can be formed thereon. Specifically, examples of the single-crystalline substrate 7 include sapphire, Si, SiC, MgO, Ga2O3, ZnO, GaN, InN, AlN, or a mixed crystal substrate thereof. From the viewpoint of reducing the lattice constant difference from the n-type nitride semiconductor layer formed on the upper layer side of the single-crystalline substrate 7 and reducing threading dislocations by growing in a lattice matching system, and from the viewpoint of increasing the lattice strain for hole gas generation, it is preferable to use a single-crystalline substrate having a nitride semiconductor such as GaN, AlN, or AlGaN as a bulk, or a nitride semiconductor layer (also referred to as a template) such as GaN, AlN, or AlGaN grown on a certain material as the single-crystalline substrate 7. The single-crystalline substrate 7 may contain impurities. The single-crystalline substrate 7 is preferably an AlN single-crystalline substrate, and it is more preferably that the first main surface of the single-crystalline substrate 7 is a C+ plane and the second main surface is a C- plane.

[0025] <First semiconductor layer of a first conductivity type> The first semiconductor layer of a first conductivity type (for example, the n-type semiconductor layer 6) may be directly provided on the first main surface of the single-crystalline substrate 7 as shown in FIG. 1. Also, a layer other than the n-type semiconductor layer 6 may be provided on the first main surface of the single-crystalline substrate 7, and the n-type semiconductor layer 6 may be provided thereon. For example, a buffer layer (not shown) may be provided on the single-crystalline substrate 7, and an n-type AlGaN layer may be provided as the n-type semiconductor layer 6 on this buffer layer, and a light-emitting layer 4 may be provided thereon.

[0026] The n-type semiconductor layer 6 is, for example, a nitride semiconductor, and is desirably a mixed crystal of AlN, GaN, and InN from the viewpoint of achieving high luminous efficiency. The n-type semiconductor layer 6 may contain impurities such as group V elements such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. For example, from the viewpoints of reducing electrical resistance and the availability of raw materials, the impurity contained in the n-type semiconductor layer 6 is preferably Si.

[0027] <First electrode, second electrode> The first electrode (for example, the n-type electrode 5) and the second electrode (for example, the p-type electrode 2) supply power to the light-emitting layer 4. Each arrangement of the n-type electrode 5 and the p-type electrode 2 is not particularly limited. However, when the laminated structure portion including the n-type semiconductor layer 6, the light-emitting layer 4, and the p-type semiconductor layer 12 has a mesa structure, an example is to arrange one of the electrodes (for example, the p-type electrode 2) at the mesa top and the other electrode (for example, the n-type electrode 5) at the mesa bottom.

[0028] The n-type electrode 5 and the p-type electrode 2 are composed of, for example, a Ni / Au alloy (typically used for p-type contacts) or a Ti / Al / Ti / Au stack (typically used for n-type contacts), and are provided, for example, by sputtering or evaporation. The n-type electrode 5 and the p-type electrode 2 may also include an ultraviolet light (UV) reflector. The UV reflector is designed to redirect photons emitted toward the n-type electrode 5 and the p-type electrode 2 (so that the photons cannot escape from the semiconductor layer structure), and to improve the extraction efficiency of photons generated in the active region of the device by redirecting the photons toward a desired light-emitting surface (for example, the bottom surface). Also, the materials of the n-type electrode 5 and the p-type electrode 2 may be conductive materials such as gold, nickel, aluminum, titanium, and combinations thereof. Note that in the present disclosure, the configurations of the n-type electrode 5 and the p-type electrode 2 are not limited to the above.

[0029] <Light-emitting layer> The light-emitting layer 4 may be provided directly on the n-type semiconductor layer 6 as shown in FIG. 1. Further, a layer other than the light-emitting layer 4 may be provided on the n-type semiconductor layer 6, and the light-emitting layer 4 may be provided thereon. The formation position of the light-emitting layer 4 is not particularly limited. Specifically, an undoped AlGaN layer may be provided on the n-type semiconductor layer 6, and the light-emitting layer 4 may be provided thereon. The light-emitting layer 4 is, for example, a nitride semiconductor, and is desirably a mixed crystal of AlN, GaN, and InN from the viewpoint of realizing high luminous efficiency. Other group V elements such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si may be mixed into the light-emitting layer 4 in addition to N.

[0030] Further, the light-emitting layer 4 may have a quantum well structure or a single-layer structure, but desirably has at least one well structure from the viewpoint of realizing high luminous efficiency. Further, the single-crystalline substrate 7 is particularly desirably an AlN single crystal. In that case, from the viewpoint of lattice matching of the nitride semiconductor layer formed on the single-crystalline substrate 7, the wavelength range of the ultraviolet light emitted from the light-emitting layer 4 is desirably 200 nm or more and 300 nm or less.

[0031] <Second semiconductor layer of the second conductivity type> The second semiconductor layer of the second conductivity type (for example, the p-type semiconductor layer 12) may be provided directly on the light-emitting layer 4 as shown in FIG. 1. Further, a layer other than the p-type semiconductor layer 12 may be provided on the light-emitting layer 4, and the p-type semiconductor layer 12 may be provided thereon. For example, a graded composition layer (not shown) in which the ratio of constituent elements changes continuously or discretely may be provided on the light-emitting layer 4, and the p-type semiconductor layer 12 may be provided thereon. The formation position of the p-type semiconductor layer 12 is not particularly limited. The ultraviolet light-emitting element 1 may further have a barrier layer (not shown) having a relatively large bandgap between the light-emitting layer 4 and the graded composition layer. In another form, the p-type semiconductor layer 12 may be provided directly or indirectly on the single-crystalline substrate 7.

[0032] The p-type semiconductor layer 12 is, for example, a nitride semiconductor. The p-type semiconductor layer 12 may contain impurities such as group V elements such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. For example, from the viewpoints of reducing electrical resistance and the ease of obtaining raw materials, the impurity contained in the p-type semiconductor layer 12 is preferably Mg. The p-type semiconductor layer 12 may be p-type AlGaN doped with Mg, or p-type GaN doped with Mg.

[0033] <Side absorption region> As shown in FIG. 1, the side absorption region 9 is formed on at least one side surface of the single crystal substrate 7 and the n-type semiconductor layer 6. That is, the side absorption region 9 is formed on at least a part of the side surface of the base 10. The wafer after the LED process is diced and broken into individual pieces. Forming the layer that becomes the starting point of breaking by laser dicing is important for ensuring the yield of breaking. This layer that becomes the starting point of breaking becomes the side absorption region 9. The side absorption region 9 is formed by laser dicing (laser scribing) and appears on the side surface of the base 10 fragmented by breaking.

[0034] The height of the side absorption region 9 can be increased by increasing the output and scanning speed of the laser during laser scribing. The height of the side absorption region 9 is the length in the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6 (that is, the thickness direction of the base 10).

[0035] <Low refractive index region> As shown in FIG. 1, the low refractive index region 8 is directly provided inside at least one of the single crystal substrate 7 and the n-type semiconductor layer 6 (that is, the base 10). The low refractive index region 8 has a lower refractive index than the single crystal substrate 7 and the n-type semiconductor layer 6 (that is, the base 10) located around it. Among the light emitted from the light emitting layer 4, the low refractive index region 8 reflects the light in the oblique direction, suppressing the incident of the light L1 in the oblique direction on the side absorption region 9. The presence of the low refractive index region 8 can reduce the light loss due to the side absorption region 9 by light reflection.

[0036] Therefore, the existence of the low refractive index region 8 is important regardless of its shape. On the other hand, the shape of the low refractive index region 8 in cross-section is preferably an inverted triangle or an inverted trapezoid whose width gradually narrows as it approaches the surface of the single crystal substrate 7 on the opposite side of the surface on which the n-type semiconductor layer 6 is disposed in the n-type semiconductor layer 6 (the upper surface of the n-type semiconductor layer 6 in FIG. 1).

[0037] Here, the shape in cross-section means the shape in the cross-section obtained by cutting the single crystal substrate 7 and the n-type semiconductor layer 6 (i.e., the base 10) with a plane passing through the n-type electrode 5 and the p-type electrode 2 (for example, the X-Z plane). It is more desirable that the n-type semiconductor layer 6 has a shape such as an inverted triangle or an inverted trapezoid because it can effectively guide lateral light downward.

[0038] Further, when the low refractive index region 8 is below the light emitting layer 4, the direct light from the light emitting layer 4 may be reflected by the low refractive index region 8, resulting in a decrease in light extraction efficiency. For this reason, the low refractive index region 8 is preferably provided in a second region AR2 that is different in position from the first region AR1 where the light emitting layer 4 is disposed. Further, the low refractive index region 8 is preferably arranged so as to surround the first region AR1. Here, as shown in FIG. 1, the boundary BL between the first region AR1 and the second region AR2 is, for example, the boundary between a region located directly below the light emitting layer 4 and a region not located directly below the light emitting layer 4. That is, the boundary BL is a location where the n-type semiconductor layer 6 is exposed on the surface.

[0039] FIGS. 2 to 4 are cross-sectional views schematically showing Configuration Examples 2 to 4 of the ultraviolet light emitting element 1 according to the embodiment of the present disclosure. Examples of the second region AR2 include a region located directly below the n-type electrode 5 as shown in FIG. 1 and a region that is not located directly below the light emitting layer 4 and is also not located directly below the n-type electrode 5 as shown in FIG. 2.

[0040] It is desirable that the height of the low refractive index region 8 be higher than that of the side absorption region 9 because the light loss due to the absorption of the side absorption region 9 can be reduced. Here, the "height" refers to the length in the thickness direction of the single crystal substrate 7 and the n-type semiconductor layer 6 (that is, the thickness direction of the base 10, for example, the Z-axis direction).

[0041] As shown in FIG. 3, a plurality of low refractive index regions 8 may exist in the second region AR2. In FIG. 3, the low refractive index region 8 has a first low refractive index region 81 located below the n-type electrode 5 and a second low refractive index region 82 located on the outer peripheral side of the first low refractive index region 81. For example, the first low refractive index region 81 and the second low refractive index region 82 may have the same refractive index as each other, or may have different refractive indices from each other. The lower the refractive index of each of the first low refractive index region 81 and the second low refractive index region 82, the more preferable it is.

[0042] Also, the first low refractive index region 81 and the second low refractive index region 82 have the same shape and the same size as each other. Alternatively, the first low refractive index region 81 and the second low refractive index region 82 may have the same shape but different sizes from each other. The first low refractive index region 81 and the second low refractive index region 82 may have different shapes from each other. The second low refractive index region 82 may be higher (that is, longer in the Z-axis direction) than the first low refractive index region 81.

[0043] The first low refractive index region 81 is arranged so as to surround the first region AR1. The second low refractive index region 82 is arranged so as to surround the first low refractive index region 81 from the outside.

[0044] As a method for forming the low refractive index region 8, internal processing by a stealth laser as in a known document (NEW GLASS Vol.27 No.106 2012) can be mentioned. In the internal processing by a stealth laser, a laser is focused at an arbitrary position inside the base 10, and a modified layer is locally formed near the focus point. In this modified layer, the crystal structure of the base 10 is destroyed by the laser light and becomes amorphous. Further, in this modified layer, minute cracks (voids) may be formed by the irradiation of the laser light. In the internal processing by a stealth laser, since the laser is focused inside the base 10 instead of on the surface of the base 10 (the upper surface in FIGS. 1 to 3), there is almost no (substantially no) damage to the front or back surface of the base 10. The low refractive index region 8 may contain voids, amorphous aluminum nitride, or aluminum oxide.

[0045] Further, as shown in FIG. 4, the low refractive index region 8 may be formed to include not only the single crystal substrate 7 but also the n-type semiconductor layer 6. As shown in FIG. 4, the low refractive index region 8 may be continuously provided from the n-type semiconductor layer 6 to the single crystal substrate 7. Also, although not shown, the low refractive index region 8 may be provided only in the n-type semiconductor layer 6.

[0046] This disclosure is more effective because the TE (Transverse Electric) polarization is larger and the forward light component is larger.

[0047] FIG. 5 is a cross-sectional view showing the angle when taking out the light L from the light emitting layer 4 from the single crystal substrate 7 side in the ultraviolet light emitting element 101 according to the comparative example of this disclosure. In FIG. 5, for example, when the single crystal substrate 7 is an aluminum nitride substrate, since the refractive index difference between the aluminum nitride substrate and air is large and the total reflection critical angle is low, only light at a small angle can be taken out.

[0048] FIG. 6 shows the light rays when the light L from the light-emitting layer 4 cannot be extracted from the single-crystalline substrate 7 side in the ultraviolet light-emitting element 101 according to the comparative example of the present disclosure. Among the light L from the light-emitting layer 4, the light L1 reflected at the interface between the single-crystalline substrate 7 and the air is absorbed by the side surface absorption region 9, the n-type semiconductor layer 6, the light-emitting layer 4, the p-type semiconductor layer 12, the n-type electrode 5, the p-type electrode 2, and the like. As a result, the light extraction efficiency decreases.

[0049] FIG. 7 is a diagram showing that in the ultraviolet light-emitting element 1 according to the embodiment of the present disclosure, the low refractive index region 8 located directly below the n-type electrode 5 reflects the obliquely directed light L1, and the light that was absorbed in FIG. 6 can be extracted outward from the light extraction surface (the lower surface in FIG. 7) of the single-crystalline substrate 7.

[0050] <Shape in plan view> FIG. 8 is a plan view schematically showing Configuration Example 5 of the ultraviolet light-emitting element 1 according to the embodiment of the present disclosure. The cross section obtained by cutting the plan view shown in FIG. 8 along line A-A' corresponds to the cross-sectional view shown in FIG. 1. As shown in FIG. 8, the n-type electrode 5 and the low refractive index region 8 located below the n-type electrode 5 are arranged so as to surround the light-emitting layer 4 in plan view. Thereby, it becomes easy to surely suppress the obliquely directed light L1 from reaching the side surface absorption region 9.

[0051] Further, at least a part of the low refractive index region 8 is provided at a position directly below the n-type electrode 5. Thereby, compared with the case where the low refractive index region 8 is disposed at a position deviated from directly below the n-type electrode 5 (for example, a position on the outer peripheral side rather than directly below the n-type electrode 5), the substrate area can be reduced, which contributes to the miniaturization of the ultraviolet light-emitting element 1.

[0052] FIG. 9 is a plan view schematically showing Configuration Example 6 of the ultraviolet light-emitting element 1 according to an embodiment of the present disclosure. As shown in FIG. 9, the n-type electrode 5 is provided on both sides of the light-emitting layer 4 in the left-right direction (for example, the X-axis direction) in a plan view, and may not be provided on both sides of the light-emitting layer 4 in the up-down direction (for example, the Y-axis direction). Even with such a configuration, it is desirable that the low refractive index region 8 is arranged so as to surround the light-emitting layer 4 in a plan view. Thereby, similarly to the configuration example shown in FIG. 8, it becomes easy to surely suppress the obliquely incident light L1 from reaching the side absorption region 9.

[0053] FIG. 10 is a plan view showing Configuration Example 7 of the ultraviolet light-emitting element 1 according to an embodiment of the present disclosure. As shown in FIG. 10, the light-emitting layer 4 may be formed in a strip shape in a plan view. A plurality of light-emitting layers 4 may be arranged at regular intervals in the left-right direction (for example, the X-axis direction) in a plan view. A strip-shaped n-type electrode 5 may be arranged between one light-emitting layer 4 and the other light-emitting layer 4 adjacent to each other in a plan view. Even with such a configuration, it is desirable that the low refractive index region 8 is arranged so as to surround the light-emitting layer 4 in a plan view. Thereby, similarly to the configuration example shown in FIG. 8, it becomes easy to surely suppress the obliquely incident light L1 from reaching the side absorption region 9.

Example

[0054] To confirm the effects of the present disclosure, ray tracing simulation by ZEMAX was used. The output of the light emitted outside the light-emitting element was estimated and compared for 1 mW of light isotropically emitted from the light-emitting layer.

[0055] [Example 1] FIG. 11 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1A according to Example 1 of the present disclosure. The width of the p-type electrode 2 is 108 μm, the width of the n-type electrode 5 is 40 μm, a 100-μm aluminum nitride substrate is used as the single-crystalline substrate 7, a low refractive index region 8 having a triangular shape with a height of 65 μm in which no semiconductor is formed inside the single-crystalline substrate 7, and a 40-μm partial side absorption region 9 are provided.

[0056] [Comparative Example 1] FIG. 12 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 101A according to Comparative Example 1 of the present disclosure. The low refractive index region 8 was not provided as compared with Example 1.

[0057] [Example 2] FIG. 13 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1B according to Example 2 of the present disclosure. The width of the p-type electrode 2 was 108 μm, the width of the n-type electrode 5 was 40 μm, a triangular low refractive index region 8, and side absorption regions 9 were provided on all side surfaces of the base 10.

[0058] [Comparative Example 2] FIG. 14 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 101B according to Comparative Example 2 of the present disclosure. The low refractive index region 8 was not provided as compared with Example 2.

[0059] [Example 3] FIG. 15 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1C according to Example 3 of the present disclosure. The height of the side absorption region 9 was set to 20 μm as compared with Example 1.

[0060] [Example 4] FIG. 16 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1D according to Example 4 of the present disclosure. The height of the side absorption region 9 was set to 85 μm as compared with Example 1.

[0061] [Example 5] FIG. 17 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1E according to Example 5 of the present disclosure. The low refractive index region 8 was increased as compared with Example 1. Specifically, as the low refractive index region 8, a first low refractive index region 81 and a second low refractive index region 82 were provided.

[0062] [Example 6] FIG. 18 is a cross-sectional view showing the configuration of the ultraviolet light-emitting element 1F according to Example 6 of the present disclosure. The height of the side absorption region 9 was set to 85 μm as compared with Example 1.

[0063] [Comparison] FIG. 19 is a table showing the simulation results of the examples and comparative examples of the present disclosure. As shown in FIG. 19, when looking at the output of the light emitted outside the light-emitting element of Example 1 and Comparative Example 1, it can be seen that the output of Example 1 is 32% higher than that of Comparative Example 1, and the effect of providing the low refractive index region 8 was confirmed.

[0064] When looking at the output of the light emitted outside the light-emitting element of Example 2 and Comparative Example 2, it can be seen that the output of Example 2 is 43% higher than that of Comparative Example 2, and the effect of providing the low refractive index region 8 was confirmed.

[0065] FIG. 20 is a graph showing the relationship between the height of the side absorption region 9 and the light output in the example of the present disclosure. This graph was created based on the data shown in FIG. 19. As shown in FIG. 20, as a result of changing the height of the side absorption region 9, when the height of the low refractive index region 8 became larger than 65 μm, the change rate of the output with respect to the height of the side absorption region 9 became smaller. The height of the side absorption region 9 is 40 μm. From this, it was confirmed that when the height of the low refractive index region 8 is higher than the height of the side absorption region 9, the effect of the present disclosure becomes greater.

[0066] When looking at the output of the light emitted outside the light-emitting element of Example 5 and Example 1, it was confirmed that the output was further improved. It was found that the light extraction efficiency can be further improved by increasing the low refractive index region 8.

[0067] <Effect of the Embodiment> As described above, the ultraviolet light-emitting device 1 according to the embodiment of the present disclosure includes a single-crystalline substrate 7 having a first region AR1 and a second region AR2 whose position is different from that of the first region AR1, an n-type semiconductor layer 6 disposed on the single-crystalline substrate 7, a light-emitting layer 4 disposed on the n-type semiconductor layer 6 in the first region AR1, a p-type semiconductor layer 12 disposed on the light-emitting layer 4, an n-type electrode 5 disposed on the n-type semiconductor layer 6 in the second region AR2, a p-type electrode 2 disposed on the n-type semiconductor layer 6, a side absorption region 9 provided on at least one side surface of the single-crystalline substrate 7 and the n-type semiconductor layer 6, which absorbs the light emitted from the light-emitting layer 4, and a low refractive index region 8 provided inside at least one of the single-crystalline substrate 7 and the n-type semiconductor layer 6 in the second region AR2, having a lower refractive index than the surroundings.

[0068] According to this, the low refractive index region 8 effectively reflects the light in the oblique direction among the light emitted from the light-emitting layer 4, and suppresses the light in the oblique direction from entering the side absorption region 9. By the presence of the low refractive index region 8, the light loss due to the side absorption region 9 can be reduced by light reflection. Thereby, it is possible to improve the extraction efficiency of the light in the oblique direction.

[0069] <Modification Example> FIG. 21 is a cross-sectional view showing the configuration of the ultraviolet light-emitting device 1G according to the modification example of Example 5 of the present disclosure. In Example 5 shown in FIG. 17, the case where the first low refractive index region 81 and the second low refractive index region 82 are arranged at the same depth from the upper surface of the base 10 was shown. However, the first low refractive index region 81 and the second low refractive index region 82 may be arranged at different depths from the upper surface of the base 10. As shown in FIG. 21, for example, the second low refractive index region 82 located on the outer peripheral side of the first low refractive index region 81 may be provided at a position deeper from the upper surface of the base 10 than the first low refractive index region 81 (that is, a position closer to the light extraction surface).

[0070] According to this, among the light in the oblique direction, the light that has escaped from the first low refractive index region 81 can be reflected by the second low refractive index region 82, so that a further improvement in the light extraction efficiency can be expected.

[0071] <Ultraviolet light emitting device> The ultraviolet light emitting device according to an embodiment of the present disclosure includes, for example, an ultraviolet light emitting element according to the embodiment and a submount electrically connected to the ultraviolet light emitting element. From the viewpoint of ease of assembly, it is preferable that the ultraviolet light emitting element and the submount are electrically connected by bumps. The submount is a member for supplying power to the ultraviolet light emitting element 1.

[0072] FIG. 22 is a cross-sectional view showing a configuration example of an ultraviolet light emitting device 50 according to an embodiment of the present disclosure. As shown in FIG. 22, the ultraviolet light emitting device 50 according to an embodiment of the present disclosure includes an ultraviolet light emitting element 1 and a submount 30 electrically connected to the ultraviolet light emitting element 1.

[0073] The submount 30 includes a main body 31 made of ceramics (for example, aluminum nitride or aluminum oxide), a first electrode body 32, and a second electrode body 33. The first electrode body 32 is connected to the p-type electrode 2 of the ultraviolet light emitting element 1 via a bump 34. The second electrode body 33 is connected to the n-type electrode 5 of the ultraviolet light emitting element 1 via a bump 35. The first electrode body 91 and the second electrode body 92 are made of metal, and it is preferable that this metal includes one or more of Ag, Au, Al, Ti, Ni, Cu, Pt, W, Co, and Rh.

[0074] Since the ultraviolet light emitting device 50 includes an ultraviolet light emitting element 1 having a low refractive index region 8, light loss due to the side absorption region 9 can be reduced. Thereby, it is possible to improve the light extraction efficiency in the oblique direction.

[0075] As described above, the present disclosure has been described by way of embodiments and modifications. However, the discussions and drawings that form part of this disclosure should not be construed as limiting the present disclosure. Various alternative embodiments, examples, and operation techniques will become apparent to those skilled in the art from this disclosure. This technology naturally includes various embodiments not described herein. Without departing from the gist of the above-described embodiments and modifications, at least one of various omissions, substitutions, and changes of components can be made. Also, the effects described in this specification are merely examples and are not limiting, and there may be other effects.

[0076] Note that the present disclosure can also have the following configuration. (1) A single-crystal substrate having a first region and a second region that is different in position from the first region, A first semiconductor layer of a first conductivity type disposed on the single-crystal substrate, A light-emitting layer disposed on the first semiconductor layer in the first region, A second semiconductor layer of a second conductivity type disposed on the light-emitting layer, A first electrode disposed on the first semiconductor layer in the second region, A second electrode disposed on the second semiconductor layer, A side absorption region provided on at least one side surface of the single-crystal substrate and the first semiconductor layer, and absorbing light emitted from the light-emitting layer, In the second region, a low refractive index region provided inside at least one of the single-crystal substrate and the first semiconductor layer and having a lower refractive index than the surroundings, a light-emitting element comprising. (2) In the thickness direction of the single-crystal substrate and the first semiconductor layer, the height of the low refractive index region is higher than the height of the side absorption region, the light-emitting element according to (1) above. (3) The shape of the low refractive index region in a cross section obtained by cutting the single-crystal substrate and the first semiconductor layer in a plane passing through the first electrode and the second electrode is The light-emitting device according to (1) or (2), wherein, as approaching a surface of the single-crystalline substrate, which is located on the opposite side of the surface on which the first semiconductor layer is disposed, from the surface on which the first electrode is disposed in the first semiconductor layer, it has an inverted triangular shape or an inverted trapezoidal shape in which the width gradually becomes narrower. (4) The light-emitting device according to any one of (1) to (3), wherein at least a part of the low refractive index region is provided at a position directly below the first electrode. (5) The light-emitting device according to any one of (1) to (4), wherein the low refractive index region is arranged so as to surround the first region. (6) The low refractive index region is a first low refractive index region arranged so as to surround the first region, and a second low refractive index region arranged so as to surround the first low refractive index region from the outside, and the light-emitting device according to any one of (1) to (5). (7) A surface of the single-crystalline substrate opposite to the surface on which the first semiconductor layer is disposed is a light extraction surface, The light-emitting device according to (6), wherein the second low refractive index region is provided closer to the light extraction surface than the first low refractive index region. (8) The single-crystalline substrate contains aluminum nitride, and the light-emitting device according to any one of (1) to (7). (9) The low refractive index region contains pores, and the light-emitting device according to any one of (1) to (8). (10) The low refractive index region contains amorphous aluminum nitride, and the light-emitting device according to any one of (1) to (9). (11) The low refractive index region contains aluminum oxide, and the light-emitting device according to any one of (1) to (10). (12) A light-emitting device, and a submount electrically connected to the light-emitting device. The light-emitting element is a single-crystalline substrate having a first region and a second region that is different in position from the first region, a first semiconductor layer of a first conductivity type disposed on the single-crystalline substrate, a light-emitting layer disposed on the first semiconductor layer in the first region, a second semiconductor layer of a second conductivity type disposed on the light-emitting layer, a first electrode disposed on the first semiconductor layer in the second region, a second electrode disposed on the second semiconductor layer, a side absorption region provided on at least one side surface of the single-crystalline substrate and the first semiconductor layer, for absorbing light emitted from the light-emitting layer, and a low refractive index region provided inside at least one of the single-crystalline substrate and the first semiconductor layer in the second region, having a refractive index lower than that of the surroundings. A light-emitting device comprising the same.

Explanation of reference numerals

[0077] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 101, 101A, 101B Ultraviolet light-emitting element 2 p-type electrode 4 Light-emitting layer 5 n-type electrode 6 n-type semiconductor layer 7 Single-crystalline substrate 8 Low refractive index region 9 Side absorption region 10 Base 12 p-type semiconductor layer 30 Submount 31 Body 32 First electrode body 33 Second electrode body 34, 35 Bump 91 First electrode body 92 Second electrode body AR1 First region AR2 Second region BL Boundary L, L1 Light

Claims

1. A single crystal substrate having a first region and a second region whose position is different from that of the first region, A first semiconductor layer of a first conductivity type disposed on the single crystal substrate, A light emitting layer disposed on the first semiconductor layer in the first region, A second semiconductor layer of a second conductivity type disposed on the light emitting layer, A first electrode disposed on the first semiconductor layer in the second region, A second electrode disposed on the second semiconductor layer, A side absorption region provided on at least one side surface of the single crystal substrate and the first semiconductor layer, and absorbing light emitted from the light emitting layer, In the second region, a low refractive index region provided inside at least one of the single crystal substrate and the first semiconductor layer and having a lower refractive index than the surroundings, a light emitting device comprising.

2. The light emitting device according to claim 1, wherein in the thickness direction of the single crystal substrate and the first semiconductor layer, the height of the low refractive index region is higher than the height of the side absorption region.

3. The shape of the low refractive index region in a cross section obtained by cutting the single crystal substrate and the first semiconductor layer in a plane passing through the first electrode and the second electrode, The light emitting device according to claim 1 or 2, which is an inverted triangle or an inverted trapezoid whose width gradually narrows as it approaches a surface located on the opposite side of the surface on which the first semiconductor layer is disposed in the single crystal substrate from the surface on which the first electrode is disposed in the first semiconductor layer.

4. The light emitting device according to claim 1 or 2, wherein at least a part of the low refractive index region is provided at a position directly below the first electrode.

5. The light emitting device according to claim 1 or 2, wherein the low refractive index region is disposed so as to surround the first region.

6. The low refractive index region is, A first low refractive index region disposed so as to surround the first region, The light emitting device according to claim 1 or 2, having a second low refractive index region disposed so as to surround the first low refractive index region from the outside.

7. The surface on the opposite side of the surface on which the first semiconductor layer is disposed in the single crystal substrate is a light extraction surface, The light emitting device according to claim 6, wherein the second low refractive index region is provided closer to the light extraction surface than the first low refractive index region.

8. The single crystal substrate is the light emitting device according to claim 1 or 2 containing aluminum nitride.

9. The low refractive index region is the light emitting device according to claim 1 or 2 containing pores.

10. The light-emitting device according to claim 1 or 2, wherein the low refractive index region contains amorphous aluminum nitride.

11. The light-emitting device according to claim 1 or 2, wherein the low refractive index region contains aluminum oxide.

12. A light-emitting device, comprising: a light-emitting element; and a submount electrically connected to the light-emitting element, wherein the light-emitting element includes: a single-crystalline substrate having a first region and a second region that is different in position from the first region; a first semiconductor layer of a first conductivity type disposed on the single-crystalline substrate; a light-emitting layer disposed on the first semiconductor layer in the first region; a second semiconductor layer of a second conductivity type disposed on the light-emitting layer; a first electrode disposed on the first semiconductor layer in the second region; a second electrode disposed on the second semiconductor layer; a side absorption region provided on at least one side surface of the single-crystalline substrate and the first semiconductor layer, and configured to absorb light emitted from the light-emitting layer; and a light-emitting device, comprising: a low refractive index region provided inside at least one of the single-crystalline substrate and the first semiconductor layer in the second region and having a lower refractive index than the surroundings.

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