Light-emitting device, projector and display

Abstract

The present invention provides a light-emitting device capable of reducing leakage of current between a first semiconductor layer and a second semiconductor layer. A light-emitting device comprises: a substrate; and a stacked body, which is arranged on the substrate and has a plurality of columnar parts, the columnar part having: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type, which is different from the first conductivity type; and a light-emitting layer, which is arranged between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer is arranged between the substrate and the light-emitting layer, the light-emitting layer has a c-plane and a small plane, the second semiconductor layer is arranged on the c-plane and the small plane, the first semiconductor layer has a first part and a second part with a smaller diameter than the first part, the second part is arranged between the substrate and the first part, the c-plane overlaps with the second part when viewed from the stacking direction of the first semiconductor layer and the light-emitting layer, and the diameter of the c-plane is smaller than the diameter of the second part.

Description

Technical Field

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

[0002] Semiconductor lasers are expected to be the next generation of high-brightness light sources. Among them, semiconductor lasers using nanorods are expected to achieve high-output light emission at a narrow radiation angle by using the photonic crystal effect of the nanorods.

[0003] For example, Patent Document 1 describes a light-emitting device including a columnar portion, wherein the columnar portion has: a first semiconductor layer, a second semiconductor layer having a conductivity type different from that of the first semiconductor layer, and a light-emitting layer disposed between the first semiconductor layer and the second semiconductor layer. In Patent Document 1, the first semiconductor layer and the light-emitting layer have a c-plane and a facet.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-57640 Summary of the invention

[0005] In a light emitting device including a columnar portion as described above, crystal defects are likely to occur on the side surfaces of the columnar portion. The crystal defects may serve as a leakage path for current between the n-type semiconductor layer and the p-type semiconductor layer.

[0006] One aspect of the light emitting device of the present invention includes:

[0007] substrate; and

[0008] A laminated body is provided on the substrate and has a plurality of columnar portions.

[0009] The columnar portion has:

[0010] a first semiconductor layer of a first conductivity type;

[0011] a second semiconductor layer of a second conductivity type different from the first conductivity type; and

[0012] a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer,

[0013] The first semiconductor layer is disposed between the substrate and the light emitting layer.

[0014] The light-emitting layer has a c-plane and a facet,

[0015] The second semiconductor layer is disposed on the c-plane and the small plane,

[0016] The first semiconductor layer comprises a first portion and a second portion having a diameter smaller than that of the first portion.

[0017] The second portion is disposed between the substrate and the first portion,

[0018] In a plan view from the stacking direction of the first semiconductor layer and the light emitting layer, the c-plane overlaps with the second portion, and a diameter of the c-plane is smaller than a diameter of the second portion.

[0019] One aspect of a projector according to the present invention includes one aspect of the above-mentioned light emitting device.

[0020] One aspect of a display according to the present invention includes one aspect of the above-mentioned light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional view schematically showing the light emitting device of this embodiment.

[0022] Figure 2 FIG. 1 is a cross-sectional view schematically showing a columnar portion of the light emitting device according to the present embodiment.

[0023] Figure 3 It is a plan view schematically showing a columnar portion of the light emitting device according to the present embodiment.

[0024] Figure 4 It is a cross-sectional view schematically showing the manufacturing process of the light emitting device of this embodiment.

[0025] Figure 5 It is a cross-sectional view schematically showing the manufacturing process of the light emitting device of this embodiment.

[0026] Figure 6 It is a diagram schematically showing a projector according to this embodiment.

[0027] Figure 7 It is a plan view schematically showing a display according to this embodiment.

[0028] Figure 8 It is a cross-sectional view schematically showing the display according to this embodiment.

[0029] Explanation of symbols

[0030] 2: Step difference

[0031] 10: Substrate

[0032] 20: Laminated

[0033] 22: Buffer layer

[0034] 24: Insulation layer

[0035] 25: Opening

[0036] 30: Columnar part

[0037] 32: First semiconductor layer

[0038] 32a: Part I

[0039] 32b: Part 2

[0040] 33: Well layer

[0041] 33a: c side

[0042] 33b: Facet

[0043] 34: Luminous layer

[0044] 35: Barrier layer

[0045] 35a: c side

[0046] 35b: Facet

[0047] 36: Second semiconductor layer

[0048] 36a: High concentration part

[0049] 36b: Low concentration part

[0050] 40: First electrode

[0051] 42: Second electrode

[0052] 100: Light-emitting device

[0053] 100R: Red light source

[0054] 100G: Green light source

[0055] 100B: Blue light source

[0056] 900: Projector

[0057] 902R: First optical element

[0058] 902G: Secondary optical element

[0059] 902B: Third optical element

[0060] 904R: First light modulation device

[0061] 904G: Second optical modulation device

[0062] 904B: Third light modulation device

[0063] 906: Cross dichroic prism

[0064] 908: Projection Device

[0065] 910: Screen

[0066] 1000: Display

[0067] 1010: Circuit board

[0068] 1012: Display area

[0069] 1014: Data line driving circuit

[0070] 1016: Scan line driving circuit

[0071] 1018: Control circuit

[0072] 1020: Lens array

[0073] 1022: Lens

[0074] 1030: Radiator DETAILED DESCRIPTION

[0075] Hereinafter, the preferred embodiments of the present invention will be described in detail using the accompanying drawings. In addition, the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the structures described below are essential components of the present invention.

[0076] 1. Light-emitting device

[0077] 1.1. Overall structure

[0078] First, a light emitting device according to this embodiment will be described with reference to the drawings. Figure 1 2 is a cross-sectional view schematically showing the light emitting device 100 according to the present embodiment.

[0079] like Figure 1 As shown, the light emitting device 100 includes a substrate 10, a stacked body 20, a first electrode 40, and a second electrode 42. The light emitting device 100 is, for example, a semiconductor laser.

[0080] The substrate 10 is, for example, a Si substrate, a GaN substrate, a sapphire substrate, a SiC substrate, or the like.

[0081] The laminated body 20 is provided on the substrate 10. In the example shown in the figure, the laminated body 20 is provided on the substrate 10. The laminated body 20 has a buffer layer 22 and a columnar portion 30, for example.

[0082] In this specification, in the stacking direction of the first semiconductor layer 32 and the light emitting layer 34 (hereinafter, also referred to as the "stacking direction"), with the light emitting layer 34 as a reference, the direction from the light emitting layer 34 toward the second semiconductor layer 36 is set as "upward", and the direction from the light emitting layer 34 toward the first semiconductor layer 32 is set as "downward" for description. In addition, the direction orthogonal to the stacking direction is also referred to as the "in-plane direction".

[0083] The buffer layer 22 is disposed on the substrate 10 . The buffer layer 22 is, for example, an n-type GaN layer doped with Si. An insulating layer 24 is disposed on the buffer layer 22 .

[0084] The insulating layer 24 functions as a mask layer for forming the columnar portion 30. The insulating layer 24 has a plurality of openings 25. The openings 25 are holes that penetrate the insulating layer 24. The insulating layer 24 is, for example, a silicon oxide layer, a silicon nitride layer, a silicon layer, a titanium oxide layer, a titanium nitride layer, an aluminum oxide layer, a tantalum oxide layer, a hafnium oxide layer, a germanium layer, or the like.

[0085] The columnar portion 30 is provided on the buffer layer 22. The columnar portion 30 has a columnar shape protruding 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 nanocolumn. The planar shape of the columnar portion 30 is, for example, a polygon or a circle.

[0086] The diameter of the columnar portion 30 is, for example, not less than 50 nm and not more than 500 nm. By setting the diameter of the columnar portion 30 to not more than 500 nm, a high-quality crystalline light-emitting layer 34 can be obtained, and the inherent strain in the light-emitting layer 34 can be reduced. As a result, the light generated in the light-emitting layer 34 can be amplified with high efficiency.

[0087] In addition, the so-called "diameter of the columnar portion" is the diameter when the planar shape of the columnar portion 30 is a circle, and is the diameter of the smallest circle when the planar shape of the columnar portion 30 is not a circle. For example, the diameter of the columnar portion 30 is the diameter of the smallest circle that includes the polygon inside when the planar shape of the columnar portion 30 is a polygon, and is the diameter of the smallest circle that includes the ellipse inside when the planar shape of the columnar portion 30 is an ellipse. In addition, the diameter of each layer constituting the columnar portion is similarly the diameter when the planar shape of each layer is a circle, and is the diameter of the smallest circle that includes the ellipse when the planar shape of each layer is not a circle.

[0088] There are multiple columnar portions 30. The interval between adjacent columnar portions 30 is, for example, greater than 1 nm and less than 500 nm. When viewed from the stacking direction, the multiple columnar portions 30 are arranged at a specified interval in a specified direction. The multiple columnar portions 30 are, for example, arranged in a triangular lattice or a square lattice. The multiple columnar portions 30 can show the effect of a photonic crystal.

[0089] In addition, the so-called "pitch between columnar portions" refers to the distance between the centers of the columnar portions 30 adjacent to each other along a predetermined direction. The so-called "center of the columnar portion" is the center of the circle when the planar shape of the columnar portion 30 is a circle, and is the center of the smallest circle when the planar shape of the columnar portion 30 is not a circle. For example, the center of the columnar portion 30 is the center of the smallest circle that includes the polygon when the planar shape of the columnar portion 30 is a polygon, and is the center of the smallest circle that includes the ellipse when the planar shape of the columnar portion 30 is an ellipse.

[0090] The columnar portion 30 includes a first semiconductor layer 32, a light emitting layer 34, and a second semiconductor layer 36. The detailed shape and the like of the columnar portion 30 will be described later.

[0091] The first semiconductor layer 32 is disposed on the buffer layer 22. The first semiconductor layer 32 is disposed between the substrate 10 and the light emitting layer 34. The first semiconductor layer 32 is, for example, an n-type GaN layer doped with Si.

[0092] The light emitting layer 34 is disposed on the first semiconductor layer 32. The light emitting layer 34 is disposed between the first semiconductor layer 32 and the second semiconductor layer 36. The light emitting layer 34 generates light by injecting current. The light emitting layer 34, for example, has a well layer 33 and a barrier layer 35. The well layer 33 and the barrier layer 35 are i-type semiconductor layers that are not intentionally doped with impurities. The well layer 33 is, for example, an InGaN layer. The barrier layer 35 is, for example, a GaN layer. The light emitting layer 34 has a multiple quantum well (MQW) structure including the well layer 33 and the barrier layer 35.

[0093] In addition, there is no particular limitation on the number of well layers 33 and barrier layers 35 constituting the light emitting layer 34. For example, only one well layer 33 may be provided, in which case the light emitting layer 34 has a single quantum well (SQW) structure.

[0094] The second semiconductor layer 36 is provided on the light emitting layer 34. The second semiconductor layer 36 is a layer of conductivity type different from that of the first semiconductor layer 32. 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 having a function of confining light in the light emitting layer 34.

[0095] In addition, although not shown, an optical confinement layer (OCL) including an i-type InGaN layer may be provided between the first semiconductor layer 32 and the light emitting layer 34. In addition, although not shown, an OCL including an i-type InGaN layer may be provided between the light emitting layer 34 and the second semiconductor layer 36. In addition, the second semiconductor layer 36 may also have an electron blocking layer (EBL) including a p-type AlGaN layer.

[0096] In the light emitting device 100, a pin diode is formed by a p-type second semiconductor layer 36, an i-type light emitting layer 34 not doped with impurities, and an n-type first semiconductor layer 32. In the light emitting device 100, if a forward bias voltage of the pin diode is applied between the first electrode 40 and the second electrode 42, current is injected into the light emitting layer 34, and recombination of electrons and holes occurs in the light emitting layer 34. Light emission is generated by the recombination. The light generated in the light emitting layer 34 propagates in the in-plane direction, forms a standing wave by the effect of the photonic crystal based on the plurality of columnar portions 30, receives gain through the light emitting layer 34, and performs laser oscillation. Then, the light emitting device 100 emits +1st order diffracted light and -1st order diffracted light as laser light in the stacking direction.

[0097] In addition, although not shown in the figure, 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 distributed Bragg reflector (DBR) layer. The reflective layer can reflect the light generated in the light-emitting layer 34, so that the light-emitting device 100 can emit light only from the second electrode 42 side.

[0098] The first electrode 40 is provided on the buffer layer 22. The buffer layer 22 may be in ohmic contact with the first electrode 40. The first electrode 40 is electrically connected to the first semiconductor layer 32. In the example shown in the figure, the first electrode 40 is electrically connected to the first semiconductor layer 32 via the buffer layer 22. The first electrode 40 is one of the electrodes for injecting current into the light emitting layer 34. As the first electrode 40, for example, an electrode stacked in the order of a Cr layer, a Ni layer, and an Au layer from the buffer layer 22 side is used.

[0099] The second electrode 42 is provided on the second semiconductor layer 36. The second electrode 42 is provided on the side of the stacked body 20 opposite to the substrate 10. The second electrode 42 is electrically connected to the second semiconductor layer 36. The second semiconductor layer 36 can be in ohmic contact with the second electrode 42. The second electrode 42 is another electrode for injecting current into the light emitting layer 34. As the second electrode 42, for example, indium tin oxide (ITO) or the like is used.

[0100] 1.2. Detailed shape of columnar portion, etc.

[0101] Figure 2 2 is a cross-sectional view schematically showing the columnar portion 30 . Figure 3 30 is a schematic plan view of the columnar portion 30. Figure 3 , for the sake of convenience, only the second portion 32 b of the first semiconductor layer 32 , the light emitting layer 34 , and the c-plane 35 a of the light emitting layer 34 are illustrated.

[0102] The first semiconductor layer 32 , the light emitting layer 34 , and the second semiconductor layer 36 are, for example, group III nitride semiconductors and have a wurtzite crystal structure.

[0103] like Figure 2 As shown, the first semiconductor layer 32 has a first portion 32 a and a second portion 32 b .

[0104] The first portion 32a is provided between the second portion 32b and the light emitting layer 34. The first portion 32a is provided on the second portion 32b and on the insulating layer 24. The first portion 32a has a c-plane 33a and a facet 33b. The c-plane 33a is parallel to the main surface of the substrate 10, and the facet 33b is inclined relative to the main surface of the substrate 10. The main surface of the substrate 10 is the surface on which the buffer layer 22 is formed.

[0105] The second portion 32b is disposed between the substrate 10 and the first portion 32a. Figure 1 In the example shown, the second portion 32b is disposed on the buffer layer 22. Figure 1 As shown, the second portion 32b is disposed in the opening 25 of the insulating layer 24. The insulating layer 24 is disposed between the substrate 10 and the first portion 32a.

[0106] In a top view from the stacking direction (hereinafter, also referred to as "in a top view"), the first portion 32a overlaps the second portion 32b. In a top view, the second portion 32b is provided only on the inner side of the outer edge of the first portion 32a. The diameter D2 of the second portion 32b is smaller than the diameter D1 of the first portion 32a. Since the diameter D1 of the first portion 32a is different from the diameter D2 of the second portion 32b, a step 2 is provided at the boundary between the first portion 32a and the second portion 32b.

[0107] In addition, the so-called "diameter of the first portion" is the diameter when the planar shape of the first portion 32a is a circle, and is the diameter of the smallest included circle when the planar shape of the first portion 32a is not a circle. Similarly, the so-called "diameter of the second portion" is the diameter when the planar shape of the second portion 32b is a circle, and is the diameter of the smallest included circle when the planar shape of the second portion 32b is not a circle.

[0108] The light emitting layer 34 has a c-plane 35a and a small plane 35b. In a top view, the c-plane 35a is surrounded by the small plane 35b. Figure 3 As shown, in a plan view, the c-surface 35a overlaps with the second portion 32b, and the diameter D3 of the c-surface 35a is smaller than the diameter D2 of the second portion 32b. For example, in a plan view, the c-surface 35a is only provided on the inner side of the outer edge of the second portion 32b. In a plan view, the entire area of ​​the c-surface 35a overlaps with the second portion 32b.

[0109] In addition, the “diameter of the c-surface” refers to the diameter when the shape of the c-surface 35a is a circle, and refers to the diameter of the smallest including circle when the shape of the c-surface 35a is not a circle.

[0110] The second semiconductor layer 36 is provided on the c-plane 35a and the facet 35b of the light emitting layer 34. Although not shown, when other layers such as OCL exist between the light emitting layer 34 and the second semiconductor layer 36, the second semiconductor layer 36 may also be provided on the c-plane 35a and the facet 35b via the other layers.

[0111] The impurity concentration of the second semiconductor layer 36 overlapping with the c-plane 35a in a plan view is greater than the impurity concentration of the second semiconductor layer 36 overlapping with the facet 35b in a plan view. That is, the second semiconductor layer 36 has a high concentration portion 36a with a high impurity concentration and a low concentration portion 36b with an impurity concentration lower than that of the high concentration portion 36a, the high concentration portion 36a overlaps with the c-plane 35a in a plan view, and the low concentration portion 36b overlaps with the facet 35b in a plan view. When the second semiconductor layer 36 is epitaxially grown, the impurity concentration of the second semiconductor layer 36 grown on the c-plane 35a is higher than the impurity concentration of the second semiconductor layer 36 grown on the facet 35b. Thus, a second semiconductor layer 36 having a high concentration portion 36a and a low concentration portion 36b is formed.

[0112] The high concentration portion 36a is formed, for example, along the central axis of the columnar portion 30, and the low concentration portion 36b surrounds the high concentration portion 36a in a plan view. The impurity concentration of the high concentration portion 36a is, for example, 5×10 19 cm -3 The impurity concentration of the low concentration portion 36b is, for example, 2×10 19 cm -3 When the impurity concentration of the second semiconductor layer 36 becomes higher, that is, when the concentration of Mg doped in GaN becomes higher, the resistance becomes lower.

[0113] The diameter D4 of the light emitting layer 34 is larger than the diameter D3 of the c-plane 35a and the diameter D2 of the second portion 32b. For example, in a plan view, the second portion 32b is provided only inside the outer edge of the light emitting layer 34.

[0114] The “diameter of the light-emitting layer” refers to the diameter when the planar shape of the light-emitting layer 34 is a circle, and refers to the diameter of the smallest included circle when the planar shape of the light-emitting layer 34 is not a circle.

[0115] In the above, the light emitting layer 34 of the InGaN system is described, but various material systems that can emit light by injecting current can be used as the light emitting layer 34 according to the wavelength of the emitted light. For example, semiconductor materials such as AlGaN system, AlGaAs system, InGaAs system, InGaAsP system, InP system, GaP system, and AlGaP system can be used.

[0116] In the above description, the light emitting device 100 is described as a surface emitting laser utilizing the photonic crystal effect, but the light emitting device 100 may be a light emitting diode (LED) or a resonant light emitting diode or other light emitting device.

[0117] In addition, in the above, Figure 2 In the embodiment, the diameters of the first portion 32a of the first semiconductor layer 32, the light emitting layer 34, and the second semiconductor layer 36 are the same, but not limited thereto. The diameter of the first portion 32a and the diameter of the light emitting layer 34 may also be different from each other, the diameter of the first portion 32a and the diameter of the second semiconductor layer 36 may also be different from each other, and the diameter of the light emitting layer 34 and the diameter of the second semiconductor layer 36 may also be different from each other. In addition, the diameter of the first portion 32a of the first semiconductor layer 32 may also change in the stacking direction. For example, the diameter of the first portion 32a may also gradually increase upward in the stacking direction. In addition, the diameter of the light emitting layer 34 may also change in the stacking direction. For example, the diameter of the light emitting layer 34 may also gradually increase upward in the stacking direction. In addition, the diameter of the second semiconductor layer 36 may also change in the stacking direction. For example, the diameter of the second semiconductor layer 36 may also gradually increase upward in the stacking direction, and the diameter of the second semiconductor layer 36 may also gradually decrease upward in the stacking direction.

[0118] 1.3. Effects

[0119] In the light emitting device 100, the first semiconductor layer 32 has a first portion 32a and a second portion 32b having a smaller diameter than the first portion 32a. In a plan view, the c-plane 35a of the light emitting layer 34 overlaps with the second portion 32b, and the diameter D3 of the c-plane 35a is smaller than the diameter D2 of the second portion 32b. Therefore, in the light emitting device 100, the current flowing through the side surface of the columnar portion 30 where crystal defects are easily generated can be reduced. Thus, the leakage of the current between the first semiconductor layer 32 and the second semiconductor layer 36 can be reduced. As a result, in the light emitting device 100, the current can be efficiently injected into the light emitting layer 34.

[0120] Specifically, in the light-emitting device 100, since the first semiconductor layer 32 has a second portion 32b having a smaller diameter than the first portion 32a, the expansion of the current below the light-emitting layer 34, that is, the expansion of the current in the first semiconductor layer 32, can be reduced in the path of the current flowing through the columnar portion 30.

[0121] Furthermore, in the light emitting device 100, the diameter D3 of the c-plane 35a of the light emitting layer 34 is smaller than the diameter D2 of the second portion 32b. Here, the resistance of the high concentration portion 36a overlapping the c-plane 35a in a plan view is lower than the resistance of the low concentration portion 36b overlapping the facet 35b in a plan view. Therefore, in the path of the current flowing through the columnar portion 30, the spread of the current above the light emitting layer 34, that is, the spread of the current in the second semiconductor layer 36 can be reduced.

[0122] As such, in the light emitting device 100 , the spread of the current flowing through the columnar portion 30 can be reduced, and thus the current flowing through the side surface of the columnar portion 30 can be reduced.

[0123] In addition, in the light emitting device 100, the diameter D3 of the c-plane 35a of the light emitting layer 34 is smaller than the diameter D2 of the second portion 32b. Therefore, in the light emitting device 100, for example, compared with the case where the diameter D3 of the c-plane 35a of the light emitting layer 34 is greater than the diameter D2 of the second portion 32b, the current that does not contribute to light emission across the crystal defect generated by the step 2 can be reduced. As a result, the light emitting efficiency can be improved.

[0124] Here, the step 2 formed at the boundary between the first portion 32a and the second portion 32b is likely to generate crystal defects. In addition, the current crossing the crystal defects does not contribute to light emission. In the light emitting device 100, the diameter D3 is smaller than the diameter D2. Therefore, compared with the case where the diameter D3 is larger than the diameter D2, for example, the current can be concentrated in the center of the first semiconductor layer 32, and the current crossing the crystal defects generated by the step 2 can be reduced.

[0125] In the light emitting device 100, the diameter D4 of the light emitting layer 34 is larger than the diameter D3 of the c-plane 35a and the diameter D2 of the second portion 32b. Therefore, in the light emitting device 100, the current flowing through the side of the light emitting layer 34 can be reduced. Thus, the leakage of the current between the first semiconductor layer 32 and the second semiconductor layer 36 can be reduced. Furthermore, by reducing the current flowing through the side of the light emitting layer 34, the non-luminescent recombination at the side of the light emitting layer 34 can be reduced.

[0126] In the light emitting device 100, a step 2 is provided at the boundary between the first portion 32a and the second portion 32b. Therefore, in the light emitting device 100, the diameter D2 of the second portion 32b can be made smaller than the diameter D1 of the first portion 32a.

[0127] In the light emitting device 100, the insulating layer 24 having the opening 25 is provided on the substrate 10, and the second portion 32b is provided in the opening 25. Therefore, in the light emitting device 100, the first semiconductor layer 32 having the first portion 32a and the second portion 32b having a smaller diameter than the first portion 32a can be easily formed.

[0128] In the light emitting device 100, the insulating layer 24 is provided between the substrate 10 and the first portion 32a. Therefore, in the light emitting device 100, the first semiconductor layer 32 having the first portion 32a and the second portion 32b can be easily formed.

[0129] In light emitting device 100, in plan view, the impurity concentration of second semiconductor layer 36 overlapping c-plane 35a is higher than that of second semiconductor layer 36 overlapping facet 35b. Therefore, in light emitting device 100, the spread of current flowing through second semiconductor layer 36 can be reduced.

[0130] 2. Method for manufacturing a light-emitting device

[0131] Next, a method for manufacturing the light emitting device 100 according to the present embodiment will be described with reference to the drawings. Figure 4 and Figure 5 It is a cross-sectional view schematically showing the manufacturing process of the light emitting device 100 of this embodiment.

[0132] like Figure 4 As shown, the buffer layer 22 is epitaxially grown on the substrate 10. Examples of epitaxial growth methods include Metal Organic Chemical Vapor Deposition (MOCVD) and Molecular Beam Epitaxy (MBE).

[0133] Next, an insulating layer 24 having a plurality of openings 25 is formed on the buffer layer 22. The insulating layer 24 is formed by film formation and patterning using, for example, electron beam evaporation or sputtering. Patterning is performed, for example, by photolithography and etching. The diameter D2 of the second portion 32b is determined by the diameter of the opening 25.

[0134] like Figure 5 As shown, the first semiconductor layer 32 is epitaxially grown on the buffer layer 22 using the insulating layer 24 as a mask. Examples of epitaxial growth methods include MOCVD and MBE.

[0135] The first semiconductor layer 32 is epitaxially grown using the insulating layer 24 as a mask, and the second portion 32b is formed in the opening 25, and the first portion 32a is formed on the second portion 32b and the insulating layer 24. In this way, the first semiconductor layer 32 having the first portion 32a and the second portion 32b having a smaller diameter than the first portion 32a is formed. In this step, the growth conditions such as the growth temperature and the growth rate are adjusted so that the c-plane 33a and the small facet 33b are formed in the first semiconductor layer 32.

[0136] Next, the light emitting layer 34 is epitaxially grown on the first semiconductor layer 32. Examples of epitaxial growth methods include MOCVD and MBE. In this step, growth conditions such as growth temperature and growth rate are adjusted so that the c-plane 35a and the facet 35b are formed in the light emitting layer 34.

[0137] Next, the second semiconductor layer 36 is epitaxially grown on the light emitting layer 34. Examples of epitaxial growth methods include MOCVD and MBE. By epitaxially growing the second semiconductor layer 36 on the light emitting layer 34 having the c-plane 35a and the facet 35b, a high concentration portion 36a having a high impurity concentration is formed on the c-plane 35a, and a low concentration portion 36b having a low impurity concentration is formed on the facet 35b.

[0138] Through the above steps, the laminated body 20 having the columnar portion 30 can be formed.

[0139] Next, a first electrode 40 is formed on the buffer layer 22, and a second electrode 42 is formed on the second semiconductor layer 36. The first electrode 40 and the second electrode 42 are formed, for example, by vacuum deposition. In addition, the order of forming the first electrode 40 and the second electrode 42 is not particularly limited. Thereafter, the substrate 10 is cut into a predetermined shape.

[0140] Through the above steps, the light emitting device 100 can be manufactured.

[0141] 3. Projector

[0142] Next, a projector according to the present embodiment will be described with reference to the drawings. Figure 6 It is a diagram schematically showing a projector 900 according to this embodiment.

[0143] The projector 900 includes, for example, a light emitting device 100 as a light source.

[0144] The projector 900 includes a housing (not shown) and a red light source 100R, a green light source 100G, and a blue light source 100B, which are provided in the housing and emit red light, green light, and blue light, respectively. Figure 6 In FIG. 1 , the red light source 100R, the green light source 100G, and the blue light source 100B are simplified.

[0145] The projector 900 further includes a first optical element 902R, a second optical element 902G, a third optical element 902B, a first light modulator 904R, a second light modulator 904G, a third light modulator 904B, and a projection device 908, which are arranged in a housing. The first light modulator 904R, the second light modulator 904G, and the third light modulator 904B are, for example, transmissive liquid crystal light valves. The projection device 908 is, for example, a projection lens.

[0146] The light emitted from the red light source 100R enters the first optical element 902R. The light emitted from the red light source 100R is collected by the first optical element 902R. In addition, the first optical element 902R may have functions other than collecting light. The same is true for the second optical element 902G and the third optical element 902B described later.

[0147] The light collected by the first optical element 902R is incident on the first light modulator 904R. The first light modulator 904R modulates the incident light according to image information. Then, the projection device 908 magnifies the image formed by the first light modulator 904R and projects it onto the screen 910.

[0148] The light emitted from the green light source 100G enters the second optical element 902G. The light emitted from the green light source 100G is collected by the second optical element 902G.

[0149] The light collected by the second optical element 902G is incident on the second light modulator 904G. The second light modulator 904G modulates the incident light according to the image information. Then, the projection device 908 magnifies the image formed by the second light modulator 904G and projects it onto the screen 910.

[0150] The light emitted from the blue light source 100B enters the third optical element 902B. The light emitted from the blue light source 100B is collected by the third optical element 902B.

[0151] The light collected by the third optical element 902B is incident on the third light modulator 904B. The third light modulator 904B modulates the incident light according to the image information. Then, the projection device 908 magnifies the image formed by the third light modulator 904B and projects it onto the screen 910.

[0152] In addition, the projector 900 may include a cross dichroic prism 906 that combines the light emitted from the first light modulator 904R, the second light modulator 904G, and the third light modulator 904B and guides the combined light to the projection device 908 .

[0153] The three colors of light modulated by the first light modulator 904R, the second light modulator 904G, and the third light modulator 904B are incident on the cross dichroic prism 906. The cross dichroic prism 906 is formed by bonding four right-angle prisms, and a dielectric multilayer film reflecting red light and a dielectric multilayer film reflecting blue light are arranged on its inner surface. The three colors of light are synthesized by these dielectric multilayer films to form light for displaying a color image. Then, the synthesized light is projected onto the screen 910 by the projection device 908, and the enlarged image is displayed.

[0154] In addition, the red light source 100R, the green light source 100G, and the blue light source 100B can also directly form an image by controlling the light emitting device 100 according to the image information of the pixels as the image, without using the first light modulator 904R, the second light modulator 904G, and the third light modulator 904B. Furthermore, the projection device 908 can also enlarge the image formed by the red light source 100R, the green light source 100G, and the blue light source 100B and project it onto the screen 910.

[0155] In the above example, a transmissive liquid crystal light valve is used as the light modulating device, but a light valve other than liquid crystal may be used, and a reflective light valve may be used. Examples of such light valves include reflective liquid crystal light valves and digital micro mirror devices. In addition, the structure of the projection device may be appropriately changed according to the type of light valve used.

[0156] Furthermore, the light source can also be applied to a light source device of a scanning type image display device having a scanning unit that is an image forming device that displays an image of a desired size on a display surface by scanning light from a light source on a screen.

[0157] 4. Display

[0158] Next, a display according to the present embodiment will be described with reference to the drawings. Figure 7 1 is a plan view schematically showing a display 1000 according to this embodiment. Figure 8 1 is a cross-sectional view schematically showing the display 1000 of this embodiment. Figure 7 The X-axis and the Y-axis are shown in the figure as two axes that are orthogonal to each other.

[0159] The display 1000 has, for example, a light emitting device 100 as a light source.

[0160] The display 1000 is a display device for displaying images. The images include images that only display text information. The display 1000 is a self-luminous display. Figure 7 and Figure 8As shown, the display 1000 includes: a circuit substrate 1010 , a lens array 1020 , and a heat sink 1030 .

[0161] A driving circuit for driving the light emitting device 100 is mounted on the circuit substrate 1010. The driving circuit is, for example, a circuit including a complementary metal oxide semiconductor (CMOS). The driving circuit drives the light emitting device 100 based on input image information, for example. Although not shown in the figure, a substrate for protecting the light transmittance of the circuit substrate 1010 is arranged on the circuit substrate 1010.

[0162] The circuit substrate 1010 includes a display area 1012 , a data line driving circuit 1014 , a scanning line driving circuit 1016 , and a control circuit 1018 .

[0163] The display area 1012 includes a plurality of pixels P. In the example shown in the figure, the pixels P are arranged along the X-axis and the Y-axis.

[0164] Although not shown, a plurality of scan lines and a plurality of data lines are provided on the circuit substrate 1010. For example, the scan lines extend along the X axis, and the data lines extend along the Y axis. The scan lines are connected to the scan line driving circuit 1016. The data lines are connected to the data line driving circuit 1014. Pixels P are provided corresponding to the intersections of the scan lines and the data lines.

[0165] One pixel P includes, for example, one light emitting device 100, one lens 1022, and a pixel circuit (not shown). The pixel circuit includes a switching transistor that functions as a switch of the pixel P. The switching transistor has a gate connected to a scanning line and one of a source or a drain connected to a data line.

[0166] The data line driving circuit 1014 and the scanning line driving circuit 1016 are circuits for controlling the driving of the light emitting device 100 constituting the pixel P. The control circuit 1018 controls the display of an image.

[0167] The image data is supplied from the upper circuit to the control circuit 1018. The control circuit 1018 supplies various signals based on the image data to the data line drive circuit 1014 and the scanning line drive circuit 1016.

[0168] When the scan line driving circuit 1016 selects a scan line by activating a scan signal, the switching transistor of the selected pixel P is turned on. At this time, the data line driving circuit 1014 supplies a data signal from the data line to the selected pixel P, whereby the light emitting device 100 of the selected pixel P emits light according to the data signal.

[0169] The lens array 1020 includes a plurality of lenses 1022 . For example, one lens 1022 is provided for each light emitting device 100 . Light emitted from the light emitting device 100 enters one lens 1022 .

[0170] The heat sink 1030 is in contact with the circuit substrate 1010 . The heat sink 1030 is made of metal such as copper or aluminum. The heat sink 1030 releases heat generated in the light emitting device 100 .

[0171] The light emitting device of the above-described embodiment can also be used for purposes other than projectors or displays. In applications other than projectors or displays, for example, there are light sources for indoor and outdoor lighting, laser printers, scanners, vehicle-mounted lights, sensing devices using light, and communication devices. In addition, it can also be used as a display device for a head-mounted display.

[0172] The present invention includes structures that are substantially the same as the structures described in the embodiments, such as structures with the same functions, methods and results, or structures with the same purposes and effects. In addition, the present invention includes structures in which the non-essential parts of the structures described in the embodiments are replaced. In addition, the present invention includes structures that can exert the same effects as the structures described in the embodiments, or structures that can achieve the same purposes. In addition, the present invention includes structures in which the structures described in the embodiments are added with known technologies.

[0173] The following contents are derived from the above-described embodiments and modifications.

[0174] One form of the light emitting device includes:

[0175] substrate; and

[0176] A laminated body is provided on the substrate and has a plurality of columnar portions.

[0177] The columnar portion has:

[0178] a first semiconductor layer of a first conductivity type;

[0179] a second semiconductor layer of a second conductivity type different from the first conductivity type; and

[0180] a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer,

[0181] The first semiconductor layer is disposed between the substrate and the light emitting layer.

[0182] The light-emitting layer has a c-plane and a facet,

[0183] The second semiconductor layer is disposed on the c-plane and the small plane,

[0184] The first semiconductor layer comprises a first portion and a second portion having a smaller diameter than the first portion.

[0185] The second portion is disposed between the substrate and the first portion,

[0186] In a plan view from the stacking direction of the first semiconductor layer and the light emitting layer, the c-plane overlaps with the second portion, and a diameter of the c-plane is smaller than a diameter of the second portion.

[0187] According to the light emitting device, the current flowing through the side surface of the columnar portion where crystal defects are likely to occur can be reduced, thereby reducing the leakage of current between the first semiconductor layer and the second semiconductor layer.

[0188] In one form of the light emitting device, it may also be:

[0189] The diameter of the light emitting layer is larger than the diameter of the c-plane and the diameter of the second portion.

[0190] According to the light-emitting device, it is possible to reduce current that does not contribute to light emission due to a crystal defect generated by a step difference at the boundary between the first portion and the second portion of the first semiconductor layer.

[0191] In one form of the light emitting device, it may also be:

[0192] A step is provided at a boundary between the first portion and the second portion.

[0193] According to the light emitting device, the diameter of the second portion can be made smaller than the diameter of the first portion.

[0194] In one form of the light emitting device, it may also be:

[0195] An insulating layer having an opening is provided on the substrate,

[0196] The second portion is disposed at the opening.

[0197] According to the light-emitting device, the first semiconductor layer including the first portion and the second portion having a smaller diameter than the first portion can be easily formed.

[0198] In one form of the light emitting device, it may also be:

[0199] The insulating layer is disposed between the substrate and the first portion.

[0200] According to the light-emitting device, the first semiconductor layer including the first portion and the second portion having a smaller diameter than the first portion can be easily formed.

[0201] In one form of the light emitting device, it may also be:

[0202] In the plan view, an impurity concentration of the second semiconductor layer overlapping the c-plane is higher than an impurity concentration of the second semiconductor layer overlapping the facet.

[0203] According to the light emitting device, the spread of the current flowing in the second semiconductor layer can be reduced.

[0204] One form of a projector has one form of the light emitting device.

[0205] A form of a display has a form of the light emitting device.

Claims

1. A light emitting device, characterized in that: include: substrate; as well as A laminated body is provided on the substrate and has a plurality of columnar portions. The columnar portion has: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type, which is different from the first conductivity type; as well as a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer, The first semiconductor layer is disposed between the substrate and the light emitting layer. The light-emitting layer has a c-plane and a facet, The second semiconductor layer is disposed on the c-plane and the small plane, The first semiconductor layer comprises a first portion and a second portion having a diameter smaller than that of the first portion. The second portion is disposed between the substrate and the first portion, When viewed from above in the stacking direction of the first semiconductor layer and the light-emitting layer, the c-plane overlaps with the second part, the diameter of the c-plane is smaller than the diameter of the second part, and when viewed from above, the impurity concentration of the second semiconductor layer overlapping with the c-plane is higher than the impurity concentration of the second semiconductor layer overlapping with the small plane.

2. The light emitting device according to claim 1, wherein: The diameter of the light emitting layer is larger than the diameter of the c-plane and the diameter of the second portion.

3. The light emitting device according to claim 1 or 2, wherein: A step is provided at a boundary between the first portion and the second portion.

4. The light emitting device according to claim 1, wherein: An insulating layer having an opening is provided on the substrate, The second portion is disposed at the opening.

5. The light emitting device according to claim 4, wherein: The insulating layer is disposed between the substrate and the first portion.

6. A projector, comprising the light emitting device according to any one of claims 1 to 5.

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

Images