WO2017014100A1 - 発光素子 - Google Patents
発光素子 Download PDFInfo
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- WO2017014100A1 WO2017014100A1 PCT/JP2016/070515 JP2016070515W WO2017014100A1 WO 2017014100 A1 WO2017014100 A1 WO 2017014100A1 JP 2016070515 W JP2016070515 W JP 2016070515W WO 2017014100 A1 WO2017014100 A1 WO 2017014100A1
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- Prior art keywords
- concavo
- light
- convex structure
- diffractive surface
- emitting element
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- 239000004065 semiconductor Substances 0.000 claims abstract description 38
- 230000003287 optical effect Effects 0.000 claims abstract description 15
- 239000000758 substrate Substances 0.000 claims description 45
- 229910052594 sapphire Inorganic materials 0.000 claims description 26
- 239000010980 sapphire Substances 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 230000000737 periodic effect Effects 0.000 claims description 5
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 238000000605 extraction Methods 0.000 abstract description 54
- 230000000694 effects Effects 0.000 abstract description 4
- 230000001788 irregular Effects 0.000 abstract 3
- 238000000034 method Methods 0.000 description 44
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 26
- 229910002601 GaN Inorganic materials 0.000 description 23
- 238000004088 simulation Methods 0.000 description 21
- 238000004364 calculation method Methods 0.000 description 18
- 238000005530 etching Methods 0.000 description 7
- 238000005229 chemical vapour deposition Methods 0.000 description 5
- 239000010408 film Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 150000004767 nitrides Chemical class 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 238000000149 argon plasma sintering Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 238000001771 vacuum deposition Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000008033 biological extinction Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005136 cathodoluminescence Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009499 grossing Methods 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000012780 transparent material Substances 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
- H01L33/22—Roughened surfaces, e.g. at the interface between epitaxial layers
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/10—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a light reflecting structure, e.g. semiconductor Bragg reflector
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/26—Materials of the light emitting region
- H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
- H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0008—Processes
- H01L2933/0016—Processes relating to electrodes
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
- H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/12—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a stress relaxation structure, e.g. buffer layer
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
- H01L33/145—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure with a current-blocking structure
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
- H01L33/40—Materials therefor
Definitions
- the present invention relates to a light emitting element with improved light extraction efficiency.
- a light-emitting diode basically has a structure in which an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer are stacked on a substrate.
- An electrode is formed on the p-type semiconductor layer and the n-type semiconductor layer, and light is generated in the light-emitting layer by recombination of holes and electrons injected from the semiconductor layer.
- the light is adopted as a structure in which the light is extracted from the translucent electrode or the substrate on the p-type semiconductor layer.
- the translucent electrode is a translucent electrode made of a metal thin film or a transparent conductive film formed on almost the entire surface of the p-type semiconductor layer.
- the flatness of the substrate is processed to a mirror surface level in order to control the laminated structure at the atomic level. Therefore, the semiconductor layer, the light emitting layer, and the electrode on the substrate have a laminated structure parallel to each other. ing. In this case, since the refractive index of the semiconductor layer is larger than that of the substrate or the translucent electrode, a waveguide that sandwiches the semiconductor layer between the substrate and the translucent electrode is formed.
- Patent Document 1 discloses a structure in which a two-dimensional uneven structure is formed on a sapphire substrate and light is reflected within a critical angle to improve external quantum efficiency.
- an object of the present invention is to provide a light emitting element in which the light extraction efficiency is further improved by forming a concavo-convex structure suitable for diffraction in consideration of the behavior of light.
- the light-emitting element of the present invention is formed at a boundary between a stacked portion in which at least a semiconductor layer including a light-emitting layer is stacked and a layer included in the stacked portion.
- the diffractive surface has the concavo-convex structure arranged in a lattice pattern.
- the uneven structure may be a polygonal lattice, for example, and there are rectangles and squares as polygons.
- the diffractive surface has a plurality of regions in which the directions of the gratings of the concavo-convex structure are different. For example, it is only necessary to have a plurality of regions in which the direction of the lattice of the concavo-convex structure differs by an equal angle.
- the ratio S / P of the width S of the recess to the period P in the shortest period (pitch) direction of the concavo-convex structure is preferably 60% or more.
- the diffractive surface may be one in which the uneven structure is arranged in a checkered pattern (check).
- the concavo-convex structure may be a checkered pattern in which polygonal convex portions and concave portions are alternately arranged, and examples of the polygon include a rectangle and a square.
- the diffractive surface has a plurality of regions in which directions of the checkered pattern of the uneven structure are different. For example, what is necessary is just to make it have the some area
- the diffractive surface may be one in which the concavo-convex structure is arranged in a line-and-space manner.
- the diffractive surface has a plurality of regions having different line and space directions of the concavo-convex structure.
- the line-and-space direction may have a plurality of regions that are different from each other by equal angles.
- the concavo-convex structure is any of a lattice, checkered pattern, and line and space
- the direction of the concavo-convex structure is the same It is preferable to arrange them so that they are not continuous.
- the lower limit of the period of the concavo-convex structure is preferably not less than 1 ⁇ 4 times the optical wavelength of the incident light, and the upper limit is not more than 12 times the optical wavelength of the incident light. good.
- the lower limit of the height of the concavo-convex structure is preferably 0.1 ⁇ m or more, and the upper limit of the diffraction surface is preferably 1.5 ⁇ m or less.
- the light emitting element of the present invention has a concavo-convex structure in consideration of three-dimensional reflection of light by the diffraction surface, the extraction efficiency can be improved as compared with the conventional one. Further, since the shape of the concavo-convex structure is smaller than that of the conventional structure, the cost of etching and the like can be reduced and the throughput can be improved.
- the light-emitting element 1 of the present invention is mainly configured by a stacked portion in which at least a semiconductor layer 8 including a light-emitting layer is stacked, and a diffractive surface 2 formed at any boundary of the layers included in the stacked portion. .
- the laminated portion means a portion where the semiconductor layer 8 and the substrate are laminated, and is composed of a group III nitride semiconductor layer and a sapphire substrate 70 as shown in FIG.
- the light-emitting element 1 shown in FIG. 1 is one in which light is extracted from the side opposite to the sapphire substrate 70 (hereinafter referred to as the light extraction side), but may be one in which light is extracted from the sapphire substrate 70 side.
- the group III nitride semiconductor layer includes, for example, a buffer layer 82, an n-type GaN layer 83, a multiple quantum well active layer (light emitting layer 84), an electron block layer 85, and a p-type GaN layer 86. It is formed in order.
- a p-side electrode 91 is formed on the p-type GaN layer 86 and an n-side electrode 92 is formed on the n-type GaN layer 83.
- the buffer layer 82 is formed on the diffraction surface 2 of the sapphire substrate 70 and is made of AlN.
- the buffer layer 82 may be formed by MOCVD (Metal Organic Organic Chemical Vapor Deposition) method or sputtering method.
- An n-type GaN layer 83 as a first conductivity type layer is formed on the buffer layer 82 and is made of n-GaN.
- the multiple quantum well active layer (light emitting layer 84) as a light emitting layer is formed on the n-type GaN layer 83, is composed of GalnN / GaN, and emits light by injection of electrons and holes.
- the electron block layer 85 is formed on the multiple quantum well active layer (light emitting layer 84) and is made of p-AIGaN.
- a p-type GaN layer 86 as a second conductivity type layer is formed on the electron block layer 85 and is made of p-GaN.
- the n-type GaN layer 83 to the p-type GaN layer 86 are formed by epitaxial growth of a group III nitride semiconductor. In addition, it has at least a first conductivity type layer, an active layer, and a second conductivity type layer, and when a voltage is applied to the first conductivity type layer and the second conductivity type layer, the active layer is recombined by recombination of electrons and holes. As long as light can be emitted at, the structure of the semiconductor layer 8 in the stacked portion may be other.
- the p-side electrode 91 is formed on the p-type GaN layer 86 and is made of a transparent material such as ITO (Indium Tin Oxide).
- the p-side electrode 91 may be formed by, for example, a vacuum deposition method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like.
- the n-side electrode 92 is formed on the exposed n-type GaN layer 83 by etching the n-type GaN layer 83 from the p-type GaN layer 86.
- the n-side electrode 92 is made of, for example, Ti / Al / Ti / Au, and may be formed by a vacuum deposition method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like.
- a reflective film 90 made of Al or the like may be formed on the reverse side of the light extraction side, for example, on the back side of the sapphire substrate 70.
- the boundary surface between the reflective film 90 and the sapphire substrate 70 forms a reflective surface, and light transmitted through the sapphire substrate 70 is reflected by the reflective surface. Thereby, the light transmitted through the sapphire substrate 70 can be returned to the light extraction side.
- the diffractive surface is a layer included in the laminated portion, that is, formed at the boundary of either the semiconductor layer 8 or the substrate, and is formed so as to reflect incident light emitted from the light emitting layer according to Bragg diffraction conditions. It has a concavo-convex structure 20.
- the boundary mainly means the uppermost surface or the lowermost surface of the semiconductor layer 8, but may be provided in the middle of the semiconductor layer 8 or on the surface of the substrate.
- the diffractive surface 2 is formed at the boundary between the stacked portion and the sapphire substrate 70, the sapphire substrate 70 has a c-plane ( ⁇ 0001 ⁇ ) on which a nitride semiconductor grows on the surface side. This plane becomes the diffraction plane 2.
- the diffractive surface 2 is formed with a plurality of concavo-convex structures 20 that are regularly arranged regularly.
- the light diffraction effect can be obtained by the convex portion 21 of the concave-convex structure 20.
- the concave-convex structure 20 since total reflection of light occurs when light enters from a medium having a high refractive index to a medium having a low refractive index, the concave-convex structure 20 includes a medium having a low refractive index that constitutes the convex portion 21 among the media sandwiching the boundary. Is formed so as to fill the recess 22. Therefore, since the sapphire substrate 70 has a refractive index lower than that of the buffer layer 82 in the concavo-convex structure 20 in FIG. 2, the portion composed of the material on the sapphire substrate side is filled with the convex portion 21 and the material on the buffer layer 82 side. The part which becomes is the recessed part 22.
- Such a concavo-convex structure may be formed by a conventionally known method.
- a resist film may be formed on a substrate on which a concavo-convex structure is to be formed, a predetermined pattern may be transferred to the resist film using an imprint technique, and then the concavo-convex structure may be formed on the substrate by etching.
- the shape of the concavo-convex structure a shape such as a weight or a weight base obtained by cutting off the upper part of the weight is known.
- these are mainly considering light scattering, and none designed to increase the light extraction efficiency in consideration of light diffraction is not known. The reason is that the calculation of the behavior of light with respect to diffraction is complicated and simulation is difficult.
- RCWA method Ragorous Coupled Wave Analysis
- FDTD method Finite Difference Time Domain method
- the LED shown in FIG. 3 includes a light emitting layer 111, an upper layer 12 having a uniform structure with the same refractive index distribution formed on the upper model 100 side, and an uneven structure 113 formed on the surface of the upper layer 12. And a lower layer 14 having a uniform structure formed on the lower model 200 side and continuing with the same refractive index distribution.
- the LED structure is divided into the upper model 100 on one side and the lower model 200 on the other side with the position of the light emitting layer 111 as a boundary, and the light generated in the light emitting layer 111 is transmitted as incident light and transmitted through the upper model 100 of the LED.
- Information on diffraction efficiency of transmitted light A 1 Information on diffraction efficiency of reflected light reflected by upper model 100 and returned to the boundary B 1
- the diffraction efficiency information A k of the transmitted light that has passed through the upper model 100 is reflected by the upper model 100 and returns to the boundary.
- the diffraction efficiency information B k of the reflected light is calculated by the RCWA method, and the diffraction efficiency information C k of the reflected light reflected by the lower model 200 using the light of the diffraction efficiency information B k ⁇ 1 as a light source and returning to the boundary.
- the structure of the LED means a structure necessary for the calculation of the RCWA method, which means a cross-sectional structure in a direction perpendicular to the stacked portion including the light emitting layer 111 and a periodic structure.
- the diffraction efficiency is a value indicating how much energy is included as diffracted light among the energy of incident light.
- the light extraction efficiency is the value of the extracted light energy when the total energy of the light output from the light source is 1.
- the calculation in step 1, the calculation in step 2, and the calculation in step 3 may be performed using software or a computer.
- the shape and period of the cross-sectional structure in the direction perpendicular to the light emitting layer of the LED, the thickness of each layer including the light emitting layer, the refractive index and extinction coefficient of the material of each layer, the light generated in the light emitting layer Information is input to a computer, and information A 1 , information B 1 , information D 1 , and information D 1 are obtained by calculation of the RCWA method by the computer.
- the computer stores information C k ⁇ 1 in the upper model.
- Input as information on the light source input information B k-1 as information on the light source of the lower model, obtain information A k , information B k , information D k , information D k by calculation of the RCWA method by the computer,
- the computer may calculate the light extraction efficiency from the information A 1 to An and D 1 to D n .
- Information on the light generated in the light emitting layer is information necessary for the calculation of the RCWA method, such as the light emission wavelength and light intensity, the interval between the incident angles of light, and whether the light extraction direction is the upper model side, the lower model side, or both. Means.
- the first step to the third step will be described in further detail.
- ⁇ First step> In the first step, as shown in FIG. 4A, it is assumed that the light generated in the light emitting layer 111 is an assembly of plane waves that isotropically spread. This is because in the FDTD method, as shown in FIG. 4B, the light source is assumed to be a collection of point light sources, but the RCWA method can handle only a single plane wave. This plane wave has the same energy at any angle.
- the structure of the LED is divided into two models with the middle position of the light emitting layer 111 as a boundary, one side of the LED being the upper model 100 and the other side being the lower model 200.
- the diffraction efficiency of the diffracted light generated in the upper model 100 and the lower model 200 with respect to the light (incident light) of the light emitting layer 111 is calculated using the RCWA method. Specifically, the diffraction efficiency for each angle of diffracted light is calculated for each incident angle of incident light. The calculation may be performed using software or a computer capable of calculation using the RCWA method.
- the diffracted light is transmitted light that is transmitted through the upper model 100, reflected light that is reflected by the upper model 100 and returned to the boundary, and reflected by the lower model 200 and returned to the boundary.
- the light is classified into four types: reflected light, which is light, and transmitted light, which is light transmitted through the lower model 200.
- the diffraction efficiency for each angle of the diffracted light is calculated and aggregated, and information A 1 on the diffraction efficiency of the transmitted light of the upper model 100 and the diffraction efficiency of the reflected light of the upper model 100 are collected.
- Information B 1 information C 1 on the diffraction efficiency of the reflected light of the lower model 200, and information D 1 on the diffraction efficiency of the transmitted light of the lower model 200.
- the incident angle interval may be arbitrarily determined according to the accuracy required for the light extraction efficiency simulation. The smaller the angle interval, the more accurately the light extraction efficiency can be simulated. For example, the incident angle of incident light may be calculated at intervals of 1 degree. Further, the angular interval of the diffracted light may be appropriately approximated according to the accuracy required for the light extraction efficiency simulation.
- ⁇ Second step> The transmitted light in the upper model and the lower model in the first step is light extracted from the LED. Therefore, the information A 1 of the transmitted light becomes part of the light extraction efficiency of the information to the upper side, the information D 1 of the transmitted light becomes part of the light extraction efficiency of information in the lower side.
- the reflected light of the upper model 100 in the first step can be regarded as a light source in the lower model 200
- the reflected light of the lower model 200 can be regarded as a light source in the upper model 100.
- the second step considering the light of the information C 1 and incident light to the upper model 100, as in the first step, the information A 2 of the diffraction efficiency of the transmitted light in the upper model 100, the diffraction efficiency of the reflected light the information B 2 calculated by RCWA method. Further, the light of the information B 1 is considered as the incident light to the lower model 200, and similarly to the first step, the transmission light diffraction efficiency information A 2 and the reflected light diffraction efficiency information B 2 in the lower model 200 are Calculate with the RCWA method.
- the reflected light on the upper side can be regarded as the light source in the lower model 200, and the reflected light on the lower side can be regarded as the light source in the upper model 100.
- the transmitted light in the upper model 100 is obtained using the light of the information C k ⁇ 1 as the light source.
- the diffraction efficiency information A k and the diffraction efficiency information B k of the reflected light in the upper model 100 can be calculated by the RCWA method.
- the information C k on the diffraction efficiency of reflected light in the lower model 200 and the information D k on the diffraction efficiency of transmitted light in the lower model 200 can be calculated by the RCWA method using the light of information B k ⁇ 1 as a light source. Even in this case, the calculation may be performed using software or a computer capable of calculation using the RCWA method.
- the natural number n may be arbitrarily determined according to the accuracy required for the light extraction efficiency simulation. The larger n is, the more accurately the light extraction efficiency can be simulated, but the calculation time becomes longer.
- the sum of diffraction efficiency based on information A 1 to A k-1 and information D 1 to D k-1 and diffraction efficiency based on information A 1 to A k and information D 1 to D k may be set to n when the difference from the sum of is less than a certain ratio, for example, 1% or less, with respect to the total energy of the light source.
- ⁇ Third step> In the third step, the information A 1 to An and D 1 to D n obtained in the first step and the second step are aggregated.
- the light extraction efficiency of the LED can be calculated by calculating the energy of the extracted light when the total energy of the light source is 1. The calculation may be performed using conventionally known software or a computer.
- the light extraction efficiency with respect to various structures of the LED is calculated, the structure of the LED is determined based on the result, and the LED is manufactured.
- the uneven structure found using the simulation method will be described.
- the uneven structure preferably had a side wall inclination of 75 degrees or less.
- the present application mainly uses diffraction, and in order to maximize the effect of diffraction, the concavo-convex structure preferably has an inclination of the side wall of the convex portion with respect to the diffractive surface close to 90 degrees.
- a slight inclination may be required in the concavo-convex structure in consideration of releasability.
- the inclination of the side wall of a convex part is the inclination of the side wall of the convex part with respect to a diffraction surface, Comprising: The inclination of an acute angle side is meant.
- the diffractive surface has a concavo-convex structure arranged in a lattice shape as shown in FIG.
- the lattice shape is a regular arrangement of concave portions surrounded by a frame of convex portions.
- the shape of the lattice (planar shape of the recesses) is preferably a polygon, such as a triangle, a quadrangle, or a hexagon.
- a quadrangle such as a square, a rectangle, a rhombus, and a parallelogram is preferable, and a square is the most preferable because the period of the concavo-convex structure important for the control of diffraction can be aligned.
- the period P means the minimum length of the repeating unit structure included in the concavo-convex structure, as shown in FIGS.
- the interval between the line structures is minimized, and this is set as the period P.
- the period of the concavo-convex structure on the diffractive surface is preferably 1/4 or more times the optical wavelength, preferably 1/2 or more, and more preferably 1 or more times. However, if the period is too large, cost and time are required for etching. Therefore, the period is preferably 12 times or less of the optical wavelength, preferably 10 times or less, and more preferably 6 times or less.
- the optical wavelength means the optical wavelength in the smaller refractive index of both layers constituting the boundary of the concavo-convex structure for the lower limit value, and constitutes the boundary of the concavo-convex structure for the upper limit value. It means the optical wavelength in the higher refractive index of both layers.
- the ratio S / P of the concave width S to the period P is preferably 60% or more, preferably 65% or more, and more preferably 70. % Or more is good.
- the width of the convex portion of the concavo-convex structure is at least a quarter of the optical wavelength of the reflected light, A half or more is preferable.
- the ratio S / P is preferably 60% or more and 80% or less, and preferably 65% or more and 75% or less.
- the height of the concavo-convex structure is preferably 0.1 ⁇ m or more, preferably 0.2 ⁇ m or more, and more preferably 0.3 ⁇ m or more. However, if the height is too large, cost and time are required for etching. Therefore, the height is preferably 1.5 ⁇ m or less, and preferably 1.2 ⁇ m or less. Depending on the wavelength of light, it may be 0.9 ⁇ m or less or 0.8 ⁇ m or less.
- the corner may have a chamfered shape such as a curve or a straight line that can buffer the corner as shown in FIGS. 6 (a) to 6 (c). .
- the length of the straight portion of the side is 60% or more of the length of the side of the polygon that is not chamfered.
- the polygon which does not chamfer can be specified by extending the linear part of a side.
- the length of the side of the polygon that is not chamfered may be calculated from the pitch P.
- angular part of adjacent polygons may be connected and the shape only of the side without a corner
- the diffractive surface has a plurality of regions having different concavo-convex structure grating directions.
- a region refers to a region in which diffraction surfaces are divided by a predetermined size, and in the same region, the directions of the gratings of the concavo-convex structure are aligned. Since the light incident from the light emitting layer is directed in all directions, the diffraction by the diffraction surface can be reliably performed by providing a plurality of regions in which the directions of the gratings of the concavo-convex structure are different. Therefore, it is preferable that the regions where the direction of the concavo-convex structure is the same on an arbitrary straight line are arranged so as not to be continuous.
- the maximum number of continuous uneven structures may be 500 cycles or less, more preferably 200 cycles or less.
- the size of the region is too small, reflection by the concavo-convex structure cannot be performed sufficiently. Therefore, in the region, it is better to have a continuous concavo-convex structure of at least a period that can sufficiently reflect light.
- the concavo-convex structure may be 50 periods or more, more preferably 100 periods or more.
- the direction of the grating in each region may be arbitrary, but it is preferable to provide a plurality of types of regions in which the directions of the grating are different from each other by equal angles in order to surely diffract incident light from any direction.
- the shape of the lattice is an equilateral triangle
- the direction of the lattice of the concavo-convex structure is 45 degrees. It is only necessary to form four different regions.
- the lattice shape is a square, it is sufficient to form two types of regions where the direction of the concavo-convex structure is 45 degrees, and when the lattice shape is a regular hexagon. Two types of regions in which the direction of the lattice of the concavo-convex structure is different by 60 degrees may be formed.
- a plurality of regions having different grating directions should be arranged as evenly as possible in order to surely diffract light in any direction.
- the concavo-convex structure may be arranged in a checkered pattern (check shape).
- the checkered pattern is a pattern in which convex portions and concave portions having the same planar shape are alternately arranged. Compared to the lattice-shaped one, there is an advantage that it is easy to form a convex portion having a high aspect ratio, which is advantageous when it is desired to increase the height of the convex portion.
- the checkered pattern shape (planar shape of the convex portion or the concave portion) is preferably a polygon, such as a triangle or a quadrangle.
- a quadrangle such as a square, a rectangle, a rhombus, and a parallelogram is preferable, and a square is the most preferable because the period of the concavo-convex structure important for the control of diffraction can be aligned.
- the diffractive surface preferably has a plurality of regions in which the directions of the checkered pattern of the concavo-convex structure are different.
- the region means a range where the directions of the checkered pattern of the concavo-convex structure are continuously arranged on the diffraction surface. Since the light incident from the light emitting layer is directed in all directions, the diffraction by the diffraction surface can be surely performed by providing a plurality of regions in which the direction of the checkered pattern of the concavo-convex structure is different. Therefore, it is preferable that the regions where the direction of the concavo-convex structure is the same on an arbitrary straight line are arranged so as not to be continuous.
- the maximum number of continuous uneven structures may be 500 cycles or less, more preferably 200 cycles or less.
- the size of the region is too small, reflection by the concavo-convex structure cannot be performed sufficiently. Therefore, in the region, it is better to have a continuous concavo-convex structure of at least a period that can sufficiently reflect light.
- the concavo-convex structure may be 50 periods or more, more preferably 100 periods or more.
- the direction of the checkered pattern in each region may be arbitrary, but it is preferable to provide a plurality of types of regions in which the directions of the checkered pattern are different from each other by equal angles in order to surely diffract the incident light from any direction. good.
- the checkerboard shape is an equilateral triangle
- two types of regions having a checkered pattern direction of 30 degrees may be formed.
- the checkerboard pattern is a rectangle, the checkered pattern direction is 45 degrees different. What is necessary is just to form an area
- the concavo-convex structure may be arranged in a line-and-space manner.
- Line-and-space is one in which linear convex portions and concave portions are alternately arranged.
- the diffractive surface preferably has a plurality of regions having different line-and-space directions of the concavo-convex structure.
- a region refers to a region in which diffraction surfaces are divided by a predetermined size, and the line and space directions of the concavo-convex structure are aligned within the same region. Since the light incident from the light emitting layer is directed in all directions, diffraction by the diffraction surface can be reliably performed by providing a plurality of regions having different line and space directions of the concavo-convex structure. Therefore, it is preferable that the portions having the same direction of the concavo-convex structure are arranged so as not to be continuous.
- the maximum number of continuous uneven structures may be 500 cycles or less, more preferably 200 cycles or less.
- the size of the region is too small, reflection by the concavo-convex structure cannot be performed sufficiently. Therefore, in the region, it is better to have a continuous concavo-convex structure of at least a period that can sufficiently reflect light.
- the concavo-convex structure may be 50 periods or more, more preferably 100 periods or more.
- the direction of the line and space may be arbitrary, but it is preferable to provide a plurality of regions in which the direction of the line and space is different from each other by an equal angle in order to surely diffract the incident light from any direction. For example, it is only necessary to form two regions whose line and space directions are different by 90 degrees.
- the interval between the concave portions is preferably 200 nm or more.
- the width of the convex portion of the concavo-convex structure is preferably at least a quarter of the optical wavelength of light to be reflected, and preferably a half or more. This is because the light cannot be sufficiently diffracted unless the width of the convex portion is at least a quarter of the optical wavelength or more.
- the diffraction of light is more likely to occur as the difference in the refractive index of the material sandwiching the diffraction surface increases. Therefore, when the concavo-convex structure 20 is formed between the substrate and the semiconductor layer 8, as shown in FIG. 9A or 9B, at least a part of the concavo-convex structure 20 includes the semiconductor layer 80 and the concavo-convex structure. It is preferable that the refractive index difference of 20 is made of a material that makes the refractive index difference between the substrate 70 and the semiconductor layer 80 larger.
- the uneven structure 20 is formed between the sapphire substrate 70 and the semiconductor layer 80 made of gallium nitride (GaN), at least a part of the uneven structure 20 is formed of silicon dioxide (SiO 2 ). Is preferred. Since the refractive index of gallium nitride is about 2.5, the refractive index of sapphire is about 1.78, and the refractive index of silicon dioxide is about 1.45. The refractive index difference from gallium nitride can be increased. Further, at least a part of the concavo-convex structure 20 can be formed of silicon oxynitride (SiON).
- the refractive index can be controlled by the ratio of oxygen to nitrogen.
- the material used for the concavo-convex structure 20 needs to be selected so that the semiconductor layer 80 can be grown on the substrate 70.
- the uneven structure 20 may be manufactured in any way, and for example, a semiconductor manufacturing technique such as lithography, imprint, or etching may be used.
- the optical element used for the actual measurement value is composed of an LED chip 101, a reflector 102, and a resin mold 103.
- the LED chip 101 has an area of 0.5 mm square and a thickness of 0.15 mm.
- the reflector 102 has a hole extending in the shape of a truncated cone in which the LED chip 101 is disposed, and the surface thereof is silver-plated.
- the upper surface of the truncated cone (the surface on the side where the LED chip 101 is disposed) The diameter was 0.75 mm, the height was 0.35 mm, and the angle of the side surface with respect to the upper surface was 45 degrees.
- the resin mold 103 is a resin having a refractive index of 1.42 to cover the LED chip 101 and the reflector 102, and the light irradiation direction of the LED chip is a hemisphere having a diameter of 5 mm. Table 1 shows the simulation results and the measured values.
- the light extraction efficiency showed almost the same value as that actually created, confirming the reliability of the simulation.
- factors relating to light extraction efficiency other than PSS such as chip size, thickness, The refractive index of the resin mold is not considered in the simulation.
- Example 1 First, the relationship between the shape of the concavo-convex structure and the light extraction efficiency was simulated.
- a general model was used for the laminated portion composed of the semiconductor layer and the substrate of the LED.
- the diffractive surface was arranged at the boundary between the substrate (refractive index 1.78) and the semiconductor layer (refractive index 2.5), and the shape of the concavo-convex structure was as follows.
- L & S The line and space shown in FIG. 8 was used, and the line width was 40% of the period.
- Lattice The recesses shown in FIG. 5 (b) were in a square lattice shape, and the line width was 30% of the period.
- the period and height of the concavo-convex structure were the same, and eight types with different periods of 0.1 ⁇ m from 0.3 ⁇ m to 1.0 ⁇ m were simulated.
- the concavo-convex structure of the micro PSS is a triangular arrangement of cones having a bottom diameter of 2.7 ⁇ m and a height of 1.6 ⁇ m with a period of 3 ⁇ m.
- the inclination of the side wall of the convex part of the concavo-convex structure with respect to the diffractive surface was 90 degrees in both the example and the comparative example. The above results are shown in Table 2 and FIG.
- the concavo-convex structure when the period and height of the concavo-convex structure is 0.5 ⁇ m or more, the concavo-convex structure is a check (triangle) and a lattice (square) than the micro PSS that has been considered good in the past.
- the light extraction efficiency was also high.
- the concavo-convex structure has a lattice (square) shape and the height and period are 0.7 ⁇ m, the light extraction efficiency is improved by 6.2% compared to the micro PSS.
- line and space although not as high as micro PSS, a certain degree of light extraction efficiency could be obtained.
- line and space has an advantage that it is easier to process than other shapes including micro PSS.
- the period of the concavo-convex structure is line and space, check (triangle), lattice (square), and the concavo-convex structure is a lattice (square) made of SiO 2 (refractive index 1.45).
- Eight types with different heights of 0.1 ⁇ m from 0.3 ⁇ m to 1.0 ⁇ m were simulated with the height fixed at 0.5 ⁇ m. Other conditions are the same as those in the first embodiment. The results are shown in Table 3 and FIG.
- the lattice (square) in which the convex portions of the concavo-convex structure were made of SiO 2 was able to obtain the highest light extraction efficiency regardless of the height of the concavo-convex structure.
- the light extraction efficiency was higher in the case where the concavo-convex structure was a check and a lattice (square) than the micro PSS, which was conventionally considered good.
- line and space although not as high as micro PSS, a certain degree of light extraction efficiency could be obtained. As described above, line and space has an advantage that it is easier to process than other shapes including micro PSS.
- Example 3 Next, the relationship between the inclination of the side wall of the convex portion of the concavo-convex structure with respect to the diffraction surface and the light extraction efficiency was simulated.
- the shape in the plane direction was a square lattice
- the period was 0.5 ⁇ m
- the height was 0.25 ⁇ m
- the width at a half position was 0.15 ⁇ m.
- simulation was performed for six types of inclinations of the side walls of the convex portions of the concavo-convex structure with respect to the diffractive surface, which are different by 5 degrees in the range of 65 to 90 degrees. Other conditions are the same as those in the first embodiment.
- the results are shown in Table 4 and FIG.
- Example 5 Next, the result of actually creating the concavo-convex structure according to the present invention will be described with reference to the photographs in FIGS.
- a resist was applied on a sapphire substrate, and a mask having the concavo-convex structure was formed using an imprint technique.
- the sapphire substrate was etched using the mask, and a convex portion having a square with a side of 300 nm and a height of 500 nm was formed on the sapphire substrate in a lattice shape with a pitch of 1 ⁇ m.
- FIG. 16 is a plan photograph in the middle of growing gallium nitride (Gan) on the concavo-convex structure formed on the sapphire substrate. As shown in FIG. 16, it can be seen that gallium nitride (GaN) is selectively grown in the recess, and the growth proceeds in the lateral direction when the selective growth proceeds to the upper surface.
- FIG. 1 a cross-sectional photograph of the concavo-convex structure thus formed is shown in FIG. It can be seen that the recess of the sapphire substrate is completely filled with gallium nitride (GaN).
- GaN gallium nitride
- the concavo-convex structure is formed such that the inclination of the side wall of the convex portion with respect to the diffractive surface is 75 to 80 degrees.
- FIG. 18A is a plan photograph obtained by the cathodoluminescence method showing dislocations of the gallium nitride layer formed in this way.
- the dislocation density was 6.1 ⁇ 10 7 cm ⁇ 2 .
- FIG. 18B shows a plan photograph when a gallium nitride layer is formed on a flat sapphire substrate.
- the dislocation density was 2.0 ⁇ 10 8 cm ⁇ 2 . That is, it can be seen that the dislocation density of the gallium nitride layer formed on the concavo-convex structure according to the present invention is lower than that of the gallium nitride layer formed on the flat sapphire substrate.
- the inclination and period P of the convex portion of the concavo-convex structure, the width S of the concave portion, the height of the concavo-convex structure, and the like are described.
- the projections and depressions are not uniform due to distortions and the like.
- the slope and period P of the concavo-convex structure, the width S of the concavo-convex structure, and the height h of the concavo-convex structure are defined, but doubts arise.
- the measurement may be defined as shown in the following explanation and FIG.
- the significance of the diffractive surface and the concavo-convex structure is taken into consideration.
- stacking part in the plane containing the straight line of the shortest periodic direction of an uneven structure is image
- SEM scanning electron microscope
- a straight line C passing through the minimum value and a straight line D passing through the maximum value of the height are determined.
- the interval between the straight line C and the straight line D is defined as the height h of the concavo-convex structure.
- the height of the straight line C is 0, and the height of the straight line D is 100. Then, a straight line G connecting a point E having a height of 10 and a point F having a height of 90 of the reference uneven line B is determined.
- the inclination of the straight line G with respect to the straight line C is defined as the inclination ⁇ of the side wall of the convex portion with respect to the diffraction surface.
- a straight line H having a height of 50 parallel to the straight line C is determined, the width of the concave portion on the straight line is S, the width of the convex portion is the line width L, and the sum of the width S of the concave portion and the line width L is the period P.
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Abstract
Description
そこで本発明は、光の挙動を考慮し、回折に適した凹凸構造を形成することにより、光取出効率を更に向上した発光素子を提供することを目的とする。
情報B1および情報C1を基礎とし、回折効率の情報Ck-1の光を光源として、上部モデル100を透過した透過光の回折効率の情報Ak、上部モデル100で反射し境界に戻った反射光の回折効率の情報BkをそれぞれRCWA法で計算し、回折効率の情報Bk-1の光を光源として下部モデル200で反射し境界に戻った反射光の回折効率の情報Ck及び下部モデル200を透過した透過光の回折効率の情報DkをそれぞれRCWA法で計算する第2ステップ(ただし、第2ステップにおけるkは2以上n以下の自然数である。また、k=nの時は、BnおよびCnは計算しなくても良い)と、
情報A1~AnおよびD1~Dnを集約し、光取り出し効率を計算する第3のステップと、
で主に構成される。そして、このシミュレーションによる光取り出し効率の計算結果に基づいて、LEDの構造を決定することができる。
<第1ステップ>
第1ステップでは、図4(a)に示すように、発光層111で生じる光を等方的に拡がる平面波の集合体であると仮定する。これは、FDTD法では、図4(b)に示すように、光源を点光源の集まりと仮定するが、RCWA法は単一の平面波しか扱えないからである。この平面波は、どの角度でも同一のエネルギーを有する。
第1ステップの上部モデル及び下部モデルにおける透過光は、LEDから取り出した光である。したがって、透過光の情報A1は上部側への光取り出し効率の情報の一部となり、透過光の情報D1は下部側への光取り出し効率の情報の一部となる。
第3ステップでは、上記第1ステップおよび第2ステップで求めた情報A1~AnおよびD1~Dnを集約する。そして、光源のトータルのエネルギーを1としたときの取り出した光のエネルギーを計算することにより、LEDの光取り出し効率を計算することができる。当該計算は、従来から知られているソフトウェアやコンピュータを用いて行えば良い。
まず、シミュレーションの信頼性を評価するために、凹凸構造のないフラットなものと、従来、光の取り出し効率が最も良いとされているマイクロPSSについてシミュレーションし、実測値と比較した。実測値に用いた光学素子は、図10(a)に示すように、LEDチップ101と、リフレクタ102と、樹脂モールド103からなるものである。LEDチップ101は、面積が0.5mm角で厚さ0.15mmのものと用いた。リフレクタ102は、LEDチップ101が内部に配置される円錐台状に広がる孔を有し、表面に銀メッキが施されたもので、円錐台の上面(LEDチップ101が配置される側の面)の直径が0.75mm、高さが0.35mm、側面の上面に対する角度が45度のものを用いた。また、樹脂モールド103は、屈折率が1.42の樹脂でLEDチップ101及びリフレクタ102を覆うもので、LEDチップの光照射方向は、直径5mmの半球状としたものを用いた。シミュレーションの結果と実測値を表1に示す。
まず、凹凸構造の形状と光取り出し効率との関係をシミュレーションした。ここで、LEDの半導体層や基板からなる積層部は一般的なモデルを用いた。また、回折面は基板(屈折率1.78)と半導体層(屈折率2.5)の境界に配置し、その凹凸構造の形状は、下記の通りとした。
L&S:図8に示すラインアンドスペース状とし、ラインの幅は周期の40%とした。
チェック(市松模様):図7(a)に示す三角形のチェック状とした。
格子:図5(b)に示す凹部が正方形の格子状とし、ラインの幅は周期の30%とした。
次に、凹凸構造がラインアンドスペース、チェック(三角)、格子(正方形)であるものと、凹凸構造の凸部がSiO2(屈折率1.45)からなる格子(正方形)であるものについて、周期を0.5μmに固定し、高さが0.3μmから1.0μmまで0.1μmずつ異なる8種類をシミュレーションした。その他の条件は、実施例1と同じである。その結果を表3及び図12に示す。
次に、回折面に対する凹凸構造の凸部の側壁の傾きと光取り出し効率との関係をシミュレーションした。凹凸構造は、平面方向の形状を正方格子、周期を0.5μm、高さを0.25μm、高さの半分(高さ0.125μm)の位置における幅を0.15μmとした。そして、図13に示すように、回折面に対する凹凸構造の凸部の側壁の傾きを、65~90度の範囲で5度ずつ異なる6種類についてシミュレーションした。その他の条件は、実施例1と同じである。その結果を表4及び図14に示す。
次に、回折面における凹凸構造の最短周期方向の周期Pに対する凹部の幅Sの割合S/Pと光取り出し効率との関係をシミュレーションした。凹凸構造は、平面方向の形状を正方格子、周期を0.5μm、高さを0.5μm、とした。そして、凹凸構造の最短周期方向の周期Pに対する凹部の幅をSとしたときの割合S/Pが50%、60%、70%のときの3種類についてシミュレーションした。その他の条件は、実施例1と同じである。その結果を表5及び図15に示す。
次に、本発明に係る凹凸構造を実際に作成した結果を、図16~図18の写真を用いて説明する。凹凸構造は、まず、サファイア基板上にレジストを塗布し、インプリント技術を用いて凹凸構造を有するマスクを形成した。次に、当該マスクを用いてサファイア基板にエッチングを行い、サファイア基板上に上面の一辺が300nmの正方形で高さ500nmの凸部を、ピッチ1μmで格子状に形成した。次に、当該凹凸構造上に窒化ガリウム(GaN)を成長させて、本発明の凹凸構造を作成した。図16は、サファイア基板に形成された凹凸構造上に窒化ガリウム(Gan)を成長させる途中の平面写真である。図16に示すように、凹部において窒化ガリウム(GaN)が選択的に結晶成長され、上面まで選択成長が進んだところで横方向に成長が進んでいることがわかる。
(1)凹凸構造の最短周期方向の直線を含む平面で積層部を切った断面写真を走査型電子顕微鏡(SEM)で撮影する。
(2)回折面のおおよその方向を考慮した上で、断面写真から凹凸構造の境界上の点を測定し、それを最小二乗法で計算して近似直線Aを導く。
(3)近似直線Aを基準として、断面写真の凹凸構造の境界の高さを測定し、近似直線A上の10nm間隔で当該高さの平均を取り、直線補間でスムージングを行う。これにより、特異な欠陥や歪みを取り除いた基準凹凸線Bが作成される。
(4)傾きの測定をする側壁を挟む基準凹凸線B上の凸部と凹部に対し、近似直線Aと平行な直線であって、近似直線Aを基準とした基準凹凸線Bの高さの最小値を通る直線Cと、高さの最大値を通る直線Dを決定する。直線Cと直線Dの間隔を凹凸構造の高さhとする。
(5)直線Cの高さを0、直線Dの高さを100とする。そして基準凹凸線Bの10の高さの点Eと90の高さの点Fを結んだ直線Gを決定する。この直線Gの直線Cに対する傾きを、回折面に対する凸部の側壁の傾きθとする。
(6)直線Cと平行な高さ50の直線Hを決定し、当該直線上の凹部の幅をS、凸部の幅を線幅L、凹部の幅Sと線幅Lの和を周期Pとする。
2 回折面
8 積層部
20 凹凸構造
21 凸部
22 凹部
70 サファイア基板
84 発光層
P 周期
S 凹部の幅
Claims (22)
- 発光層を含む半導体層が少なくとも積層された積層部と、
前記積層部に含まれる層のいずれかの境界に形成され、前記発光層から発せられる入射光をブラッグの回折条件に従って反射するように形成された凹凸構造を有する回折面と、を具備し、
前記凹凸構造は、前記回折面に対する凸部の側壁の傾きが75度より大きく形成されたものであることを特徴とする発光素子。 - 前記回折面は、前記凹凸構造が格子状で配列されたものであることを特徴とする請求項1記載の発光素子。
- 前記回折面は、前記凹凸構造が多角形の格子状で配列されたものであることを特徴とする請求項2記載の発光素子。
- 前記回折面は、前記凹凸構造が長方形又は正方形の格子状で配列されたものであることを特徴とする請求項2記載の発光素子。
- 前記回折面は、前記凹凸構造の格子の方向が異なる複数の領域を有することを特徴とする請求項2ないし4のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の格子の方向が等角度ずつ異なる複数の領域を有することを特徴とする請求項2ないし4のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の最短周期方向の周期Pに対する凹部の幅Sの割合S/Pが60%以上であることを特徴とする請求項1ないし6のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造が市松模様で配列されたものであることを特徴とする請求項1記載の発光素子。
- 前記回折面は、前記凹凸構造が多角形の市松模様で配列されたものであることを特徴とする請求項8記載の発光素子。
- 前記回折面は、前記凹凸構造が長方形又は正方形の市松模様で配列されたものであることを特徴とする請求項8記載の発光素子。
- 前記回折面は、前記凹凸構造の市松模様の方向が異なる複数の領域を有することを特徴とする請求項8ないし10のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の市松模様の方向が等角度ずつ異なる複数の領域を有することを特徴とする請求項9又は10記載の発光素子。
- 前記回折面は、前記凹凸構造がラインアンドスペース状で配列されたものであることを特徴とする請求項1記載の発光素子。
- 前記回折面は、前記凹凸構造のラインアンドスペースの方向が異なる複数の領域を有することを特徴とする請求項13記載の発光素子。
- 前記回折面は、前記凹凸構造のラインアンドスペースの方向が等角度ずつ異なる複数の領域を有することを特徴とする請求項12記載の発光素子。
- 前記回折面は、前記凹凸構造の方向が異なる複数の領域を有すると共に、前記凹凸構造の方向が同一である領域が連続しないように配列されることを特徴とする請求項5、6、11、12、14、15のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の周期が前記入射光の光学波長の4分の1倍以上であることを特徴とする請求項1ないし16のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の周期が前記入射光の光学波長の12倍以下であることを特徴とする請求項1ないし17のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の高さが0.1μm以上であることを特徴とする請求項1ないし18のいずれかに記載の発光素子。
- 前記回折面は、前記凹凸構造の高さが1.5μm以下であることを特徴とする請求項1ないし19のいずれかに記載の発光素子。
- 前記凹凸構造は、基板と前記半導体層との間に形成され、当該凹凸構造の少なくとも一部は、前記半導体層と前記凹凸構造の屈折率差が、前記基板と前記半導体層の屈折率差よりも大きくなる材料からなることを特徴とする請求項1ないし20のいずれかに記載の発光素子。
- 前記凹凸構造は、サファイア基板と前記半導体層との間に形成され、当該凹凸構造の少なくとも一部は、二酸化ケイ素(SiO2)又は酸窒化ケイ素(SiON)からなることを特徴とする請求項1ないし20のいずれかに記載の発光素子。
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JP2017529560A JPWO2017014100A1 (ja) | 2015-07-17 | 2016-07-12 | 発光素子 |
CN201680041849.0A CN107851690A (zh) | 2015-07-17 | 2016-07-12 | 发光元件 |
US15/310,323 US20180248076A1 (en) | 2015-07-17 | 2016-07-12 | Light emitting device |
EP16788404.8A EP3163634A4 (en) | 2015-07-17 | 2016-07-12 | Light emitting element |
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- 2016-07-12 WO PCT/JP2016/070515 patent/WO2017014100A1/ja active Application Filing
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EP3163634A4 (en) | 2018-01-17 |
EP3163634A1 (en) | 2017-05-03 |
JPWO2017014100A1 (ja) | 2018-04-26 |
CN107851690A (zh) | 2018-03-27 |
TW201712892A (zh) | 2017-04-01 |
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