Light-emitting element and light-emitting device

Abstract

To provide a light-emitting element of which a light output and a life are improved.SOLUTION: A light-emitting element of which a light emitting wavelength using a III nitride semiconductor containing Al is 200 to 280nm, includes: a substrate 10; a semiconductor layer that is laminated onto the substrate 10 in order of an n-type layer 11, a light emitting layer 12, and a p-type layer 14; a hole 23 that is provide to a predetermined region of a front surface of the p-type layer 14, and has a depth reached to the n-type layer 11; a p-side electrode 15 which is provided so as to be contacted onto the p-type layer 14, and of which a reflection ratio of an ultraviolet light of the light emitting wavelength is 50% or more; and a n-side electrode 16 that is provided onto the n-type layer 11 exposed to a bottom surface of the hole 23. The hole 23 and the n-side electrode 16 are a pattern to which a plurality of dots is two-dimensionally arranged, and an area of the p-side electrode 15 is 0.75 mm2 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light-emitting element and a light-emitting device. [Background technology]

[0002] Sterilization devices that sterilize bacteria and viruses in running water by irradiating them with ultraviolet light are known. Mercury lamps are widely used as the light source. Mercury lamps have the problem that they are highly toxic and have a large environmental impact because they use mercury. Another problem is that the sterilization device becomes large when a mercury lamp is used.

[0003] On the other hand, the wavelength of ultraviolet light emitted by light-emitting elements using group III nitride semiconductors corresponds to a wavelength band of approximately 210 to 400 nm. UVC (wavelength 100 to 280 nm) is known to be effective for sterilization and disinfection, and is attracting attention for its use in sterilizing and disinfecting water and air. For this reason, efforts are underway to replace mercury lamps with light-emitting elements using group III nitride semiconductors with an emission wavelength of UVC.

[0004] Patent Documents 1 and 2 disclose a structure in which n-side electrodes are arranged two-dimensionally in a dot shape in a light emitting device using a group III nitride semiconductor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2017-513234 [Patent Document 2] International Publication No. 2010 / 146808 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the light output and lifespan of conventional UVC light-emitting elements did not reach the performance required to replace mercury lamps, and there was also room for improvement in the light output of light-emitting devices in which UVC light-emitting elements were mounted on a submount.

[0007] The present invention has been made in view of the above background, and aims to first provide a light emitting element with improved light output and life span, and secondly, to provide a light emitting device having improved light output in which a light emitting element is mounted on a submount. [Means for solving the problem]

[0008] One aspect of the present invention is In a light-emitting device using an Al-containing Group III nitride semiconductor and emitting light with a wavelength of 200 to 280 nm, A substrate; a semiconductor layer in which an n-type layer, a light emitting layer, and a p-type layer are stacked on the substrate in this order from the substrate side; a hole provided in a predetermined region of a surface of the p-type layer and having a depth reaching the n-type layer; a p-side electrode provided on and in contact with the p-type layer and having a reflectance of 50% or more for ultraviolet light having an emission wavelength; an n-side electrode provided on the n-type layer exposed at a bottom surface of the hole; the holes and the n-side electrode are patterned in such a way that a plurality of dots are arranged two-dimensionally; The area of ​​the p-side electrode is 0.75 mm 2 The above is the light-emitting device.

[0009] Another aspect of the present invention is The light-emitting element according to the above aspect, a submount on which the light-emitting element is flip-chip mounted and which has a reflective layer provided on a surface of the mounting side; The light-emitting device is characterized in that the reflective layer has a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element, and the planar pattern of the reflective layer is a pattern in which the reflective layer is provided in at least an area of ​​0 μm to 500 μm outward from the side end face of the light-emitting element.

[0010] Another aspect of the present invention is A light-emitting device using an Al-containing Group III nitride semiconductor and emitting light with a wavelength of 200 to 280 nm; a flat submount on which the light-emitting element is flip-chip mounted, the submount having a reflective layer provided on a surface of the mounting side and a surface electrode layer bonded to the light-emitting element; the reflective layer has an insulating layer as a bottom layer, a planar pattern of the surface electrode layer is a pattern in which a part of the surface electrode layer is provided outside a side end surface of the light emitting element, The light-emitting device is characterized in that the reflective layer has a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element, and the planar pattern of the reflective layer is a pattern in which the reflective layer is provided at least in an area of ​​0 μm to 500 μm from a side end face of the light-emitting element. Effect of the Invention

[0011] In the light-emitting device of the above embodiment, the n-side electrodes are arranged two-dimensionally in the form of dots, which allows the area of ​​the p-side electrodes to be large. 2 This makes it possible to improve the light output and lifespan. In addition, in the light emitting device of the above aspect, the planar pattern of the reflective layer is a pattern in which the reflective layer is provided at least in an area from 0 μm to 500 μm outward from the side end face of the light emitting element, so that the light output can be improved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing the configuration of a light-emitting device in embodiment 1, taken along a direction perpendicular to a main surface of a substrate. [Diagram 2] FIG. 2 is a diagram showing a planar pattern of electrodes of the light-emitting element according to the first embodiment. [Diagram 3] 4 is a graph showing the relationship between the area of ​​the p-side electrode 15 and the optical output. [Figure 4] 1 is a graph showing the relationship between the area of ​​the p-side electrode 15 and the chip lifespan. [Diagram 5] FIG. 4 is a cross-sectional view showing the configuration of a light-emitting device in a modified embodiment of the first embodiment, taken along a direction perpendicular to a main surface of a substrate. [Figure 6] FIG. 13 is a diagram showing a planar pattern of electrodes of a light-emitting element in a modified embodiment of the first embodiment. [Figure 7] FIG. 13 is a diagram showing a planar pattern of electrodes of a light-emitting element in a modified embodiment of the first embodiment. [Figure 8] FIG. 13 is a diagram showing a planar pattern of electrodes of a light-emitting element in a modified embodiment of the first embodiment. [Figure 9] 11 is a cross-sectional view showing the configuration of a light-emitting device in accordance with Embodiment 2, the cross-section being perpendicular to the main surface of the submount. [Figure 10] FIG. [Figure 11] 4 is a cross-sectional view showing the configuration of a first reflective layer, the cross-section being perpendicular to the main surface of the submount. [Figure 12] FIG. 1 shows the radiation intensity on the surface of a submount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The light-emitting device uses an Al-containing III-nitride semiconductor and has an emission wavelength of 200 to 280 nm. The light-emitting device has a substrate, a semiconductor layer in which an n-type layer, a light-emitting layer, and a p-type layer are laminated on the substrate in this order, 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 reflectance of ultraviolet light of the emission wavelength of 50% or more, and an n-side electrode provided on the n-type layer exposed at the bottom of the hole, the hole and the n-side electrode being a pattern in which a plurality of dots are two-dimensionally arranged, and the area of ​​the p-side electrode is 0.75 mm 2 That's all.

[0014] In the light-emitting device, the diameter of the dots of the n-side electrode may be 5 to 100 μm, and the center-to-center distance between adjacent dots may be 50 to 200 μm. This can improve the in-plane diffusion of current while ensuring a sufficiently wide area of ​​the p-side electrode.

[0015] In the light-emitting device, the ratio of the area of ​​the p-side electrode to the total area of ​​the hole and the p-type layer in a plan view may be 70% or more, which can increase the reflection of ultraviolet light by the p-side electrode and improve the light extraction efficiency.

[0016] In the above light emitting device, the total thickness of the light emitting device may be 0.5 mm or more and 1 mm or less, thereby improving the light output and life span.

[0017] The light-emitting device has a p-side pad electrode provided on the upper part of the p-side electrode and an n-side pad electrode provided on the upper part of the n-side electrode, and the sum of the area of ​​the p-side pad electrode and the area of ​​the n-side pad electrode is 0.7 mm 2 The contact area between the light emitting element and the mounting substrate is increased, and the heat dissipation performance can be improved. As a result, the life span can be improved.

[0018] In the light-emitting device, the area of ​​the p-side electrode, the diameter of the dots on the n-side electrode, and the center-to-center distance between adjacent dots may be set so that the light output is 150 mW or more and the lifetime is 10,000 hours or more when driven at 350 mA.

[0019] The light emitting device comprises the above-mentioned light emitting element, and a submount on which the light emitting element is flip-chip mounted and which has a reflective layer provided on the surface of the mounting side, the reflective layer having a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light emitting element, and the reflective layer is provided in an area extending from at least 0 μm to 500 μm outward from the side end face of the light emitting element in a planar view.

[0020] In the light emitting device, the reflective layer may be provided over the entire area extending from the side end face of the light emitting element to the outside by 0 μm or more in plan view, thereby making it possible to further improve the light output.

[0021] In the above light-emitting device, the submount has a surface electrode layer that is joined to the light-emitting element, the reflective layer has an insulating layer as a lowermost layer, and the surface electrode layer may be such that, in a planar view, a portion of the surface electrode layer is provided outside a side end surface of the light-emitting element.

[0022] In the light emitting device, the reflective layer may have an insulating layer and a metal reflective layer provided on the insulating layer and made of a metal having a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light emitting element.

[0023] In the above light emitting device, the reflective layer may include a DBR reflective layer having a reflectance of 90% or more for ultraviolet light having an emission wavelength of the light emitting element.

[0024] In the above light-emitting device, the reflective layer may have an insulating layer, a metal reflective layer provided on the insulating layer and made of a metal having a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element, and a DBR layer provided on the metal reflective layer and having a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light-emitting element.

[0025] In the light emitting device, the substrate of the light emitting element may have a thickness of 900 μm or more.

[0026] The light emitting device includes a light emitting element using an Al-containing Group III nitride semiconductor and having an emission wavelength of 200 to 280 nm, a flat submount on which the light emitting element is flip-chip mounted, a reflective layer provided on the surface of the mounting side, and a surface electrode layer bonded to the light emitting element, the reflective layer having an insulating layer as a bottom layer, and the surface electrode layer being provided such that a portion of the surface electrode layer is provided outside a side end face of the light emitting element in a planar view, the reflective layer has a reflectance of 50% or more for ultraviolet light of the emission wavelength of the light emitting element, and the reflective layer is provided in at least a region from 0 μm to 500 μm from the side end face of the light emitting element in a planar view.

[0027] (Embodiment 1) Fig. 1 is a cross-sectional view showing the configuration of the light-emitting element in embodiment 1, taken along a direction perpendicular to the main surface of the substrate. Fig. 2 is a diagram showing a planar pattern of electrodes of the light-emitting element in embodiment 1. The light-emitting element in embodiment 1 is a flip-chip type ultraviolet light-emitting element, and emits light with a wavelength of UVC, for example, 200 to 280 nm.

[0028] 1. Structure of the light-emitting element 1, the light-emitting device in the first embodiment has a substrate 10, an n-type layer 11, an emission 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, 17B, a protective film 18, a reflective film 19, a p-side pad electrode 20, and an n-side pad electrode 21. Each component will be described below. Hereinafter, the laminate of the n-type layer 11, the emission layer 12, the electron blocking layer 13, and the p-type layer 14 may be referred to as a semiconductor layer.

[0029] The substrate 10 is a substrate made of sapphire with a c-plane as the main surface. Any material other than sapphire may be used as long as it has a high transmittance for the emission wavelength and can grow a group III nitride semiconductor. The thickness of the substrate 10 is preferably 0.5 to 1 mm. This can improve the light extraction efficiency.

[0030] An anti-reflection film may be provided on the back surface of the substrate 10 (the surface opposite to the n-type layer 11 side, the light extraction side). By providing the anti-reflection film, ultraviolet light is prevented from being reflected on the back surface of the substrate 10 and returning to the element side, improving light extraction. The anti-reflection film is, for example, SiO2 with a thickness of ¼ of the emission wavelength.

[0031] The n-type layer 11 is located on the substrate 10 via a buffer layer (not shown). The n-type layer 11 is made of n-AlGaN. The n-type impurity is Si, and the Si concentration is 5×10 18 ~5×10 19 / cm 3 The n-type layer 11 may be made up of multiple layers.

[0032] The light emitting layer 12 is located on the n-type layer 11. The light emitting layer 12 has an MQW structure in which well layers and barrier layers are alternately and repeatedly stacked. The number of repetitions is, for example, 2 to 5. The well layers are made of AlGaN, and the Al composition is set according to the desired emission wavelength. The barrier layers are AlGaN with a higher Al composition than the well layers. They may also be AlGaInN with a higher band gap energy than the well layers. The light emitting layer 12 may also have an SQW structure.

[0033] The electron blocking layer 13 is located on the light emitting layer 12. The electron blocking layer 13 is made of p-AlGaN having a higher Al composition ratio than the barrier layer of the light emitting layer 12. The electron blocking layer 13 prevents the electrons injected from the n-side electrode 16 from diffusing beyond the light emitting layer 12 toward the p-type layer 14.

[0034] The p-type layer 14 is located on the electron blocking layer 13. The p-type layer 14 is made of p-AlGaN. In the light emitting device of the first embodiment, all the semiconductor layers from the n-type layer 11 to the p-type layer 14 are made of AlGaN, which suppresses the absorption of ultraviolet rays by the semiconductor layers. The Al composition of the p-type layer 14 is, for example, 5 to 80%. The p-type impurity is Mg. The Mg concentration is 1×10 19 / cm 3 That is all. The p-type layer 14 may be composed of multiple layers with different Al compositions or Mg concentrations. In that case, the layer in contact with the p-side electrode 15 may be p-AlGaN with an Al composition of 5 to 80%. The p-type layer 14 is not limited to AlGaN, and may be any III-nitride semiconductor containing Al, such as AlGaInN.

[0035] Furthermore, the uppermost layer (contact layer in contact with the p-side electrode 15) of the p-type layer 14 made up of multiple layers may be a thin GaN layer having a thickness of one molecular layer or more and 50 nm or less.

[0036] Holes 23 are formed in a portion of the surface of the p-type layer 14, the depth of which reaches the n-type layer 11. The holes 23 are dot-shaped, and a plurality of the holes 23 are arranged in a lattice pattern (see FIG. 2). The n-type layer 11 is exposed at the bottom of the holes 23. By arranging the holes 23 for exposing the n-type layer 11 in a dot-shaped pattern, uniformity of light emission within the surface is ensured, while the reduction in the light-emitting area (area of ​​the p-type layer 14) caused by the holes 23 is minimized, and the area of ​​the p-side electrode 15 is increased, thereby improving the light output.

[0037] The planar pattern of each hole 23 is a circle. Alternatively, it may be a polygon such as a square or a regular hexagon. In the case of a regular hexagon, it is preferable that the side surface of the hole 23 be an m-plane. The arrangement pattern of the holes 23 is a regular triangular lattice. Alternatively, it may be a two-dimensional arrangement pattern such as a square lattice or honeycomb. A regular triangular lattice or a square lattice is preferable.

[0038] The diameter of the holes 23 is preferably 5 to 100 μm. The center-to-center distance between adjacent holes 23 is preferably 50 to 200 μm. By setting the diameter and spacing of the holes 23 in this manner, it is possible to improve the in-plane diffusibility of current while ensuring a sufficient area for the p-side electrode 15. Here, the diameter of the holes 23 is the diameter of a circumscribing circle.

[0039] The p-side electrode 15 is provided on the p-type layer 14. The p-side electrode 15 is provided on the surface of the p-type layer 14, excluding the area where the holes 23 are not provided and the vicinity of the edge of the p-type layer 14 (see FIG. 2), thereby making the light-emitting area large. The p-side electrode 15 is a reflective electrode that reflects ultraviolet light emitted from the light-emitting layer 12 toward the substrate 10 to increase the light extraction efficiency. The material of the p-side electrode 15 is a material with a reflectance of 50% or more for ultraviolet light of the emission wavelength. For example, Ru, Rh, an alloy mainly composed of Ru or Rh, ITO / Al, etc. Ru and Rh have high reflectance in UVC and low contact resistance with the p-type layer 14, which is p-AlGaN, and are therefore suitable as the p-side electrode 15 in a UVC light-emitting element. A more preferable reflectance is 70% or more.

[0040] The area of ​​the p-side electrode 15 is 0.75 mm 2 That is all. The element area, the diameter of the holes 23, and the arrangement pattern are set to satisfy this. This makes it possible to improve the light output and lifespan of the light-emitting element in embodiment 1. The reason for the improvement in light output is that the reflective area of ​​the p-side electrode 15 increases. The reason for the improvement in lifespan is that the current density decreases due to the increase in the p-side electrode 15.

[0041] In particular, the area of ​​the p-side electrode 15 is set to 0.75 mm 2By setting the above, the performance is sufficient to replace a mercury lamp with the light emitting element of embodiment 1. To replace a mercury lamp, a light output of 150 mW at 350 mA drive and a life of 10,000 hours at 350 mA drive are required, but the area of ​​the p-side electrode 15 can be reduced to 0.75 mm 2 This can be achieved by the above.

[0042] The area of ​​the p-side electrode 15 is 8 mm 2 It is preferable that the area of ​​the p-side electrode is less than or equal to 100 nm. If the area of ​​the p-side electrode is too large, the probability that the semiconductor layer will contain crystal defects increases, resulting in a decrease in production yield.

[0043] Moreover, the area of ​​the p-side electrode 15 is preferably 70% or more of the element area (the total area of ​​the p-type layer 14 and the hole 23). This can increase the reflection of ultraviolet light by the p-side electrode 15 and improve the light extraction efficiency. Moreover, the area of ​​the p-side electrode 15 is preferably 95% or less of the element area. This is to ensure a sufficient area for the hole 23 and not impair the in-plane diffusibility of the current.

[0044] The n-side electrode 16 is provided on the n-type layer 11 exposed at the bottom of each hole 23. Therefore, the n-side electrode 16 also has a dot-like pattern (see FIG. 2).

[0045] The planar pattern of the dots on the n-side electrode 16 is a reduced pattern of the planar pattern of the holes 23. If the planar pattern of the holes 23 is a circle, the planar pattern of the n-side electrode 16 is a circle with a smaller diameter. The arrangement pattern of the dots on the n-side electrode 16 is similar to the arrangement pattern of the holes 23. By arranging the n-side electrodes 16 two-dimensionally in this way in the form of dots, it is possible to improve the in-plane diffusibility of current while ensuring a wide area for providing the p-side electrode 15.

[0046] The material of the n-side electrode 16 is a structure obtained by heat-treating V / Al / Ti. Alternatively, Ti / Al / Ti may be used. The structure obtained by heat-treating V / Al / Ti is specifically AlN xA structure in which a layer made of [material 1], a layer made of a metal mainly composed of Al and containing V and Ti, and a layer made of Ti are laminated in this order.

[0047] AlN x The layer made of [material 2] has a thickness of 1 to 3 nm. x is, for example, 0.4 to 0.7. Also, x may decrease as it moves away from the n-type layer 11 in the thickness direction. In this case, the average of x in the thickness direction is 0.4 to 0.7. Also, there may be diffusion of Ga from the n-type layer 11 side. In that case, Al with a higher Al composition ratio than the n-type layer 11 y Ga 1-y N x (0.4 ≤ x ≤ 0.7). If the Al composition ratio of the n-type layer 11 is a, then a < y ≤ 1. y is, for example, 0.7 or more. Also in this case, x may decrease as it moves away from the n-type layer 11 in the thickness direction, and y may increase as it moves away from the n-type layer 11 in the thickness direction.

[0048] The layer made of a metal mainly composed of Al and containing V and Ti has a thickness of 50 to 500 nm. The ratios of Al, V, and Ti are, for example, Al is 50 to 85 mol%, V is 5 to 20 mol%, and Ti is 10 to 30 mol%.

[0049] In the n-side electrode 16 of the above structure, the contact resistance to the n-type layer 11 is reduced. For example, the contact resistivity of the n-side electrode 16 to the n-type layer 11 is 4×10 ―4 Ω·cm 2 or less. The reason is, firstly, considered to be that the layer made of AlN x functions as a good contact layer to the n-type layer 11. Secondly, it is considered that nitrogen vacancies are generated on the surface of the n-type layer 11, resulting in n-type formation and a decrease in contact resistance.

[0050] The layer made 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.

[0051] The intermediate electrodes 17A and 17B are provided on the p-side electrode 15 and the n-side electrode 16, respectively. The planar pattern of the intermediate electrode 17A is similar to that of the p-side electrode 15. The planar pattern of the intermediate electrode 17B is similar to that of the n-side electrode 16, and is a pattern in which a plurality of dots are arranged. The material of the intermediate electrodes 17A and 17B is, for example, Ti / Ni / Au / Al.

[0052] Alternatively, the intermediate electrodes 17A and 17B may be omitted, the p-side wiring electrode 19A and the p-side electrode 15 may be directly connected, and the n-side wiring electrode 19B and the n-side electrode 16 may be directly connected.

[0053] The protective film 18 is provided so as to cover the entire upper surface of the element. That is, it is provided continuously on 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 element isolation trench, and the inside of the hole 23. The protective film 18 has a structure in which a first protective film 18A and a second protective film 18B are laminated in this order from the semiconductor layer side.

[0054] The protective film 18 is an insulator, such as SiO2. Other materials that can be used include SiN, Al2O3, TiO2, and AlN. A laminate of a plurality of materials may also be used. Also, the first protective film 18A and the second protective film 18B may be made of different materials.

[0055] 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 through a hole formed in the first protective film 18A, and is connected to the p-side pad electrode 20 through a hole formed in the second protective film 18B. The n-side wiring electrode 19B is connected to each intermediate electrode 17B through a hole formed in the first protective film 18A, and is connected to the n-side pad electrode 21 through a hole formed in the second protective film 18B. The material of the p-side wiring electrode 19A and the n-side wiring electrode 19B is, for example, Ti / Ni / Au / Al.

[0056] By providing the p-side wiring electrode 19A and the n-side wiring electrode 19B between the intermediate electrodes 17A, 17B and the p-side pad electrode 20 and the n-side pad electrode 21, it is possible to freely set the patterns of the p-side pad electrode 20 and the n-side pad electrode 21. In addition, since it is possible to arrange the holes 23 over the entire surface, it is possible to improve the in-plane uniformity of light emission.

[0057] The p-side pad electrode 20 and the n-side pad electrode 21 are provided on the protective film 18 at a distance from each other. The p-side pad electrode 20 is connected to the p-side wiring electrode 19A through a hole formed in the second protective film 18B. The n-side pad electrode 21 is connected to the n-side wiring electrode 19B through a hole formed in the second protective film 18B. The material of the p-side pad electrode 20 and the n-side pad electrode 21 is, for example, Ti / Pt / Au / AuSn.

[0058] As shown in FIG. 2, the p-side pad electrode 20 and the n-side pad electrode 21 are patterns obtained by dividing a rectangular pattern slightly inside the rectangular pattern of the element into two equal parts by a strip-shaped linear region along a straight line parallel to the side of the rectangle.

[0059] The total area of ​​the p-side pad electrode 20 and the n-side pad electrode 21 is 0.7 mm 2 It is preferable that the ratio is 70% or more. The contact area between the light emitting element in embodiment 1 and the mounting substrate is increased, and heat dissipation can be improved. As a result, the chip life can be improved. For the same reason, it is preferable that the ratio of the total area of ​​the p-side pad electrode 20 and the n-side pad electrode 21 to the light emitting area (area of ​​the p-side electrode 15) is 70% or more.

[0060] The overall thickness of the light emitting device in embodiment 1 (the distance from the rear 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, the light output and life can be improved.

[0061] As described above, in the light emitting device of the first embodiment, a plurality of n-side electrodes 16 are provided in the form of dots, and the dots are arranged in a two-dimensional pattern. This reduces the area of ​​the n-side electrodes 16 and increases the area of ​​the p-side electrodes 15 without impairing the in-plane diffusibility of the current. In addition, the area of ​​the p-side electrodes 15 is increased to 0.75 mm2. 2 This makes it possible to improve the light output and lifespan of the light-emitting element. In particular, it is possible to achieve a light output of 150 mW at 350 mA drive and a lifespan of 10,000 hours at 350 mA drive, which are the performance required to replace mercury lamps. Here, the lifespan is the time it takes for the light output to reach 70% of the initial operating value.

[0062] 2. Experimental Results Next, experimental results regarding the light-emitting device in the first embodiment will be described.

[0063] Regarding the light-emitting element in embodiment 1, light-emitting elements were fabricated with various values ​​of the area of ​​the p-side electrode 15, and the light output and chip life were measured when driven at 350 mA. The area of ​​the p-side electrode 15 was changed by changing the outer shape of the p-side electrode 15, the diameter of the hole 23, and the n-side electrode 16. The chip life was defined as the time until the light output became 70% of the initial value when driven at 350 mA.

[0064] FIG. 3 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 values ​​normalized with 150 mW as 1. As shown in FIG. 3, it was found that the light output tends to increase as the area of ​​the p-side electrode 15 becomes larger. The light output required to replace a mercury lamp is said to be 150 mW when driven at 350 mA, but as can be seen from FIG. 3, when the area of ​​the p-side electrode 15 is 0.5 mm 2 It turns out that this can be achieved if we do the above.

[0065] FIG. 4 is a graph showing the relationship between the area of ​​the p-side electrode 15 and the chip lifespan. As shown in FIG. 4, it was found that the chip lifespan increases linearly with an increase in the area of ​​the p-side electrode 15. The chip lifespan required to replace a mercury lamp is said to be 10,000 hours at 350 mA drive, but FIG. 4 shows that the chip lifespan exceeds 10,000 hours when the area of ​​the p-side electrode 15 is 0.75 mm 2 It turned out that this was the case.

[0066] As shown in Figures 3 and 4, in order to satisfy the light output and chip life required for replacing a mercury lamp, the area of ​​the p-side electrode 15 must be 0.75 mm 2 I found that more than this would suffice.

[0067] (Modification of the first embodiment) Fig. 5 is a cross-sectional view showing the configuration of a light-emitting device in a modified form of embodiment 1, taken along a direction perpendicular to the main surface of the substrate. As shown in Fig. 5, the light-emitting device in the modified form has a configuration in which the p-side wiring electrode 19A and the n-side wiring electrode 19B are omitted from the light-emitting device in embodiment 1, and the planar patterns 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 changed to connect the intermediate electrode 17A to the p-side pad electrode 20, and the intermediate electrode 17B to the n-side pad electrode 21.

[0068] If the p-side wiring electrode 19A and the n-side wiring electrode 19B are omitted, restrictions arise in the patterns of the n-side electrode 16, the p-side pad electrode 20, and the n-side pad electrode 21, but the configuration of the light-emitting element can be simplified.

[0069] 6 to 8 are diagrams showing electrode patterns of light-emitting elements in modified embodiments. The electrode patterns in Figs. 6 to 8 will be described below.

[0070] The electrode pattern in Fig. 6 is as follows. The planar patterns of the p-side pad electrode 20 and the n-side pad electrode 21 are a rectangular pattern slightly inside the rectangular pattern of the element, which is divided into two by a linear region that extends along an edge of the element in the vicinity of the edge, with the smaller area being the p-side pad electrode 20 and the larger area being the n-side pad electrode 21. The n-side pad electrode 21 is a wide rectangle, and the p-side pad electrode 20 is a long and narrow rectangle.

[0071] The holes 23 and the n-side electrodes 16 are in the form of circular dots and are arranged in a regular triangular lattice pattern in the region below the n-side pad electrode 21, but are not arranged in the region below the p-side pad electrode 20 or below the linear region.

[0072] The holes 24 for connecting the p-side electrode 15 and the p-side pad electrode 20 are included in the p-side pad electrode 20 in a plan view. The holes 24 are in the form of circular dots, and are arranged at predetermined intervals in a straight line along the edge of the element.

[0073] 7 is as follows: The planar patterns of the p-side pad electrode 20 and the n-side pad electrode 21 are formed by dividing a rectangular pattern slightly inside the rectangular pattern of the element in half at a corner of the rectangle by a linear region along a straight line that forms an angle of 45° with the sides of the rectangle, with the p-side pad electrode 20 being the one that forms an isosceles right triangle, and the n-side pad electrode 21 being the other (a pentagon with the corners of the rectangle rounded off).

[0074] As in Figure 6, the holes 23 and the n-side electrodes 16 are in the form of circular dots and are arranged in a regular triangular lattice pattern in the region below the n-side pad electrode 21, but are not arranged in the region below the p-side pad electrode 20 or below the linear region.

[0075] The hole 24 for connecting the p-side electrode 15 and the p-side pad electrode 20 is included in the p-side pad electrode 20 in a plan view, and has a pattern obtained by reducing the right-angled isosceles triangle of the p-side pad electrode 20 .

[0076] The electrode pattern in Fig. 8 is the same as that in Fig. 7, except that the planar pattern of the holes 23 and the dots of the n-side electrode 16 in Fig. 7 is changed from circles to squares, and the diameter and intervals of the dots are reduced.

[0077] By forming the electrode patterns as shown in FIGS. 6 to 8, the sum of the areas of the p-side pad electrode 20 and the n-side pad electrode 21 can be made large, thereby improving heat dissipation.

[0078] In the light emitting device of the modified embodiment described above, the area of ​​the p-side electrode 15 is set to 0.75 mm 2 This makes it possible to improve the light output and life span, and in particular to provide the light output and life span required to replace a mercury lamp.

[0079] (Embodiment 2) FIG. 9 is a diagram showing the configuration of a light emitting device in embodiment 2, and is a cross-sectional view perpendicular to the submount. As shown in FIG. 9, the light emitting device in embodiment 2 has an ultraviolet light emitting element 100 and a submount 101. The light emitting element in embodiment 1 can be used for the light emitting element 100. In particular, the thickness of the substrate of the light emitting element 100 is preferably 400 μm or more. This is because light extraction from the side surface is improved, and the light output is improved by reflection by the first reflective layer 105 described later. It is more preferably 600 μm or more, and even more preferably 900 μm or more. There is no particular upper limit to the thickness, but it is preferably 2000 μm or less in consideration of mass productivity and processability.

[0080] The light emitting element 100 is of a flip chip type and is flip chip mounted on a submount 101. The light emitting element 100 has a p-side pad electrode 100a and an n-side pad electrode 100b. The p-side pad electrode 100a and the n-side pad electrode 100b are bonded to two surface electrode layers 103 of the submount 101 via bonding electrodes 108a and 108b, respectively.

[0081] The submount 101 has a substrate layer 102, a front 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 viewed from above.

[0082] The substrate layer 102 is a flat plate made of ceramic and has a square shape in a plan view. The ceramic is preferably a material with high thermal conductivity, in order to efficiently conduct heat from the light emitting element 100 to the outside. For example, AlN is preferable.

[0083] The front electrode layer 103 is provided in two separate parts on the front surface of the substrate layer 102. The front electrode layer 103 is connected to a p-side pad electrode 100a and an n-side pad electrode 100b of the light emitting element 100 via bonding electrodes 108a and 108b. The front electrode layer 103 is made of a material such as Au.

[0084] 10, the surface electrode layer 103 has an outer shape in which two rectangles are arranged at a distance from each other in the center of the square of the submount 101 in a plan view. In addition, a stepped notch is provided at the corner of each rectangle for aligning the light emitting element 100. In a plan view, a portion of the surface electrode layer 103 is located outside the side end surface 109 of the light emitting element 100.

[0085] The back electrode layer 104 is provided on the back surface of the substrate layer 102 in two separate parts. The back electrode layer 104 is connected to the front electrode layer 103 through a hole 107. The back electrode layer 104 is also electrically connected to the outside. The material of the back electrode layer 104 is, for example, Au.

[0086] The second reflective layer 106 is provided in a predetermined region on the surface of the substrate layer 102. The first reflective layer 105 is a layer for improving light output by reflecting ultraviolet light emitted from the light emitting element 100 upward. The second reflective layer 106 is made of, for example, Au. By using the same material as the front electrode layer 103, the second reflective layer 106 and the front electrode layer 103 can be formed simultaneously.

[0087] As shown in FIG. 10, the second reflective layer 106 has a square annular outer shape in plan view, and the surface electrode layer 103 is located inside the inner periphery of the ring.

[0088] The first reflective layer 105 is provided in a predetermined planar pattern on the surface electrode layer 103, the substrate layer 102, and the second reflective layer 106. The first reflective layer 105 is a layer for reflecting ultraviolet light emitted from the light emitting element 100 upward to improve the light output.

[0089] 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 laminated in this order from the substrate layer 102 side.

[0090] The reflectance of the first reflective layer 105 is 50% or more. Here, the reflectance is the reflectance for ultraviolet light of the emission wavelength of the light emitting element 100, in the case of normal incidence. Hereinafter, the reflectance has the same meaning unless otherwise specified. It is more preferably 70% or more, and further preferably 90% or more.

[0091] The first insulating layer 105A is a layer made of an insulator. For example, it is SiO2. The first insulating layer 105A is a layer provided to ensure insulation between the surface electrode layer 103 and the metal reflective layer 105B. This is because the first reflective layer 105 is also provided on the surface electrode layer 103, and therefore the bottom layer needs to be an insulator. The thickness of the first insulating layer 105A may be any thickness that provides sufficient insulation between the surface electrode layer 103 and the metal reflective layer 105B, and is, for example, 500 nm.

[0092] Metal reflective layer 105B is a layer made of a metal with a reflectance of 50% or more. More preferably, it is 60% or more, and even more preferably, it is 80% or more. For example, Al, Mg, Ru, Rh, or alloys containing these as main components can be used. In particular, Al, Mg, or alloys containing these as main components are preferable because of their high reflectance. The thickness of metal reflective layer 105B may be a thickness that sufficiently reduces the transmittance of metal reflective layer 105B. For example, it may be 50 nm or more.

[0093] The second insulating layer 105C is a layer made of an insulator. For example, it is SiO2. The second insulating layer 105C is a layer provided to protect the metal reflective layer 105B. The thickness of the second insulating layer 105C is, for example, 200 nm.

[0094] The planar pattern of the first reflective layer 105 is as shown by the diagonal lines in Fig. 10. That is, in plan view, the first reflective layer 105 is provided on the entire area (the entire area 0 µm or more outward from the side end face 109 of the light emitting element 100) within the square area of ​​the submount 101 except for the area of ​​the light emitting element 100 in the planar view. If the substrate of the light emitting element 100 is thick, the amount of ultraviolet light extracted from the side end face 109 increases, but the ultraviolet light can be reflected upward by the first reflective layer 105, thereby improving the light output.

[0095] In the second embodiment, the first reflective layer 105 is provided in the entire region of the light emitting element 100 that is 0 μm or more outward from the side end face 109, but the present invention is not limited to this. It is sufficient that the first reflective layer 105 is provided at least in a region of the light emitting element 100 that is 0 μm or more and 500 μm or less outward from the side end face 109. Such a region is a region where the radiation intensity of ultraviolet light from the light emitting element 100 is strong. Therefore, if the first reflective layer 105 is provided in such a region, the ultraviolet light from the light emitting element 100 can be efficiently reflected upward by the first reflective layer 105, and the light output can be improved.

[0096] In addition, in the second embodiment, the first reflective layer 105 has a structure in which reflection is achieved by the metal reflective layer 105B, but may have a structure in which reflection is achieved by a DBR (Distributed Bragg reflector) reflective layer, or a combination of a DBR reflective layer and a metal reflective layer 105B. For example, a DBR reflective layer may be provided between the metal reflective layer 105B and the second insulating layer 105C, or in place of the second insulating layer 105C.

[0097] In particular, from the viewpoint of the angle dependency of reflectance, it is preferable to use a structure in which a DBR reflective layer and a metal reflective layer 105B are combined. The reflectance of the DBR reflective layer is angle dependent, and the reflectance may be low depending on the incident angle. On the other hand, the reflectance of the metal reflective layer 105B is not angle dependent. Therefore, by using a structure in which the first reflective layer 105 is a combination of a DBR reflective layer and a metal reflective layer 105B, it is possible to achieve a high reflectance for any incident angle.

[0098] The DBR reflective layer is a layer with a DBR structure in which two or more materials with different refractive indices are alternately laminated to a predetermined thickness. The reflectance of the DBR reflective layer is set to 90% or more, preferably 95%, and more preferably 98% or more. The material of the DBR reflective layer is, for example, SiO2, TiO2, HfO2, Nb2O5, ZrO2, MgF2, or the like.

[0099] As described above, in the light emitting device of the second embodiment, the first reflective layer 105 is provided in at least an area 500 μm or less from the side end surface 109 of the light emitting element 100. Therefore, the ultraviolet light emitted from the light emitting element 100 can be efficiently reflected upward by the first reflective layer 105, and the light output can be improved.

[0100] Next, experimental results regarding the second embodiment will be described.

[0101] Experiment 1 For the light emitting device of embodiment 2, the radiation intensity on the submount 101 when the light emitting element 100 was caused to emit light was obtained by simulation. 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 the thickness of the light emitting element 100 was 950 μm.

[0102] FIG. 12 shows the radiation intensity (W / μm 212 , it was found that a region with high radiation intensity exists in a region 500 μm or less from the side end face 109 of the light-emitting element 100. As a result, it was found that it is possible to efficiently improve the light output by providing a reflective layer in a region 500 μm or less from the side end face 109 of the light-emitting element 100.

[0103] Experiment 2 In the second embodiment, the range of the first reflective layer 105 was changed to a region of 500 μm or more and 1220 μm or less from the side end surface 109 of the light emitting element 100, and the light output was obtained. Then, the output improvement rate was obtained 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 400 μm and 950 μm. The other conditions were the same as those of the first experiment. As a result, when the thickness of the sapphire substrate was 400 μm, the output improvement rate was 0.88%, and when it was 950 μm, it was 2.85%. As a result, it was found that the thicker the substrate, the greater the effect of improving the light output by the first reflective layer 105.

[0104] Experiment 3 In the second embodiment, the range of the first reflective layer 105 was changed to a region of 0 μm to 1220 μm from the side end surface 109 of the light emitting element 100, and the light output was obtained. Then, the output improvement rate was obtained with respect 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 950 μm. The other conditions were the same as those of the first experiment. As a result, the output improvement rate was 3.88%. From a comparison with the second experiment, when the first reflective layer 105 was provided in a region of 0 μm to 500 μm from the side end surface 109 of the light emitting element 100, the light output improvement effect per unit area was higher than when the first reflective layer 105 was provided in a region of 500 μm to 1220 μm from the side end surface 109. Therefore, it was found that the first reflective layer 105 should be provided at least in a region of 0 μm to 500 μm from the side end surface 109 of the light emitting element 100. [Explanation of symbols]

[0105] 10: Substrate 11:n-type layer 12: Light-emitting layer 13: Electron block layer 14:p-type layer 15:p side electrode 16:n side electrode 17A, 17B: Intermediate electrode 18:Protective film 19A:p side wiring electrode 19B:n side wiring electrode 20: p-side pad electrode 21: n-side pad electrode 100: Light emitting element 101: Submount 102: Substrate layer 103: Surface electrode layer 104: Back electrode layer 105: 1st reflective layer 105A: First insulating layer 105B: Metal reflective layer 105C: Second insulating layer 106:Second reflective layer

Claims

1. In a light emitting device using an Al-containing Group III nitride semiconductor and emitting light with a wavelength of 200 to 280 nm, A substrate; a semiconductor layer including an n-type layer, a light-emitting layer, and a p-type layer stacked on the substrate in this order from the substrate side; a hole provided in a predetermined region of a surface of the p-type layer and having a depth reaching the n-type layer; a p-side electrode provided on and in contact with the p-type layer and having a reflectance of 50% or more for ultraviolet light having an emission wavelength; an n-side electrode provided on the n-type layer exposed at a bottom surface of the hole; the holes and the n-side electrode are formed in a pattern in which a plurality of dots are two-dimensionally arranged, The area of ​​the p-side electrode is 0.75 mm ２ That is the light-emitting element.

2. 2. The light-emitting device according to claim 1, wherein the diameter of the dots of the n-side electrode is 5 to 100 μm, and the center-to-center distance between adjacent dots is 50 to 200 μm.

3. 3. The light-emitting element according to claim 1, wherein a ratio of an area of ​​said p-side electrode to a total area of ​​said hole and said p-type layer is 70% or more.

4. The light-emitting element according to claim 1 or 2, wherein the entire thickness of the light-emitting element is 0.5 mm or more and 1 mm or less.

5. a p-side pad electrode provided on an upper portion of the p-side electrode, and an n-side pad electrode provided on an upper portion of the n-side electrode, The sum of the area of ​​the p-side pad electrode and the area of ​​the n-side pad electrode is 0.7 mm ２ The light-emitting device according to claim 1 or 2, wherein:

6. 3. The light-emitting element according to claim 1, wherein the area of ​​the p-side electrode, the diameter of the dots of the n-side electrode, and the center-to-center distance of adjacent dots are set so that the light output is 150 mW or more and the lifetime is 10,000 hours or more when driven at 350 mA.

7. A light emitting device according to claim 1 ; a submount on which the light-emitting element is flip-chip mounted and which has a reflective layer provided on a surface of the mounting side; the reflective layer has a reflectance of 50% or more for ultraviolet light having an emission wavelength of the light emitting element, The light emitting device, wherein the reflective layer is provided in an area that is at least 0 μm to 500 μm outward from a side end face of the light emitting element in a plan view.

8. The light emitting device according to claim 7 , wherein the reflective layer is provided over an entire area that is 0 μm or more outward from a side end face of the light emitting element in a plan view.

9. the submount has a surface electrode layer that is bonded to the light emitting element; the reflective layer has an insulating layer as a bottom layer, The light emitting device according to claim 7 , wherein a portion of the surface electrode layer is provided outside a side end surface of the light emitting element in a plan view.

10. 8. The light emitting device according to claim 7, wherein the reflective layer comprises an insulating layer and a metal reflective layer provided on the insulating layer and made of a metal having a reflectance of 50% or more for ultraviolet light having an emission wavelength of the light emitting element.

11. 8. The light emitting device according to claim 7, wherein the reflective layer comprises a DBR reflective layer having a reflectance of 90% or more for ultraviolet light having an emission wavelength of the light emitting element.

12. The reflective layer is An insulating layer; a metal reflective layer provided on the insulating layer and made of a metal having a reflectance of 50% or more for ultraviolet light having an emission wavelength of the light emitting element; 8. The light emitting device according to claim 7, further comprising: a DBR layer provided on the metal reflective layer, the DBR layer having a reflectance of 50% or more for ultraviolet light having an emission wavelength of the light emitting element.

13. The light emitting device according to claim 7 , wherein the substrate of the light emitting element has a thickness of 900 μm or more.

14. a light emitting element using an Al-containing Group III nitride semiconductor and emitting light with a wavelength of 200 to 280 nm; a flat submount on which the light-emitting element is flip-chip mounted, the submount having a reflective layer provided on a surface of the mounting side and a surface electrode layer bonded to the light-emitting element; the reflective layer has an insulating layer as a bottom layer, a portion of the surface electrode layer is provided outside a side end surface of the light emitting element in a plan view, the reflective layer has a reflectance of 50% or more for ultraviolet light having an emission wavelength of the light-emitting element, and the reflective layer is provided in at least an area from 0 μm to 500 μm from a side end surface of the light-emitting element in a planar view.

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