Light-emitting device

Abstract

To provide a light-emitting device having high light extraction efficiency and reliability.SOLUTION: A light-emitting device includes: a substrate 10; a pattern of a plurality of protrusions 11 protruding from the substrate; a first semiconductor layer 20 provided on the substrate; an active layer 30 provided on the first semiconductor layer; and a second semiconductor layer 40 provided on the active layer. Each of the protrusions includes: a first layer 13 formed integrally with and inseparably from the substrate and protruding from an upper surface of the base substrate; and a second layer 15 provided on the first layer and formed of a material different from that of the first layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Exemplary embodiments relate to light emitting devices and methods for making the same. [Background technology]

[0002] Light-emitting diodes (LEDs) have been used in recent years as a type of self-luminous light source. Light-emitting diodes utilize the properties of compound semiconductors to convert electrical signals into light, such as infrared light, visible light, and ultraviolet light. As the luminous efficiency of light-emitting devices has increased, they have come to be applied in a variety of fields, including display devices and general lighting. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting device with high light extraction efficiency and reliability and a method for manufacturing the same. [Means for solving the problem]

[0004] A light emitting device according to an exemplary embodiment includes a substrate, a pattern of a plurality of protrusions protruding from the substrate, a first semiconductor layer provided on the substrate, an active layer provided on the first semiconductor layer, and a second semiconductor layer provided on the active layer, each of the protrusions being formed integrally and inseparably with the substrate, and including a first layer protruding from an upper surface of the base substrate and a second layer provided on the first layer and made of a material different from the first layer, and when the distance between the centers of two adjacent protrusions is called the pitch, the ratio of the diameter of the protrusion to the pitch is about 0.8 to about 1.0.

[0005] According to an exemplary embodiment, the diameter of each of the protrusions can be between about 2.5 micrometers and about 3.5 micrometers, and the pitch can be between about 2.5 micrometers and about 3.5 micrometers.

[0006] According to an exemplary embodiment, the diameter of each of the protrusions can be between about 2.6 micrometers and about 2.8 micrometers, and the pitch can be between about 2.9 micrometers and about 3.1 micrometers.

[0007] According to an exemplary embodiment, the diameter of each of the protrusions may be approximately 2.8 micrometers.

[0008] According to exemplary embodiments, the ratio of the height of the first layer to the height of the second layer may be about 0.2 to about 1.5, or about 0.75 to about 1.5, or the height of the second layer may be greater than the height of the first layer.

[0009] According to an exemplary embodiment, the diameter of the protrusions may be equal to or less than the pitch.

[0010] According to an exemplary embodiment of the present disclosure, the side of the first layer and the side of the second layer may have different inclination angles.

[0011] According to an exemplary embodiment, the first semiconductor layer may be provided with a void in a part of the region corresponding to the side surface of the protrusion.

[0012] An exemplary embodiment of a light-emitting device may include a substrate, a pattern of multiple protrusions formed integrally and inseparably with the substrate, the pattern including a first layer protruding from an upper surface of the substrate and a second layer formed on the first layer and made of a material different from the first layer, and an emitting stack formed on the substrate and emitting light, the emitting stack may have an air gap formed on at least one side of the first layer of the protrusion, and the ratio of the height of the first layer to the height of the second layer may be greater than 2.5 and less than 9.5.

[0013] According to an exemplary embodiment, the light-emitting stack may include a first semiconductor layer provided on a substrate, an active layer provided on the first semiconductor layer, and a second semiconductor layer provided on the active layer, and the void may be provided within the first semiconductor layer.

[0014] According to an exemplary embodiment, the height of the top of the void from the surface of the substrate and the height of the top of the first layer from the surface of the substrate may be substantially the same.

[0015] According to an exemplary embodiment of the present disclosure, when the upper surface of the first layer is circular in plan view, the voids may be provided corresponding to the vertices of a regular hexagon inscribed in the circle.

[0016] According to an exemplary embodiment, when cut along a plane perpendicular to the top surface of the substrate and passing through the center of the circle, the void may be a right triangle, and the hypotenuse of the right triangle may be a side of the first layer.

[0017] According to an exemplary embodiment, the ratio of the height of the first layer to the height of the second layer may be greater than 2.5 and less than 9.5.

[0018] According to an exemplary embodiment, the height of the first layer may be greater than or equal to about 0.25 and less than or equal to about 0.55, and the combined height of the first and second layers may be about 2.1 micrometers.

[0019] A method for manufacturing a light-emitting device according to the exemplary embodiment described above may include a step of forming a pattern of a plurality of protrusions on a substrate, each of the protrusions including a first layer protruding from an upper surface of the substrate and a second layer provided on the first layer and formed of a material different from the first layer, and a step of sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on the substrate, wherein the step of forming the first semiconductor layer may include a step of three-dimensionally (3D) growing a material of the first semiconductor layer on the substrate, and a step of two-dimensionally (2D) growing a material of the first semiconductor layer on the substrate.

[0020] An exemplary embodiment of a light-emitting device may include a substrate, a pattern of multiple protrusions formed integrally and inseparably with the substrate, each of the protrusions including a first layer protruding from a surface of the substrate and a second layer formed on the first layer and made of a material different from the first layer, and an emitting stack formed on the substrate and emitting light, wherein the first layer may include a top surface and a side surface connecting the surface of the substrate and the top surface of the first layer, and the top surface of the first layer may have a rough surface.

[0021] According to an exemplary embodiment, the roughness standard deviation Rq of the roughened surface of the upper surface of the first layer may be about 0.300 nm to about 0.550 nm, and the roughness arithmetic mean Ra may be about 0.250 nm to about 0.400 nm.

[0022] According to an exemplary embodiment, the light-emitting stack may include a first semiconductor layer provided on the substrate and covering the pattern of protrusions, an active layer provided on the first semiconductor layer, and a second semiconductor layer provided on the active layer, and light emitted from the active layer may travel toward the substrate through the first semiconductor layer.

[0023] According to an exemplary embodiment, the refractive index of the first layer may be greater than the refractive index of the second layer.

[0024] According to an exemplary embodiment, the refractive index of the first layer may be from about 1.6 to about 2.45, and the refractive index of the second layer may be from about 1.3 to about 2.0.

[0025] According to an exemplary embodiment, the refractive index of the first layer and the second layer may be smaller than the refractive index of the first semiconductor layer, and according to an exemplary embodiment, the refractive index of the first semiconductor layer may be about 2.0 to about 2.5.

[0026] According to an exemplary embodiment, the substrate may have a roughened surface in areas where the plurality of protrusions are not provided.

[0027] According to an exemplary embodiment, the side surface may be a reflective surface that reflects 90% or more of light traveling from the first semiconductor layer toward the side surface.

[0028] According to an exemplary embodiment, a method for manufacturing a light-emitting device having the above-described structure may include the steps of preparing a substrate, roughening an upper surface of the substrate, forming an insulating layer of a material having a refractive index different from that of the substrate, forming a photoresist on the insulating layer and patterning the photoresist using photolithography, reflowing the photoresist, etching the insulating layer and the substrate using the photoresist as a mask, and forming a light-emitting stack on the substrate.

[0029] According to an exemplary embodiment, the roughened surface may be formed by at least one of wet etching, dry etching, and grinding.

[0030] According to an exemplary embodiment, the step of etching the insulating layer and the substrate may be performed anisotropically. [Effects of the Invention]

[0031] The illustrative embodiments provide a light emitting device and a method for fabricating the same with high light extraction efficiency and reliability. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment. [Figure 2] FIG. 2 is a plan view of a substrate on which a protruding pattern is provided, among the elements of the light emitting device of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line II' in FIG. [Figure 4a] 1A and 1B are diagrams illustrating a substrate provided with protrusions and the growth direction of the substrate in a light-emitting device according to an exemplary embodiment. [Figure 4b]1 is a photograph showing a first semiconductor layer actually grown on a substrate with protrusions. [Figure 5a] FIG. 4b is an enlarged view of the rectangle indicated by the dotted line in FIG. 4a. [Figure 5b] 5a is a photograph of a portion of FIG. 5a. [Figure 6] 1 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment showing a lateral semiconductor chip. [Figure 7] 1 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment, showing a flip-chip type semiconductor chip. [Figure 8] 10 is a graph showing luminous efficiency according to the pitch of the protrusion pattern in Table 1. [Figure 9] 10 is a graph showing luminous efficiency according to the pitch of the protrusion pattern in Table 2. [Figure 10] 1 is a graph showing the luminous efficiency according to the diameter in Tables 3 to 6. [Figure 11] 1 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment. [Figure 12] FIG. 12 is a plan view of a substrate on which a protruding pattern is provided, among the elements of the light emitting device of FIG. 11. [Figure 13] FIG. 13 is a cross-sectional view taken along line II' in FIG. [Figure 14] FIG. 14 is an enlarged cross-sectional view of P1 in FIG. [Figure 15a] 10A and 10B are diagrams illustrating the structure of a protrusion of a light-emitting device in which no gap is provided. [Figure 15b] 10A and 10B are diagrams illustrating the structure of a protrusion of a light-emitting device in which no gap is provided. [Figure 15c] 10A and 10B are diagrams illustrating the structure of a protrusion of a light-emitting device in which no gap is provided. [Figure 15d] 10A and 10B are diagrams illustrating the structure of a protrusion of a light-emitting device in which no gap is provided. [Figure 16a] 10A and 10B are diagrams illustrating the structure of a protrusion of a light emitting device having a gap therein. [Figure 16b] 10A and 10B are diagrams illustrating the structure of a protrusion of a light emitting device having a gap therein. [Figure 16c]10A and 10B are diagrams illustrating the structure of a protrusion of a light emitting device having a gap therein. [Figure 16d] 10A and 10B are diagrams illustrating the structure of a protrusion of a light emitting device having a gap therein. [Figure 17] 10 is a graph showing the simulation results in Table 11. [Figure 18a] 1A to 1C are cross-sectional views showing some steps of manufacturing a protruding pattern. [Figure 18b] 1A to 1C are cross-sectional views showing some steps of manufacturing a protruding pattern. [Figure 19] 4 is a photograph of a protrusion pattern and a first semiconductor layer according to an exemplary embodiment manufactured by the above-described method. [Figure 20a] 10 is a photograph of the light path and light intensity of a light-emitting device having a structure without a void. [Figure 20b] 10 is a photograph showing the light path and light intensity of a light-emitting device having a structure in which a gap is provided. [Figure 21] 1 is a cross-sectional view illustrating a semiconductor chip according to an exemplary embodiment. [Figure 22] 1 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment. [Figure 23] FIG. 23 is a plan view of a substrate on which a protruding pattern is provided, among the elements of the light emitting device of FIG. 22. [Figure 24] FIG. 24 is a cross-sectional view taken along line II' in FIG. 23. [Figure 25a] FIG. 25 is an enlarged cross-sectional view of P1 in FIG. 24. [Figure 25b] FIG. 25b is an enlarged cross-sectional view of P4 in FIG. 25a. [Figure 26a] 1 is a photograph of the top surface of the first layer of a conventional light-emitting device. [Figure 26b] 1 is a photograph of the top surface of a first layer of a light emitting device according to an exemplary embodiment of the present disclosure. [Figure 27a] 25 is a transmission electron microscope (TEM) photograph of a portion corresponding to portion P2 of FIG. 24 during the manufacture of a light emitting device according to an exemplary embodiment. [Figure 27b]25 is a transmission electron microscope (TEM) photograph of a portion corresponding to portion P3 of FIG. 24 during the manufacture of a light emitting device according to an exemplary embodiment. [Figure 28a] This is a PhET simulation image showing the optical path depending on the shape of the side of the first layer. [Figure 28b] This is a PhET simulation image showing the optical path depending on the shape of the side of the first layer. [Figure 29a] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29b] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29c] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29d] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29e] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29f] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 29g] 1A to 1C are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment. [Figure 30] 1 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment showing a lateral semiconductor chip; [Figure 31] 1 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment, showing a flip-chip type semiconductor chip. [Figure 32] 10 is a graph showing the wavelength-dependent emission intensity of the light emitting devices according to Comparative Example 1, Comparative Example 3, and this example. DETAILED DESCRIPTION OF THE INVENTION

[0033] The inventive concept may be applied to various modifications and may have various forms, and specific exemplary embodiments are shown in the drawings and described in detail in the following description. However, it is not intended that the inventive concept be limited to the particular forms disclosed, but rather should be understood to include all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

[0034] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0035] FIG. 1 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment.

[0036] Referring to FIG. 1, a light emitting device according to an exemplary embodiment includes a substrate 10 and a light emitting stack disposed on the substrate 10 .

[0037] The light emitting stack includes a first semiconductor layer 20 , an active layer 30 , and a second semiconductor layer 40 disposed successively on a substrate 10 .

[0038] The substrate 10 may be a transparent or non-transparent substrate, a conductive or insulating substrate, or a growth substrate for growing a semiconductor single crystal, such as a nitride single crystal.

[0039] A sapphire substrate can be used as the substrate 10. However, the concept of the present invention is not limited thereto, and the substrate 10 can be formed of various materials, such as SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga2O3. In particular, sapphire may have a crystalline structure with hexa-rhombohedral (Hexa-Rhombohedral) symmetry. The lattice constants of sapphire in the c-axis direction and the a-axis direction are 13.001 Å and 4.758 Å, respectively, and sapphire has the c(0001) plane, the a(1120) plane, and the r(1102) plane. The c-plane of sapphire is relatively easy to grow nitride thin films on and is stable at high temperatures, so it can be used as a substrate for growing nitride semiconductors.

[0040] In an exemplary embodiment of the present disclosure, the substrate 10 is patterned to provide a pattern of a plurality of protrusions 11 on its upper surface. That is, the protrusions 11 are provided in a form that protrudes upward from the upper surface of the substrate 10. In an exemplary embodiment, the protrusions 11 may be provided in an inverted cone shape whose width decreases in the upward direction, and therefore, when the protrusions 11 are cut in a plane perpendicular to the substrate 10, the cross section of the protrusions 11 may be approximately triangular.

[0041] The protrusion 11 has a first layer 13 and a second layer 15 that are continuously laminated on the upper surface of the substrate 10. The first layer 13 is provided on the substrate 10, and the second layer 15 is provided on the first layer 13.

[0042] The first layer 13 is formed integrally with and inseparably from the substrate 10. Thus, the first layer 13 is made of the same material as the substrate 10. The upper surface of the first layer 13 may have a circular shape when the shape of the protrusion 11 is conical.

[0043] The second layer 15 is formed of a material different from that of the first layer 13. The material of the second layer 15 may have a different refractive index from that of the material of the first layer 13. In an exemplary embodiment of the present disclosure, the refractive index of the first layer 13 may be higher than that of the second layer 15. In this case, various insulating materials having a lower refractive index than that of the first layer 13, for example, an insulating material having a refractive index of about 1.0 to about 1.7, may be used as the material of the second layer 15. The second layer 15 may include, for example, SiOx, SiOxNy, SiNx, or other materials having a reflectivity. In an exemplary embodiment, the first layer 13 may be composed of sapphire, and the second layer 15 may be composed of SiO2. Here, the refractive index of the first layer 13 is about 1.76, and the refractive index of the second layer 15 is about 1.46, which is lower than the refractive index of the substrate 10.

[0044] The substrate 10 having the protrusion 11 may have multiple compound semiconductor layers formed thereon. The multiple compound semiconductor layers may be formed by various methods, such as electron beam evaporation, physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma laser deposition (PLD), dual thermal evaporation, sputtering, metalorganic chemical vapor deposition (MOCVD), etc. However, the concept of the present invention is not limited thereto.

[0045] The first semiconductor layer 20 may be provided on the substrate 10. The first semiconductor layer 20 is a semiconductor layer doped with a first conductivity type dopant. The first conductivity type dopant may be an n-type dopant. The first conductivity type dopant may be Si, Ge, Se, Te, or C.

[0046] In exemplary embodiments of the present disclosure, the first semiconductor layer 20 may include a nitride-based semiconductor material. For example, the first semiconductor layer 20 may include In x Al y Ga 1-x-y N(0≦x≦1, The first semiconductor layer 20 is made of a semiconductor material having a composition formula where 0≦y≦1, 0≦x+y≦1. In an exemplary embodiment, the semiconductor material having the composition formula may include GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, etc. The first semiconductor layer 20 may be formed using a semiconductor material that is grown to include an n-type dopant such as Si, Ge, Sn, Se, or Te.

[0047] In an exemplary embodiment of the present disclosure, the first semiconductor layer 20 may be configured by alternately stacking two types of layers having different bandgaps. The structure formed by alternately stacking two types of layers having different bandgaps may be a superlattice structure, and therefore, the first semiconductor layer 20 can improve current spreading and relieve stress.

[0048] Two types of layers having different band gaps are alternately formed, which may include different thin film crystal layers. In this case, when two layers having different band gaps are alternately stacked, a periodic structure may be formed with a crystal lattice longer than the basic unit lattice. The two layers having different band gaps are a layer having a wide band gap and a layer having a narrow band gap. In an exemplary embodiment, the layer having a wide band gap is Al a Ga b In (1-a-b) N (0 ≦ a < 1, 0 < b ≦ 1), for example, it may be a GaN layer. The layer having a narrow band gap is Al a Ga b In (1-a-b) N (0 ≦ a < 1, 0 < b ≦ 1), for example, it may be Ga b In (1-b) N (0 < b ≦ 1).

[0049] In an exemplary embodiment of the present disclosure, at least one of the wide band gap layer and the narrow band gap layer may contain n-type impurities.

[0050] The active layer 30 is provided on the first semiconductor layer 20 and corresponds to the light emitting layer.

[0051] The active layer 30 is a layer in which electrons (or holes) injected through the first conductive type semiconductor layer and holes (or electrons) injected through the second semiconductor layer collide with each other, and light is emitted due to the difference in the band gaps of the energy bands corresponding to the formation material of the active layer 30. The active layer 30 may emit at least one peak wavelength of ultraviolet, blue, green, and red.

[0052] The active layer 30 may be formed of a compound semiconductor. For example, the active layer 30 may be realized by at least one of a compound semiconductor formed by a combination of a Group 3 element and a Group 5 element, or a combination of a Group 2 element and a Group 6 element. The active layer 30 may have a quantum well structure, such as a multiple quantum well structure in which quantum well layers and barrier layers are alternately stacked. However, the structure of the active layer 30 is not limited thereto, and may also be a quantum wire structure, a quantum dot structure, or the like.

[0053] In exemplary embodiments of the present disclosure, the quantum well layer comprises In x Al y Ga 1-x-y The barrier layer may be made of a material having a composition formula of InN(0≦x≦1, 0≦y≦1, 0≦x+y≦1). x Al y Ga 1-x-y The barrier layer may be formed of a semiconductor material having a composition formula of N(0≦x≦1, 0≦y≦1, 0≦x+y≦1) and may be provided with a different composition ratio from that of the well layer. Here, the barrier layer may have a wider band gap than the well layer.

[0054] The well layer and the partition layer may include at least one pair selected from the group consisting of AlGaAs / GaAs, InGaAs / GaAs, InGaN / GaN, GaN / AlGaN, AlGaN / AlGaN, InGaN / AlGaN, InGaN / InGaN, InGaP / GaP, AlInGaP / InGaP, and InP / GaAs. In an exemplary embodiment, the well layer of the active layer 30 may be composed of InGaN, and the partition layer may be composed of an AlGaN-based semiconductor. In an exemplary embodiment of the present disclosure, the indium composition of the well layer may be higher than that of the partition layer, and the partition layer may be free of the indium composition. Alternatively, the well layer may be free of aluminum, and the partition layer may contain aluminum. However, the compositions of the well layer and the partition layer are not limited thereto.

[0055] According to an exemplary embodiment, the barrier layer may have a thickness greater than that of the well layer. However, if the well layer is too thin, the carrier confinement efficiency may decrease, and if the well layer is too thick, the carriers may be confined excessively. If the barrier layer is too thin, the electron blocking efficiency may decrease, and if the barrier layer is too thick, the electrons may be blocked excessively.

[0056] In this way, by appropriately adjusting the thicknesses of the barrier layers and well layers, it is possible to effectively confine the respective carriers in the well layers according to the wavelength of light and the structure of the quantum well.

[0057] In exemplary embodiments of the present disclosure, the thickness of each well layer is not particularly limited, and may be substantially the same or different. When the thickness of each well layer is substantially the same, the quantum levels are substantially the same, and therefore the emission wavelengths of each well layer may be substantially the same. In this case, an emission spectrum with a narrow half-width may be obtained. When the thickness of each well layer is different, the emission wavelength of each well layer can be changed, and the width of the emission spectrum can be accordingly broadened.

[0058] In an exemplary embodiment of the present invention, at least one of the plurality of barrier layers may contain a dopant, for example, at least one of an n-type dopant and a p-type dopant. When an n-type dopant is added, the barrier layer may be an n-type semiconductor layer. When the barrier layer is an n-type semiconductor layer, the injection efficiency of electrons injected into the active layer 30 can be improved.

[0059] In exemplary embodiments of the present disclosure, the barrier layers can have a variety of thicknesses, with the top barrier layer having substantially the same thickness as the other barrier layers or a greater thickness.

[0060] When the active layer 30 has a multiple quantum well structure, the compositions of the quantum well layers and the barrier layers may be set according to the emission wavelength required for the light emitting device. In an exemplary embodiment, all of the compositions of the multiple well layers may or may not be substantially the same. For example, the lower well layer may contain impurities, while the upper well layer may not contain impurities.

[0061] The second semiconductor layer 40 is provided on the active layer 30 .

[0062] The second semiconductor layer 40 is a semiconductor layer having a second conductivity type dopant having a polarity opposite to that of the first conductivity type dopant. The second conductivity type dopant may be a p-type dopant, and may include, for example, Mg, Zn, Ca, Sr, Ba, etc.

[0063] In exemplary embodiments of the present disclosure, the second semiconductor layer 40 may include a nitride-based semiconductor material. x Al y Ga 1-x-y The second semiconductor layer 40 may be formed of a semiconductor material having a composition formula of GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, etc. The second semiconductor layer 40 may be formed by growing a semiconductor material so as to include a p-type dopant such as Mg, Zn, Ca, Sr, or Ba.

[0064] Although not shown, in addition to the substrate 10, the first semiconductor layer 20, the active layer 30, and the second semiconductor layer 40, a functional layer such as a buffer layer and / or an electron blocking layer may be further provided.

[0065] For example, a buffer layer may be provided on the substrate 10 and the first semiconductor layer 20. The buffer layer may be formed as a single layer or as a multilayer. In an exemplary embodiment, the buffer layer is formed of In x Al yGa 1-x-y N (0≦x≦1, 0≦y≦1, 0≦x+y≦1), and may include at least one of materials such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAsP, AlGaInP, and ZnO.

[0066] The buffer layer can be formed to have a superlattice structure by alternately arranging different semiconductor layers. The buffer layer can be arranged to reduce the difference in lattice constant between the substrate 10 and the nitride-based semiconductor layer, and can be defined as a defect control layer. The lattice constant of the buffer layer may have a value between the lattice constant of the substrate 10 and the lattice constant of the nitride-based semiconductor layer. The buffer layer does not necessarily have to be formed, but the concept of the present invention is not limited to this.

[0067] Furthermore, an electron blocking layer may be further disposed between the second semiconductor layer 40 and the active layer 30. The electron blocking layer can reduce the degradation of crystallinity due to dopants in the second semiconductor layer 40 and can prevent the dopants in the second semiconductor layer 40 from diffusing into the active layer 30. Furthermore, the electron blocking layer can prevent electrons from the active layer 30 from traveling to the second semiconductor layer 40, thereby preventing the diffusion of current between the electron blocking layer and the second semiconductor layer 40. In an exemplary embodiment, the electron blocking layer is made of In x Al y Ga 1-x-y The electron blocking layer may be formed of a semiconductor material having a composition formula of 0≦x≦1, 0≦y≦1, 0≦x+y≦1. The electron blocking layer may be formed of, for example, at least one of GaN, AlGaN, InGaN, InAlGaN, and AlInN.

[0068] The electron blocking layer may have a wider bandgap than the barrier layer of the active layer 30. The bandgap of the electron blocking layer may vary depending on the composition of the material that makes up the electron blocking layer. For example, if the electron blocking layer is made of AlGaN, the aluminum composition ratio may be changed to set different bandgaps, and the electron blocking effect may improve as the bandgap widens.

[0069] In exemplary embodiments of the present disclosure, the electron blocking layer may be arranged in a single layer or multiple layers and may include a second conductivity type dopant, for example, a p-type conductivity type dopant. Thus, the electron blocking layer may be a p-type semiconductor layer having a p-type dopant, such as Mg, Zn, Ca, Sr, or Ba, or may be at least one of GaN, AlGaN, and InGaN containing a p-type dopant. In exemplary embodiments, the electron blocking layer may be formed as a superlattice structure in which at least two different layers are alternately arranged.

[0070] Although the present embodiment has been described using the buffer layer and the electron blocking layer as examples, at least one of the buffer layer and the electron blocking layer may be omitted. Needless to say, the light-emitting device may further include functional layers other than the buffer layer and the electron blocking layer.

[0071] As described above, in the light emitting device according to the exemplary embodiment of the present disclosure, a pattern of a plurality of protrusions 11 is provided on the substrate 10. The protrusions 11 will be described in detail.

[0072] 2 is a plan view of a substrate 10 provided with a protrusion 11, one of the elements of the light emitting device of FIG. 1, and FIG. 3 is a cross-sectional view taken along line II' of FIG.

[0073] Referring to FIGS. 2 and 3, protrusions 11 are provided on the upper surface of a substrate 10, and each protrusion 11 has a first layer 13 and a second layer 15.

[0074] Each of the protrusions 11 may have a circular shape when viewed in a plane. If the protrusions 11 are provided in a conical shape, the apex of the cone will be the center.

[0075] The protrusions 11 can be sized to have a predetermined diameter DM and height HT. Here, the diameter DM refers to the width of the bottom end of the protrusion 11 in a cross-sectional view, and the height HT refers to the distance from the top surface of the substrate 10 to the apex of the protrusion 11. In an exemplary embodiment, each of the protrusions 11 can have the same diameter DM and height HT as the others. However, the protrusions 11 do not have to have exactly the same diameter DM and height HT, and the diameters DM and heights HT may vary within a predetermined range.

[0076] The first layer 13 and the second layer 15 may have different diameters when viewed in a plane, or may be arranged concentrically with the same center. When the protrusion 11 is arranged in a conical shape, the diameter of the first layer 13 is larger than the diameter of the second layer 15. Here, the diameters of the first and second layers 13, 15 are defined as the widths of the bottom ends of the first and second layers 13, 15 when viewed in cross section.

[0077] In the exemplary embodiment of the present disclosure, the protrusions 11 can be arranged in various forms on the upper surface of the substrate 10. For example, the protrusions 11 may be arranged at each vertex of a square in a square lattice pattern, or at each vertex of a hexagon in a hexagonal lattice pattern. In the exemplary embodiment of the present disclosure, the protrusions 11 are illustrated as being arranged at each vertex of a square in a square lattice pattern.

[0078] The protrusions 11 may be arranged at a predetermined pitch PT and distance DT from each other. The pitch PT is the distance between the centers of two adjacent protrusions 11 when viewed on a plane, and the distance DT is the distance between the edges of two adjacent protrusions 11 when viewed on a plane.

[0079] In an exemplary embodiment of the present disclosure, the diameter DM of the protrusions 11 may be equal to or less than the pitch PT. If the diameter DM of the protrusions 11 is greater than the pitch PT, the protrusions 11 will overlap each other in a plane, and the area of ​​the upper surface of the substrate 10 where the protrusions 11 are not provided will be excessively small. The upper surface of the substrate 10 not covered by the protrusions 11 is where the growth of the first semiconductor layer 20 will occur later. Therefore, if the diameter DM of the protrusions 11 is greater than the pitch PT, the growth of the first semiconductor layer 20 (see FIG. 1) will not occur sufficiently, which is disadvantageous in manufacturing the light-emitting device.

[0080] According to an exemplary embodiment, the pitch PT and the distance DT may have different values ​​depending on the direction of arrangement. In the exemplary embodiment, the pitch PT and / or the distance DT are illustrated as being the same, but this is for convenience of explanation, and the pitch PT and the distance DT do not all need to be the same, and may have slight differences within a predetermined range.

[0081] In an exemplary embodiment of the present disclosure, the pitch PT of the pattern of the protrusions 11 has a value within a predetermined range according to the diameter DM, and the ratio of the diameter DM of the protrusions 11 to the pitch PT may be in the range of about 0.8 to about 1.0. For example, when the diameter DM of the protrusions 11 is 2.5 micrometers to 3.5 micrometers, the pitch PT may be 2.5 micrometers or more and less than 3.5 micrometers. Alternatively, when the diameter DM of the protrusions 11 is 2.6 micrometers to 2.8 micrometers, the pitch PT may be 2.9 micrometers to 3.1 micrometers.

[0082] In an exemplary embodiment of the present disclosure, the first layer 13 and the second layer 15 in the protrusion 11 may be formed with various height ratios. Here, the height H1 of the first layer 13 is formed to be equal to or greater than a predetermined value. If the height H1 of the first layer 13 is 0, the growth of the first semiconductor layer 20 from the substrate 10 is inhibited by impurities remaining on the upper surface of the substrate 10 during processing. In an exemplary embodiment, the ratio of the height H1 of the first layer 13 to the height H2 of the second layer 15 may be 0.2 to 1.5. In another exemplary embodiment, the ratio of the height H1 of the first layer 13 to the height H2 of the second layer 15 may be 0.75 to 1.5, or the ratio of the height H1 of the first layer 13 to the height H2 of the second layer 15 may be greater than 1. In an exemplary embodiment, the ratio of the height H1 of the first layer 13 to the height H2 of the second layer 15 is 0.75, the height of the first layer 13 is 0.9 μm, the height of the second layer 15 is 1.2 μm, and the diameter DM of the protrusion 11 is about 2.7 to about 2.9 μm, for example 2.8 μm.

[0083] In an exemplary embodiment of the present disclosure, when the height H2 of the second layer 15 is formed to have a value greater than the height H1 of the first layer 13, lateral crystal growth of the first layer 13 is reduced, improving the crystal quality.

[0084] In exemplary embodiments of the present disclosure, the inclination angles of the side surfaces of the first layer 13 and the second layer 15 may be at least partially the same or different from each other. In the drawings, the inclination angles of the first layer 13 and the second layer 15 are shown to have the same value, but the concept of the present invention is not limited thereto. The inclination angles of the side surfaces of the first layer 13 and the second layer 15 may be at least partially the same or different from each other. In particular, the inclination angles at the contact portion between the first layer 13 and the second layer 15 may be different from each other. Because the first layer 13 and the second layer 15 are made of different materials, the inclination degrees of their side surfaces may be set to different values ​​depending on the process conditions during the etching process. In exemplary embodiments, the inclination angles of the first layer 13 and the second layer 15 are formed to be different, thereby increasing the degree of scattering of light emitted from the light emitting device and improving luminous efficiency.

[0085] In the exemplary embodiment of the present disclosure, the protrusions 11 may be arranged regularly as shown in the drawing, but the concept of the present invention is not limited thereto. For example, the protrusions 11 may be arranged irregularly. Even in this case, when viewed as a whole on the substrate 10, the spacing PT and spacing DT of the protrusions 11 per area are within a predetermined range, and in this case, the densities thereof can be made substantially the same.

[0086] In the exemplary embodiment of the present disclosure, for convenience of explanation, the protrusion 11 is shown to have only a conical shape, but the shape of the protrusion 11 may be changed to various other shapes within limits without departing from the concept of the present disclosure. For example, the shape of the protrusion 11 may be a polygonal pyramid. In addition, even if the protrusion 11 is provided in a conical shape, the shape of the curved surface forming the side surface may be partially changed.

[0087] The light emitting device configured as above will be described below with reference to FIGS. 1 to 3. FIG.

[0088] First, the substrate 10 is prepared, and an insulating layer is deposited on the substrate 10 using a material for forming the second layer 15. As described above, the substrate 10 may include a material such as SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, or Ga2O3, and the insulating layer may include SiOx, SiOxNy, SiNx, or the like.

[0089] Next, photoresist is applied to the insulating layer, and a photoresist pattern is formed by exposure and development. The photoresist pattern is then used as a mask to etch the insulating layer and a portion of the substrate 10. In this manner, the second layer 15 is formed by etching the insulating layer except for the portion where the protrusion 11 is to be formed. The upper surface of the substrate 10 is exposed in the portion where the second layer 15 is not formed. Here, the first layer 13 is formed by over-etching the upper surface of the substrate 10 through additional etching. If only the second layer 15 is formed and etching is performed to expose the original upper surface of the substrate 10, theoretically, it is expected that the growth of a semiconductor layer will occur easily after the upper surface of the substrate 10 is exposed. However, in reality, the growth of the first semiconductor layer 20 does not occur properly due to etching residues and impurities present on the upper surface of the substrate 10. In this manner, additional etching is performed to completely remove the etching residues, impurities, and the like from the substrate 10. This results in the formation of the first layer 13.

[0090] The etching for forming the first layer 13 and the second layer 15 can be performed using various methods under various conditions depending on the material. For example, the insulating layer and portions of the substrate 10 may be patterned using dry etching.

[0091] In the above-described method, the second layer 15 and the first layer 13 may be formed successively and may be patterned using the same or different etching gases.

[0092] The first semiconductor layer 20 is formed on the substrate 10 on which the protrusion 11 is formed. The first semiconductor layer 20 first grows upward from the exposed surface of the substrate 10, and then grows upward and laterally.

[0093] Figure 4a shows a substrate 10 provided with a protrusion 11 and the growth direction of the substrate 10 in a light-emitting device according to an exemplary embodiment, and Figure 4b is a photograph showing a first semiconductor layer 20 actually grown on the substrate with the protrusion. Figure 5a is an enlarged view of the rectangle indicated by the dotted line in Figure 4a, and Figure 5b is a photograph of a portion of Figure 5a. For ease of explanation, arrows are used in Figures 4a and 5a to indicate the main direction in which the semiconductor layers are grown.

[0094] Referring to Figures 4a, 4b, 5a and 5b, first, a first semiconductor layer 20 is formed above.

[0095] The first semiconductor layer 20 can be formed of a semiconductor layer of various materials, for example, an n-type nitride-based semiconductor layer, and can be formed using metalorganic chemical vapor deposition, molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE) methods.

[0096] The initial growth of the first semiconductor layer 20 occurs primarily upward from the exposed surface of the substrate 10 , and no growth occurs on the top surface of the second layer 15 .

[0097] After the first semiconductor layer 20 is partially grown upward, the first semiconductor layer 20 grows upward and laterally. For ease of explanation, the figure shows a first growth pattern 21 that grows mainly upward, and a second growth pattern 23 that grows upward and laterally, but grows predominantly laterally.

[0098] In an exemplary embodiment of the present disclosure, epitaxial lateral overgrowth (ELOG) may be used as a metalorganic chemical vapor deposition (MOCVD) method for growing the first semiconductor layer 20 in the lateral direction (horizontal direction in the figure). The first semiconductor layer 20 grows continuously in the lateral and upward directions, thereby bonding to cover the entire surface of the substrate 10, including the surface of the second layer 15. In this way, the first semiconductor layer 20 has a plate shape that covers the entire surface of the substrate 10.

[0099] In an exemplary embodiment of the present disclosure, when forming the protrusions 11, the ratio of the diameter DM of the protrusions 11 to the pitch is formed to be approximately 0.8 to approximately 1.0, in order to reduce defects during the growth of the first semiconductor layer 20.

[0100] In an exemplary embodiment of the present disclosure, the exposed upper surface of the substrate 10 between the protrusions 11 essentially serves as a growth nucleus, and the substrate 10 grows upward from the upper surface as shown in first growth pattern 21. The first semiconductor layer 20 is then grown laterally by the ELOG method as shown in second growth pattern 23. In the growth of the first semiconductor layer 20, the surface of the first semiconductor layer 20 growing upward is sometimes referred to as the top surface, and the surface of the first semiconductor layer 20 growing laterally is sometimes referred to as the side surface. When the first semiconductor layer 20 is epitaxially grown by the ELOG method, the side surface growth occurs more predominantly than the top surface growth, and the growth ratio of the m-axis to the c-axis is approximately 2:1. During growth, the side surface of the first semiconductor layer 20 may be perpendicular to the top surface of the first semiconductor layer 20, but is not limited thereto and may be a facet inclined relative to the top surface of the first semiconductor layer 20. In an exemplary embodiment, the top surface of the first semiconductor layer 20 may correspond to the (0001) plane, and the side surface of the first semiconductor layer 20 may correspond to the (10-11) plane.

[0101] In the exemplary embodiment of the present disclosure, the pitch between the protrusions 11 is within the above range, which facilitates the growth of the first semiconductor layer 20 and improves the light extraction efficiency of the final light emitting device.

[0102] If the pitch is smaller than the above range, the spacing between adjacent protrusions 11 is insufficient, resulting in slow crystal growth. Furthermore, even if growth does occur, subsequent lateral growth occurs with a small growth area, resulting in the formation of voids VD on the side surfaces. Here, the voids VD are formed in accordance with the growth direction of the crystal plane, on the edges corresponding to the vertices of the hexagon, with the center of the protrusion 11 as the reference. If the voids VD are large, crystals grow in directions different from the overall growth direction on the side surfaces of the protrusions 11 of the first layer 13 corresponding to the portions where the voids VD are formed (portions indicated by dotted ellipses in the figure), resulting in defects. These defects ultimately result in a decrease in the light extraction efficiency of the light-emitting device. If the pitch is larger than the above range, the spacing between adjacent protrusions 11 is sufficiently wide, resulting in faster crystal growth. This reduces the size of the voids and the occurrence of defects on the side surfaces of the protrusions, but the reduced distance between the protrusions 11 reduces the light scattering effect of the protrusions 11, resulting in a decrease in light extraction efficiency.

[0103] After the first semiconductor layer 20 is completely grown laterally, the first semiconductor layer 20 may be selectively grown further upward using HVPE. When the first semiconductor layer 20 is formed using MOCVD, the deposition rate is slower than that of HVPE, so HVPE may be used to quickly grow the first semiconductor layer 20 to a sufficient thickness.

[0104] 1 to 3 , in an exemplary embodiment of the present disclosure, a buffer layer may be further formed on the substrate 10 before forming the first semiconductor layer 20. In an exemplary embodiment, a superlattice structure may be formed by alternately stacking two types of layers having different bandgaps on the first semiconductor layer 20. The active layer 30 is formed on the first semiconductor layer 20. In an exemplary embodiment, a quantum well structure may be formed by alternately stacking quantum well layers and barrier layers as the active layer 30. After forming the electron blocking layer on the active layer 30, a second semiconductor layer 40 may be formed on the active layer 30 to manufacture a light-emitting stack.

[0105] The light emitting device having the above structure has high light extraction efficiency and high reliability due to the reduced defects.

[0106] A light emitting device having the above structure may be mounted on various types of semiconductor chips.

[0107] FIG. 6 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment showing a lateral semiconductor chip.

[0108] 6, the semiconductor chip includes a light emitting device, and a first electrode 110 and a second electrode 120 connected to the light emitting device. The light emitting device includes a substrate 10, a first semiconductor layer 20 provided on the substrate 10, an active layer 30, and a second semiconductor layer 40.

[0109] In an exemplary embodiment, the first electrode 110 is disposed on the first semiconductor layer 20 where the active layer 30 and the second semiconductor layer 40 are not provided, and the second electrode 120 is disposed on the second semiconductor layer 40.

[0110] The first electrode 110 and / or the second electrode 120 may be made of a single layer or multiple layers of metal. Materials for the first electrode 110 and / or the second electrode 120 may include Al, Ti, Cr, Ni, Au, Ag, Cr, Cu, Ti, Ru, Rh, Ir, Mg, Zn, Al, In, Ta, Pd, Co, and various metals and alloys thereof.

[0111] Here, in order to improve light-emitting efficiency, a plurality of protrusions 11 are provided on the upper surface of the substrate 10. The protrusions may be provided on the substrate 10 in a conical shape including the first layer 13 and the second layer 15, as described in the above exemplary embodiment.

[0112] An insulating layer 130 is provided on the first electrode 110 and the second electrode 120, and contact holes are provided on the insulating layer 130 to expose the first electrode 110 and the second electrode 120. The insulating layer 130 may be disposed on the top surface of the second semiconductor layer 40 and on the side surfaces of the semiconductor layer, and may selectively contact the first electrode 110 and the second electrode 120. The insulating layer 130 may include an insulating material made of at least one of oxides, nitrides, fluorides, and sulfides containing at least one of Al, Cr, Si, Ti, Zn, and Zr, or an insulating resin. The insulating layer 130 may be selectively formed from, for example, SiO2, Si3N4, Al2O3, or TiO2. The insulating layer 130 may be formed as a single layer or a multilayer, but is not limited thereto.

[0113] In an exemplary embodiment of the present disclosure, the first electrode 110 and the second electrode 120 may be connected to other elements through contact holes. For example, the first electrode 110 and the second electrode 120 may be provided with a first pad and a second pad connected through contact holes. Furthermore, in the exemplary embodiment of the present disclosure, the light-emitting device will be briefly described using the drawings, but may further include elements having additional functions in addition to the layers described above. For example, various layers may further be included, such as a reflective layer that reflects light, an additional insulating layer for insulating certain elements, and an anti-solder layer that prevents solder diffusion.

[0114] Furthermore, when forming a horizontal light emitting device, the mesa can be formed in various shapes, and the positions and shapes of the first electrode 110 and the second electrode 120 can also be changed in various ways.

[0115] The light emitting device according to the exemplary embodiment of the present disclosure emits light by being turned on by applying a signal to the first electrode 110 and the second electrode 120, and the emitted light may travel below the first semiconductor layer 20 or above the second semiconductor layer 40.

[0116] Although the semiconductor chip including the light emitting device according to the above exemplary embodiment is illustrated as a horizontal type, the present invention is not limited thereto. For example, the light emitting device according to the exemplary embodiment may be applied to a vertical type or a flip-chip type semiconductor chip.

[0117] 7 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment, showing a flip-chip semiconductor chip, which is shown in an inverted form in the figure because it is formed on a substrate 10 and then flipped over and mounted on another component.

[0118] 7, the semiconductor chip includes a light emitting device, and a first electrode 110 and a second electrode 120 connected to the light emitting device. The light emitting device includes a substrate 10, a first semiconductor layer 20 provided on the substrate 10, an active layer 30, and a second semiconductor layer 40.

[0119] In an exemplary embodiment, the light emitting device may include at least one mesa including an active layer 30 and a second semiconductor layer 40. The mesa may include multiple protrusions 11, which may be spaced apart from one another. An insulating layer 130 is provided on the mesa, and the insulating layer 130 has contact holes between the mesas that expose the first semiconductor layer 20 and a portion of the second semiconductor layer 40. A first electrode 110 is connected to the exposed first semiconductor layer 20 through the contact hole between the mesas, and a second electrode 120 is connected to the exposed second semiconductor layer 40 through the contact hole on the second semiconductor layer 40.

[0120] The luminous efficiency of the light emitting device according to the exemplary embodiment described above will now be described.

[0121] Table 1 shows data on the luminous efficiency of a light-emitting device as a function of the pitch when the diameter and height of the protrusions on the substrate are constant. Figure 8 is a graph showing the luminous efficiency as a function of the pitch of the protrusion pattern in Table 1.

[0122] In the following exemplary embodiments, the rate of increase or decrease in the amount of light refers to the rate of increase or decrease in the amount of light of a conventional light-emitting device consisting only of a first layer without a second layer relative to the amount of light of the light-emitting device according to the exemplary embodiment. The protrusion pattern of the conventional light-emitting device had a pitch of 3 μm, a total height of 1.7 μm, and a diameter of 2.7 μm.

[0123] [Table 1]

[0124] Table 2 shows data on the luminous efficiency of a light-emitting device as a function of the pitch when the diameter and height of the protrusions on the substrate are constant. Figure 9 is a graph showing the luminous efficiency as a function of the pitch of the protrusion pattern in Table 2.

[0125] [Table 2]

[0126] As described above, when the height and diameter are constant, the light intensity varies depending on the pitch, and the rate of increase in light intensity was greatest when the ratio of the diameter of the protrusions to the pitch was in the range of approximately 0.8 to approximately 1.0. In particular, as shown in Tables 1 and 2, although there were slight differences depending on the height of the first layer and the height of the second layer, the rate of increase in light intensity was highest at 3 μm. Tables 3 to 6 show data on the light-emitting device showing the luminous efficiency as a function of the diameter when the pitch and height of the protrusions on the substrate are constant. Fig. 10 is a graph showing the luminous efficiency as a function of the diameter in Tables 3 to 6. The graphs shown as Examples 1 to 4 in Fig. 10 show the data in Tables 3 to 6, respectively.

[0127] [Table 3]

[0128] [Table 4]

[0129] [Table 5]

[0130] [Table 6]

[0131] As shown in Tables 3 to 5 and Figure 10, when the diameter of the protrusions is 2.8 μm, the luminous efficiency is relatively high regardless of the pitch or height, and the highest luminous efficiency is observed when the ratio of the first layer to the second layer is 0.75. Tables 7 to 10 show data showing the luminous efficiency of a light-emitting device as a function of the height of the first and second layers when the pitch and diameter of the protrusions on the substrate are constant.

[0132] [Table 7]

[0133] [Table 8]

[0134] [Table 9]

[0135] [Table 10]

[0136] Referring to Tables 7 and 8, the rate of increase or decrease in the amount of light differs depending on the height of the first layer and the second layer, and generally, when the height of the second layer is higher than the height of the first layer, the rate of increase or decrease in the amount of light is large, but in some cases this is not the case. As described above, the present disclosure provides a light emitting device with significantly higher luminous efficiency by setting different diameters of protrusions on a substrate, protrusion heights, and protrusion pattern pitches.

[0137] Detailed Description of the Illustrated Exemplary Embodiments FIG. 11 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment of the present disclosure.

[0138] In the following embodiments, in order to avoid repetitive explanation, differences from the above-described embodiments will be mainly described, and explanations of the above-described embodiments and matters that are obvious to those skilled in the art will be omitted.

[0139] Referring to FIG. 11 , a light-emitting device according to an exemplary embodiment includes a substrate 10 and a light-emitting stack provided on the substrate 10. The light-emitting stack includes a first semiconductor layer 20, an active layer 30, and a second semiconductor layer 40, which are successively provided on the substrate 10. In an exemplary embodiment of the present disclosure, the substrate 10 is patterned to provide a pattern of multiple protrusions 11 on its upper surface. The first semiconductor layer 20 may be provided on the substrate 10. The first semiconductor layer 20 may cover the protrusions 11 on the substrate 10. To achieve this, the first semiconductor layer 20 may be epitaxially grown from the upper surface of the substrate 10. In this case, the first semiconductor layer 20 may be grown upward so as to completely cover the side and upper surfaces of the protrusions 11. The first semiconductor layer 20 has multiple voids at positions corresponding to the sides of the protrusions 11, as will be described later.

[0140] 12 is a plan view of a substrate having a protrusion thereon, one of the elements of the light-emitting device of FIG. 11, FIG. 13 is a cross-sectional view taken along line II' in FIG. 12, and FIG. 14 is an enlarged cross-sectional view of P1 in FIG. 13.

[0141] 12 to 14, a protrusion 11 including a first layer 13 and a second layer 15 is provided on the upper surface of a substrate 10, and a plurality of voids VD are provided adjacent to the protrusion 11.

[0142] In an exemplary embodiment of the present disclosure, the pitch PT of the pattern of the protrusions 11 can have a value within a predetermined range depending on the diameter DM. For example, the ratio of the diameter DM of the protrusions 11 to the pitch PT may be in the range of about 0.3 to about 2.0. However, the ratio of the diameter DM of the protrusions 11 to the pitch PT is not limited to this and may be other values.

[0143] In an exemplary embodiment of the present disclosure, a plurality of voids VD are formed on the side surfaces of the protrusion 11, i.e., between the protrusion 11 and the first semiconductor layer 20. In particular, the voids VD are formed near the end of the interface between the first layer 13 and the second layer 15 of the protrusion 11. The voids VD have a shape that extends downward of the extended surface relative to the extended surface of the interface between the first layer 13 and the second layer 15, i.e., toward the substrate 10. Thus, the voids VD are formed on at least one side along the outer edge of the top of the first layer 13.

[0144] Here, the voids VD are formed in accordance with the growth direction of the crystal plane and are formed on sides corresponding to the vertices of a hexagon with the center of the protrusion 11 as the reference. Each of the voids VD may have a triangular shape when viewed in a plane. Specifically, when the protrusion 11 is conical, the top surface of the first layer 13 is circular. In this case, the voids VD are provided corresponding to the vertices of a regular hexagon inscribed in the circle when viewed in a plane. Furthermore, the voids VD may have a right-angled triangular shape when cut along a plane perpendicular to the top surface of the substrate 10 and passing through the center of the circle. In this case, the hypotenuse of the right-angled triangle may be a side surface of the first layer 13. Furthermore, in each void VD, the surface forming the top of the void VD may be substantially flush with the surface extending on the top surface of the first layer 13. In other words, each void VD is formed in the first semiconductor layer 20 corresponding to the outside of the top surface of the first layer 13, and the top surface of the first layer 13 is the top surface of the structure forming each void VD.

[0145] According to an exemplary embodiment of the present disclosure, the first semiconductor layer 20 undergoes a process of merging into a single crystal during growth in an upward and / or lateral direction from the upper surface of the substrate 10. The voids VD may be intentionally formed by controlling the merging process so that portions of the protrusions 11 that are not in close contact with the side surfaces of the first layer 13 are formed.

[0146] The voids VD are gaps where the first layer 13 and the first semiconductor layer 20 are not provided. As such, the voids VD have a refractive index different from the refractive indexes of the first layer 13 and the first semiconductor layer 20. Light refraction, scattering, reflection, etc. occur at the interface between the first layer 13 and each void, thereby improving the light extraction efficiency of the voids. However, although increased light refraction, scattering, reflection, etc. usually improves the light extraction efficiency, if the location where the voids VD occur is too close or too far from the top surface of the substrate 10, the light extraction efficiency may decrease.

[0147] According to an exemplary embodiment of the present disclosure, the heights of the first layer 13 and the second layer 15 within the protrusion 11 are maintained within a predetermined range to improve the light extraction efficiency of the void VD. As described above, the position of the void VD is provided at a position corresponding to the interface between the first layer 13 and the second layer 15. Therefore, the position of the void can also be adjusted by adjusting the positions of the first layer 13 and the second layer 15 within a specific range. Here, the height H1 of the first layer 13 is formed to be equal to or greater than a predetermined value. If the height H1 of the first layer 13 is zero, the growth of the first semiconductor layer 20 from the substrate 10 is inhibited by impurities remaining on the upper surface of the substrate 10 during processing. Furthermore, if the height H2 of the second layer 15 is greater than the height H1 of the first layer 13, the quality of the crystal can be improved by reducing crystal growth in the lateral direction of the first layer 13. Therefore, the height H2 of the second layer 15 can be greater than the height H1 of the first layer 13.

[0148] That is, to sufficiently improve the light extraction efficiency through the voids VD, the heights of the first layer 13 and the second layer 15 and the position of the voids VD corresponding to the interface between the first layer 13 and the second layer 15 only need to be within a predetermined range. For example, the ratio of the height of the first layer 13 to the height of the second layer 15 may be greater than approximately 2.5 and less than approximately 9.5, and in an exemplary embodiment, the ratio of the height of the first layer 13 to the height of the second layer 15 may be approximately 4.25. Specifically, for example, when the total height of the first layer 13 and the second layer 15 is approximately 2.1 micrometers, the first layer 13 may have a height greater than approximately 0.2 micrometers and less than approximately 0.6 micrometers. In another exemplary embodiment, when the total height of the first layer 13 and the second layer 15 is approximately 2.1 micrometers, the first layer 13 may have a height of approximately 0.25 micrometers or more and approximately 0.55 micrometers or less, and in another exemplary embodiment, the first layer 13 may have a height of approximately 0.3 micrometers or more and approximately 0.5 micrometers or less.

[0149] If the height of the first layer 13 is lower than the above range from the surface of the substrate 10, the voids VD may not be formed sufficiently, and even if the voids VD are formed, the light scattering effect of the voids VD may not be fully exhibited. Also, if the size of the voids VD is small, the voids VD may not be formed sufficiently and may act as defects, which may reduce the transmittance of light passing through the voids VD. As a result, the incidence rate of light from the first semiconductor layer 20 toward the inside of the substrate 10 may decrease.

[0150] When the height of the first layer 13 is within the above-mentioned range from the surface of the substrate 10, the voids VD are sufficiently formed, the scattering effect of the voids VD is increased, and the proportion of light incident from the first semiconductor layer 20 toward the substrate 10 through the voids VD increases. In particular, in addition to the light directly incident on the substrate 10 from the first semiconductor layer 20, after passing through the voids VD, additional light passes through the surface of the substrate 10 and is refracted, thereby improving the overall light-emitting efficiency.

[0151] If the height of first layer 13 from the surface of substrate 10 is higher than the above range, the number of paths of light traveling inside substrate 10 increases for light traveling in the direction from first semiconductor layer 20 toward substrate 10, increasing the light absorptivity of substrate 10 and reducing the amount of light passing through substrate 10. Furthermore, in this case, because the height of first layer 13 becomes relatively high, crystal growth occurs in the lateral direction of first layer 13, which may degrade the crystal quality and reduce light efficiency.

[0152] In the light emitting device having the above structure, the light extraction efficiency is improved by the protruding patterns and voids.

[0153] Table 11 shows the simulation results showing the light extraction efficiency of a light-emitting device with and without voids. Each light-emitting device was paired with the same structure and size, except for the presence or absence of voids. The light-emitting devices were prepared in a flip-chip format. The light extraction efficiency was measured by measuring the brightness of light passing through the substrate, and the light propagation direction was set to pass from the active layer to the first semiconductor layer.

[0154] Here, the extraction efficiency of light-emitting devices was measured while varying the protrusion pattern structure, i.e., the height of the first and second layers. The protrusion structures of devices without voids are shown in Figures 15a-15d, and the protrusion structures with voids are shown in Figures 16a-16d. The drawings in Figures 15a-15d and 16a-16d do not completely correspond to the scale of the actual simulation conditions, and some drawings are exaggerated or reduced for ease of explanation. Figure 17 is a graph showing the simulation results in Table 11. For ease of explanation, the structures in Figures 15a-15b are shown as Comparative Examples 1-4, and the structures in Figures 16a-16d are shown as Examples 1-4.

[0155] [Table 11]

[0156] Referring to Table 11, in Comparative Example 1 and Example 1, the height of the first layer was 0.2 μm, which corresponds to a case where the top surface of the first layer was located very close to the substrate surface. Looking at Comparative Example 1 and Example 1, the light-emitting devices with voids had a lower amount of light transmitted through the substrate than conventional light-emitting devices without voids, and in particular, the overall luminous efficiency was reduced by -3.6%. This is thought to be because the low height of the first layer prevented sufficient void formation, and even if voids were formed, the light scattering effect of the voids was not fully realized. In Comparative Example 3 and Example 3, and Comparative Example 4 and Example 4, the light-emitting devices with voids also had a lower amount of light transmitted through the substrate than conventional light-emitting devices without voids, and in particular, the overall luminous efficiency was reduced by -4.8% and -4.2%, respectively. This is thought to be because when the height of the first layer is greater than the above-mentioned range from the substrate surface, the optical path of light traveling through the substrate is increased relative to the light traveling from the first semiconductor layer through the voids to the substrate, thereby increasing the light absorption rate in the substrate. In contrast, in Comparative Example 2 and Example 2, the amount of light transmitted through the substrate in the light-emitting devices with voids increased by 4.4% compared to the conventional light-emitting device without voids. This is thought to be because the first layer was sufficiently high, allowing for sufficient voids to be formed; if the first layer were too high, side effects such as reduced crystallinity and increased light absorption due to an increased optical path through the substrate could occur. Therefore, when voids are formed as in Example 2, in addition to the light directly incident on the substrate from the first semiconductor layer, additional light passes through the substrate surface after passing through the voids and is refracted, improving the overall light-emitting efficiency.

[0157] From the above, it can be seen that when voids are provided on the protrusion side and the heights of the first and second layers are within the above ranges, the light efficiency is significantly improved. In particular, when voids are provided on the side of the protrusion, the total height of the first and second layers is 2.1 micrometers, and the height of the first layer is between 0.2 micrometers and 0.6 micrometers, the light efficiency is significantly increased.

[0158] Furthermore, the light emitting device having the structure according to the above-described exemplary embodiment can be manufactured by adjusting the process conditions when forming the first semiconductor layer so that a plurality of voids are formed on the side surface of the protrusion.

[0159] 18a and 18b are cross-sectional views showing a part of the process for manufacturing the protruding pattern of the above-mentioned structure, showing a substrate on which the protruding pattern is formed so as to form voids, and showing the direction in which the first semiconductor layer is subsequently grown. For convenience of explanation, arrows are used to indicate the main direction in which the semiconductor layer is grown in Fig. 18a and 18b.

[0160] 11 to 14, 18a and 18b, first, a first semiconductor layer 20 is formed above.

[0161] The first semiconductor layer 20 can be formed of a semiconductor layer of various materials, for example, an n-type nitride-based semiconductor layer, and can be formed using metalorganic chemical vapor deposition or molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE).

[0162] The initial growth of the first semiconductor layer 20 is 3D growth (e.g., Volmer-Weber growth) occurring primarily upward from the exposed surface of the substrate 10, and growth does not occur on the top surface of the second layer 15. The conditions for 3D growth have relatively low growth temperatures and high growth pressures compared to the conditions for 2D growth (e.g., Frank van der Merwe growth) where growth occurs primarily horizontally.

[0163] After the first semiconductor layer 20 is partially grown upward, the first semiconductor layer 20 grows upward and laterally. For ease of explanation, the figure shows a first growth pattern 21 that grows primarily upward, and a second growth pattern 23 that grows upward and laterally but primarily laterally. In this case, in the case of the second growth pattern 23, 2D growth that grows primarily horizontally can be achieved by maintaining a higher growth temperature and a lower growth pressure than in the above-mentioned 3D growth.

[0164] In an exemplary embodiment of the present disclosure, epitaxial lateral overgrowth (ELOG) may be used as a metalorganic chemical vapor deposition (MOCVD) method for the lateral (horizontal in the figures) growth of the first semiconductor layer 20 .

[0165] The first semiconductor layer 20 is continuously grown in the lateral and upward directions, and is bonded to cover the entire surface of the substrate 10, including the surface of the second layer 15. The first semiconductor layer 20 undergoes a process of coalescing into a single crystal during the process of growing upward from the substrate surface and / or lateral directions, and voids VD may be formed by intentionally controlling the formation of portions of the protrusion 11 that are not in close contact with the side surfaces of the first layer 13 during the coalescence process. In particular, the size and position of the voids VD formed in the first semiconductor layer 20 can be intentionally controlled by adjusting the thickness ratio of the first semiconductor layer 20 according to the respective growths of 3D growth and 2D growth.

[0166] In an exemplary embodiment of the present disclosure, the exposed upper surface of the substrate 10 between the protrusions 11 essentially serves as a growth nucleus and grows upward from the upper surface of the substrate 10 as shown in first growth pattern 21. The first semiconductor layer 20 is then grown laterally by the ELOG method as shown in second growth pattern 23. In the growth of the first semiconductor layer 20, the surface of the first semiconductor layer 20 growing upward is sometimes referred to as the top surface, and the surface of the first semiconductor layer 20 growing laterally is sometimes referred to as the side surface. When the first semiconductor layer 20 is epitaxially grown by the ELOG method, the side surface growth occurs more predominantly than the top surface growth, and the growth ratio of the m-axis to the c-axis is approximately 2:1. During growth, the side surface of the first semiconductor layer 20 may be perpendicular to the top surface of the first semiconductor layer 20, but is not limited thereto and may be a facet inclined relative to the top surface of the first semiconductor layer 20. In an exemplary embodiment, the top surface of the first semiconductor layer 20 may correspond to the (0001) plane, and the side surface of the first semiconductor layer 20 may correspond to the (10-11) plane.

[0167] After the first semiconductor layer 20 is completely grown laterally, the first semiconductor layer 20 may be selectively grown further upward using HVPE. When the first semiconductor layer 20 is formed using MOCVD, the deposition rate is slower than that of HVPE, so HVPE may be used to quickly grow the first semiconductor layer 20 to a sufficient thickness.

[0168] The first semiconductor layer 20 formed as described above covers the surfaces of the substrate 10 and the protruding portion 11 with voids formed therein.

[0169] In an exemplary embodiment of the present disclosure, a buffer layer may be further formed on the substrate 10 before forming the first semiconductor layer 20. In an exemplary embodiment, a superlattice structure may be formed by alternately stacking two types of layers having different bandgaps on the first semiconductor layer 20. An active layer 30 is formed on the first semiconductor layer 20. In an exemplary embodiment, a quantum well structure may be formed by alternately stacking quantum well layers and barrier layers as the active layer 30. After forming an electron blocking layer on the active layer 30, a second semiconductor layer 40 may be formed on the active layer 30 to manufacture a light-emitting stack.

[0170] 19 is a photograph showing a protrusion and a first semiconductor layer according to an exemplary embodiment manufactured by the above-described method. As shown in FIG. 19, in a light emitting device according to an exemplary embodiment of the present disclosure, a plurality of protrusions are formed on a substrate, and six voids are provided for each protrusion. Each void is provided at a position corresponding to a vertex of a hexagon related to the crystal growth direction of the semiconductor layer.

[0171] 20a and 20b are photographs showing the light path and light intensity of a light-emitting device with and without voids, respectively. In Fig. 20a and Fig. 20b, if the apex of the protrusion in the figure is on the upper side, the light travels from the top to the bottom.

[0172] 20a and 20b, light traveling from the top to the bottom passes through the protrusion and the inclined surface of the substrate and is incident on the bottom of the substrate. Referring to Fig. 20b, when voids are provided on the side surfaces of the protrusions, light that is refracted and scattered through the voids is incident on the bottom of the substrate, and it is clear that this is significantly greater than in Fig. 20a, where no voids are provided.

[0173] As described above, by forming voids in the first semiconductor layer in the region corresponding to the side surface of the protrusion, the amount of light traveling downward can be significantly increased, and as a result, a light-emitting device with high light efficiency can be manufactured.

[0174] Exemplary light emitting devices of the present disclosure may be used in various types of semiconductor chips, such as those shown in Figures 6 and 7, or those described below.

[0175] 21 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment, showing a flip-chip semiconductor chip, which is shown inverted in the figure because the flip-chip semiconductor is formed on a substrate and then flipped over and mounted on another component.

[0176] Referring to FIG. 21, the light emitting device includes a substrate 10, a light emitting stack provided on an upper surface 1OR of the substrate 10, and a first electrode 110 and a second electrode 120 connected to the light emitting stack.

[0177] In an exemplary embodiment of the present invention, substrate 10 is patterned to provide a plurality of protrusions and voids on its upper surface.

[0178] The light emitting stack includes a first semiconductor layer 20, an active layer 30, and a second semiconductor layer 40 sequentially stacked on the top surface 1OR of the substrate 10. In an exemplary embodiment, the light emitting stack may be provided in the form of at least one mesa including the active layer 30 and the second semiconductor layer 40. When the light emitting stack is provided in the form of a mesa, the light emitting stack may include a pattern of multiple protrusions, and the protrusions may be spaced apart from one another.

[0179] An insulating layer 130a is provided on the light emitting stack. At least one contact hole CH is provided in the light emitting stack, passing through the active layer 30, the second semiconductor layer 40, and the insulating layer 130a to expose a portion of the first semiconductor layer 20. The first electrode 110 is connected to the exposed first semiconductor layer 20 through the contact hole CH. The second electrode 120 is connected to the exposed second semiconductor layer 40 through an opening formed in the insulating layer 130a. An additional insulating layer 130b may be further provided on the side of the light emitting stack. The additional insulating layer 130b may be formed of various types of mirrors (e.g., metal mirrors or dielectric mirrors) to prevent light emitted from the active layer 30 from being emitted in the direction of the side of the light emitting stack.

[0180] In the light emitting device according to the exemplary embodiment of the present disclosure, the first electrode 110 and the second electrode 120 are disposed on the same plane and are small in size, so that they can be easily mounted on the wiring of the substrate 10.

[0181] The light emitting device according to the exemplary embodiment of the present disclosure emits light by turning on the first electrode 110 and the second electrode 120 by applying a signal to them. The emitted light travels downward through the first semiconductor layer 20 and the substrate 10, and the downward light extraction efficiency is increased by the protrusions 11 and voids provided in the substrate 10.

[0182] In the exemplary embodiment of the present disclosure, for convenience of explanation, the protrusions are shown only in a conical shape, but the protrusions may be modified into various shapes within limits without departing from the concept of the present disclosure. For example, the shape of the protrusions may be a polygonal pyramid. Alternatively, the protrusions may be provided in a conical shape, or the shape of the curved surface forming the side surface may be partially modified. Furthermore, the cross section of the protrusions may be close to a semi-elliptical sphere.

[0183] FIG. 22 is a schematic cross-sectional view illustrating a light emitting device according to an exemplary embodiment of the present disclosure.

[0184] Referring to FIG. 22, a light emitting device according to an exemplary embodiment of the present disclosure includes a substrate 10 and a light emitting stack disposed on the substrate 10 .

[0185] In an exemplary embodiment of the present invention, substrate 10 is patterned, and a pattern of a plurality of protrusions 11 is provided on the upper surface thereof. That is, protrusions 11 are provided in a form that protrudes upward from the upper surface of substrate 10. In an exemplary embodiment, protrusions 11 may be provided in a shape that narrows in width toward the top, so that when protrusions 11 are cut along a plane perpendicular to substrate 10, the cross section of protrusions 11 may be approximately semi-elliptical, or in some cases, may be shaped like a triangle.

[0186] The protrusion 11 has a first layer 13 and a second layer 15 that are continuously laminated on the upper surface of the substrate 10. The first layer 13 is provided on the substrate 10, and the second layer 15 is provided on the first layer 13.

[0187] The first semiconductor layer 20 may be provided on the substrate 10. The first semiconductor layer 20 may cover the protruding portion 11 on the substrate 10. To achieve this, the first semiconductor layer 20 may be epitaxially grown from the upper surface of the substrate 10. In this case, the first semiconductor layer 20 may be grown upward so as to completely cover the side and upper surfaces of the protruding portion 11.

[0188] In an exemplary embodiment of the present disclosure, the refractive index of the first semiconductor layer may be greater than the refractive indexes of the first layer 13 and the second layer 15. For example, the refractive index of the first layer 13 may be about 1.6 to about 2.45, and the refractive index of the second layer 15 may be about 1.3 to about 2.0.

[0189] Fig. 23 is a plan view of a substrate having a protruding pattern thereon, among the elements of the light-emitting device of Fig. 22. Fig. 24 is a cross-sectional view taken along line II' in Fig. 23. Fig. 25a is an enlarged cross-sectional view of P1 in Fig. 24, and Fig. 25b is an enlarged cross-sectional view of P4 in Fig. 25a.

[0190] 23, 24, 25a and 25b, a protrusion 11 including a first layer 13 and a second layer 15 is provided on the upper surface of a substrate 10.

[0191] The first layer 13 is formed integrally with and inseparably from the substrate 10. In this way, the first layer 13 is made of the same material as the substrate 10. The top surface of the first layer 13 may have a circular shape.

[0192] The second layer 15 is formed of a material different from that of the first layer 13. The material of the second layer 15 may be a material having a refractive index different from that of the material of the first layer 13, and in an exemplary embodiment of the present disclosure, the refractive index of the first layer 13 may be higher than the refractive index of the second layer 15. In this case, various insulating materials having different refractive indices may be used as the materials of the first layer 13 and the second layer 15.

[0193] For example, within the range in which the first layer 13 and the second layer 15 are made of materials with different refractive indices, the first layer 13 may be made of a material with a refractive index of approximately 1.6 to approximately 2.45, and the second layer 15 may be made of a material with a refractive index of approximately 1.3 to approximately 2.0. As materials with such reflectance, the first layer 13 may include sapphire, and the second layer 15 may include, for example, SiOx, SiOxNy, SiNx, etc. In an exemplary embodiment, the first layer 13 may be made of sapphire, and the second layer 15 may be made of SiO2. In this case, the refractive index of the first layer 13 is approximately 1.76, and the refractive index of the second layer 15 is approximately 1.46.

[0194] Each of the protrusions 11 may have a circular shape when viewed in a plane. When the protrusion pattern 11 is conical or elliptical, the apex of the cone or elliptical sphere is the center.

[0195] The protrusions 11 can be sized to have a predetermined diameter DM and height HT. Here, the diameter DM refers to the width of the bottom end of the protrusion 11 in a cross-sectional view, and the height HT refers to the distance from the top surface of the substrate 10 to the apex of the protrusion 11. In an exemplary embodiment, each of the protrusions 11 may have the same diameter DM and height HT. However, the protrusions 11 do not have to have exactly the same diameter DM and height HT, and the diameters DM and heights HT may vary within a predetermined range.

[0196] In an exemplary embodiment of the present disclosure, the height H1 of the first layer 13 is formed to be equal to or greater than a predetermined value. If the height H1 of the first layer 13 is zero, the growth of the first semiconductor layer 20 from the substrate 10 is inhibited by impurities remaining on the upper surface of the substrate 10 during processing. Furthermore, if the height H2 of the second layer 15 is greater than the height H1 of the first layer 13, the quality of the crystal can be improved by reducing the crystal growth in the lateral direction of the first layer 13, so the height of the second layer 15 can be greater than the height of the first layer 13.

[0197] In an exemplary embodiment of the present disclosure, if the height of the first layer 13 from the surface of the substrate 10 is higher than the above range, the optical path that travels inside the substrate 10 increases for light traveling in a direction from the first semiconductor layer 20 toward the substrate 10, increasing the light absorption rate within the substrate 10 and reducing the amount of light passing through the substrate 10. Furthermore, in this case, since the height of the first layer 13 becomes relatively high, crystal growth occurs in the lateral direction of the first layer 13, which may degrade the crystal quality and reduce the optical efficiency.

[0198] In exemplary embodiments of the present disclosure, the inclination angles of the side surfaces of the first layer 13 and the second layer 15 may be at least partially the same or different from each other. In the drawings, the inclination angles of the first layer 13 and the second layer 15 are shown to have the same value, but the concept of the present invention is not limited thereto. The inclination angles of the side surfaces of the first layer 13 and the second layer 15 may be at least partially the same or different from each other. In particular, the inclination angles at the contact portion between the first layer 13 and the second layer 15 may be different from each other. Because the first layer 13 and the second layer 15 are made of different materials, the inclination angles of the side surfaces may be set to be different depending on the process conditions during the etching process. In exemplary embodiments, the inclination angles of the first layer 13 and the second layer 15 are formed to be different, thereby increasing the reflectivity of light emitted from the light emitting device and thereby improving the luminous efficiency.

[0199] In the exemplary embodiment of the present disclosure, the protrusions 11 may be arranged regularly as shown in the figure, but the concept of the present invention is not limited to this. For example, the protrusions 11 may be arranged irregularly. Even in this case, when viewed on the substrate 10, the pitch PT and distance DT of the protrusions 11 per area are within a predetermined range, and in this case, the density can be approximately the same.

[0200] In the exemplary embodiment of the present disclosure, for convenience of explanation, the protrusion 11 is shown to have only a conical shape, but the protrusion 11 may be changed to various forms within limits without departing from the concept of the present disclosure. For example, the shape of the protrusion 11 may be a polygonal pyramid. In addition, even if the protrusion 11 is provided in a conical shape, the shape of the curved surface forming the side surface may be partially changed.

[0201] In an exemplary embodiment of the present disclosure, the pitch PT of the pattern of the protrusions 11 can have a value within a predetermined range depending on the diameter DM. For example, the ratio of the diameter DM to the pitch PT of the protrusions 11 may be in the range of about 0.3 to about 2.0. However, the ratio of the diameter DM to the pitch PT of the protrusions 11 is not limited to this and may be other values.

[0202] In an exemplary embodiment of the present disclosure, the interface between the first layer 13 and the second layer 15 is formed substantially parallel to the substrate surface, ie, the top surface of the substrate 10, and the surface has roughness.

[0203] This is explained in more detail below.

[0204] With reference to the first layer 13, the first layer 13 may have a generally truncated cone shape with a flat top surface. Therefore, the first layer 13 may have a top surface that is substantially parallel to the substrate surface and side surfaces that connect the top surface to the substrate surface. The top surface of the first layer 13 is roughened (i.e., has protrusions and depressions) so that as much light as possible entering the substrate 10 from the first semiconductor layer 20 in the direction toward the substrate 10 (downward in the figure) enters the substrate 10. In other words, the top surface of the first layer has protrusions and depressions, with convex portions protruding upward from the substrate surface and concave portions recessed downward from the substrate surface. The top surface of the first layer 13, i.e., a flat surface without protrusions or depressions at the interface between the second layer 15 and the first layer 13, has a higher light reflectivity than a surface with protrusions or depressions, and therefore the amount of light traveling downward through the substrate 10 is reduced. When protrusions and depressions are formed on the upper surface of the first layer 13, light is scattered or refracted rather than reflected at the portions where the protrusions and depressions are formed, and this makes it easier for the light to travel into the substrate 10. Light incident on the first substrate 10 passes through the substrate 10 and is emitted from the rear surface of the substrate 10.

[0205] The protrusions and depressions between the first and second layers are shown in Figures 25a and 25b. Also, Figures 26a and 26b show photographs of the top surface of the first layer of a conventional light-emitting device and the top surface of a light-emitting device according to an exemplary embodiment of the present disclosure, respectively. In Figures 26a and 26b, each photograph is an atomic force microscope (AFM) photograph, and the sample corresponding to the top surface of the first layer was fabricated with a width of 2 μm and a length of 2 μm, respectively.

[0206] 26a, in the case of the conventional technology, the upper surface of the first layer is flat without any protrusions or depressions. In the case of the roughness of the conventional technology, the standard deviation Rq of the roughness may be 0.200 nm to 0.300 nm, and the arithmetic mean Ra of the roughness may be 0.140 nm to 0.190 nm, for example, Rq may be 0.216 nm and Ra may be 0.169 nm.

[0207] In an exemplary embodiment of the present disclosure, a roughened surface, i.e., protrusions and depressions, is provided on the upper surface of the first layer, as shown in Figure 26b. While the roughness may be provided at various degrees, the roughness according to the present invention may have a standard deviation Rq of about 0.300 nm to about 0.550 nm and an arithmetic mean roughness Ra of about 0.250 nm to about 0.400 nm, for example, a standard deviation Rq of 0.447 nm and an arithmetic mean Ra of 0.327 nm.

[0208] As described above, in the light-emitting device according to the exemplary embodiment of the present disclosure, the substrate is provided with a protruding pattern. When light in a predetermined direction is transmitted through the protruding pattern, the light extraction efficiency is significantly improved. In particular, light generated in the active layer passes through the first semiconductor layer and then travels through the substrate. As the light passes through the substrate, the protruding pattern causes light diffusion and scattering, significantly enhancing the light extraction efficiency toward the rear of the substrate. The light diffusion and scattering caused by the protruding pattern is primarily enhanced by the roughened surface at the interface between the first and second layers, thereby increasing the amount of light traveling downward. In addition, in the present disclosure, by providing protrusions and depressions at the interface between the first and second layers, reflection of light passing through the first and second layers can be minimized. In particular, in the exemplary embodiment of the present disclosure, the first layer, the second layer, and the first semiconductor layer are formed with different refractive indices. Therefore, the refractive indices decrease in the order of the first semiconductor layer, the first layer, and the second layer. The refraction or reflection of light passing through the first semiconductor layer, the first layer, and the second layer maximizes downward light emission.

[0209] In this embodiment, the first layer has substantially no roughened surface on its side surfaces except for its top surface. The side surfaces may be provided as reflective surfaces that allow substantially less light to pass through the side surfaces. In this embodiment, the side surfaces may be reflective surfaces that reflect 80% or more, for example, 90% or more, and preferably 95% or more, of the light directed from the first semiconductor layer (described below) toward the side surfaces of the first layer. In an exemplary embodiment of the present invention, regions of the substrate surface where no protrusions are provided may not be roughened.

[0210] 27a and 27b are transmission electron microscope (TEM) photographs of portions corresponding to portions P2 and P3 in FIG. 24, respectively, when manufacturing a light emitting device according to an exemplary embodiment.

[0211] 27a, the portion shown in white is the second layer 15, and the portion disposed below the second layer 15 corresponds to the first layer 13. As shown in the figure, protrusions and depressions may be irregularly formed on the upper surface of the first layer 13.

[0212] Referring to FIG. 27b, the side surfaces of the first layer 13 except for the top surface are substantially not roughened, and the first layer 13 is provided as a substantially flat surface without protrusions or depressions.

[0213] The substrate surface, that is, the upper surface of the substrate 10, may be a substantially flat surface without protrusions or depressions.

[0214] However, in an exemplary embodiment of the present disclosure, the upper surface of the substrate 10 may be provided as a flat surface without protrusions or depressions, but the concept of the present invention is not limited thereto. Similar to the upper surface of the first layer 13, protrusions and depressions may be formed on the upper surface of the substrate to improve the downward incidence of light. That is, a rough surface may be formed on the substrate surface on which no protrusions are formed, thereby increasing the scattering rate of light traveling downward through the areas on which no protrusions are formed. As a result, the light extraction efficiency of the light emitting device can be improved.

[0215] Figures 28a and 28b are PhET simulation photographs showing the optical path depending on the shape of the side surface of the first layer. Figures 28a and 28b show the light propagation direction for a configuration in which the first layer is formed on a substrate and then the first semiconductor layer is grown, but all conditions except for the shape of the side surface of the first layer are the same. In Figure 28a, the configuration was such that protrusions and depressions are formed on the side surface of the first layer, while in Figure 28b, the configuration was such that a flat reflective surface without protrusions or depressions is formed on the side surface of the first layer.

[0216] 28a, when light travels from the first semiconductor layer to the side surface of the first layer, the light is scattered and reflected in various directions by the protrusions and depressions formed on the side surface of the first layer. Since the light extraction efficiency of the light emitting device is determined by how much light travels from the active layer through the first semiconductor layer and the substrate to the back surface of the substrate, when light is reflected or scattered radially, as shown in FIG. 28a, a problem occurs in that the light efficiency in lower directions is significantly reduced.

[0217] Conversely, referring to Figure 28b, when light travels from the first semiconductor layer to the side surface of the first layer, if the side surface of the first layer acts as a reflective surface, most of the light is reflected in a specific direction from the side surface of the first layer because the reflective surface is flat, but the reflected light enters the substrate, and the light traveling downward is significantly increased.

[0218] As described above, the light extraction efficiency of a light emitting device having a protruding pattern, particularly a protruding pattern having a rough surface on the upper surface of the first layer and a reflective side surface, is significantly higher than conventional devices.

[0219] The protruding pattern having the above structure can be manufactured as follows.

[0220] 29a to 29g are cross-sectional views sequentially illustrating a method for manufacturing a protrusion pattern of a light emitting device according to an exemplary embodiment of the present disclosure.

[0221] 29a, a substrate 10 is first prepared. As described above, the substrate 10 may include a material such as SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, or Ga2O3, and the insulating layer may be made of SiOx, SiOxNy, or SiNx.

[0222] Referring to FIG. 29b, a roughened surface, i.e., protrusions and depressions PR, are formed on the upper surface of the substrate 10. The protrusions and depressions PR can be formed by various methods, such as wet etching, dry etching, grinding, or a combination thereof, but the concept of the present invention is not limited thereto.

[0223] 29c, an insulating layer 15i is stacked on the substrate 10 using a material for forming a second layer. The insulating layer 15i is formed of a material that can form a second layer on the substrate 10, and may be formed of a material having a refractive index different from that of the substrate 10.

[0224] Referring to FIG. 29d, next, a pattern of photoresist 50 is formed by applying the photoresist 50 onto the insulating layer 15i and performing photolithography including exposure and development.

[0225] 29e, the pattern of photoresist 50 is reflowed. Reflowing the photoresist 50 causes the thickness of the photoresist 50 to vary in different areas, which subsequently changes the etched shape of the insulating layer 15i and the underlying substrate 10.

[0226] Referring to Figures 29e and 29f, the insulating layer 15i and the substrate 10 are etched using the photoresist 50 as a mask, forming a protrusion 11 having the first layer 13 and the second layer 15. Then, using the photoresist pattern as a mask, the insulating layer 15i and a portion of the substrate 10 are etched, excluding the portion where the protrusion 11 is to be formed, to form the second layer 15. The upper surface of the substrate 10 is exposed in the portion where the second layer 15 is not formed. Here, the first layer 13 is formed by overetching the upper surface of the substrate 10 through additional etching. If only the second layer 15 is formed and etching is performed to expose the original upper surface of the substrate 10, theoretically, it is expected that the growth of a semiconductor layer will occur easily after the upper surface of the substrate 10 is exposed. However, in reality, the growth of the first semiconductor layer 20 does not occur properly due to etching residues and impurities present on the upper surface of the substrate 10. In this manner, additional etching is performed to completely remove the etching residues, impurities, and the like on the substrate 10. This results in the formation of the first layer 13.

[0227] The etching for forming the first layer 13 and the second layer 15 can be performed using various methods under various conditions depending on the material. For example, the insulating layer and portions of the substrate 10 may be patterned using dry etching.

[0228] In the above-described method, the second layer 15 and the first layer 13 may be formed successively and patterned using the same or different etching gases.

[0229] The insulating layer 15i and the substrate 10 may be anisotropic so that etching is performed in the vertical direction, but etching in the left-right direction does not have to be performed relatively.

[0230] 29g, a light emitting device may be formed by successively forming a light emitting stack including a first semiconductor layer 20 on a substrate having a protrusion 11 formed thereon. First, the first semiconductor layer 20 is formed on the substrate 10 having a protrusion 11 formed thereon. The first semiconductor layer 20 first grows upward from the exposed surface of the substrate 10, and then grows upward and laterally. After the first semiconductor layer 20 is grown, an active layer 30 (see FIG. 22) and a second semiconductor layer 40 (see FIG. 22) may be successively formed on the first semiconductor layer 20.

[0231] More specifically, first, a first semiconductor layer 20 is formed on the upper surface. The first semiconductor layer 20 may be formed from a semiconductor layer of various materials, for example, an n-type nitride-based semiconductor layer, and may be formed using metalorganic chemical vapor deposition, molecular beam epitaxy (MBE), or hydride chemical vapor phase epitaxy (HVPE).

[0232] The initial growth of the first semiconductor layer 20 is 3D growth (e.g., Volmer-Weber growth) occurring primarily upward from the exposed surface of the substrate 10, and no growth occurs on the top surface of the second layer 15. After the first semiconductor layer 20 is partially grown upward, the first semiconductor layer 20 grows upward and laterally. In an exemplary embodiment, epitaxial lateral overgrowth (ELOG) can be used as a metalorganic chemical vapor deposition (MOCVD) method for the lateral (horizontal in the figure) growth of the first semiconductor layer 20.

[0233] The first semiconductor layer 20 grows continuously in the lateral and upward directions, and thereby bonds to cover the entire surface of the substrate 10, including the surface of the second layer 15. In the process of growing in the upward and / or lateral directions from the substrate surface, the first semiconductor layer 20 undergoes a process of bonding into one crystal.

[0234] After the first semiconductor layer 20 is completely grown laterally, the first semiconductor layer 20 may be selectively grown further upward using HVPE. When the first semiconductor layer 20 is formed using MOCVD, the deposition rate is slower than that of HVPE, so HVPE may be used to quickly grow the first semiconductor layer 20 to a sufficient thickness.

[0235] The first semiconductor layer 20 formed as described above covers the surfaces of the substrate 10 and the protruding portion 11 with voids formed therein.

[0236] In an exemplary embodiment of the present disclosure, a buffer layer may be further formed on the substrate 10 before forming the first semiconductor layer 20. In an exemplary embodiment, a superlattice structure may be formed by alternately stacking two types of layers having different bandgaps on the first semiconductor layer 20. An active layer 30 is formed on the first semiconductor layer 20. In an exemplary embodiment, a quantum well structure may be formed by alternately stacking quantum well layers and barrier layers as the active layer 30. After forming an electron blocking layer on the active layer 30, a second semiconductor layer 40 may be formed on the active layer 30 to manufacture a light-emitting stack.

[0237] As described above, by forming protrusions and depressions on the top surface of the first layer, the amount of light traveling downward can be significantly increased, and as a result, a light emitting device with high light efficiency can be manufactured.

[0238] A light emitting device having the above structure may be mounted on various types of semiconductor chips.

[0239] FIG. 30 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment showing a lateral semiconductor chip.

[0240] 30, the semiconductor chip includes a light emitting device, and a first electrode 110 and a second electrode 120 connected to the light emitting device. The light emitting device includes a substrate 10, a first semiconductor layer 20 provided on the substrate 10, an active layer 30, and a second semiconductor layer 40.

[0241] In an exemplary embodiment, the first electrode 110 is disposed on the first semiconductor layer 20 where the active layer 30 and the second semiconductor layer 40 are not provided, and the second electrode 120 is disposed on the second semiconductor layer 40.

[0242] The first electrode 110 and / or the second electrode 120 may be made of a single layer or multiple layers of metal. Materials for the first electrode 110 and / or the second electrode 120 may include Al, Ti, Cr, Ni, Au, Ag, Cr, Cu, Ti, Ru, Rh, Ir, Mg, Zn, Al, In, Ta, Pd, Co, and various metals and alloys thereof.

[0243] Here, in order to improve light emission efficiency, a plurality of protrusions 11 are provided on the upper surface of the substrate 10. As described in the above exemplary embodiment, the protrusions 11 are provided on the substrate 10 in a conical shape including the first layer 13 and the second layer 15, and voids may be provided near the interface between the first layer and the second layer.

[0244] An insulating layer 130 is provided on the first electrode 110 and the second electrode 120, and contact holes are provided on the insulating layer 130 to expose the first electrode 110 and the second electrode 120. The insulating layer 130 can be disposed on the top surface of the second semiconductor layer 40 and on the side surfaces of the semiconductor layer, and can selectively contact the first electrode 110 and the second electrode 120. The insulating layer 130 may include an insulating material or insulating resin made of at least one of oxides, nitrides, fluorides, and sulfides containing at least one of Al, Cr, Si, Ti, Zn, and Zr. The insulating layer 130 can be selectively formed from, for example, SiO2, Si3N4, Al2O3, or TiO2. The insulating layer 130 may be formed as a single layer or a multilayer, but is not limited thereto.

[0245] In an exemplary embodiment of the present disclosure, the first electrode 110 and the second electrode 120 may be connected to other elements through contact holes. For example, the first electrode 110 and the second electrode 120 may be provided with first and second pads connected through contact holes. Furthermore, in the exemplary embodiment of the present disclosure, the light-emitting device will be briefly described using the drawings. However, in addition to the layers described above, the light-emitting device may further include elements with additional functions. For example, various layers may further be included, such as a reflective layer that reflects light, an additional insulating layer that insulates certain elements, and an anti-solder layer that prevents solder diffusion.

[0246] Furthermore, when forming a horizontal light emitting device, the mesa can be formed in various shapes, and the positions and shapes of the first electrode 110 and the second electrode 120 can also be changed in various ways.

[0247] The light emitting device according to the exemplary embodiment of the present disclosure emits light by applying a signal to the first electrode 110 and the second electrode 120 to turn them on. The emitted light travels downward through the first semiconductor layer 20 and the substrate 10, and the downward light extraction efficiency is increased by the protrusions 11 and voids provided in the substrate 10.

[0248] Although the semiconductor chip including the light emitting device according to the above exemplary embodiment is illustrated as a horizontal type, the present invention is not limited thereto. For example, the light emitting device according to the exemplary embodiment may be applied to a vertical type or a flip-chip type semiconductor chip.

[0249] 31 is a cross-sectional view of a semiconductor chip according to an exemplary embodiment, showing a flip-chip semiconductor chip, which is shown inverted in the figure because the flip-chip semiconductor is formed on a substrate and then flipped over and mounted on another component.

[0250] Referring to FIG. 31, the light emitting device includes a substrate 10, a light emitting stack provided on an upper surface 1OR of the substrate 10, and a first electrode 110 and a second electrode 120 connected to the light emitting stack.

[0251] In an exemplary embodiment of the present invention, substrate 10 is patterned to provide a plurality of protrusions and voids on its upper surface.

[0252] The light emitting stack includes a first semiconductor layer 20, an active layer 30, and a second semiconductor layer 40 that are sequentially stacked on the top surface 1OR of the substrate 10. In an exemplary embodiment, the light emitting stack may be provided in the form of at least one mesa including the active layer 30 and the second semiconductor layer 40. When the light emitting stack is provided in the form of a mesa, the light emitting stack may include multiple protrusions, and the multiple protrusions may be spaced apart from each other.

[0253] An insulating layer 130a is provided on the light emitting stack. At least one contact hole CH is provided in the light emitting stack, passing through the active layer 30, the second semiconductor layer 40, and the insulating layer 130a to expose a portion of the first semiconductor layer 20. The first electrode 110 is connected to the exposed first semiconductor layer 20 through the contact hole CH. The second electrode 120 is connected to the exposed second semiconductor layer 40 through an opening formed in the insulating layer 130a. An additional insulating layer 130b may be further provided on the side of the light emitting stack. The additional insulating layer 130b may be formed of various types of mirrors (e.g., metal mirrors or dielectric mirrors) to prevent light emitted from the active layer 30 from being emitted in the direction of the side of the light emitting stack.

[0254] In the light emitting device according to the exemplary embodiment of the present disclosure, the first electrode 110 and the second electrode 120 are disposed on the same plane and are small in size, so that they can be easily mounted on the wiring of the substrate 10.

[0255] The light emitting device according to the exemplary embodiment of the present disclosure emits light by applying a signal to the first electrode 110 and the second electrode 120 to turn them on. The emitted light travels downward through the first semiconductor layer 20 and the substrate 10, and the downward light extraction efficiency is increased by the protrusions 11 and voids provided in the substrate 10.

[0256] Since the light emitting device with the above structure has high light extraction efficiency, an experiment was conducted to compare the light emitting efficiency of the exemplary light emitting device of the present disclosure with that of a light emitting device of the prior art.

[0257] In the following experiments, first, Comparative Examples 1 and 2 are light-emitting devices using a substrate on which protrusions consisting of only the first layer with total heights of 1.7 μm and 2.1 μm, respectively, are formed, and Comparative Example 3 is a light-emitting device using a substrate on which protrusions consisting of the first and second layers are formed. The light extraction efficiency of Comparative Examples 1 to 3 was investigated. In this experiment, the substrate and first layer were formed of sapphire, and the second layer was formed of SiO2. Elements other than the protrusion pattern were the same in Comparative Examples 1 to 3. In Comparative Example 3, the height of the first layer was 0.4 μm, and the height of the second layer was 1.7 μm.

[0258] Table 12 shows the luminous efficiencies of Comparative Examples 1 to 3.

[0259] [Table 12]

[0260] Referring to Table 12, looking at Comparative Examples 1 and 2 in which protrusions were formed only in the first layer, Comparative Example 2, in which the protrusion height was higher than Comparative Example 1, had a 2.2% improvement in luminous efficiency compared to Comparative Example 1. When the protrusion height was fixed at 2.1 μm, Comparative Example 3, in which the protrusions were formed using the first and second layers, had a significantly higher luminous efficiency than Comparative Example 2, in which the protrusions were formed using only the first layer, and the luminous efficiency of Comparative Example 2 was improved by 2.2% compared to Comparative Example 1, and the luminous efficiency of Comparative Example 3 was significantly improved by 5.7% compared to Comparative Example 1. Thus, it was confirmed that when protrusions were formed using the first and second layers, the luminous efficiency was significantly higher than in the other cases.

[0261] Next, a light-emitting device in which a protrusion pattern having a rough surface was formed at the interface between the first and second layers was used as an example, and the luminous efficiency of this example was measured in conjunction with Comparative Examples 1 and 3. FIG. 32 is a graph showing the luminous intensity as a function of wavelength for the light-emitting devices of Comparative Example 1, Comparative Example 3, and this example. In FIG. 32, the light-emitting device of this example was fabricated under the same conditions as Comparative Example 3, except for the protrusion. In the case of the protrusion of this example, unlike Comparative Example 3, protrusions and depressions were formed at the interface between the first and second layers.

[0262] 32, it can be seen that the luminous efficiency of Comparative Example 3 is higher than that of Comparative Example 1, and is almost the same as the results in Table 12 above. Also, referring to FIG. 30, the luminous efficiency of this example was significantly higher than that of Comparative Example 3 in most wavelength bands, particularly in the range of about 450 nm to about 460 nm. Since Comparative Example 3 and this example were formed identically except for the protrusions and depressions on the upper surface of the first layer of this example, the difference in luminous efficiency was interpreted as being due to the protrusions and depressions on the upper surface of the first layer.

[0263] While certain exemplary embodiments and examples have been described herein, other embodiments and variations will be apparent from this description. Accordingly, the inventive concept is not limited to such embodiments, but rather is limited by the broader scope of the appended claims and various obvious modifications and equivalent arrangements that will be apparent to those skilled in the art.

[0264] Therefore, the technical scope of the present disclosure should not be limited to the contents set forth in the detailed description of this specification, but should be defined by the claims.

Claims

1. A substrate; a pattern of a plurality of protrusions protruding from the substrate; a first semiconductor layer provided on the substrate; an active layer provided on the first semiconductor layer; a second semiconductor layer provided on the active layer; Including, each of the protrusions includes a first layer that is integrally and inseparably formed with the substrate and protrudes from an upper surface of the substrate; and a second layer that is provided on the first layer and is made of a material having a refractive index smaller than that of the first layer; a diameter of the first layer in a plan view is larger than a diameter of the second layer; a diameter of each of the protrusions is 2.8 micrometers or more and 3.5 micrometers or less, and a ratio of the diameter of each of the protrusions to the center-to-center spacing between two adjacent protrusions is 0.8 or more and 1.0 or less; the refractive index of the second layer is smaller than the refractive index of the substrate; The height of the second layer is greater than the height of the first layer; A light-emitting device, wherein the distance between the centers of two adjacent protrusions is equal to or greater than 2.9 micrometers and equal to or less than 3.1 micrometers.

2. 10. The light emitting device of claim 1, wherein the material of the first layer is the same as the material of the substrate.

3. The light emitting device according to claim 1 , wherein a ratio of a height of the first layer to a height of the second layer is equal to or greater than 0.2 and less than 1.

0.

4. The light emitting device of claim 1 , wherein the plurality of protrusions are arranged in a hexagonal pattern.

5. The light emitting device according to claim 1 , wherein the diameter of the protrusion is equal to or smaller than the distance between the centers of two adjacent protrusions.

6. The light-emitting device according to claim 1 , wherein the inclination angle of the side surface of the first layer is different from the inclination angle of the side surface of the second layer.

7. The light emitting device according to claim 6 , wherein the side surface of the second layer has a curved shape.

8. A substrate; a pattern of a plurality of protrusions including a first layer formed integrally and inseparably with the substrate and protruding from a surface of the substrate, and a second layer provided on the first layer and made of a material having a refractive index lower than that of the first layer; a light-emitting stack disposed on the substrate and emitting light; Including, a diameter of the first layer in a plan view is larger than a diameter of the second layer; a diameter of each of the protrusions is 2.8 micrometers or more and 3.5 micrometers or less, and a ratio of the diameter of each of the protrusions to the center-to-center spacing between two adjacent protrusions is 0.8 or more and 1.0 or less; The refractive index of the second layer is smaller than the refractive index of the substrate. The height of the second layer is greater than the height of the first layer; A light-emitting device, wherein the distance between the centers of two adjacent protrusions is equal to or greater than 2.9 micrometers and equal to or less than 3.1 micrometers.

9. the light emitting stack includes a first semiconductor layer disposed on a substrate, an active layer disposed on the first semiconductor layer, and a second semiconductor layer disposed on the active layer; The light emitting device according to claim 8 .

10. 9. The light emitting device of claim 8, wherein a ratio of a height of the second layer to a height of the first layer is greater than 2.5 and less than 9.

5.

11. The light emitting device according to claim 10 , wherein the height of the first layer is not less than 0.25 micrometers and not more than 0.55 micrometers, and the sum of the heights of the first layer and the second layer is 2.1 micrometers.

12. the refractive index of the first layer is 1.6 to 2.45; 10. The light emitting device according to claim 9, wherein the second layer has a refractive index of 1.3 to 2.

0.

13. The light emitting device according to claim 12 , wherein the refractive indexes of the first layer and the second layer are smaller than the refractive index of the first semiconductor layer.

14. 14. The light emitting device according to claim 13, wherein the refractive index of the first semiconductor layer is 2.0 to 2.5.

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