Light-emitting device, projector, and display

Abstract

To provide a light-emitting device capable of reducing variation in emission.SOLUTION: A light-emitting device includes: a substrate; a plurality of columnar parts each including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, and a light-emitting layer provided between the first semiconductor layer and the second semiconductor layer; and an electrode including a first electrode layer electrically connected to the second semiconductor layer of each of the columnar parts and a second electrode layer provided on the first electrode layer on an opposite side to the substrate, the second electrode layer having an electrical resistivity smaller than that of the first electrode layer. The first electrode layer has a first portion that is in contact with the second electrode layer on an opposite side to the substrate, and a second portion that is not in contact with the second electrode layer on an opposite side to the substrate and that has a larger thickness than the first portion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Semiconductor lasers are expected to be the next generation of high-brightness light sources. In particular, semiconductor lasers that incorporate nanocolumns are expected to be able to achieve high-power emission with a narrow beam angle due to the photonic crystal effect of the nanocolumns.

[0003] For example, Patent Document 1 describes a light-emitting device having a plurality of columnar portions and an electrode, the electrode comprising a first electrode layer connected to the plurality of columnar portions and a second electrode layer connected to the first electrode layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-100048 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the light-emitting device described in Patent Document 1, the thickness of the electrode connection portion where the first electrode layer and the second electrode layer are connected is thicker than the thickness of the first electrode layer. Therefore, the sheet resistance of the electrode connection portion is lower than the sheet resistance of the first electrode layer. This causes a difference in the amount of injected current between the columnar portion overlapping the electrode connection portion and the columnar portion overlapping only with the first electrode layer. This difference in the amount of injected current results in a difference in light emission intensity and uneven light emission. [Means for solving the problem]

[0006] One aspect of the light emitting device according to the present invention is A substrate; a plurality of columnar sections each having a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, and a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; an electrode including: a first electrode layer electrically connected to the second semiconductor layer of each of the plurality of columnar portions; and a second electrode layer provided on the opposite side of the first electrode layer from the substrate, the second electrode layer having an electrical resistivity lower than that of the first electrode layer; and The first electrode layer has a first portion that contacts the second electrode layer on the side opposite the substrate, and a second portion that does not contact the second electrode layer on the side opposite the substrate and has a thickness greater than that of the first portion.

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

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

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a light-emitting device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a plan view schematically showing a light emitting device according to an embodiment of the present invention. [Figure 3] FIG. 1 is a cross-sectional view schematically showing a light-emitting device according to an embodiment of the present invention. [Figure 4] 5A to 5C are cross-sectional views schematically showing the manufacturing process of the light emitting device according to the embodiment. [Figure 5] 5A to 5C are cross-sectional views schematically showing the manufacturing process of the light emitting device according to the embodiment. [Figure 6] 5A to 5C are cross-sectional views schematically showing the manufacturing process of the light emitting device according to the embodiment. [Figure 7] FIG. 10 is a cross-sectional view schematically showing a light emitting device according to a first modified example of the present embodiment. [Figure 8] FIG. 10 is a cross-sectional view schematically showing a light emitting device according to a second modified example of the present embodiment. [Figure 9]FIG. 10 is a cross-sectional view schematically showing a light emitting device according to a third modified example of the present embodiment. [Figure 10] FIG. 1 is a diagram schematically showing a projector according to an embodiment. [Figure 11] FIG. 1 is a plan view schematically showing a display according to an embodiment of the present invention. [Figure 12] FIG. 1 is a cross-sectional view schematically showing a display according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[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 content of the present invention as defined in the claims. Furthermore, 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 this embodiment will be described with reference to the drawings. Fig. 1 is a cross-sectional view schematically showing the light emitting device 100 according to this embodiment. Fig. 2 is a plan view schematically showing the light emitting device 100 according to this embodiment. Fig. 1 is a cross-sectional view taken along line II in Fig. 2.

[0012] 1 and 2, the light emitting device 100 includes, for example, a substrate 10, a laminate 20, a first electrode 50, a second electrode 52, and wiring 60. The light emitting device 100 is, for example, a semiconductor laser.

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

[0014] As shown in Fig. 1, the laminate 20 is provided on a substrate 10. In the illustrated example, the laminate 20 is provided on the substrate 10. The laminate 20 has, for example, a buffer layer 22, a plurality of columnar sections 30, and an insulating layer 40. For convenience, components other than the columnar sections 30, the second electrode 52, and the wiring 60 are not shown in Fig. 2.

[0015] In this specification, in the stacking direction of the stacked body 20 (hereinafter also simply referred to as the "stacking direction"), when the light emitting layer 34 of the columnar section 30 is used as a reference, the direction from the light emitting layer 34 toward the second semiconductor layer 36 of the columnar section 30 is described as "up," and the direction from the light emitting layer 34 toward the first semiconductor layer 32 of the columnar section 30 is described as "down." In addition, a direction perpendicular to the stacking direction is also referred to as an "in-plane direction." The "stacking direction of the stacked body 20" refers to the stacking direction of the first semiconductor layer 32 and the light emitting layer 34.

[0016] The buffer layer 22 is provided on the substrate 10. The buffer layer 22 is, for example, an n-type GaN layer doped with Si. Although not shown, a mask layer for growing a plurality of columnar sections 30 may be provided on the buffer layer 22. The mask layer is, for example, a titanium layer, a silicon oxide layer, a titanium oxide layer, an aluminum oxide layer, or the like.

[0017] The columnar portion 30 is provided on the buffer layer 22. The columnar portion 30 has a columnar shape that protrudes upward from the buffer layer 22. In other words, the columnar portion 30 protrudes upward from the substrate 10 via the buffer layer 22. The columnar portion 30 is also called, for example, a nanocolumn, a nanowire, a nanorod, or a nanopillar. The planar shape of the columnar portion 30 is, for example, a polygon such as a hexagon, or a circle. In the example shown in FIG. 2, the planar shape of the columnar portion 30 is a regular hexagon.

[0018] The diameter of the columnar section 30 is, for example, 50 nm or more and 500 nm or less. By setting the diameter of the columnar section 30 to 500 nm or less, it is possible to obtain a light-emitting layer 34 with high-quality crystals and reduce strain inherent in the light-emitting layer 34. This allows the light generated in the light-emitting layer 34 to be amplified with high efficiency.

[0019] It should be noted that the "diameter of the columnar portion 30" refers to the diameter when the planar shape of the columnar portion 30 is circular, and refers to the diameter of the smallest encompassing circle when the planar shape of the columnar portion 30 is not circular. For example, when the planar shape of the columnar portion 30 is polygonal, the diameter of the smallest circle that includes the polygon inside, and when the planar shape of the columnar portion 30 is elliptical, the diameter of the smallest circle that includes the ellipse inside.

[0020] A plurality of columnar sections 30 are provided. The columnar sections 30 are provided at a distance from each other. The interval between adjacent columnar sections 30 is, for example, 1 nm or more and 500 nm or less. The columnar sections 30 are arranged in a predetermined direction at a predetermined pitch when viewed from the stacking direction. The columnar sections 30 are arranged in, for example, a triangular lattice pattern or a square lattice pattern. In the example shown in FIG. 2, the columnar sections 30 are arranged in a regular triangular lattice pattern. The columnar sections 30 can exhibit the effect of a photonic crystal.

[0021] The "pitch of the columnar portions 30" refers to the distance between the centers of adjacent columnar portions 30 in a predetermined direction. When the planar shape of the columnar portions 30 is a circle, the "center of the columnar portion 30" refers to the center of the circle. When the planar shape of the columnar portions 30 is a shape other than a circle, the "center of the columnar portion 30" refers to the center of the smallest circle that contains the polygon. For example, when the planar shape of the columnar portions 30 is a polygon, the center of the smallest circle that contains the polygon. When the planar shape of the columnar portions 30 is an ellipse, the center of the smallest circle that contains the ellipse.

[0022] As shown in FIG. 1, the columnar section 30 has a first semiconductor layer 32, a light emitting layer , and a second semiconductor layer .

[0023] The first semiconductor layer 32 is provided on the buffer layer 22. The first semiconductor layer 32 is provided between the substrate 10 and the light emitting layer 34. The first semiconductor layer 32 is a semiconductor layer of a first conductivity type. The first semiconductor layer 32 is, for example, an n-type GaN layer doped with Si.

[0024] The light emitting layer 34 is provided between the first semiconductor layer 32 and the second semiconductor layer 36. 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 that are not intentionally doped with impurities. 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 the well layer and the barrier layer.

[0025] There is no particular limitation on the number of well layers and barrier layers that make up the light-emitting layer 34. For example, only one well layer may be provided, in which case the light-emitting layer 34 has an SQW (Single Quantum Well) structure.

[0026] 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 second electrode 52. The second semiconductor layer 36 is a semiconductor layer of a second conductivity type different from the first conductivity type. The second semiconductor layer 36 is, for example, a p-type GaN layer doped with Mg. The first semiconductor layer 32 and the second semiconductor layer 36 are cladding layers that have the function of confining light in the light emitting layer 34.

[0027] Although not shown, an OCL (Optical Confinement Layer) made of an i-type InGaN layer and a GaN layer may be provided at least one between the first semiconductor layer 32 and the light emitting layer 34 and between the light emitting layer 34 and the second semiconductor layer 36. The second semiconductor layer 36 may also have an EBL (Electron Blocking Layer) made of a p-type AlGaN layer.

[0028] In the light-emitting device 100, a p-type second semiconductor layer 36, an i-type light-emitting layer 34 that is not intentionally doped with impurities, and an n-type first semiconductor layer 32 form a p-i-n diode. In the light-emitting device 100, when a forward bias voltage of the p-i-n diode is applied between the first electrode 50 and the second electrode 52, a current is injected into the light-emitting layer 34, causing recombination of electrons and holes in the light-emitting layer 34. This recombination generates light. The light generated in the light-emitting layer 34 propagates in the in-plane direction and forms a standing wave due to the photonic crystal effect of the multiple columnar portions 30. The light-emitting device 100 then emits the +1st-order diffracted light and the −1st-order diffracted light as laser light in the stacking direction.

[0029] Although not shown, a reflective layer may be provided between the substrate 10 and the buffer layer 22 or below the substrate 10. The reflective layer is, for example, a DBR (Distributed Bragg Reflector) layer. The reflective layer can reflect light generated in the light-emitting layer 34, and the light-emitting device 100 can emit light only from the second electrode 52 side.

[0030] The insulating layer 40 is provided on the side of the multiple columnar sections 30 opposite the substrate 10. In the illustrated example, the insulating layer 40 is provided on the buffer layer 22 and the first electrode layer 54. The insulating layer 40 surrounds the multiple columnar sections 30 when viewed from the stacking direction. A contact hole 42 is provided in the insulating layer 40. The contact hole 42 penetrates the insulating layer 40 in the stacking direction. The insulating layer 40 is, for example, a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer, a polyimide layer, or the like.

[0031] The first electrode 50 is provided on the buffer layer 22. In the illustrated example, a portion of the buffer layer 22 is recessed, and the first electrode 50 is provided in the recessed portion of the buffer layer 22. The buffer layer 22 may be in ohmic contact with the first electrode 50. The first electrode 50 is electrically connected to the first semiconductor layer 32. In the illustrated example, the first electrode 50 is electrically connected to the first semiconductor layer 32 via the buffer layer 22. The first electrode 50 may be, for example, a layer formed by laminating a Cr layer, a Ni layer, and an Au layer in this order from the buffer layer 22 side. The first electrode 50 is one of the electrodes for injecting a current into the light-emitting layer 34.

[0032] The second electrode 52 is provided on the second semiconductor layer 36. Furthermore, the second electrode 52 is provided on the insulating layer 40. The second semiconductor layer 36 may be in ohmic contact with the second electrode 52. The second electrode 52 is the other electrode for injecting current into the light-emitting layer 34. Details of the second electrode 52 will be described later.

[0033] As shown in FIG. 1 , the wiring 60 is connected to the second electrode 52. The wiring 60 is provided on the insulating layer 40. The wiring 60 is connected to a pad (not shown). Although not shown, the pad is connected, for example, to a wire bonding or FPC (Flexible Printed Circuits) electrically connected to a power supply. A transistor for controlling the current flowing through the wiring 60 may be provided between the power supply and the pad. The wiring 60 supplies current to the multiple columnar sections 30 via the second electrode 52. The wiring 60 may be made of a metal material such as copper or gold, or may be made of the same transparent electrode material as the second electrode layer 58. If the wiring 60 is made of a transparent electrode material, the wiring 60 may be provided integrally with the second electrode layer 58.

[0034] Although the above description has been given of an InGaN-based light emitting layer 34, various material systems that can emit 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.

[0035] Furthermore, the light emitting device 100 is not limited to a laser, but may also be an LED (Light Emitting Diode).

[0036] 1.2. Second electrode FIG. 3 is a cross-sectional view schematically showing the light emitting device 100 according to this embodiment, and is an enlarged view of region A shown in FIG.

[0037] As shown in FIGS. 1 to 3, the second electrode 52 has a first electrode layer 54 and a second electrode layer 58.

[0038] As shown in FIGS. 1 and 3, the first electrode layer 54 is provided on the plurality of columnar sections 30. The first electrode layer 54 is provided between the plurality of columnar sections 30 and the second electrode layer 58. The first electrode layer 54 is electrically connected to the second semiconductor layer 36. The first electrode layer 54 is in contact with the second semiconductor layer 36, for example. The second semiconductor layer 36 may be in ohmic contact with the first electrode layer 54. In the example shown in FIG. 2, the shape of the first electrode layer 54 is circular.

[0039] The first electrode layer 54 is made of, for example, a metal material. The first electrode layer 54 is, for example, a layer stacked in this order from the second semiconductor layer 36 side, of a Pd layer, a Pt layer, a Ni layer, and an Au layer, or is a single metal layer. The electrical resistivity of the first electrode layer 54 is lower than the electrical resistivity of the second electrode layer 58. This makes it possible to reduce the contact resistance between the second electrode 52 and the second semiconductor layer 36 compared to when the second electrode layer 58 is in contact with the second semiconductor layer 36.

[0040] As shown in FIG. 3, the first electrode layer 54 has a first portion 55 and a second portion 56.

[0041] The first portion 55 does not overlap the insulating layer 40 when viewed in the stacking direction. The first portion 55 is in contact with the second electrode layer 58. An upper surface 2 of the first portion 55 is in contact with the second electrode layer 58. The upper surface 2 is the surface of the first portion 55 opposite the substrate 10. In the example shown, the upper surface 2 is a flat surface. The first portion 55 is in contact with the second electrode layer 58 on the side opposite the substrate 10. The planar shape of the first portion 55 is, for example, a circle.

[0042] The thickness T1 of the first portion 55 is, for example, 5 nm or more and 100 nm or less, preferably 10 nm or more and 50 nm or less, and even more preferably 30 nm. Note that the "thickness T1 of the first portion 55" refers to the size of the first portion 55 in the direction of the perpendicular N to the upper surface of the columnar portion 30 on which the first portion 55 is provided, and this size is the minimum. In the illustrated example, the upper surface of the columnar portion 30 is formed by the c-plane, and the direction of the perpendicular N to the upper surface of the columnar portion 30 is the stacking direction. The upper surface of the columnar portion 30 is, for example, parallel to the upper surface of the substrate 10.

[0043] The first portion 55 has, for example, a constant thickness portion 55a and a varying thickness portion 55b. The constant thickness portion 55a has a constant thickness in an in-plane direction. The planar shape of the constant thickness portion 55a is, for example, a circle. The varying thickness portion 55b is connected to the constant thickness portion 55a and the second portion 56. The varying thickness portion 55b gradually increases in thickness from the constant thickness portion 55a toward the second portion 56. The thickness of the varying thickness portion 55b is greater than the thickness of the constant thickness portion 55a. The planar shape of the varying thickness portion 55b is, for example, a ring shape.

[0044] The second portion 56 surrounds the first portion 55 when viewed from the stacking direction. The planar shape of the second portion 56 is, for example, a ring shape. The second portion 56 overlaps the insulating layer 40 when viewed from the stacking direction. The second portion 56 is not in contact with the second electrode layer 58. The top surface 4 of the second portion 56 is not in contact with the second electrode layer 58. The top surface 4 is the surface of the second portion 56 opposite to the substrate 10. In the illustrated example, the top surface 4 is a flat surface. The second portion 56 is not in contact with the second electrode layer 58 on the side opposite to the substrate 10.

[0045] The thickness T2 of the second portion 56 is greater than the thickness T1 of the first portion 55. The thickness T2 of the second portion 56 is, for example, constant in the in-plane direction. The thickness T2 of the second portion 56 is, for example, 50 nm or more and 200 nm or less, preferably 70 nm or more and 150 nm or less, and more preferably 100 nm. Note that the "thickness T2 of the second portion 56" refers to the size of the second portion 56 in the direction of the perpendicular N to the top surface of the columnar section 30 on which the second portion 56 is provided, and this size is the minimum.

[0046] The sheet resistance (surface resistivity) of second portion 56 may be higher than the sheet resistance of connection portion 59 at which first portion 55 and second electrode layer 58 are connected, but is preferably the same as or lower than the sheet resistance of connection portion 59. Note that the in-plane size of first portion 55 and the in-plane size of second portion 56 are not particularly limited.

[0047] The second electrode layer 58 is connected to the first electrode layer 54. The second electrode layer 58 is provided on the side of the first electrode layer 54 opposite the substrate 10. The second electrode layer 58 is provided on the first electrode layer 54. Furthermore, the second electrode layer 58 is provided on the insulating layer 40 and on the inner surface of the contact hole 42. The "inner surface of the contact hole 42" refers to the side surface 41 of the insulating layer 40 that defines the contact hole 42. In the illustrated example, the side surface 41 is inclined with respect to the stacking direction. The insulating layer 40 is provided between the first electrode layer 54 and the second electrode layer 58. In the example shown in FIG. 2, the planar shape of the second electrode layer 58 is circular. The second electrode layer 58 is connected to wiring 60.

[0048] The thickness T3 of the second electrode layer 58 is, for example, 100 nm or more and 500 nm or less, preferably 200 nm or more and 400 nm or less, and more preferably 300 nm. The thickness T2 of the second portion 56 is, for example, smaller than the thickness T3 of the second electrode layer 58. Note that the "thickness T3 of the second electrode layer 58" refers to the size of the second electrode layer 58 in the direction of the perpendicular N to the top surface of the columnar section 30 on which the second electrode layer 58 is provided via the first electrode layer 54, and this size is the minimum.

[0049] The second electrode layer 58 is made of a transparent electrode material such as ITO (Indium Tin Oxide) or ZnO. The work function of the second electrode layer 58 is smaller than the work function of the first electrode layer 54. The work function of the first electrode layer 54 is smaller than the work function of the second semiconductor layer 36.

[0050] 1.3. Effects The device includes a substrate 10, a plurality of columnar sections 30 each having a first semiconductor layer 32 of a first conductivity type, a second semiconductor layer 36 of a second conductivity type different from the first conductivity type, and a light-emitting layer 34 provided between the first semiconductor layer 32 and the second semiconductor layer 36, a first electrode layer 54 electrically connected to the second semiconductor layer 36 of each of the plurality of columnar sections 30, and a second electrode layer 58 provided on the side of the first electrode layer 54 opposite the substrate 10 and having an electrical resistivity lower than that of the first electrode layer 54. The first electrode layer 54 has a first portion 55 in contact with the second electrode layer 58 on the side opposite the substrate 10, and a second portion 56 not in contact with the second electrode layer 58 on the side opposite the substrate 10 and having a thickness greater than that of the first portion 55.

[0051] Therefore, in the light-emitting device 100, the difference between the thickness of the connection portion 59 between the first portion 55 and the second electrode layer 58 and the thickness of the second portion 56 can be made smaller than when the thickness of the second portion is the same as that of the first portion. This reduces the difference in sheet resistance between the connection portion 59 and the sheet resistance of the second portion 56. Therefore, when viewed from the stacking direction, the difference in the amount of injection current between the columnar portion 30 overlapping the connection portion 59 and the columnar portion 30 overlapping the second portion 56 can be made smaller. As a result, light emission unevenness can be reduced. Furthermore, changes in light emission wavelength caused by differences in the amount of injection current can be suppressed.

[0052] In the light emitting device 100, the work function of the first electrode layer 54 is smaller than the work function of the second semiconductor layer 36, and the work function of the second electrode layer 58 is smaller than the work function of the first electrode layer 54. Therefore, in the light emitting device 100, the energy barrier between the first electrode layer 54 and the second semiconductor layer 36 and the energy barrier between the second electrode layer 58 and the first electrode layer 54 can be reduced in stages. This makes it easier for current to flow from the second electrode layer 58 to the second semiconductor layer 36.

[0053] In the light-emitting device 100, the thickness T2 of the second portion 56 is smaller than the thickness T3 of the second electrode layer 58, the first electrode layer 54 is made of a metal material, and the second electrode layer 58 is made of a transparent electrode material. Therefore, in the light-emitting device 100, the amount of light that passes through the second portion 56 can be increased compared to when, for example, the thickness T2 is greater than the thickness T3.

[0054] 2. Light-emitting device manufacturing method Next, a method for manufacturing the light emitting device 100 according to this embodiment will be described with reference to the drawings. Figures 4 to 6 are cross-sectional views that schematically show the manufacturing process for the light emitting device 100 according to this embodiment.

[0055] 4, a buffer layer 22 is epitaxially grown on a substrate 10. Examples of methods for epitaxial growth include MOCVD (Metal Organic Chemical Vapor Deposition) and MBE (Molecular Beam Epitaxy).

[0056] Next, a mask layer (not shown) is formed on the buffer layer 22. The mask layer is formed by, for example, electron beam evaporation or sputtering.

[0057] Next, using the mask layer as a mask, the first semiconductor layer 32, the light emitting layer 34, and the second semiconductor layer 36 are epitaxially grown in this order on the buffer layer 22. Examples of methods for epitaxial growth include MOCVD and MBE. This process allows the formation of multiple columnar sections 30. After the formation of the multiple columnar sections 30, portions of the buffer layer 22 may be recessed by etching.

[0058] 5, a first electrode layer 54 is formed on the plurality of columnar sections 30. The first electrode layer 54 is formed by, for example, sputtering, vacuum deposition, or the like.

[0059] Next, the insulating layer 40 is formed so as to cover the plurality of columnar sections 30 and the first electrode layer 54. The insulating layer 40 is formed by a method such as spin coating or CVD (Chemical Vapor Deposition).

[0060] As shown in FIG. 6, the insulating layer 40 is patterned to form a contact hole 42 in the insulating layer 40. The patterning is performed by, for example, photolithography and etching. During patterning, overetching can be performed to engrave a portion of the first electrode layer 54, thereby forming the first electrode layer 54 having a first portion 55 and a second portion 56. The etching can be either dry etching or wet etching, but dry etching has a higher etching rate for the first electrode layer 54 and can therefore shorten the processing time.

[0061] 1, a second electrode layer 58 is formed on the first portion 55 of the first electrode layer 54, on the inner surface of the contact hole 42, and on the upper surface of the insulating layer 40. The second electrode layer 58 is formed by, for example, a sputtering method or a vacuum deposition method. This process allows the second electrode 52 having the first electrode layer 54 and the second electrode layer 58 to be formed.

[0062] Next, the first electrode 50 is formed on the buffer layer 22. The first electrode 50 is formed by, for example, a sputtering method or a vacuum deposition method. The order of the step of forming the first electrode 50 and the step of forming the second electrode layer 58 is not particularly limited.

[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 200 according to a first modified example of this embodiment will be described with reference to the drawings. Fig. 7 is a cross-sectional view that schematically shows the light emitting device 200 according to the first modified example of this embodiment.

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

[0066] In the light emitting device 100 described above, as shown in FIG. 3, the upper surface of the columnar section 30 is formed by the c-plane.

[0067] In contrast, in the light emitting device 200, as shown in Fig. 7, the upper surface of the columnar section 30 is configured as a facet surface. The upper surface of the columnar section 30 is inclined with respect to the upper surface of the substrate 10. The direction of the normal N to the upper surface of the columnar section 30 is inclined with respect to the stacking direction. By controlling the temperature and film formation rate during epitaxial growth of the columnar section 30, the upper surface of the columnar section 30 can be configured as a facet surface or a c-plane.

[0068] 3.2. Second Variant Next, a light emitting device 300 according to a second modification of this embodiment will be described with reference to the drawings. Figure 8 is a cross-sectional view that schematically shows the light emitting device 300 according to the second modification of this embodiment.

[0069] As shown in FIG. 8, the light emitting device 300 differs from the above-described light emitting device 100 in that the stacked body 20 includes a third semiconductor layer 70.

[0070] The third semiconductor layer 70 is provided on the multiple columnar sections 30. The third semiconductor layer 70 is provided across the multiple columnar sections 30. The third semiconductor layer 70 is provided between the multiple columnar sections 30 and the first electrode layer 54. The third semiconductor layer 70 may be in ohmic contact with the first electrode layer 54.

[0071] The third semiconductor layer 70 is a semiconductor layer of the second conductivity type, which is the same conductivity type as the second semiconductor layer 36. The third semiconductor layer 70 is, for example, a p-type GaN layer doped with Mg. The second electrode 52 is electrically connected to the second semiconductor layer 36 via the third semiconductor layer 70. The third semiconductor layer 70 is formed by, for example, epitaxial growth. Examples of methods for epitaxial growth include MOCVD and MBE.

[0072] The light emitting device 300 has a third semiconductor layer 70 of the second conductivity type provided between the multiple columnar sections 30 and the first electrode layer 54. Therefore, in the light emitting device 300, it is possible to prevent the electrode material from penetrating between adjacent columnar sections 30 when the first electrode layer 54 is formed. Furthermore, it is possible to increase the distance between the light emitting layer 34 and the first electrode layer 54 compared to when the third semiconductor layer 70 is not provided. Therefore, it is possible to reduce the amount of light absorbed by the first electrode layer 54 when light generated in the light emitting layer 34 propagates in the in-plane direction.

[0073] 3.3. Third Variant Next, a light emitting device 400 according to a third modification of this embodiment will be described with reference to the drawings. Fig. 9 is a cross-sectional view that schematically shows the light emitting device 400 according to the third modification of this embodiment.

[0074] 9, in the light emitting device 400, the thickness T1 of the first portion 55 of the first electrode layer 54 is smaller than that of the light emitting device 100. In the illustrated example, the thickness T1 of the first portion 55 is smaller than the difference ΔT between the thickness T2 of the second portion 56 and the thickness T1 of the first portion 55. For example, by increasing the overetching time when forming the contact hole 42, the thickness T1 can be made smaller than the difference ΔT.

[0075] In the light emitting device 400, the thickness T1 of the first portion 55 is smaller than the difference ΔT between the thickness T2 of the second portion 56 and the thickness T1 of the first portion 55. Therefore, the sheet resistance of the first portion 55 can be made higher than when the thickness T1 is larger than the difference ΔT.

[0076] 4. Projector Next, a projector according to this embodiment will be described with reference to the drawings. Fig. 10 is a diagram schematically showing a projector 800 according to this embodiment.

[0077] The projector 800 includes, for example, a light emitting device 100 as a light source.

[0078] Projector 800 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 simplified in FIG. 10.

[0079] The projector 800 further includes, within the housing, a first optical element 802R, a second optical element 802G, a third optical element 802B, a first light modulation device 804R, a second light modulation device 804G, a third light modulation device 804B, and a projection device 808. The first light modulation device 804R, the second light modulation device 804G, and the third light modulation device 804B are, for example, transmissive liquid crystal light valves. The projection device 808 is, for example, a projection lens.

[0080] Light emitted from red light source 100R is incident on first optical element 802R. The light emitted from red light source 100R is collected by first optical element 802R. Note that first optical element 802R may have a function other than collecting light. The same applies to second optical element 802G and third optical element 802B, which will be described later.

[0081] The light collected by the first optical element 802R is incident on the first light modulation device 804R. The first light modulation device 804R modulates the incident light in accordance with image information. The projection device 808 then enlarges the image formed by the first light modulation device 804R and projects it onto a screen 810.

[0082] The light emitted from green light source 100G is incident on second optical element 802G. The light emitted from green light source 100G is collected by second optical element 802G.

[0083] The light collected by the second optical element 802G is incident on the second light modulation device 804G. The second light modulation device 804G modulates the incident light in accordance with image information. The projection device 808 then enlarges the image formed by the second light modulation device 804G and projects it onto the screen 810.

[0084] The light emitted from blue light source 100B is incident on third optical element 802B. The light emitted from blue light source 100B is collected by third optical element 802B.

[0085] The light collected by the third optical element 802B enters the third light modulation device 804B. The third light modulation device 804B modulates the incident light in accordance with image information. The projection device 808 then enlarges the image formed by the third light modulation device 804B and projects it onto the screen 810.

[0086] The projector 800 may also have a cross dichroic prism 806 that combines the light emitted from the first light modulation device 804R, the second light modulation device 804G, and the third light modulation device 804B and guides the combined light to the projection device 808.

[0087] The three colored lights modulated by the first light modulation device 804R, the second light modulation device 804G, and the third light modulation device 804B enter the cross dichroic prism 806. The cross dichroic prism 806 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. These dielectric multilayer films combine the three colored lights to form light that represents a color image. The combined light is then projected onto a screen 810 by a projection device 808, and an enlarged image is displayed.

[0088] 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 804R, second light modulation device 804G, and third light modulation device 804B, by controlling light emitting device 100 as pixels of the image in accordance with image information. Then, projection device 808 may enlarge and project the image formed by red light source 100R, green light source 100G, and blue light source 100B onto screen 810.

[0089] In the above example, a transmissive liquid crystal light valve is used as the light modulation device, but a light valve other than a liquid crystal light valve or a reflective light valve may also be used. Examples of such light valves include a reflective liquid crystal light valve and a digital micromirror device. The configuration of the projection device can be changed as appropriate depending on the type of light valve used.

[0090] 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.

[0091] 5. Display Next, a display according to this embodiment will be described with reference to the drawings. Fig. 11 is a plan view schematically showing a display 900 according to this embodiment. Fig. 12 is a cross-sectional view schematically showing the display 900 according to this embodiment. For convenience, Fig. 11 illustrates an X-axis and a Y-axis as two axes that are orthogonal to each other.

[0092] The display 900 includes, for example, a light emitting device 100 as a light source.

[0093] The display 900 is a display device that displays images. Images include images that display only text information. The display 900 is a self-luminous display. As shown in FIGS. 11 and 12 , the display 900 has a circuit board 910, a lens array 920, and a heat sink 930.

[0094] A drive circuit for driving the light emitting device 100 is mounted on the circuit board 910. The drive circuit is, for example, a circuit including a CMOS (Complementary Metal Oxide Semiconductor). The drive 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 910 is disposed on the circuit board 910.

[0095] The circuit board 910 has a display area 912 , a data line driving circuit 914 , a scanning line driving circuit 916 , and a control circuit 918 .

[0096] The display area 912 is made up of a plurality of pixels P. In the illustrated example, the pixels P are arranged along the X-axis and Y-axis.

[0097] Although not shown, a plurality of scanning lines and a plurality of data lines are provided on the circuit board 910. 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 916. The data lines are connected to a data line driving circuit 914. Pixels P are provided at intersections of the scanning lines and the data lines.

[0098] One pixel P includes, for example, one light-emitting device 100, one lens 922, and a pixel circuit (not shown). The pixel circuit includes 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 either the source or the drain is connected to a data line.

[0099] The data line driving circuit 914 and the scanning line driving circuit 916 are circuits that control the driving of the light emitting devices 100 that constitute the pixels P. The control circuit 918 controls the display of images.

[0100] Image data is supplied from a higher-level circuit to the control circuit 918. The control circuit 918 supplies various signals based on the image data to the data line driving circuit 914 and the scanning line driving circuit 916.

[0101] When the scanning line driving circuit 916 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 914 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 accordance with the data signal.

[0102] The lens array 920 has a plurality of lenses 922. For example, one lens 922 is provided for each light emitting device 100. Light emitted from the light emitting device 100 is incident on one lens 922.

[0103] The heat sink 930 is in contact with the circuit board 910. The material of the heat sink 930 is, for example, a metal such as copper or aluminum. The heat sink 930 dissipates heat generated by the light emitting device 100.

[0104] The light-emitting devices according to the above-described embodiments can be used for purposes other than projectors and displays. Examples of uses other than projectors and displays include indoor and outdoor lighting, laser printers, scanners, in-vehicle lights, light-using sensing devices, communication devices, and other light sources. Furthermore, the light-emitting devices according to the above-described embodiments can be used as display devices for head-mounted displays.

[0105] 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 combined as appropriate.

[0106] 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 effects. The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations that add publicly known technology to the configurations described in the embodiments.

[0107] The following can be derived from the above-described embodiment and modifications.

[0108] One aspect of the light emitting device is A substrate; a plurality of columnar sections each having a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, and a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; an electrode including: a first electrode layer electrically connected to the second semiconductor layer of each of the plurality of columnar portions; and a second electrode layer provided on the opposite side of the first electrode layer from the substrate, the second electrode layer having an electrical resistivity lower than that of the first electrode layer; and The first electrode layer has a first portion that contacts the second electrode layer on the side opposite the substrate, and a second portion that does not contact the second electrode layer on the side opposite the substrate and has a thickness greater than that of the first portion.

[0109] According to this light emitting device, it is possible to reduce unevenness in light emission.

[0110] In one embodiment of the light emitting device, a work function of the first electrode layer is smaller than a work function of the second semiconductor layer; The second electrode layer may have a work function smaller than the work function of the first electrode layer.

[0111] According to this light emitting device, it is possible to facilitate the flow of current from the second electrode layer to the second semiconductor layer.

[0112] In one embodiment of the light emitting device, The thickness of the first portion may be smaller than the difference between the thickness of the second portion and the thickness of the first portion.

[0113] According to this light emitting device, the sheet resistance of the first portion can be increased.

[0114] In one embodiment of the light emitting device, The semiconductor device may further include a third semiconductor layer of the second conductivity type provided between the plurality of columnar portions and the first electrode layer.

[0115] According to this light emitting device, when the first electrode layer is formed, it is possible to prevent the electrode material from entering between the adjacent columnar portions.

[0116] In one embodiment of the light emitting device, the thickness of the second portion is smaller than the thickness of the second electrode layer; the first electrode layer is made of a metal material, The second electrode layer may be made of a transparent electrode material.

[0117] According to this light emitting device, the amount of light that passes through the second portion can be increased.

[0118] One aspect of the projector is The light emitting device has one aspect.

[0119] One embodiment of the display is The light emitting device has one aspect. [Explanation of symbols]

[0120] 2, 4...top surface, 10...substrate, 20...laminated body, 22...buffer layer, 30...columnar portion, 32...first semiconductor layer, 34...light-emitting layer, 36...second semiconductor layer, 40...insulating layer, 41...side surface, 42...contact hole, 50...first electrode, 52...second electrode, 54...first electrode layer, 55...first portion, 55a...constant thickness portion, 55b...variable thickness portion, 56...second portion, 58...second electrode layer, 59...connection portion, 60...wiring, 70...third semiconductor layer, 100, 200, 300, 400...light-emitting device, 800...project vector, 802R...first optical element, 802G...second optical element, 802B...third optical element, 804R...first optical modulation device, 804G...second optical modulation device, 804B...third optical modulation device, 806...cross dichroic prism, 808...projection device, 810...screen, 900...display, 910...circuit board, 912...display area, 914...data line drive circuit, 916...scanning line drive circuit, 918...control circuit, 920...lens array, 922...lens, 930...heat sink

Claims

1. A substrate; a plurality of columnar sections each having a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, and a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; an electrode including: a first electrode layer electrically connected to the second semiconductor layer of each of the plurality of columnar portions and transmitting light emitted from the light emitting layer; and a second electrode layer provided on the opposite side of the first electrode layer from the substrate, having a sheet resistance smaller than that of the first electrode layer and transmitting light emitted from the light emitting layer, the electrode injecting a current into the light emitting layer of each of the plurality of columnar portions; and the first electrode layer has a first portion in contact with the second electrode layer on the side opposite to the substrate, and a second portion not in contact with the second electrode layer on the side opposite to the substrate and having a thickness greater than that of the first portion; the first portion overlaps with the second electrode layer in a plan view, the first portion and the second portion overlap with the light-emitting layer of each of the plurality of columnar portions in a plan view; the second electrode layer overlaps with the light-emitting layers of the plurality of columnar portions in a plan view.

2. In claim 1, a work function of the first electrode layer is smaller than a work function of the second semiconductor layer; A light emitting device, wherein the second electrode layer has a work function smaller than the work function of the first electrode layer.

3. In claim 1 or 2, A light emitting device, wherein the thickness of the first portion is smaller than the difference between the thickness of the second portion and the thickness of the first portion.

4. In any one of claims 1 to 3, a third semiconductor layer of the second conductivity type provided between the plurality of columnar portions and the first electrode layer;

5. In any one of claims 1 to 4, the thickness of the second portion is smaller than the thickness of the second electrode layer; the first electrode layer is made of a metal material, The second electrode layer is made of a transparent electrode material.

6. A projector comprising the light emitting device according to claim 1 .

7. A display comprising a light-emitting device according to any one of claims 1 to 5.

Images