Light emitting element and light emitting device

Abstract

This invention aims to provide a light-emitting element that improves light output and lifespan. The light-emitting element 1, using a group III nitride semiconductor containing Al and having an emission wavelength of 200-280 nm, comprises: a substrate 10; a semiconductor layer formed by stacking an n-type layer 11, a light-emitting layer 12, and a p-type layer 14 on the substrate 10 in that order; an aperture 23 disposed in a predetermined area on the surface of the p-type layer 14 and having a depth reaching the n-type layer 11; a p-side electrode 15 disposed in contact with the p-type layer 14 and having a reflectivity of 50% or more for ultraviolet light of the emission wavelength; and an n-side electrode 16 disposed above or on the n-type layer 11 exposed at the bottom surface of the aperture 23. The aperture 23 and the n-side electrode 16 have a pattern of multiple points arranged in a two-dimensional array, and the area of ​​the p-side electrode 15 is 0.75 mm² or more.

Description

Light-emitting element and light-emitting device The present invention relates to a light emitting element and a light emitting device. Conventional sterilization devices sterilize bacteria and viruses in running water by irradiating them with ultraviolet light. Mercury lamps are widely used as light sources. Because they use mercury, mercury lamps are highly toxic and pose a significant environmental burden. Furthermore, the use of mercury lamps increases the size of the sterilization device. Meanwhile, the ultraviolet wavelength of light-emitting devices using Group III nitride semiconductors corresponds to a wavelength band of approximately 210 to 400 nm. UVC (Ultra Violet C radiation; short-wavelength ultraviolet C-band) (wavelength 100 to 280 nm) is known for its effective sterilization and disinfection capabilities, and has attracted attention for its use in sterilizing and disinfecting water, air, and other objects. Consequently, efforts are underway to replace mercury lamps with light-emitting devices using Group III nitride semiconductors with UVC wavelengths. Patent Documents 1 and 2 disclose a light-emitting device using a Group III nitride semiconductor in which the n-side electrode has a structure in which a plurality of dots are arranged in a two-dimensional pattern. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Application Publication No. 2017-513234 [Patent Document 2] International Publication No. 2010 / 146808 [Problems to be Solved by the Invention] However, the light output and lifespan of conventional UVC light-emitting elements do not meet the performance required to replace mercury lamps. Furthermore, the light output of light-emitting devices that package UVC light-emitting elements in submounts also needs to be improved. The present invention is based on this background. First, the present invention provides a light-emitting element with improved light output and lifespan. Second, the present invention provides a light-emitting device with improved light output by encapsulating the light-emitting element in a submount. [Means for Solving the Problems] One aspect of the present invention is a light-emitting element that uses a Group III nitride semiconductor containing Al and has a light emission wavelength of 200 to 280 nm, comprising: a substrate; a semiconductor layer formed on the substrate by stacking an n-type layer, a light-emitting layer, and a p-type layer in order from the substrate side; a hole provided in a predetermined region on the surface of the p-type layer and having a depth reaching the n-type layer; a p-side electrode provided in contact with the p-type layer and having a reflectivity of 50% or more for ultraviolet light of the light emission wavelength; and an n-side electrode provided on or above the n-type layer exposed at the bottom surface of the hole; the hole and the n-side electrode having a pattern of multiple points arranged in two dimensions; and the area of ​​the p-side electrode is 0.75 mm. 2 above. In addition, another aspect of the present invention is a light-emitting device, comprising: a light-emitting element of the above-mentioned aspect; and a sub-mount, in which the light-emitting element is flip-chip packaged and a reflective layer is provided on the surface of the package side; the reflectivity of the reflective layer for ultraviolet light of the emission wavelength of the light-emitting element is greater than 50%; when the reflective layer is viewed from above, the reflective layer is provided in an area at least 0 μm to 500 μm outward from the side end face of the light-emitting element. Another aspect of the present invention is a light-emitting device comprising: a light-emitting element using a Group III nitride semiconductor containing Al and having an emission wavelength of 200 to 280 nm; and a submount formed in a planar shape and comprising: a reflective layer disposed on a surface of the package side in which the light-emitting element is flip-chip packaged, and bonded to the light-emitting element; the reflective layer having an insulating layer as its lowermost layer; a portion of the surface electrode layer being disposed outside a side surface of the light-emitting element in a plan view; the reflective layer having a reflectivity of 50% or greater for ultraviolet light having an emission wavelength of the light-emitting element; and the reflective layer being disposed in a region at least 0 μm to 500 μm outward from the side surface of the light-emitting element in a plan view. [Effects of the Invention] In the above-mentioned light-emitting element, the n-side electrode has a pattern of multiple dots arranged in two dimensions. Therefore, the area of ​​the p-side electrode can be increased. Furthermore, the area of ​​the p-side electrode is set to 0.75 mm 2 This improves light output and lifespan. Furthermore, in the light-emitting device of the aforementioned aspect, a reflective layer is provided in a region extending from a side surface of the light-emitting element to a distance of at least 0 μm and no greater than 500 μm from the side surface when viewed from above. This improves light output. The light-emitting element uses a III-type nitride semiconductor containing Al and has a light emission wavelength of 200 to 280 nm. It also has: a substrate; a semiconductor layer, wherein an n-type layer, a light-emitting layer, and a p-type layer are stacked in this order on the substrate; a hole provided in a predetermined area on the surface of the p-type layer and having a depth reaching the n-type layer; a p-side electrode provided in contact with the p-type layer and having a reflectivity of 50% or more for ultraviolet light of the light emission wavelength; and an n-side electrode provided on or above the n-type layer exposed at the bottom of the hole. Furthermore, the hole and the n-side electrode have a pattern of multiple points arranged in two dimensions. The area of ​​the p-side electrode is 0.75 mm 2 above. In the above-mentioned light-emitting element, the diameter of the n-side electrode dots is 5 to 100 μm, and the center-to-center distance between adjacent dots can be 50 to 200 μm. This can sufficiently increase the area of ​​the p-side electrode and improve the in-plane diffusion of current. In the above-described light-emitting element, the ratio of the area of ​​the p-side electrode to the total area of ​​the hole and the area of ​​the p-type layer in a plan view can be 70% or greater. This can increase the reflection of ultraviolet light by the p-side electrode, thereby improving light extraction efficiency. In the above-mentioned light-emitting element, the overall thickness of the light-emitting element can be greater than 0.5 mm and less than 1 mm, thereby improving light output and lifespan. In the above-mentioned light-emitting element, there are: a p-side pad electrode, which is provided on or above the p-side electrode; and an n-side pad electrode, which is provided on or above the n-side electrode; the total area of ​​the p-side pad electrode and the area of ​​the n-side pad electrode can be 0.7mm 2 The contact area between the light emitting element and the package substrate is increased, thereby improving heat dissipation and, as a result, increasing the lifespan. In the above-mentioned light-emitting element, the area of ​​the p-side electrode, the diameter of the n-side electrode point, and the center-to-center distance between adjacent points can also be set so that the light output is above 150 mW and the life is above 10,000 hours when driven by 350 mA. The light-emitting device comprises: the above-mentioned light-emitting element; and a submount having a flip-chip package with the light-emitting element and a reflective layer provided on the surface of the package side; the reflective layer has a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element, and the reflective layer can also be provided in a portion of an area at least 0 μm to 500 μm outward from the side end surface of the light-emitting element when viewed from above. In the above-mentioned light-emitting device, the reflective layer may be provided over the entire region of 0 μm or more from the side end surface of the light-emitting element in a plan view, thereby further improving light output. In the above-mentioned light-emitting device, the submount has a surface electrode layer bonded to the light-emitting element, the reflective layer has an insulating layer as the bottom layer, and a portion of the surface electrode layer can also be arranged outside the side end surface of the light-emitting element when viewed from above. In the above-mentioned light-emitting device, the reflective layer may also include: an insulating layer; and a metal reflective layer provided on or above the insulating layer and composed of a metal having a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element. In the above-mentioned light-emitting device, the reflective layer may include a DBR (distributed Bragg reflector) reflective layer having a reflectivity of 90% or more for ultraviolet light having a wavelength of light emitted by the light-emitting element. In the above-mentioned light-emitting device, the reflective layer may also include: an insulating layer; a metal reflective layer, which is provided on or above the insulating layer and is composed of a metal having a reflectivity of 50% or more for ultraviolet rays at the emission wavelength of the light-emitting element; and a DBR layer, which is provided on or above the metal reflective layer and has a reflectivity of 50% or more for ultraviolet rays at the emission wavelength of the light-emitting element. In the above-mentioned light-emitting device, the thickness of the substrate of the light-emitting element may be greater than 900 μm. The light-emitting device comprises: a light-emitting element using a Group III nitride semiconductor containing Al and having an emission wavelength of 200 to 280 nm; and a submount formed in a planar shape and comprising: a flip-chip package with the light-emitting element, a reflective layer disposed on the surface of the package side, and a surface electrode layer bonded to the light-emitting element. The reflective layer comprises an insulating layer as its lowermost layer, and a portion of the surface electrode layer is disposed outward of a side surface of the light-emitting element in a plan view. The reflective layer has a reflectivity of 50% or greater for ultraviolet light having an emission wavelength of the light-emitting element, and the reflective layer is disposed in a region at least 0 μm to 500 μm outward of the side surface of the light-emitting element in a plan view. (First Embodiment) FIG1 is a cross-sectional view showing the structure of a light-emitting element according to the first embodiment, and is a cross-sectional view taken perpendicularly to the principal surface of substrate 10. FIG2 is a top view showing the electrode configuration of the light-emitting element according to the first embodiment. The light-emitting element according to the first embodiment is a flip-chip type and emits ultraviolet light. The light-emitting element 1 emits light at a wavelength of UVC, for example, 200 to 280 nm. 1. Configuration of Light-Emitting Element 1 As shown in FIG1 , the light-emitting element 1 in the first embodiment comprises a substrate 10, an n-type layer 11, a light-emitting layer 12, an electron blocking layer 13, a p-type layer 14, a p-side electrode 15, an n-side electrode 16, intermediate electrodes 17A and 17B, a protective film 18, a p-side wiring electrode 19A, an n-side wiring electrode 19B, a p-side pad electrode 20, and an n-side pad electrode 21. Each of these elements is described below. Hereinafter, the stack of the n-type layer 11, the light-emitting layer 12, the electron blocking layer 13, and the p-type layer 14 may be referred to as a semiconductor layer. Substrate 10 is made of sapphire with a c-plane as its principal surface. Any material other than sapphire can be used as substrate 10, as long as it has high transmittance at the emission wavelength and can grow a Group III nitride semiconductor. The thickness of substrate 10 can be set to 0.5 to 1 mm, which improves light extraction efficiency. An anti-reflection film may be provided on the back side of the substrate 10. The back side of the substrate 10 corresponds to the side opposite to the n-type layer 11 and corresponds to the light output side. By providing an anti-reflection film, it is possible to suppress the reflection of ultraviolet rays on the back side of the substrate 10 and return to the element side, thereby improving the light extraction efficiency. The anti-reflection film is made of, for example, SiO2 with a thickness of 1 / 4 of the emission wavelength. 2. The n-type layer 11 is located on the substrate 10 via a buffer layer (not shown). The n-type layer 11 is composed of n-AlGaN. The n-type impurity is composed of Si, and the Si concentration is 5×10 18 ~5×10 19 / cm 3 The n-type layer 11 may be composed of a plurality of layers. The light-emitting layer 12 is located on the n-type layer 11. It has an MQW structure consisting of alternating and repeated well layers and barrier layers. The number of repetitions can be, for example, 2 to 5. The well layers are composed of AlGaN, with the Al composition set according to the desired emission wavelength. The barrier layers are composed of AlGaN with a higher Al composition than the well layers. The barrier layers can also be AlGaInN with a larger bandgap energy than the well layers. Alternatively, the light-emitting layer 12 can have a SQW structure. The electron blocking layer 13 is located on the light-emitting layer 12. The electron blocking layer 13 is composed of p-AlGaN with a higher Al content than the barrier layer of the light-emitting layer 12. The electron blocking layer 13 prevents electrons injected from the n-side electrode 16 from exceeding the light-emitting layer 12 and diffusing to the p-type layer 14. The p-type layer 14 is located on the electron blocking layer 13. The p-type layer 14 is composed of p-AlGaN. In the light-emitting element 1 of the first embodiment, all semiconductor layers from the n-type layer 11 to the p-type layer 14 are composed of AlGaN. This can suppress the absorption of ultraviolet light by the semiconductor layer. The Al composition of the p-type layer 14 is, for example, 5 to 80%. The p-type impurity is composed of Mg. The Mg concentration is 1×10 19 / cm 3 The p-type layer 14 can also be composed of multiple layers with different Al compositions or Mg concentrations. In this case, the layer in contact with the p-side electrode 15 can be composed of p-AlGaN with an Al composition of 5 to 80%. Furthermore, the p-type layer 14 is not limited to AlGaN; any Group III nitride semiconductor containing Al will suffice, and it can also be composed of AlGaInN. Furthermore, the top layer of the p-type layer 14 composed of multiple layers can be made of thin GaN with a thickness of at least 1 molecular layer and at most 50 nm. The top layer of the p-type layer 14 serves as a contact layer with the p-side electrode 15 . Holes 23 are formed in a portion of the surface of the p-type layer 14, reaching a depth that reaches the n-type layer 11. Holes 23 have a pattern of multiple points, and the multiple holes 23 are arranged in a grid pattern (see Figure 2). The n-type layer 11 is exposed at the bottom of the holes 23. The holes 23 that expose the n-type layer 11 have a pattern of multiple points, thereby ensuring uniformity of light emission within the surface. Furthermore, by having holes 23 have a pattern of multiple points, the reduction in the light-emitting area (the area of ​​the p-type layer 14) caused by the holes 23 can be minimized, and the area of ​​the p-side electrode 15 can be increased, thereby promoting an increase in light output. Each hole 23 is circular in plan view. Each hole 23 may also be formed in a polygonal shape, such as a square or regular hexagon. In the case of a regular hexagon, the side surfaces of the hole 23 are preferably formed as m-planes. The arrangement pattern of the holes 23 is a regular triangular lattice. The arrangement pattern of the holes 23 may also be a two-dimensional arrangement pattern, such as a square lattice or a honeycomb. A regular triangular lattice or a square lattice is preferred. The diameter of the holes 23 is preferably 5 to 100 μm. Furthermore, the center-to-center distance between adjacent holes 23 is preferably 50 to 200 μm. By adjusting the diameter and spacing of the holes 23 in this manner, the in-plane current diffusion can be improved while ensuring a sufficient area for the p-side electrode 15. The diameter of the holes 23 is defined as the diameter of the circumscribed circle of the holes 23. The p-side electrode 15 is provided in contact with the p-type layer 14. The p-side electrode 15 is provided excluding the area on the surface of the p-type layer 14 where the hole 23 is not provided and the vicinity of the end edge of the p-type layer 14 (see FIG2 ). This widens the light-emitting area. The p-side electrode 15 constitutes a "reflective electrode that improves the light extraction efficiency by reflecting the ultraviolet rays emitted from the light-emitting layer 12 toward the substrate 10." The p-side electrode 15 is made of "a material with a reflectivity of 50% or more for ultraviolet rays of the emission wavelength." For example, it is made of Ru, Rh, an alloy mainly composed of Ru or Rh, ITO / Al, etc. Ru and Rh have high reflectivity in UVC and low contact resistance with the p-type layer 14 composed of p-AlGaN, so they are suitable as the p-side electrode 15 in the UVC light-emitting element 1. A reflectivity of 70% or more is more preferred. The area of ​​the p-side electrode 15 is 0.75 mm 2The element area, the diameter of the holes 23, and the arrangement pattern are set to meet these requirements. This improves the light output and lifetime of the light-emitting element 1 in the first embodiment. The improvement in light output is due to the increased reflection area of ​​the p-side electrode 15. The improved lifetime is due to the reduced current density caused by the increased area of ​​the p-side electrode 15. In particular, by setting the area of ​​the p-side electrode 15 to 0.75 mm 2 As described above, the light emitting element 1 in the first embodiment can achieve sufficient performance to replace the mercury lamp. In order to replace the mercury lamp with the light emitting element 1, a light output of 150 mW is required when driven at 350 mA, and a life of 10,000 hours is required when driven at 350 mA. By setting the area of ​​the p-side electrode 15 to 0.75 mm 2 The above can meet this requirement. The area of ​​the p-side electrode 15 is preferably 8 mm 2 This is because if the area of ​​the p-side electrode 15 is too large, the probability of the semiconductor layer containing crystal defects increases, resulting in a decrease in production yield. Furthermore, the area of ​​the p-side electrode 15 is preferably set to be at least 70% of the device area (the total area of ​​the p-type layer 14 and the area of ​​the hole 23). This increases the reflection of ultraviolet light by the p-side electrode 15, thereby improving light extraction efficiency. Furthermore, the area of ​​the p-side electrode 15 is preferably set to be no more than 95% of the device area. This is to ensure a sufficient area for the hole 23 so as not to impair the in-plane diffusion of current. The n-side electrode 16 is provided on or above the n-type layer 11 exposed to the bottom surface of each hole 23. Therefore, the n-side electrode 16 also has a pattern of multiple dots (see FIG. 2 ). The top-view shape of the dots of n-side electrode 16 is a reduced version of the top-view shape of hole 23. If hole 23 is circular in top view, the top-view shape of n-side electrode 16 is a circle with a smaller diameter than hole 23. The arrangement pattern of the dots of n-side electrode 16 is also the same as the arrangement pattern of hole 23. By having a two-dimensional dot pattern on n-side electrode 16, the area for providing p-side electrode 15 is expanded, while also improving the in-plane diffusion of current. The n-side electrode 16 is composed of a heat-treated V / Al / Ti structure. Other materials, such as Ti / Al / Ti, can also be used for the n-side electrode 16. Specifically, the heat-treated V / Al / Ti structure comprises a layer composed of AlNx, a layer composed primarily of Al and containing V and Ti, and a layer composed of Ti, stacked in this order. AlN xThe thickness of the layer is 1 to 3 nm. x is, for example, 0.4 to 0.7. Alternatively, x may decrease in the thickness direction as it moves away from the n-type layer 11. In this case, the average value of x in the thickness direction is 0.4 to 0.7. In addition, Ga may diffuse from the n-type layer 11. In this case, the AlN x The layer is composed of Al, which is higher than the n-type layer 11. y Ga 1 － y N x (0.4 ≤ x ≤ 0.7). If the Al composition of n-type layer 11 is a, then a<y ≤ 1. For example, y is 0.7 or greater. In this case, x may decrease in the thickness direction away from n-type layer 11, and y may increase in the thickness direction away from n-type layer 11. The layer composed mainly of Al and containing V and Ti has a thickness of 50 to 500 nm. The ratio of Al, V, and Ti is, for example, 50 to 85 mol % Al, 5 to 20 mol % V, and 10 to 30 mol % Ti. In the n-side electrode 16 having the above structure, the contact resistance to the n-type layer 11 is reduced. For example, the contact resistance of the n-side electrode 16 to the n-type layer 11 is 4×10 -4 Ω・cm 2 The reasons are as follows: First, AlN x The thus formed layer can function as a good contact layer for the n-type layer 11. Second, nitrogen vacancies are generated on the surface of the n-type layer 11, and the contact resistance is reduced by converting the layer into an n-type layer. The layer composed of Ti is provided as a cover to suppress the evaporation of Al in the n-side electrode 16 during alloying. In addition to Ti, TiN, Ni, Pt, Au, etc. can also be used. Intermediate electrodes 17A and 17B are provided on p-side electrode 15 and n-side electrode 16, respectively. The top-view shape of intermediate electrode 17A is identical to that of p-side electrode 15. Furthermore, the top-view shape of intermediate electrode 17B is identical to that of n-side electrode 16, and has a multiple-dot pattern. Intermediate electrodes 17A and 17B are composed of, for example, Ti / Ni / Au / Al. Alternatively, the intermediate electrodes 17A and 17B may be omitted, and the p-side wiring electrode 19A may be directly connected to the p-side electrode 15 , and the n-side wiring electrode 19B may be directly connected to the n-side electrode 16 . The protective film 18 is provided to cover the entire top surface of the device. Specifically, the protective film 18 is provided continuously along the side surfaces and surfaces of the p-side electrode 15 and the n-side electrode 16, the surface and side surfaces of the semiconductor layer, the side surfaces of the device isolation trench, and the interior of the hole 23. Furthermore, the protective film 18 has a structure in which a first protective film 18A and a second protective film 18B are stacked in this order from the semiconductor layer side. The protective film 18 is made of an insulator, such as SiO 2. In addition, SiN, Al 2O 3. TiO 2. AlN, etc. A stacked layer of multiple materials may also be used. In addition, the materials of the first protective film 18A and the second protective film 18B may be changed. The p-side wiring electrode 19A and the n-side wiring electrode 19B are provided between the first protective film 18A and the second protective film 18B. The p-side wiring electrode 19A is connected to the intermediate electrode 17A via a hole in the first protective film 18A, and is connected to the p-side pad electrode 20 via a hole in the second protective film 18B. Furthermore, the n-side wiring electrode 19B is connected to each intermediate electrode 17B via a hole in the first protective film 18A, and is connected to the n-side pad electrode 21 via a hole in the second protective film 18B. The p-side wiring electrode 19A and the n-side wiring electrode 19B are composed of, for example, Ti / Ni / Au / Al. By placing p-side wiring electrode 19A and n-side wiring electrode 19B between intermediate electrodes 17A and 17B and p-side pad electrode 20 and n-side pad electrode 21, the shapes of p-side pad electrode 20 and n-side pad electrode 21 can be freely set. Furthermore, since holes 23 can be arranged across the entire surface, the in-plane uniformity of light emission can be improved. The p-side pad electrode 20 and the n-side pad electrode 21 are separately provided on the protective film 18. The p-side pad electrode 20 is connected to the p-side wiring electrode 19A via a hole formed in the second protective film 18B. The n-side pad electrode 21 is connected to the n-side wiring electrode 19B via a hole formed in the second protective film 18B. The p-side pad electrode 20 and the n-side pad electrode 21 are composed of, for example, Ti / Pt / Au / AuSn. As shown in Figure 2 , the p-side pad electrode 20 and the n-side pad electrode 21 are arranged within a small rectangular shape slightly inward of the outer rectangular shape of the light-emitting element 1. The p-side pad electrode 20 and the n-side pad electrode 21 each have a region that divides the small rectangular shape. The p-side pad electrode 20 and the n-side pad electrode 21 are bisected by a stripe-shaped boundary region parallel to one side of the small rectangular shape. In Figure 2 , the stripe-shaped boundary region extends vertically from the center in the horizontal direction. The total area of ​​the p-side pad electrode 20 and the n-side pad electrode 21 is preferably set to 0.7 mm 2 The above. The contact area between the light-emitting element 1 and the package substrate in the first embodiment is increased, which can improve heat dissipation. As a result, the lifespan can be improved. Furthermore, for similar reasons, the ratio of the combined area of ​​the p-side pad electrode 20 and the n-side pad electrode 21 to the light-emitting area (the area of ​​the p-side electrode 15) is preferably set to 70% or greater. The overall thickness of the light emitting element 1 in the first embodiment (the distance from the back surface of the substrate 10 to the surfaces of the p-side pad electrode 20 and the n-side pad electrode 21) is preferably 0.5 to 1 mm. Within this range, light output and life can be improved. As described above, in the light emitting element 1 of the first embodiment, the n-side electrode 16 has a pattern of multiple dots, and the dots are arranged two-dimensionally. This allows the area of ​​the n-side electrode 16 to be reduced while the area of ​​the p-side electrode 15 to be increased without impairing the in-plane diffusion of current. Furthermore, the area of ​​the p-side electrode 15 is set to 0.75 mm. 2 As a result, the light output and lifespan of the light-emitting element 1 can be improved. In particular, it can achieve the performance required to replace a mercury lamp: a light output of 150 mW at a drive current of 350 mA and a lifespan of 10,000 hours at a drive current of 350 mA. Here, lifespan refers to the time it takes for light output to reach 70% of its initial level. 2. Experimental Results Next, experimental results related to the light-emitting element 1 in the first embodiment will be described. For the light-emitting element 1 in the first embodiment, various values ​​of the area of ​​the p-side electrode 15 were produced, and the light output and lifetime were measured when the elements were driven at 350 mA. The area of ​​the p-side electrode 15 was varied according to the shape of the p-side electrode 15, the diameter of the hole 23, and the diameter of the n-side electrode 16. The lifetime was defined as the time it took for the light output to reach 70% of the initial driving level when driven at 350 mA. FIG3 is a graph showing the relationship between the area of ​​the p-side electrode 15 and the light output. The vertical axis of the graph shows a value normalized by setting it to 1 when the light output is 150 mW. As shown in FIG3 , it can be seen that the larger the area of ​​the p-side electrode 15, the greater the light output. The light output required for replacing the mercury lamp is 150 mW when driven at 350 mA. As shown in FIG3 , if the area of ​​the p-side electrode 15 is 0.5 mm 2 The above can meet this requirement. FIG4 is a graph showing the relationship between the area of ​​the p-side electrode 15 and the lifespan. As shown in FIG4 , the lifespan increases linearly with the increase in the area of ​​the p-side electrode 15. The lifespan required for replacement of the mercury lamp is 10,000 hours at a drive current of 350 mA. As shown in FIG4 , the lifespan exceeds 10,000 hours when the area of ​​the p-side electrode 15 is 0.75 mm. 2 In the above situation. As shown in FIG3 and FIG4, it can be seen that in order to meet the light output and life required for the replacement of the mercury lamp, the area of ​​the p-side electrode 15 is set to 0.75 mm. 2 That’s all. (Variation of the First Embodiment) Figure 5 is a cross-sectional view showing the structure of a light-emitting element 2 in a variation of the first embodiment, and is a cross-sectional view taken perpendicularly to the main surface of the substrate. As shown in Figure 5, the light-emitting element 2 in the variation is derived from the light-emitting element 1 in the first embodiment by omitting the p-side wiring electrode 19A and the n-side wiring electrode 19B. The top-view shapes of the p-side electrode 15, the n-side electrode 16, the p-side pad electrode 20, and the n-side pad electrode 21 are modified from those of the light-emitting element 1 in the first embodiment. The light-emitting element 2 has a structure in which the intermediate electrode 17A is connected to the p-side pad electrode 20, and the intermediate electrode 17B is connected to the n-side pad electrode 21. When the p-side wiring electrode 19A and the n-side wiring electrode 19B are omitted, the shapes of the n-side electrode 16 or the p-side pad electrode 20 and the n-side pad electrode 21 are limited, but the structure of the light emitting element 2 can be simplified. 6 to 8 are diagrams showing various electrode shapes of the light emitting element 2 in the modified form shown in Fig. 5. The electrode shapes of Figs. 6 to 8 will be described below. The electrode shape shown in FIG6 is as follows. The p-side pad electrode 20 and the n-side pad electrode 21 are arranged in a small rectangular shape that is slightly inside the outer rectangular shape of the light-emitting element 2 when viewed from above. The p-side pad electrode 20 and the n-side pad electrode 21 have regions that divide the small rectangular shape into unequal parts. The p-side pad electrode 20 and the n-side pad electrode 21 are divided into two by a straight boundary area along the end edge near the end edge of the light-emitting element 2. In FIG6 , the straight boundary area has a shape that extends in the up-down direction on the right side in the left-right direction. The one with a smaller area is set as the p-side pad electrode 20, and the one with a larger area is set as the n-side pad electrode 21. The n-side pad electrode 21 is formed as a rectangle with wide sides, and the p-side pad electrode 20 is formed as an elongated rectangle. The holes 23 and the n-side electrode 16 have circular dot shapes and are arranged in an equilateral triangular lattice in the region corresponding to the lower portion of the n-side pad electrode 21. The holes 23 and the n-side electrode 16 are not arranged in the region corresponding to the lower portion of the p-side pad electrode 20 or the lower portion of the linear region. Holes 24 for connecting the p-side electrode 15 and the p-side pad electrode 20 are formed inside the p-side pad electrode 20 in a plan view. The holes 24 have a circular dot shape and are arranged in a straight line along the edge of the light emitting element 2 at predetermined intervals. The electrode shape shown in FIG7 is as follows. The electrode shape shown in FIG7 is an example different from the electrode shape shown in FIG6 . The p-side pad electrode 20 and the n-side pad electrode 21 are arranged in a small rectangular shape that is slightly inside the outer rectangular shape of the light-emitting element 2 when viewed from above. The p-side pad electrode 20 and the n-side pad electrode 21 have regions that divide the small rectangular shape into unequal parts. The p-side pad electrode 20 and the n-side pad electrode 21 are divided into two by a boundary area of ​​a straight line at a corner thereof that is 45 degrees to the side of the rectangle. One of the right-angled equilateral triangles is set as the p-side pad electrode 20, and the other (a pentagon after removing the corners of the rectangle) is set as the n-side pad electrode 21. As in FIG6 , holes 23 and n-side electrodes 16 have circular dot shapes and are arranged in an equilateral triangular lattice pattern in the region corresponding to the lower portion of n-side pad electrode 21. Holes 23 and n-side electrodes 16 are not arranged in the region corresponding to the lower portion of p-side pad electrode 20 or the lower portion of the linear region. The hole 24 for connecting the p-side electrode 15 and the p-side pad electrode 20 is provided inside the p-side pad electrode 20 in a plan view and has a shape obtained by reducing the right-angled equilateral triangle of the p-side pad electrode 20 . The electrode shape shown in FIG8 is described below. The electrode shape shown in FIG8 is different from the electrode shapes shown in FIG6 and FIG7 . In FIG8 , the top-view shape of the holes 23 and the dots of the n-side electrode 16 in FIG7 is changed from circular to square, and the dot diameter and spacing are reduced. Other aspects are the same as in FIG7 . By setting the electrode shape to any of those shown in FIG. 6 to FIG. 8 , the sum of the areas of the p-side pad electrode 20 and the n-side pad electrode 21 can be increased, thereby improving heat dissipation. In the light emitting element 2 of the above-mentioned modified embodiment, the area of ​​the p-side electrode 15 can also be set to 0.75 mm 2 As a result, the light output and life can be improved. In particular, the light output and life can be set to the level required for replacement of the mercury lamp. (Second embodiment) FIG9 is a diagram showing the structure of the light-emitting device 3 in the second embodiment, which is a cross-sectional view perpendicular to the submount. As shown in FIG9 , the light-emitting device 3 in the second embodiment has a light-emitting element 100 that emits ultraviolet rays, and a submount 101 formed in a flat plate shape. The light-emitting element 100 can be the light-emitting element in the first embodiment. In particular, the thickness of the substrate of the light-emitting element 100 is preferably 400 μm or more. This is to improve the efficiency of light extraction from the side and to improve the light output by reflection caused by the first reflective layer 105 described later. The thickness of the substrate of the light-emitting element 100 is preferably 600 μm or more, and more preferably 900 μm or more. There is no particular upper limit on the thickness, but considering mass production and processability, it is preferably 2000 μm or less. Light-emitting element 100 is flip-chip packaged on submount 101. Light-emitting element 100 includes p-side pad electrode 100a and n-side pad electrode 100b. P-side pad electrode 100a and n-side pad electrode 100b are bonded to two surface electrode layers 103 of submount 101 via bonding electrodes 108a and 108b, respectively. The submount 101 includes a substrate layer 102, a surface electrode layer 103 on the substrate layer 102, a back electrode layer 104 provided on the back surface of the substrate layer 102, a first reflective layer 105, and a second reflective layer 106. Fig. 10 is a view of the submount 101 as viewed from above. The substrate layer 102 is formed using a flat plate made of ceramic, and is formed in a square shape when viewed from above. The ceramic is preferably made of a material with high thermal conductivity. This is to efficiently conduct heat from the light-emitting element 100 to the outside. For example, AlN is suitable. Two surface electrode layers 103 are provided separately on the surface of the substrate layer 102. The two surface electrode layers 103 are connected to the p-side pad electrode 100a and the n-side pad electrode 100b of the light-emitting element 100 via bonding electrodes 108a and 108b. The two surface electrode layers 103 are made of, for example, Au. As shown in Figure 10 , the two surface electrode layers 103 are located in the center of the square submount 101 when viewed from above. The two surface electrode layers 103 have a substantially rectangular shape and are spaced apart. Furthermore, stepped notches are provided at the corners of each rectangle to facilitate alignment of the light-emitting element 100. When viewed from above, portions of the two surface electrode layers 103 are located outside the side end faces 109 of the light-emitting element 100. Two back electrode layers 104 are provided on the back side of the substrate layer 102. The two back electrode layers 104 are connected to the two surface electrode layers 103 via holes 107. The two back electrode layers 104 are also electrically connected to the outside. The two back electrode layers 104 are made of, for example, Au. The second reflective layer 106 is provided in a predetermined region on the surface of the substrate layer 102. The second reflective layer 106 is configured to reflect ultraviolet light emitted from the light-emitting element 100 upward, thereby increasing light output. The second reflective layer 106 is composed, for example, of Au. The second reflective layer 106 is composed of the same material as the surface electrode layer 103, thereby allowing the second reflective layer 106 and the surface electrode layer 103 to be formed simultaneously. 10 , the second reflective layer 106 has a square ring shape in a plan view. The surface electrode layer 103 is located inside the inner circumference of the ring constituting the second reflective layer 106 . The first reflective layer 105 is formed in a predetermined shape in plan view on the surface electrode layer 103, the substrate layer 102, and the second reflective layer 106. The first reflective layer 105 reflects ultraviolet rays emitted from the light emitting element 100 upward to increase light output. As shown in FIG. 11 , the first reflective layer 105 has a structure in which a first insulating layer 105A, a metal reflective layer 105B, and a second insulating layer 105C are stacked in this order from the substrate layer 102 side. The reflectivity of the first reflective layer 105 is 50% or greater. Here, the reflectivity refers to the reflectivity of ultraviolet light at the wavelength emitted by the light-emitting element 100, and is the reflectivity at normal incidence. Unless otherwise specified, reflectivity has the same meaning as above. A reflectivity of 70% is preferred, and 90% or greater is even more preferred. The first insulating layer 105A is a layer made of an insulator. The first insulating layer 105A is made of, for example, SiO 2. The first insulating layer 105A is provided to ensure insulation between the surface electrode layer 103 and the metal reflective layer 105B. Since the first reflective layer 105 is also provided on the surface electrode layer 103, it is necessary to use an insulator as the bottom layer. The thickness of the first insulating layer 105A can be sufficient to provide insulation between the surface electrode layer 103 and the metal reflective layer 105B, and can be, for example, 500 nm. The metal reflective layer 105B is composed of a metal with a reflectivity of 50% or greater. A reflectivity of 60% or greater is preferred, and 80% or greater is even more preferred. For example, alloys primarily composed of Al, Mg, Ru, or Rh can be used for the metal reflective layer 105B. In particular, Al, Mg, or alloys primarily composed of these are particularly preferred for high reflectivity. The thickness of the metal reflective layer 105B can be any thickness sufficient to sufficiently reduce the transmittance of the metal reflective layer 105B. For example, it can be 50 nm or greater. The second insulating layer 105C is a layer made of an insulator. The second insulating layer 105C is made of, for example, SiO 2. The second insulating layer 105C is provided to protect the metal reflective layer 105B. The thickness of the second insulating layer 105C is, for example, 200 nm. The first reflective layer 105, when viewed from above, is formed in the shape indicated by the diagonal lines in Figure 10 . Specifically, when viewed from above, the first reflective layer 105 is provided throughout the entire square area of ​​the submount 101, excluding the area of ​​the light-emitting element 100 (the entire area extending from the side surface 109 of the light-emitting element 100 to a depth of 0 μm or greater). While a thick substrate of the light-emitting element 100 increases the output of ultraviolet light from the side surface 109, this ultraviolet light can be reflected upward by the first reflective layer 105, thereby improving light output. Furthermore, in the second embodiment, the first reflective layer 105 is provided over the entire region extending from the side end face 109 of the light-emitting element 100 to a distance of 0 μm or greater, but this is not limiting. Alternatively, the first reflective layer 105 may be provided over at least the region extending from the side end face 109 of the light-emitting element 100 to a distance of 0 μm or greater and 500 μm or less. In such a region, the intensity of ultraviolet radiation emitted from the light-emitting element 100 increases. Therefore, providing the first reflective layer 105 in such a region allows the ultraviolet radiation emitted from the light-emitting element 100 to be efficiently reflected upward by the first reflective layer 105, thereby improving light output. Furthermore, in the second embodiment, the first reflective layer 105 is configured to reflect light using the metal reflective layer 105B. However, a DBR (Distributed Bragg Reflector) reflective layer, or a combination of a DBR reflective layer and the metal reflective layer 105B, may also be configured to reflect light. For example, a DBR reflective layer may be provided between the metal reflective layer 105B and the second insulating layer 105C, or a DBR reflective layer may be provided in place of the second insulating layer 105C. In particular, regarding the angular dependence of reflectivity, the first reflective layer 105 preferably has a structure combining a DBR reflective layer and a metal reflective layer 105B. The reflectivity of a DBR reflective layer is angularly dependent, and its reflectivity may decrease depending on the angle of incidence. On the other hand, the reflectivity of the metal reflective layer 105B is not angularly dependent. Therefore, by combining a DBR reflective layer and a metal reflective layer 105B, the first reflective layer 105 can achieve a high reflectivity regardless of the angle of incidence. The DBR reflective layer is a layer of a DBR structure formed by stacking two or more materials with different refractive indices alternately at a predetermined thickness. The reflectivity of the DBR reflective layer can be set to be 90% or more. 95% is preferred, and 98% or more is even more preferred. The DBR reflective layer is made of, for example, SiO 2. TiO 2. HfO 2. Nb 2O 5. ZrO 2. MgF 2 grade materials. As described above, in the light-emitting device 3 according to the second embodiment, the first reflective layer 105 is provided in a region at least 500 μm away from the side surface 109 of the light-emitting element 100. Therefore, ultraviolet light emitted from the light-emitting element 100 can be efficiently reflected upward by the first reflective layer 105, thereby improving light output. Next, the experimental results related to the second embodiment will be described. Experiment 1: For the light-emitting device 3 according to the second embodiment, the radiation intensity on the surface of the submount 101 was determined by simulation when the light-emitting element 100 was emitting light. The submount 101 was a square with a side of 3.5 mm in plan view. The light-emitting element 100 was a square with a side of 1.06 mm in plan view and a thickness of 950 μm. FIG. 12 shows the radiation intensity (W / μm) on the surface of the submount 101. 2). As shown in Figure 12, a region with high radiation intensity exists within a region 500 μm or less from the side end face 109 of the light-emitting element 100. This result shows that providing a reflective layer within a region 500 μm or less from the side end face 109 of the light-emitting element 100 effectively improves light output. Experiment 2: In the second embodiment, the range of the first reflective layer 105 was changed to a region extending from 500 μm to 1220 μm outward from the side end face 109 of the light-emitting element 100, and light output was measured. Furthermore, the output improvement ratio was calculated compared to the case where the first reflective layer 105 was not provided. The thickness of the sapphire substrate of the light-emitting element 100 was set to 400 μm and 950 μm. The conditions were otherwise identical to those in Experiment 1. The results showed that the output improvement ratio was 0.88% when the sapphire substrate thickness was 400 μm, and 2.85% when the sapphire substrate thickness was 950 μm. This result demonstrates that the thicker the substrate, the greater the effect of the first reflective layer 105 on improving light output. Experiment 3: In the second embodiment, the range of the first reflective layer 105 was changed to a region extending from 0 μm to 1220 μm from the side facet 109 of the light-emitting element 100, and the light output was calculated. Furthermore, the output improvement rate compared to the case where the first reflective layer 105 was not provided was calculated. The thickness of the sapphire substrate of the light-emitting element 100 was set to 950 μm. The same conditions as in Experiment 1 were used otherwise. The result was an output improvement rate of 3.88%. A comparison with Experiment 2 shows that the light output improvement effect per unit area is higher when the first reflective layer 105 is provided in a region extending from 0 μm to 500 μm from the side facet 109 of the light-emitting element 100, and when the first reflective layer 105 is provided in a region extending from 500 μm to 1220 μm from the side facet 109. Therefore, the first reflective layer 105 is preferably provided in a region at least 0 μm to 500 μm outward from the side end surface 109 of the light emitting element 100 . 1, 2: Light-emitting element 3: Light-emitting device 10: Substrate 11: N-type layer 12: Light-emitting layer 13: Electron blocking layer 14: P-type layer 15: P-side electrode 16: N-side electrode 17A, 17B: Intermediate electrode 18: Protective film 18A: First protective film 18B: Second protective film 19A: P-side wiring electrode 19B: N-side wiring electrode 20: P-side pad electrode 21: N-side pad electrode 23: Hole 24: Hole 100: Light-emitting element 100a: P-side pad electrode 100b: N-side pad electrode 101: Submount 102: Substrate layer 103: Surface electrode layer 104: Back electrode layer 105: First reflective layer 105A: First insulating layer 105B: Metal reflective layer 105C: Second insulating layer 106: Second reflective layer 107: Hole 108a: Bonding electrode 108b: Bonding electrode 109: Side end surface [Figure 1] Figure 1 is a cross-sectional view showing the structure of a light-emitting element according to the first embodiment, and is a cross-sectional view taken in a direction perpendicular to the principal surface of the substrate. [Figure 2] Figure 2 is a diagram showing the top view of the electrode shape of the light-emitting element according to the first embodiment. [Figure 3] Figure 3 is a graph showing the relationship between the area of ​​the p-side electrode and light output. [Figure 4] Figure 4 is a graph showing the relationship between the area of ​​the p-side electrode and lifespan. [Figure 5] Figure 5 is a cross-sectional view showing the structure of a light-emitting element according to a modified embodiment of the first embodiment, and is a cross-sectional view taken in a direction perpendicular to the principal surface of the substrate. [Figure 6] Figure 6 is a diagram showing the top view of the electrode shape of the light-emitting element according to the modified embodiment of the first embodiment. [Figure 7] Figure 7 is a diagram showing the top view of the electrode shape of the light-emitting element according to the modified embodiment of the first embodiment. [Figure 8] Figure 8 is a diagram showing the top view of the electrode shape of the light-emitting element according to the modified embodiment of the first embodiment. [Figure 9] Figure 9 is a cross-sectional view showing the structure of the light-emitting device according to the second embodiment, and is a cross-sectional view perpendicular to the main surface of the submount. [Figure 10] Figure 10 is a top view of the submount as viewed from above. [Figure 11] Figure 11 is a cross-sectional view showing the structure of the first reflective layer, and is a cross-sectional view perpendicular to the main surface of the submount. [Figure 12] Figure 12 is a graph showing the radiation intensity on the submount surface. 1: Light-emitting element 10:Substrate 11: n-type layer 12: Luminous layer 13: Electron blocking layer 14: p-type layer 15: p-side electrode 16: n-side electrode 17A, 17B: Middle electrodes 18: Protective film 18A: 1st protective film 18B: Second protective film 19A: p-side wiring electrode 19B: n-side wiring electrode 20: p-side pad electrode 21: n-side pad electrode 23: Hole

Claims

1. A light-emitting element using a group III nitride semiconductor containing Al and having an emission wavelength of 200-280 nm, comprising: a substrate; a semiconductor layer, formed by sequentially stacking an n-type layer, a light-emitting layer, and a p-type layer on the substrate from the substrate side; an aperture disposed in a predetermined area on the surface of the p-type layer and having a depth reaching the n-type layer; a p-side electrode disposed in contact with the p-type layer and having a reflectivity of 50% or more for ultraviolet light of the emission wavelength; and an n-side electrode disposed above or above the n-type layer exposed at the bottom surface of the aperture; the aperture and the n-side electrode having a pattern of multiple points arranged in a two-dimensional pattern, and the area of ​​the p-side electrode being 0.75 mm² or more.

2. The light-emitting element as described in claim 1, wherein, The diameter of the points on the n-side electrode is 5–100 μm, and the distance between the centers of adjacent points is 50–200 μm.

3. The light-emitting element as requested in item 1 or 2, wherein, The area of ​​the p-side electrode is more than 70% of the total area of ​​the hole and the p-type layer.

4. The light-emitting element as requested in item 1 or 2, wherein, The overall thickness of the light-emitting element is between 0.5mm and 1mm.

5. The light-emitting element of claim 1 or 2 further comprises: a p-side pad electrode disposed above or above the p-side electrode; and an n-side pad electrode disposed above or above the n-side electrode; wherein the total area of ​​the p-side pad electrode and the area of ​​the n-side pad electrode is 0.7 mm2 or more.

6. The light-emitting element as requested in item 1 or 2, wherein, The area of ​​the p-side electrode, the diameter of the point of the n-side electrode, and the center-to-center distance between adjacent points are set so that the light output is above 150mW and the lifespan is above 10,000 hours under a 350mA drive.

7. A light-emitting device comprising: a light-emitting element as described in claim 1; and a sub-carrier having the light-emitting element encapsulated in a flip-chip package and having a reflective layer on the surface of the package side; the reflective layer having a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element, and the reflective layer, when viewed from above, being disposed in a region at least 0 μm to 500 μm outward from the side end face of the light-emitting element.

8. The light-emitting device as claimed in claim 7, wherein, When viewed from above, the reflective layer covers the entire area above 0 μm from the side end face of the light-emitting element.

9. The light-emitting device as claimed in claim 7, wherein, The subcarrier has a surface electrode layer that is coupled to the light-emitting element. The reflective layer has an insulating layer as the bottom layer. When viewed from above, a portion of the surface electrode layer is located further outward than the side end face of the light-emitting element.

10. The light-emitting device as claimed in claim 7, wherein, The reflective layer has: an insulating layer; and a metal reflective layer disposed on or above the insulating layer, and is made of a metal with a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element.

11. The light-emitting device as claimed in claim 7, wherein, The reflective layer further features: a DBR reflective layer with a reflectivity of over 90% for ultraviolet light of the emission wavelength of the light-emitting element.

12. The light-emitting device as claimed in claim 7, wherein, The reflective layer comprises: an insulating layer; a metal reflective layer disposed on or above the insulating layer and composed of a metal having a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element; and a DBR layer disposed on or above the metal reflective layer and having a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element.

13. The light-emitting device as claimed in claim 7, wherein, The substrate of the light-emitting element has a thickness of 900 μm or more.

14. A light-emitting device comprising: a light-emitting element as described in claim 1; and a sub-carrier formed in the shape of a flat plate, having: a reflective layer disposed on a surface of which the light-emitting element is flip-chip packaged and disposed on the package side, and a surface electrode layer bonded to the light-emitting element; the reflective layer having an insulating layer as the bottom layer; the surface electrode layer, when viewed from above, having a portion disposed further outward than the side end face of the light-emitting element; the reflective layer having a reflectivity of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element; and the reflective layer, when viewed from above, being disposed in a region at least 0 μm to 500 μm outward from the side end face of the light-emitting element.

Images