Light-emitting device, display, and electronic apparatus

Abstract

To provide a light-emitting device that can reduce nonradiative recombination on a side face of a luminous layer.SOLUTION: A laminate has a first electrode and a second electrode. The laminate has a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, a luminous layer, and a third semiconductor layer provided on the second semiconductor layer on the opposite side of the luminous layer and having the second conductivity type. The electric resistivity of the second semiconductor layer is higher than the electric resistivity of the third semiconductor layer. The first electrode is electrically connected with the first semiconductor layer. The second electrode is electrically connected with the third semiconductor layer. The laminate has a first portion, and a second portion in contact with the first portion when seen from a lamination direction. In the first portion, the first semiconductor layer, the luminous layer, the second semiconductor layer, and the third semiconductor layer overlap each other. In the second portion, the first semiconductor layer, the luminous layer, and the second semiconductor layer overlap each other, and the third semiconductor layer does not overlap the other layers.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light-emitting device, a display device, and an electronic device. [Background technology]

[0002] Light-emitting devices such as LEDs (Light Emitting Diodes) are used as light sources for display devices and the like.

[0003] For example, Patent Document 1 describes a light-emitting diode having a pn diode layer including an upper current spreading layer, a lower current spreading layer, an active layer between the upper current spreading layer and the lower current spreading layer, and a pn diode layer sidewall spanning the upper current spreading layer, the active layer, and the lower current spreading layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2018-505567 Summary of the Invention [Problem to be solved by the invention]

[0005] In such light emitting diodes, it is desirable to reduce non-radiative recombination at the sidewalls. [Means for solving the problem]

[0006] One aspect of the light emitting device according to the present invention is A laminate, a first electrode, and a second electrode, The laminate comprises: a first semiconductor layer having a first conductivity type; a second semiconductor layer having a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; a third semiconductor layer having the second conductivity type, the third semiconductor layer being provided on the opposite side of the second semiconductor layer from the light emitting layer; having the electrical resistivity of the second semiconductor layer is higher than the electrical resistivity of the third semiconductor layer; the first electrode is electrically connected to the first semiconductor layer; the second electrode is electrically connected to the third semiconductor layer; When viewed from a stacking direction of the first semiconductor layer and the light emitting layer, the stacked body has A first portion and a second portion in contact with the first portion, In the first portion, the first semiconductor layer, the light emitting layer, the second semiconductor layer, and the third semiconductor layer overlap each other, In the second portion, the first semiconductor layer, the light emitting layer, and the second semiconductor layer overlap, and the third semiconductor layer does not overlap.

[0007] One aspect of the display device according to the present invention is The present invention has one aspect of the light emitting device.

[0008] One aspect of the electronic device according to the present invention is The present invention has one aspect of the light emitting device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view illustrating a light emitting device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a stack of the light-emitting device according to the embodiment. [Diagram 3] FIG. 1 is a plan view illustrating a light emitting device according to an embodiment of the present invention. [Figure 4] 5A to 5C are cross-sectional views each showing a schematic process for manufacturing the light emitting device according to the embodiment. [Diagram 5] 5A to 5C are cross-sectional views each showing a schematic process for manufacturing the light emitting device according to the embodiment. [Figure 6] FIG. 4 is a cross-sectional view illustrating a stack of a light emitting device according to a first modified example of the present embodiment. [Figure 7] FIG. 11 is a cross-sectional view illustrating a stack of a light emitting device according to a second modified example of the embodiment. [Figure 8]FIG. 11 is a cross-sectional view illustrating a stack of a light emitting device according to a second modified example of the embodiment. [Figure 9] FIG. 1 is a diagram illustrating a projector according to an embodiment of the present invention. [Figure 10] FIG. 1 is a plan view illustrating a display according to an embodiment of the present invention. [Figure 11] FIG. 1 is a cross-sectional view illustrating a display according to an embodiment of the present invention. [Figure 12] FIG. 1 is a perspective view showing a schematic diagram of a head mounted display according to an embodiment of the present invention. [Figure 13] FIG. 2 is a diagram illustrating an image forming device and a light guiding device of the head mounted display according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0011] 1. Light-emitting device 1.1. Overall structure First, the light emitting device according to the present embodiment will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a light emitting device 100 according to the present embodiment. In Fig. 1, an X-axis, a Y-axis, and a Z-axis are illustrated as three mutually orthogonal axes.

[0012] 1, the light emitting device 100 includes, for example, a substrate 10, a buffer layer 20, a laminate 30, an insulating layer 40, a first electrode 50, and a second electrode 60. The light emitting device 100 is, for example, an LED.

[0013] The substrate 10 is, for example, a silicon substrate, a GaN substrate, a sapphire substrate, a SiC substrate, or the like.

[0014] The buffer layer 20 is provided on the substrate 10. The buffer layer 20 is provided between the substrate 10 and the stacked body 30. The buffer layer 20 has a first conductivity type. The buffer layer 20 is, for example, an n-type GaN layer doped with Si.

[0015] In this specification, in the stacking direction (hereinafter also simply referred to as "stacking direction") of the first semiconductor layer 32 and the light emitting layer 34 of the stacked body 30, when the light emitting layer 34 is used as a reference, the direction from the light emitting layer 34 toward the second semiconductor layer 36 of the stacked body 30 is described as "upper", and the direction from the light emitting layer 34 toward the first semiconductor layer 32 is described as "lower". In the illustrated example, the stacking direction is the Z-axis direction. Also, the direction perpendicular to the stacking direction is also referred to as the "in-plane direction".

[0016] The stacked body 30 is provided on the buffer layer 20. The stacked body 30 is provided between the buffer layer 20 and a second electrode 60. The stacked body 30 has a first semiconductor layer 32, a light emitting layer 34, a second semiconductor layer 36, and a third semiconductor layer 38. The first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38 are, for example, Group III nitride semiconductors and have a wurtzite crystal structure.

[0017] The first semiconductor layer 32 is provided on the buffer layer 20. The first semiconductor layer 32 is provided between the buffer layer 20 and the light emitting layer 34. The first semiconductor layer 32 has a first conductivity type. The first semiconductor layer 32 is, for example, an n-type GaN layer doped with Si.

[0018] The light emitting layer 34 is provided on the first semiconductor layer 32. The light emitting layer 34 is provided between the first semiconductor layer 32 and the second semiconductor layer 36. The light emitting layer 34 has an i-type conductivity in which impurities are not intentionally doped. The light emitting layer 34 generates light when a current is injected into it. The light emitting layer 34 has, for example, a well layer and a barrier layer. The well layer and the barrier layer are i-type semiconductor layers. The well layer is, for example, an InGaN layer. The barrier layer is, for example, a GaN layer. The light emitting layer 34 has an MQW (Multiple Quantum Well) structure composed of a well layer and a barrier layer.

[0019] There is no particular limitation on the number of well layers and barrier layers constituting the light-emitting layer 34. For example, only one well layer may be provided, in which case the light-emitting layer 34 has a SQW (Single Quantum Well) structure.

[0020] The second semiconductor layer 36 is provided on the light emitting layer 34. The second semiconductor layer 36 is provided between the light emitting layer 34 and the third semiconductor layer 38. The second semiconductor layer 36 has a second conductivity type different from the first conductivity type. The second semiconductor layer 36 is, for example, a p-type AlGaN layer doped with Mg. The second semiconductor layer 36 may be a p-type GaN layer.

[0021] The electrical resistivity of the second semiconductor layer 36 is higher than that of the third semiconductor layer 38. The electrical resistivity is measured, for example, by a four-terminal measurement method. The impurity concentration of the second semiconductor layer 36 is lower than that of the third semiconductor layer 38. When the second semiconductor layer 36 is an AlGaN layer and the third semiconductor layer 38 is a GaN layer, the impurity concentration of the second semiconductor layer 36 and the impurity concentration of the third semiconductor layer 38 may be the same. The impurity concentration is measured, for example, by atom probe analysis.

[0022] The third semiconductor layer 38 is provided on the second semiconductor layer 36. The third semiconductor layer 38 is provided between the second semiconductor layer 36 and the second electrode 60. The third semiconductor layer 38 is provided on the opposite side of the second semiconductor layer 36 to the light emitting layer 34. The third semiconductor layer 38 has the second conductivity type. The third semiconductor layer 38 is, for example, a p-type GaN layer doped with Mg.

[0023] In the light emitting device 100, a pin diode is formed by the p-type third semiconductor layer 38, the p-type second semiconductor layer 36, the i-type light emitting layer 34, and the n-type first semiconductor layer 32. In the light emitting device 100, when a forward bias voltage of the pin diode is applied between the first electrode 50 and the second electrode 60, a current is injected into the light emitting layer 34, causing recombination of electrons and holes in the light emitting layer 34. This recombination causes the light emitting layer 34 to generate light.

[0024] Although not shown, a reflective layer may be provided between the substrate 10 and the buffer layer 20 or under the substrate 10. The reflective layer is, for example, a DBR (Distributed Bragg Reflector) layer. The reflective layer can reflect the light generated in the light-emitting layer 34 toward the second electrode 60.

[0025] The insulating layer 40 covers the laminate 30. The insulating layer 40 is provided on the upper surface of the buffer layer 20, the side surface of the laminate 30, and the upper surface of the laminate 30. The insulating layer 40 is, for example, a silicon oxide layer, a silicon nitride layer, or a polyimide layer. A contact hole 42 is formed in the insulating layer 40. The contact hole 42 is located at the side of the second electrode 60 when viewed from the stacking direction. It overlaps with the first conductive layer 62 .

[0026] The first electrode 50 is provided on the buffer layer 20. The buffer layer 20 may be in ohmic contact with the first electrode 50. The first electrode 50 is electrically connected to the first semiconductor layer 32 via the buffer layer 20. As the first electrode 50, for example, a layer formed by laminating a Cr layer, a Ni layer, and an Au layer in this order from the buffer layer 20 side is used. The first electrode 50 is one of the electrodes for injecting a current into the light-emitting layer 34.

[0027] The second electrode 60 is provided on the stacked body 30. The second electrode 60 is electrically connected to the third semiconductor layer 38. The second electrode 60 is the other electrode for injecting a current into the light emitting layer 34.

[0028] The second electrode 60 includes, for example, a first conductive layer 62, a second conductive layer 64, and a third conductive layer 66.

[0029] The first conductive layer 62 is provided on the third semiconductor layer 38. The first conductive layer 62 is provided between the third semiconductor layer 38 and the second conductive layer 64. The third semiconductor layer 38 may be in ohmic contact with the first conductive layer 62. The first conductive layer 62 defines the bottom surface of the contact hole 42. The thickness of the first conductive layer 62 is smaller than the thickness of the second conductive layer 64. The first conductive layer 62 transmits light generated in the light emitting layer 34. The first conductive layer 62 has a thickness that allows the light generated in the light emitting layer 34 to transmit through it. The first conductive layer 62 is, for example, a layer of a Pd layer, a Pt layer, a Ni layer, and an Au layer stacked in this order from the third semiconductor layer 38 side, or a single layer of a metal layer. The electrical resistivity of the first conductive layer 62 is lower than the electrical resistivity of the second conductive layer 64. The first conductive layer 62 can reduce the contact resistance between the second electrode 60 and the third semiconductor layer 38. In a plan view seen from the stacking direction, the area of ​​the region where the first conductive layer 62 is arranged is smaller than the area of ​​the region where the third semiconductor layer 38 is arranged. In addition, in a plan view seen from the stacking direction, the region where the first conductive layer 62 is arranged is located inside the region where the third semiconductor layer 38 is arranged. In other words, in a plan view seen from the stacking direction, the entire region where the first conductive layer 62 is arranged is located inside the outer edge of the region where the third semiconductor layer 38 is arranged.

[0030] The second conductive layer 64 is provided on the first conductive layer 62. The second conductive layer 64 is provided in the contact hole 42. In the illustrated example, the second conductive layer 64 is further provided on the insulating layer 40. The second conductive layer 64 transmits light generated in the light emitting layer 34. The material of the second conductive layer 64 is, for example, ITO (Indium Tin Oxide), AZO in which zinc oxide (ZnO) is doped with aluminum (Al), or GZO in which ZnO is doped with gallium (Ga).

[0031] The third conductive layer 66 is provided on the second conductive layer 64 and the insulating layer 40. The third conductive layer 66 is formed by laminating a Cr layer and an Au layer in this order from the second conductive layer 64 side. An opening 68 is formed in the third conductive layer 66. The opening 68 overlaps with the contact hole 42 when viewed from the lamination direction.

[0032] Although the above describes the InGaN-based light emitting layer 34, various material systems capable of emitting light when a current is injected depending on the wavelength of the emitted light can be used for the light emitting layer 34. For example, semiconductor materials such as AlGaN-based, AlGaAs-based, InGaAs-based, InGaAsP-based, InP-based, GaP-based, and AlGaP-based materials can be used.

[0033] Furthermore, in the above description, the first conductivity type is n-type and the second conductivity type is p-type, but the first conductivity type may be p-type and the second conductivity type may be n-type.

[0034] Although not shown, the laminate 30 may also have a plurality of nanostructures.

[0035] The light emitting device 100 may also be a semiconductor laser.

[0036] 1.2. Laminate Fig. 2 is a cross-sectional view showing a schematic view of the laminate 30 of the light emitting device 100. Fig. 3 is a plan view showing a schematic view of the light emitting device 100. Fig. 2 is a cross-sectional view taken along line III-III in Fig. 3. For convenience, Fig. 3 omits illustration of members other than the laminate 30, the contact hole 42, and the first conductive layer 62.

[0037] As shown in FIGS. 2 and 3, the laminate 30 has a first portion 30a and a second portion 30b.

[0038] In the first portion 30a, the first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38 are overlapped as viewed from the stacking direction. The first portion 30a is composed of the first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38. The first portion 30a constitutes a side surface of the third semiconductor layer 38. In the example shown in FIG. 3, the planar shape of the first portion 30a is a square. The planar shape of the third semiconductor layer 38 is the same as the planar shape of the first portion 30a. As viewed from the stacking direction, the size of the third semiconductor layer 38 is the same as the size of the first portion 30a.

[0039] In the second portion 30b, the first semiconductor layer 32, the light emitting layer 34, and the second semiconductor layer 36 overlap with each other, and the third semiconductor layer 38 does not overlap with each other, as viewed from the stacking direction. The second portion 30b is composed of the first semiconductor layer 32, the light emitting layer 34, and the second semiconductor layer 36. The third semiconductor layer 38 does not constitute the second portion 30b. The second portion 30b constitutes the side surface of the first semiconductor layer 32, the side surface of the light emitting layer 34, and the side surface of the second semiconductor layer 36. In the example shown in FIG. 3, the planar shape of the second semiconductor layer 36 is a square. The planar shape of the first semiconductor layer 32, the planar shape of the light emitting layer 34, and the planar shape of the second semiconductor layer 36 are, for example, the same as each other. As viewed from the stacking direction, the size of the first semiconductor layer 32, the size of the light emitting layer 34, and the size of the second semiconductor layer 36 are, for example, the same as each other.

[0040] The second portion 30b is in contact with the first portion 30a. As shown in Fig. 3, the second portion 30b protrudes from the first portion 30a when viewed from the stacking direction. The second portion 30b surrounds the first portion 30a when viewed from the stacking direction. The second portion 30b has a frame-like shape that surrounds the first portion 30a.

[0041] The outer edge 31 of the second portion 30b has a first side 31a and a second side 31b when viewed in the stacking direction.

[0042] The first side 31a overlaps with the boundary line between the first portion 30a and the second portion 30b. The first side 31a is, for example, a straight line. In the illustrated example, the first side 31a overlaps with the side of the first portion 30a in the -X-axis direction. The first side 31a is, for example, parallel to the Y-axis.

[0043] The second side 31b faces the first side 31a. The second side 31b constitutes the outer edge of the laminate 30. In the illustrated example, the second side 31b is the side of the second portion 30b in the -X-axis direction. The second side 31b is, for example, parallel to the first side 31a.

[0044] The distance D between the first side 31a and the second side 31b is greater than the thickness T of the second semiconductor layer 36. The distance D is the shortest distance between the first side 31a and the second side 31b. The thickness T is the maximum thickness of the second semiconductor layer 36. The distance D is, for example, 500 nm. The thickness T is, for example, For example, it is 10 nm or more and 10 nm or less, and preferably 10 nm. The size in the X-axis direction of the first semiconductor layer 32 is, for example, 3 μm. The size in the X-axis direction of the third semiconductor layer 38 is, for example, 2 μm. The thickness T and the distance D are measured by, for example, a SEM (Scanning Electron Microscope).

[0045] 1.3. Effects In the light emitting device 100, the laminate 30 includes a first semiconductor layer 32 having a first conductivity type, a second semiconductor layer 36 having a second conductivity type different from the first conductivity type, a light emitting layer 34 provided between the first semiconductor layer 32 and the second semiconductor layer 36, and a third semiconductor layer 38 having the second conductivity type and provided on the opposite side of the second semiconductor layer 36 to the light emitting layer 34. The electrical resistivity of the second semiconductor layer 36 is higher than the electrical resistivity of the third semiconductor layer 38. The first electrode 50 is electrically connected to the first semiconductor layer 32, and the second electrode 60 is electrically connected to the third semiconductor layer 38. The laminate 30 includes a first portion 30a and a second portion 30b in contact with the first portion 30a, as viewed from the stacking direction. In the first portion 30a, the first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38 overlap each other. In the second portion 30b, the first semiconductor layer 32, the light emitting layer 34, and the second semiconductor layer 36 overlap, but the third semiconductor layer 38 does not overlap.

[0046] Therefore, in the light emitting device 100, the second semiconductor layer 36 having high electrical resistivity can reduce the current flowing through the side surfaces of the light emitting layer 34. This can reduce non-radiative recombination on the side surfaces of the light emitting layer 34.

[0047] Furthermore, when the stack is formed by etching, the side surface of the stack is damaged by etching. Therefore, leakage current is likely to occur on the side surface of the stack. To address this problem, the light emitting device 100 can reduce the current flowing through the side surface of the second portion 30b of the stack 30 by using the second semiconductor layer 36 having a high electrical resistivity, thereby reducing the leakage current.

[0048] In the light emitting device 100, as viewed in the stacking direction, the outer edge 31 of the second portion 30b has a first side 31a that overlaps with the boundary line between the first portion 30a and the second portion 30b, and a second side 31b that faces the first side 31a and constitutes the outer edge of the stacked body 30, and the distance D between the first side 31a and the second side 31b is greater than the thickness T of the second semiconductor layer 36. Therefore, in the light emitting device 100, the electrical resistance in the in-plane direction of the second semiconductor layer 36 can be made higher than in the case where, for example, the distance D is smaller than the thickness T. This makes it possible to further reduce the current flowing through the side surface of the light emitting layer 34.

[0049] In the light emitting device 100, the impurity concentration of the second semiconductor layer 36 is lower than the impurity concentration of the third semiconductor layer 38. Therefore, in the light emitting device 100, the electrical resistivity of the second semiconductor layer 36 can be made higher than the electrical resistivity of the third semiconductor layer 38.

[0050] In the light emitting device 100, the second semiconductor layer 36 is an AlGaN layer, and the third semiconductor layer 38 is a GaN layer. Therefore, in the light emitting device 100, the electrical resistivity of the second semiconductor layer 36 can be made higher than that of the third semiconductor layer 38 without changing the impurity concentration between the second semiconductor layer 36 and the third semiconductor layer 38. When the impurity concentrations are the same, the AlGaN layer has a higher electrical resistivity than the GaN layer. Furthermore, when the stacked body 30 is epitaxially grown and then etched to form the second portion 30b, the second semiconductor layer 36 can be used as an etching stopper.

[0051] In the light emitting device 100, the second portion 30b surrounds the first portion 30a when viewed from the stacking direction. Therefore, in the light emitting device 100, the current flowing through the side surface of the light emitting layer can be further reduced.

[0052] 2. Manufacturing method of light-emitting device Next, a method for manufacturing the light emitting device 100 according to this embodiment will be described with reference to the drawings. Figures 4 and 5 are cross-sectional views that typically show the manufacturing process of the light emitting device 100 according to this embodiment.

[0053] 4, a buffer layer 20 is epitaxially grown on a substrate 10. Examples of methods for epitaxial growth include a metal organic chemical vapor deposition (MOCVD) method and a molecular beam epitaxy (MBE) method.

[0054] Next, a mask layer (not shown) is formed on the buffer layer 20. The mask layer is formed by, for example, an electron beam deposition method or a sputtering method.

[0055] Next, using the mask layer as a mask, the first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38 are epitaxially grown in this order on the buffer layer 20. Examples of the epitaxial growth method include MOCVD and MBE. Next, for example, the mask layer (not shown) is removed. Note that the mask layer may be left without being removed. Through this process, the stacked body 30 is formed.

[0056] Alternatively, the laminate 30 may be formed by epitaxially growing the first semiconductor layer 32, the light emitting layer 34, the second semiconductor layer 36, and the third semiconductor layer 38 on the buffer layer 20 without using a mask layer, and then patterning the grown semiconductor layers 32, 36, 38 and the light emitting layer 34. The patterning is performed by, for example, photolithography and dry etching.

[0057] As shown in FIG. 5, the third semiconductor layer 38 is patterned to form the first portion 30a and the second portion 30b. The patterning is performed by, for example, photolithography and dry etching. When the second semiconductor layer 36 is an AlGaN layer and the third semiconductor layer 38 is a GaN layer, the second semiconductor layer 36 may be used as an etching stopper. In this case, the dry etching is performed using an etching gas such that the etching rate for the second semiconductor layer 36 is smaller than the etching rate for the third semiconductor layer 38. This process forms a stacked body 30 having the first portion 30a and the second portion 30b.

[0058] 1, a first conductive layer 62 is formed on the third semiconductor layer 38. The first conductive layer 62 is formed by, for example, a sputtering method, a CVD (Chemical Vapor Deposition) method, or a vacuum deposition method.

[0059] Next, the first electrode 50 is formed on the buffer layer 20. The first electrode 50 is formed by, for example, a sputtering method, a CVD method, or a vacuum deposition method. Note that the order of the step of forming the first electrode 50 and the step of forming the first conductive layer 62 is not particularly limited.

[0060] Next, the insulating layer 40 is formed on the buffer layer 20, the stacked body 30, and the first conductive layer 62. The insulating layer 40 is formed by, for example, a spin coating method or a CVD method.

[0061] Next, the insulating layer 40 is patterned to form the contact hole 42. The contact hole 42 is formed so as to expose the first conductive layer 62. The patterning is performed by, for example, photolithography and etching.

[0062] Next, a second conductive layer 64 is formed on the first conductive layer 62 and the insulating layer 40. Next, a third conductive layer 66 is formed on the second conductive layer 64 and the insulating layer 40. The conductive layers 64 and 66 are formed by, for example, a sputtering method, a CVD method, or a vacuum deposition method. An electrode 60 is formed.

[0063] Through the above steps, the light emitting device 100 can be manufactured.

[0064] 3. Modifications of the Light Emitting Device 3.1. First variant Next, a light emitting device according to a first modified example of this embodiment will be described with reference to the drawings. Fig. 6 is a cross-sectional view that shows a schematic view of a laminate 30 of a light emitting device 200 according to a first modified example of this embodiment.

[0065] Hereinafter, in the light emitting device 200 according to the first modification of this embodiment, the components having the same functions as the components of the light emitting device 100 according to this embodiment described above are denoted by the same reference numerals, and detailed description thereof will be omitted. This also applies to the light emitting device according to the second modification of this embodiment described later.

[0066] As shown in FIG. 6, the light emitting device 200 differs from the above-described light emitting device 100 in that the thickness Tb of the second semiconductor layer 36 in the second portion 30b is smaller than the thickness Ta of the second semiconductor layer 36 in the first portion 30a.

[0067] The thickness Ta is the maximum thickness of the second semiconductor layer 36 in the first portion 30a. The thickness Tb is the maximum thickness of the second semiconductor layer 36 in the second portion 30b. The thickness Tb is, for example, 5 nm or more and 8 nm or less. When the stacked body 30 is patterned to form the first portion 30a and the second portion 30b, the thickness Tb can be made smaller than the thickness Ta by, for example, adjusting the etching time.

[0068] In the light emitting device 200, the thickness Tb of the second semiconductor layer 36 in the second portion 30b is smaller than the thickness Ta of the second semiconductor layer 36 in the first portion 30a. Therefore, in the light emitting device 200, the electrical resistance in the in-plane direction of the second semiconductor layer 36 in the second portion 30b can be made higher than in the case where the thickness Tb is the same as the thickness Ta. This can further reduce the current flowing through the side surface of the light emitting layer 34.

[0069] 3.2. Second variant Next, a light emitting device according to a second modified example of this embodiment will be described with reference to the drawings. Fig. 7 is a cross-sectional view that shows a schematic view of a laminate 30 of a light emitting device 300 according to a second modified example of this embodiment.

[0070] The light emitting device 300 differs from the above-described light emitting device 100 in that the second semiconductor layer 36 has a first layer 136 and a second layer 236, as shown in FIG.

[0071] The first layer 136 is provided on the light emitting layer 34. The first layer 136 is provided between the light emitting layer 34 and the second layer 236. The first layer 136 is a layer on the light emitting layer 34 side. The first layer 136 is in contact with the light emitting layer 34. The electrical resistivity of the first layer 136 is higher than the electrical resistivity of the third semiconductor layer 38. The first layer 136 is, for example, a p-type AlGaN layer.

[0072] The second layer 236 is provided on the first layer 136. The second layer 236 is provided between the first layer 136 and the third semiconductor layer 38. The second layer 236 is a layer on the third semiconductor layer 38 side. The second layer 236 is in contact with the third semiconductor layer 38. The thickness T2 of the second layer 236 is smaller than the thickness T1 of the first layer 136, for example. The thickness T1 is the maximum thickness of the first layer 136. The thickness T2 is the maximum thickness of the second layer 236. Although not shown, the thickness T2 may be the same as the thickness T1 or may be larger than the thickness T1.

[0073] The electrical resistivity of the second layer 236 is higher than the electrical resistivity of the third semiconductor layer 38 and lower than the electrical resistivity of the first layer 136. The second layer 236 is, for example, a p-type GaN layer. The impurity concentration of the second layer 236 is, for example, higher than the impurity concentration of the first layer 136.

[0074] In the light emitting device 300, the second semiconductor layer 36 has a first layer 136 in contact with the light emitting layer 34 and a second layer 236 in contact with the third semiconductor layer 38, and the electrical resistivity of the second layer 236 is lower than the electrical resistivity of the first layer 136. Therefore, in the light emitting device 300, the contact resistance between the second semiconductor layer 36 and the third semiconductor layer 38 can be lower than when, for example, the electrical resistivity of the second layer is the same as that of the first layer.

[0075] In the light emitting device 300, the thickness T2 of the second layer 236 is smaller than the thickness T1 of the first layer 136. Therefore, in the light emitting device 300, the electrical resistance in the in-plane direction of the second layer 236 can be made higher than when, for example, T2 is the same as T1. This makes it possible to further reduce the current flowing through the side surface of the light emitting layer 34.

[0076] As shown in FIG. 8, the thickness T2b of the second layer 236 in the second portion 30b may be smaller than the thickness T2a of the second layer 236 in the first portion 30a. The thickness T2a is the maximum thickness of the second layer 236 in the first portion 30a. The thickness T2b is the maximum thickness of the second layer 236 in the second portion 30b. If the thickness T2b is smaller than the thickness T1a, the electrical resistance in the in-plane direction of the second layer 236 in the second portion 30b can be increased compared to the case where the thickness T2b is the same as the thickness T2a. This can further reduce the current flowing through the side surface of the light-emitting layer 34.

[0077] Although not shown, the second portion 30b may not have the second layer 236. That is, only the first portion 30a may have the second layer 236. Although not shown, the second semiconductor layer 36 may have a plurality of layers, such as three or more layers.

[0078] 4. Projector Next, a projector as a display device according to this embodiment will be described with reference to the drawings. Fig. 9 is a diagram showing a schematic diagram of a projector 700 according to this embodiment.

[0079] The projector 700 includes, for example, a light emitting device 100 as a light source.

[0080] Projector 700 has a housing (not shown), and red light source 100R, green light source 100G, and blue light source 100B that are provided in the housing and emit red light, green light, and blue light, respectively. For convenience, red light source 100R, green light source 100G, and blue light source 100B are illustrated in a simplified form in FIG. 9.

[0081] The projector 700 further includes, for example, a first optical element 702R, a second optical element 702G, a third optical element 702B, a first light modulation device 704R, a second light modulation device 704G, a third light modulation device 704B, and a projection device 708, which are provided in the housing. The first light modulation device 704R, the second light modulation device 704G, and the third light modulation device 704B are, for example, transmissive liquid crystal light valves. The projection device 708 is, for example, a projection lens.

[0082] The light emitted from red light source 100R is incident on first optical element 702R. The light emitted from red light source 100R is collected by first optical element 702R. Note that first optical element 702R may have a function other than collecting light. Second optical element 702G and third optical element 702B may also have a function other than collecting light.

[0083] The light collected by the first optical element 702R is incident on the first light modulation device 704R. The first light modulation device 704R modulates the incident light in accordance with image information. The projection device 708 then enlarges the image formed by the first light modulation device 704R and projects it onto the screen 710.

[0084] The light emitted from green light source 100G is incident on second optical element 702G. The light emitted from green light source 100G is collected by second optical element 702G.

[0085] The light collected by the second optical element 702G is incident on the second light modulation device 704G. The second light modulation device 704G modulates the incident light in accordance with image information. The projection device 708 then enlarges the image formed by the second light modulation device 704G and projects it onto the screen 710.

[0086] The light emitted from blue light source 100B is incident on third optical element 702B. The light emitted from blue light source 100B is collected by third optical element 702B.

[0087] The light collected by the third optical element 702B enters the third light modulation device 704B. The third light modulation device 704B modulates the incident light in accordance with image information. The projection device 708 then enlarges the image formed by the third light modulation device 704B and projects it onto the screen 710.

[0088] The projector 700 further includes a cross dichroic prism 706 that combines the light emitted from the first light modulation device 704R, the second light modulation device 704G, and the third light modulation device 704B, and guides the combined light to a projection device 708.

[0089] The three color lights modulated by the first light modulation device 704R, the second light modulation device 704G, and the third light modulation device 704B enter the cross dichroic prism 706. The cross dichroic prism 706 is formed by bonding four right-angle prisms together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are disposed on its inner surface. The three color lights are synthesized by these dielectric multilayer films to form light that represents a color image. The synthesized light is then projected by the projection device 708 onto a screen 710, and an enlarged image is displayed.

[0090] Note that red light source 100R, green light source 100G, and blue light source 100B may directly form an image without using first light modulation device 704R, second light modulation device 704G, and third light modulation device 704B, by controlling light emitting device 100 as a pixel of the image according to image information. Then, projection device 708 may enlarge and project the image formed by red light source 100R, green light source 100G, and blue light source 100B onto screen 710.

[0091] In the above example, a transmissive liquid crystal light valve is used as the light modulation device, but a light valve other than liquid crystal may be used, or a reflective light valve may be used. Examples of such light valves include a reflective liquid crystal light valve and a digital micro mirror device. The configuration of the projection device is appropriately changed depending on the type of light valve used.

[0092] The light source can also be applied to a light source device of a scanning type image display device having a scanning means, which is an image forming device that displays an image of a desired size on a display surface by scanning light from the light source on a screen.

[0093] 5. Display Next, a display as a display device according to this embodiment will be described with reference to the drawings. Fig. 10 is a plan view showing a display 800 according to this embodiment. Fig. 11 is a cross-sectional view showing a display 800 according to this embodiment. Note that Fig. 10 shows an X-axis and a Y-axis as two mutually orthogonal axes.

[0094] The display 800 includes, for example, a light emitting device 100 as a light source.

[0095] The display 800 is a display device that displays an image. The image includes an image that displays only text information. The display 800 is a self-luminous display. As shown in Figs. 10 and 11, the display 800 has, for example, a circuit board 810, a lens array 820, and a heat sink 830.

[0096] A driving circuit for driving the light emitting device 100 is mounted on the circuit board 810. The driving circuit is, for example, a circuit including a CMOS (Complementary Metal Oxide Semiconductor) or the like. The driving circuit drives the light emitting device 100 based on, for example, input image information. Although not shown, a light-transmitting substrate for protecting the circuit board 810 is disposed on the circuit board 810.

[0097] The circuit board 810 includes, for example, a display area 812, a data line driving circuit 814, a scanning line driving circuit 816, and a control circuit 818.

[0098] The display area 812 is made up of a plurality of pixels P. In the illustrated example, the pixels P are arranged along the X-axis and the Y-axis.

[0099] Although not shown, a plurality of scanning lines and a plurality of data lines are provided on the circuit board 810. For example, the scanning lines extend along the X-axis, and the data lines extend along the Y-axis. The scanning lines are connected to a scanning line driving circuit 816. The data lines are connected to a data line driving circuit 814. Pixels P are provided at intersections of the scanning lines and the data lines.

[0100] One pixel P has, for example, one light emitting device 100, one lens 822, and a pixel circuit (not shown). The pixel circuit has a switching transistor that functions as a switch for the pixel P. The gate of the switching transistor is connected to a scan line, and one of the source and drain is connected to a data line.

[0101] The data line driving circuit 814 and the scanning line driving circuit 816 are circuits that control the driving of the light emitting device 100 that constitutes the pixel P. The control circuit 818 controls the display of an image.

[0102] Image data is supplied from a higher-level circuit to the control circuit 818. The control circuit 818 supplies various signals based on the image data to the data line driving circuit 814 and the scanning line driving circuit 816.

[0103] When the scanning line driving circuit 816 activates a scanning signal to select a scanning line, the switching transistor of the selected pixel P is turned on. At this time, the data line driving circuit 814 supplies a data signal from the data line to the selected pixel P, causing the light emitting device 100 of the selected pixel P to emit light in response to the data signal.

[0104] The lens array 820 has a plurality of lenses 822. For example, one lens 822 is provided for each light emitting device 100. is incident on one lens 822.

[0105] The heat sink 830 is in contact with the circuit board 810. The material of the heat sink 830 is, for example, a metal such as copper or aluminum. The heat sink 830 dissipates heat generated by the light emitting device 100.

[0106] 6. Head-mounted displays 6.1. Overall structure Next, a head mounted display as an electronic device according to this embodiment will be described with reference to the drawings. Fig. 12 is a perspective view showing a schematic diagram of a head mounted display 900 according to this embodiment.

[0107] The head mounted display 900 is a head-mounted display having an appearance like glasses, as shown in Fig. 12. The head mounted display 900 is worn on the head of an observer. The observer is a user who uses the head mounted display 900. The head mounted display 900 allows the observer to view image light formed by a virtual image, and also allows the observer to view an external world image in a see-through manner.

[0108] The head mounted display 900 has, for example, a first display unit 910a, a second display unit 910b, a frame 920, a first temple 930a, and a second temple 930b.

[0109] The first display unit 910a and the second display unit 910b display images. Specifically, the first display unit 910a displays a virtual image for the observer's right eye. The second display unit 910b displays a virtual image for the observer's left eye. The display units 910a and 910b each include, for example, an image forming device 911 and a light guide device 915.

[0110] The image forming device 911 forms image light. The image forming device 911 has an optical system, such as a light source and a projection device, and an external member 912. The external member 912 houses the light source and the projection device.

[0111] The light guiding device 915 covers the viewer's eyes. The light guiding device 915 guides the image light formed by the image forming device 911 and allows the viewer to visually recognize the image light overlapping with the outside light. Details of the image forming device 911 and the light guiding device 915 will be described later.

[0112] The frame 920 supports the first display unit 910a and the second display unit 910b. The frame 920, for example, surrounds the display units 910a and 910b. In the illustrated example, the image forming device 911 of the first display unit 910a is attached to one end of the frame 920. The image forming device 911 of the second display unit 910b is attached to the other end of the frame 920.

[0113] A first temple 930a and a second temple 930b extend from the frame 920. In the illustrated example, the first temple 930a extends from one end of the frame 920. The second temple 930b extends from the other end of the frame 920.

[0114] The first temple 930a and the second temple 930b are suspended from the ears of the viewer when the viewer wears the head mounted display 900. The viewer's head is positioned between the temples 930a and 930b.

[0115] 6.2. Image forming and light directing devices 13 is a diagram illustrating an image forming device 911 and a light guide device 915 of a first display unit 910a of a head mounted display 900. The first display unit 910a and the second display unit 910b basically have the same configuration. Therefore, the following description of the first display unit 910a can be applied to the second display unit 910b.

[0116] As shown in FIG. 13, the image forming device 911 includes, for example, a light emitting device 100 as a light source, a light modulation device 913, and a projection device 914 for forming an image.

[0117] The light modulation device 913 modulates the light incident from the light emitting device 100 in accordance with image information, and emits image light. The light modulation device 913 is a transmissive liquid crystal light valve. The light emitting device 100 may be a self-luminous light emitting device that emits light in accordance with input image information. In this case, the light modulation device 913 is not provided.

[0118] The projection device 914 projects the image light emitted from the light modulation device 913 toward the light guide device 915. The projection device 914 is, for example, a projection lens. As a lens constituting the projection device 914, a lens having an axially symmetric surface as a lens surface may be used.

[0119] The light guiding device 915 is precisely positioned with respect to the projection device 914 by, for example, being screwed to the lens barrel of the projection device 914. The light guiding device 915 has, for example, an image light guiding member 916 that guides the image light, and a see-through member 918 for see-through.

[0120] The image light emitted from the projection device 914 is incident on the image light guiding member 916. The image light guiding member 916 is a prism that guides the image light toward the viewer's eye. The image light that enters the image light guiding member 916 is repeatedly reflected on the inner surface of the image light guiding member 916, and is then reflected by the reflective layer 917 and emitted from the image light guiding member 916. The image light that is emitted from the image light guiding member 916 reaches the viewer's eye. The reflective layer 917 is made of, for example, a metal or a dielectric multilayer film. The reflective layer 917 may be a half mirror.

[0121] The transparent member 918 is adjacent to the image light guiding member 916. The transparent member 918 is fixed to the image light guiding member 916. For example, the outer surface of the transparent member 918 is continuous with the outer surface of the image light guiding member 916. The transparent member 918 allows the observer to see outside light through it. The image light guiding member 916 also has a function of allowing the observer to see outside light through it, in addition to the function of guiding the image light. Note that the head mounted display 900 may be configured not to allow the observer to see outside light through it.

[0122] The light emitting device according to the above-described embodiment can be used for applications other than projectors, displays, and head-mounted displays. The light emitting device according to the above-described embodiment can be used for, for example, indoor and outdoor lighting, laser printers, scanners, sensing devices using light, EVFs (Electronic View Finders), wearable displays such as smart watches, in-vehicle lights, and in-vehicle head-up displays.

[0123] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be appropriately combined.

[0124] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effect. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0125] The following can be derived from the above-described embodiment and modifications.

[0126] One aspect of the light emitting device is A laminate, a first electrode, and a second electrode, The laminate comprises: a first semiconductor layer having a first conductivity type; a second semiconductor layer having a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; a third semiconductor layer having the second conductivity type, the third semiconductor layer being provided on the opposite side of the second semiconductor layer from the light emitting layer; having the electrical resistivity of the second semiconductor layer is higher than the electrical resistivity of the third semiconductor layer; the first electrode is electrically connected to the first semiconductor layer; the second electrode is electrically connected to the third semiconductor layer; When viewed from a stacking direction of the first semiconductor layer and the light emitting layer, the stacked body has A first portion and a second portion in contact with the first portion, In the first portion, the first semiconductor layer, the light emitting layer, the second semiconductor layer, and the third semiconductor layer overlap each other, In the second portion, the first semiconductor layer, the light emitting layer, and the second semiconductor layer overlap, and the third semiconductor layer does not overlap.

[0127] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be reduced, thereby reducing non-radiative recombination on the side surface of the light emitting layer.

[0128] In one embodiment of the light emitting device, A thickness of the second semiconductor layer in the second portion may be smaller than a thickness of the second semiconductor layer in the first portion.

[0129] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be further reduced.

[0130] In one embodiment of the light emitting device, The second semiconductor layer is a first layer in contact with the light-emitting layer; a second layer in contact with the third semiconductor layer; having The electrical resistivity of the second layer may be lower than the electrical resistivity of the first layer.

[0131] According to this light emitting device, the contact resistance between the second semiconductor layer and the third semiconductor layer can be reduced.

[0132] In one embodiment of the light emitting device, The second layer may have a thickness less than a thickness of the first layer.

[0133] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be further reduced.

[0134] In one embodiment of the light emitting device, The thickness of the second layer in the second portion may be smaller than the thickness of the second layer in the first portion.

[0135] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be further reduced.

[0136] In one embodiment of the light emitting device, When viewed from the stacking direction, the outer edge of the second portion is a first side overlapping a boundary line between the first portion and the second portion; A second side facing the first side and constituting an outer edge of the laminate; having The distance between the first side and the second side may be greater than a thickness of the second semiconductor layer.

[0137] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be further reduced.

[0138] In one embodiment of the light emitting device, The second semiconductor layer may have an impurity concentration lower than an impurity concentration of the third semiconductor layer.

[0139] In this light emitting device, the electrical resistivity of the second semiconductor layer can be made higher than the electrical resistivity of the third semiconductor layer.

[0140] In one embodiment of the light emitting device, the second semiconductor layer is an AlGaN layer; The third semiconductor layer may be a GaN layer.

[0141] According to this light emitting device, the electrical resistivity of the second semiconductor layer can be made higher than the electrical resistivity of the third semiconductor layer, even if the impurity concentrations of the second and third semiconductor layers are not different.

[0142] In one embodiment of the light emitting device, When viewed from the stacking direction, the second portion may surround the first portion.

[0143] According to this light emitting device, the current flowing through the side surface of the light emitting layer can be further reduced.

[0144] One aspect of the display device is The present invention has one aspect of the light emitting device.

[0145] One aspect of the electronic device is The present invention has one aspect of the light emitting device. [Explanation of symbols]

[0146] 10...substrate, 20...buffer layer, 30...laminated body, 30a...first portion, 30b...second portion, 31...outer edge, 31a...first side, 31b...second side, 32...first semiconductor layer, 34...light emitting layer, 36...second semiconductor layer, 38...third semiconductor layer, 40...insulating layer, 42...contact hole, 50...first electrode, 60...second electrode, 62...first conductive layer, 64...second conductive layer, 66...third conductive layer, 68...opening, 100...light emitting device, 100R...red light source, 100G...green light source, 100B...blue light source, 136...first layer, 200...light emitting device, 236...second layer, 300...light emitting device device, 700...projector, 702R...first optical element, 702G...second optical element, 702B...third optical element, 704R...first light modulation device, 704G...second light modulation device, 704B...third light modulation device, 706...cross dichroic prism, 708...projection device, 710...screen, 800...display, 810...circuit board, 812...display area, 814...data line driving circuit, 816...scanning line driving circuit, 818...control circuit, 820...lens array, 822...lens, 830...heat sink, 900...head mounted display, 91 0a...first display section, 910b...second display section, 911...image forming device, 912...external member, 913...light modulation device, 914...projection device, 915...light guide device, 916...image light guide member, 917...reflective layer, 918...transparent member, 920...frame, 930a...first temple, 930b...second temple

Claims

1. A laminate, a first electrode, and a second electrode, The laminate comprises: a first semiconductor layer having a first conductivity type; a second semiconductor layer having a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; a third semiconductor layer having the second conductivity type, the third semiconductor layer being provided on the opposite side of the second semiconductor layer from the light emitting layer; having the electrical resistivity of the second semiconductor layer is higher than the electrical resistivity of the third semiconductor layer; the first electrode is electrically connected to the first semiconductor layer; the second electrode is electrically connected to the third semiconductor layer; When viewed from a stacking direction of the first semiconductor layer and the light emitting layer, the stacked body has A first portion and a second portion in contact with the first portion, In the first portion, the first semiconductor layer, the light emitting layer, the second semiconductor layer, and the third semiconductor layer overlap each other, In the second portion, the first semiconductor layer, the light emitting layer, and the second semiconductor layer overlap, and the third semiconductor layer does not overlap.

2. In claim 1, A light emitting device, wherein a thickness of the second semiconductor layer in the second portion is smaller than a thickness of the second semiconductor layer in the first portion.

3. In claim 1, The second semiconductor layer is a first layer in contact with the light-emitting layer; a second layer in contact with the third semiconductor layer; having A light emitting device, wherein the second layer has a lower electrical resistivity than the first layer.

4. In claim 3, A light emitting device, wherein the second layer has a thickness less than a thickness of the first layer.

5. In claim 3, A light emitting device, wherein a thickness of the second layer in the second portion is smaller than a thickness of the second layer in the first portion.

6. In claim 1, When viewed from the stacking direction, the outer edge of the second portion is a first side overlapping a boundary line between the first portion and the second portion; A second side that faces the first side and constitutes an outer edge of the laminate; having A light emitting device, wherein a distance between the first side and the second side is greater than a thickness of the second semiconductor layer.

7. In claim 1, a second semiconductor layer having an impurity concentration lower than a third semiconductor layer;

8. In claim 1, the second semiconductor layer is an AlGaN layer; The third semiconductor layer is a GaN layer.

9. In claim 1, When viewed from the stacking direction, the second portion surrounds the first portion.

10. A display device comprising the light emitting device according to claim 1 .

11. An electronic device comprising the light emitting device according to claim 1 .

Images