Light emitting device and projector

Abstract

To provide a light emitting device capable of improving a light confinement coefficient.SOLUTION: A light emitting device includes a laminate having a plurality of column-like parts. Each of the plurality of column-like parts includes: a first semiconductor layer having a first conductivity type; a second semiconductor layer having a second conductivity type different from the first conductivity type; and a light emission layer provided between the first semiconductor layer and the second semiconductor layer. The maximum diameter of the column-like parts in the first semiconductor layer is smaller than the maximum diameter of the column-like parts in the second semiconductor layer. The diameter of the column-like parts in the first semiconductor layer is smaller than the minimum diameter of the column-like parts in the second semiconductor layer at a first position of the laminate in a lamination direction, and is maximum at a second position different from the first position in the lamination direction. The refractive index of the first semiconductor layer at the first position is higher than the refractive index of the second semiconductor layer and the refractive index of the first semiconductor layer at the second position.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Semiconductor lasers are expected to become the next generation of high-brightness light sources. In particular, semiconductor lasers that incorporate nanocolumns are expected to be able to achieve high-output light emission with a narrow radiation 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 each including an n-type GaN layer, a light emitting layer, and a p-type GaN layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-133517 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, the diameter of the columnar portion in the p-type GaN layer is larger than that of the n-type GaN layer, so that the average refractive index in the in-plane direction of the stack in the p-type GaN layer is larger than that in the n-type GaN layer, which may cause light generated in the light-emitting layer to leak to the p-type GaN layer side, resulting in a decrease in the optical confinement coefficient. [Means for solving the problem]

[0006] One aspect of the light emitting device according to the present invention is A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer; a diameter of the columnar portion in the first semiconductor layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer at a first position in a stacking direction of the stacked body, and is maximum at a second position different from the first position in the stacking direction; The refractive index of the first semiconductor layer at the first position is higher than the refractive index of the second semiconductor layer and the refractive index of the first semiconductor layer at the second position.

[0007] One aspect of the light emitting device according to the present invention is A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer; The first semiconductor layer is The first layer, a second layer provided between the first layer and the light-emitting layer; a third layer disposed between the first layer and the second layer; and having a diameter of the columnar portion in the first layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer and a diameter of the columnar portion in the second layer; a refractive index of the first layer is higher than a refractive index of the second semiconductor layer and a refractive index of the second layer; The refractive index of the second layer is higher than the refractive index of the third layer.

[0008] One aspect of the light emitting device according to the present invention is A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer; the first semiconductor layer comprises a first InGaN layer; a diameter of the columnar portion in the first InGaN layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer; The second semiconductor layer includes at least one of a GaN layer and an AlGaN layer.

[0009] One aspect of the projector according to the present invention is The present invention has one aspect of the light emitting device. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a light emitting device according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a columnar portion of the light emitting device according to the first embodiment. [Diagram 3] FIG. 11 is a cross-sectional view showing a columnar portion of a light emitting device according to a reference example. [Figure 4] 3A to 3C are cross-sectional views each showing a schematic process for manufacturing the light emitting device according to the first embodiment. [Diagram 5] FIG. 11 is a cross-sectional view illustrating a light emitting device according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view illustrating a first semiconductor layer of the light emitting device according to the second embodiment. [Figure 7] FIG. 11 is a cross-sectional view illustrating a schematic view of a second semiconductor layer of the light emitting device according to the second embodiment. [Figure 8] FIG. 11 is a diagram illustrating a projector according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0012] 1. First embodiment 1.1. Light-emitting device 1.1.1. Overall structure First, the light emitting device according to the first embodiment will be described with reference to the drawings. Fig. 1 is a cross-sectional view that shows a schematic view of the light emitting device 100 according to the first embodiment.

[0013] 1, the light emitting device 100 includes, for example, a substrate 10, a laminate 20, a first electrode 40, and a second electrode 42. The light emitting device 100 is a semiconductor laser.

[0014] The substrate 10 is, for example, a Si substrate, a GaN substrate, a sapphire substrate, a SiC substrate, or the like.

[0015] The laminate 20 is provided on the 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 and a columnar portion 30.

[0016] In this specification, in the stacking direction of the laminate 20 (hereinafter also simply referred to as the "stacking direction"), when the light emitting layer 34 is used as a reference, the direction from the light emitting layer 34 toward the second semiconductor layer 36 is described as "upper", and the direction from the light emitting layer 34 toward the first semiconductor layer 32 is described as "lower". A direction perpendicular to the stacking direction is also referred to as an "in-plane direction". Moreover, the "stacking direction of the laminate 20" refers to the stacking direction of the first semiconductor layer 32 and the light emitting layer 34 of the columnar section 30.

[0017] The buffer layer 22 is provided on the substrate 10. The buffer layer 22 is, for example, a Si-doped n-type GaN layer. A mask layer 24 for forming the columnar section 30 is provided on the buffer layer 22. The mask layer 24 is, for example, a silicon oxide layer, a titanium layer, a titanium oxide layer, an aluminum oxide layer, or the like.

[0018] The columnar section 30 is provided on the buffer layer 22. The columnar section 30 has a columnar shape protruding upward from the buffer layer 22. In other words, the columnar section 30 protrudes upward from the substrate 10 via the buffer layer 22. The columnar section 30 is also called, for example, a nanocolumn, a nanowire, a nanorod, or a nanopillar. The planar shape of the columnar section 30 is, for example, a polygon such as a hexagon, or a circle.

[0019] The diameter of the columnar section 30 is, for example, 50 nm or more and 500 nm or less. By making the diameter of the columnar section 30 500 nm or less, it is possible to obtain a light-emitting layer 34 of high quality crystals and reduce distortion inherent in the light-emitting layer 34. This allows the light generated in the light-emitting layer 34 to be amplified with high efficiency.

[0020] The "diameter of the columnar portion" refers to the diameter when the planar shape of the columnar portion 30 is a circle, and refers to the diameter of the smallest inclusive circle when the planar shape of the columnar portion 30 is not a circle. For example, when the planar shape of the columnar portion 30 is a polygon, the diameter of the columnar portion 30 refers to the diameter of the smallest circle that includes the polygon, and when the planar shape of the columnar portion 30 is an ellipse, the diameter of the smallest circle that includes the ellipse.

[0021] A plurality of columnar sections 30 are provided. The interval between adjacent columnar sections 30 is, for example, 1 nm or more and 500 nm or less. The plurality of columnar sections 30 are arranged at a predetermined pitch in a predetermined direction as viewed from the stacking direction. The plurality of columnar sections 30 are arranged, for example, in a triangular lattice or square lattice pattern. The plurality of columnar sections 30 can exhibit the effect of a photonic crystal.

[0022] The "pitch of the columnar portion" is the distance between the centers of adjacent columnar portions 30 along a predetermined direction. When the planar shape of the columnar portion 30 is a circle, the "center of the columnar portion" is the center of the circle, and when the planar shape of the columnar portion 30 is a shape other than a circle, the center of the smallest inclusive circle. For example, when the planar shape of the columnar portion 30 is a polygon, the center of the columnar portion 30 is the center of the smallest circle that includes the polygon inside, and when the planar shape of the columnar portion 30 is an ellipse, the center of the smallest circle that includes the ellipse inside.

[0023] The columnar section 30 includes a first semiconductor layer 32, a light emitting layer , and a second semiconductor layer .

[0024] 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 semiconductor layer doped with Si. The first semiconductor layer 32 contains Ga and N.

[0025] 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.

[0026] There is no particular limitation on the number of well layers and barrier layers constituting the light-emitting layer 34. For example, only one well layer may be provided, in which case the light-emitting layer 34 has a SQW (Single Quantum Well) structure.

[0027] The second semiconductor layer 36 is provided on the light emitting layer 34. 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 semiconductor layer doped with Mg. The second semiconductor layer 36 contains Ga and N. The first semiconductor layer 32 and the second semiconductor layer 36 are cladding layers having the function of confining light in the light emitting layer 34.

[0028] 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 have an EBL (Electron Blocking Layer) made of a p-type AlGaN layer.

[0029] In the light emitting device 100, a pin diode is formed by the p-type second semiconductor layer 36, the i-type light emitting layer 34, and the n-type first semiconductor layer 32. In the light emitting device 100, when a forward bias voltage of the pin diode is applied between the first electrode 40 and the second electrode 42, a current is injected into the light emitting layer 34, and recombination of electrons and holes occurs in the light emitting layer 34. This recombination causes light emission. The light generated in the light emitting layer 34 propagates in the in-plane direction, forms a standing wave due to the effect of the photonic crystal of the multiple columnar parts 30, receives gain in the light emitting layer 34, and oscillates as a laser. Then, the light emitting device 100 emits the +1st order diffracted light and the -1st order diffracted light as laser light in the stacking direction.

[0030] Although not shown, a reflective layer may be provided between the substrate 10 and the buffer layer 22 or under 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 42 side.

[0031] 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 illustrated example, 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 a current into the light-emitting layer 34. As the first electrode 40, 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 is used.

[0032] The second electrode 42 is provided on the second semiconductor layer 36. The second semiconductor layer 36 may be in ohmic contact with the second electrode 42. The second electrode 42 is the other electrode for injecting a current into the light emitting layer 34. The second electrode 42 is made of, for example, ITO (indium tin oxide).

[0033] Although the above describes the InGaN-based light emitting layer 34, various material systems capable of emitting light when a current is injected depending on the wavelength of the emitted light can be used for the light emitting layer 34. For example, semiconductor materials such as AlGaN-based, AlGaAs-based, InGaAs-based, InGaAsP-based, InP-based, GaP-based, and AlGaP-based materials can be used.

[0034] 1.1.2. Detailed description of the column Fig. 2 is a cross-sectional view that diagrammatically illustrates the columnar section 30. Note that in Fig. 1 described above, the columnar section 30 is illustrated in a simplified form.

[0035] 1 and 2, the diameter of the columnar section 30 increases from the substrate 10 toward the second electrode 42. The diameter of the columnar section 30 gradually increases from the substrate 10 toward the second electrode 42. The columnar section 30 has a tapered shape in which the diameter increases from the substrate 10 toward the second electrode 42.

[0036] The first semiconductor layer 32 has a first position P1 and a second position P2 in the stacking direction. The second position P2 is a position different from the first position P1 in the stacking direction. In the illustrated example, the first position P1 is the position of the end of the first semiconductor layer 32 on the substrate 10 side. The second position P2 is the position of the end of the first semiconductor layer 32 on the light emitting layer 34 side.

[0037] The diameter of the columnar portion 30 in the first semiconductor layer 32 is smallest at the first position P1. The diameter of the columnar portion 30 in the first semiconductor layer 32 is largest at the second position P2. The columnar portion 30 has a smallest diameter D1 in the first semiconductor layer 32 at the first position P1. The columnar portion 30 has a largest diameter D2 in the first semiconductor layer 32 at the second position P2. The diameter of the first semiconductor layer 32 is not constant in the stacking direction. The diameter of the columnar portion 30 in the first semiconductor layer 32 decreases as it moves away from the light emitting layer 34. That is, the diameter of the columnar portion 30 in the first semiconductor layer 32 increases from the substrate 10 toward the light emitting layer 34.

[0038] The refractive index of the first semiconductor layer 32 at the first position P1 is higher than the refractive index of the first semiconductor layer 32 at the second position P2. The refractive index of the first semiconductor layer 32 is, for example, highest at the first position P1. The refractive index of the first semiconductor layer 32 is, for example, lowest at the second position P2. The refractive index of the first semiconductor layer 32 is not constant in the stacking direction. The refractive index of the first semiconductor layer 32 at the first position P1 is higher than the refractive index of the second semiconductor layer 36. The refractive index of the first semiconductor layer 32 increases with increasing distance from the light emitting layer 34. That is, the refractive index of the first semiconductor layer 32 decreases from the substrate 10 toward the light emitting layer 34.

[0039] The first semiconductor layer 32 has an InGaN layer 50 and a GaN layer 52. The InGaN layer 50 is provided at a first position P1. The GaN layer 52 is provided at a second position P2. The In composition of the InGaN layer 50 increases with increasing distance from the light emitting layer 34. Therefore, the refractive index of the first semiconductor layer 32 increases with increasing distance from the light emitting layer 34. The refractive index of the InGaN layer 50 is higher than the refractive index of the second semiconductor layer 36. Here, "high composition" means that the number of the element in question is large in the composition formula of the constituent material. For example, when the composition formula of InGaN is In, x Ga 1-x In the case of N, the In composition is high when the composition formula is In x Ga 1-x This means that the value of x is large in N.

[0040] The second semiconductor layer 36 has a third position P3 and a fourth position P4 in the stacking direction. The fourth position P4 is a position different from the third position P3 in the stacking direction. In the illustrated example, the third position P3 is the position of the end of the second semiconductor layer 36 on the light emitting layer 34 side. The fourth position P4 is the position of the end of the second semiconductor layer 36 on the second electrode 42 side.

[0041] The diameter of the columnar portion 30 in the second semiconductor layer 36 is smallest at the third position P3. The diameter of the columnar portion 30 in the second semiconductor layer 36 is largest at the fourth position P4. The columnar portion 30 has a smallest diameter D3 in the second semiconductor layer 36 at the third position P3. The columnar portion 30 has a largest diameter D4 in the second semiconductor layer 36 at the fourth position P4. The largest diameter D2 of the columnar portion 30 in the first semiconductor layer 32 is smaller than the smallest diameter D3 of the columnar portion 30 in the second semiconductor layer 36. The largest diameter D2 of the columnar portion 30 in the first semiconductor layer 32 is smaller than the largest diameter D4 of the columnar portion 30 in the second semiconductor layer 36. The diameter of the columnar portion 30 in the first semiconductor layer 32 is smaller than the smallest diameter D3 of the columnar portion 30 in the second semiconductor layer 36 at the first position P1.

[0042] The diameter of the second semiconductor layer 36 is not constant in the stacking direction. The diameter of the columnar portion 30 in the second semiconductor layer 36 increases with increasing distance from the light emitting layer 34. In other words, the diameter of the columnar portion 30 in the second semiconductor layer 36 increases from the light emitting layer 34 toward the second electrode 42.

[0043] The refractive index of the second semiconductor layer 36 is highest, for example, at the third position P3. The refractive index of the second semiconductor layer 36 is lowest, for example, at the fourth position P4. The refractive index of the second semiconductor layer 36 is not constant in the stacking direction. The refractive index of the second semiconductor layer 36 decreases with increasing distance from the light emitting layer 34. That is, the refractive index of the second semiconductor layer 36 decreases from the light emitting layer 34 toward the second electrode 42.

[0044] The second semiconductor layer 36 has a GaN layer 60 and an AlGaN layer 62. The GaN layer 60 is provided at a third position P3. The AlGaN layer 62 is provided at a fourth position P4. The In composition of the AlGaN layer 62 increases with increasing distance from the light emitting layer 34. Therefore, the refractive index of the second semiconductor layer 36 decreases with increasing distance from the light emitting layer 34. The refractive index of the AlGaN layer 62 is lower than the refractive index of the first semiconductor layer 32.

[0045] 1.1.3. Effects In the light emitting device 100, the maximum diameter D2 of the columnar portion 30 in the first semiconductor layer 32 is smaller than the maximum diameter D4 of the columnar portion 30 in the second semiconductor layer 36. The diameter of the columnar portion 30 in the first semiconductor layer 32 at a first position P1 in the stacking direction is smaller than the minimum diameter D3 of the columnar portion 30 in the second semiconductor layer 36, and is maximum at a second position P2 different from the first position P1 in the stacking direction. The refractive index of the first semiconductor layer 32 at the first position P1 is higher than the refractive index of the second semiconductor layer 36 and the refractive index of the first semiconductor layer 32 at the second position P2.

[0046] Therefore, in the light emitting device 100, as shown in FIG. 2, the difference between the average refractive index in the in-plane direction of the stacked body 20 at the first position P1 and the average refractive index in the in-plane direction of the stacked body 20 at the second semiconductor layer 36 (the average refractive index in the in-plane direction of the stacked body 20 at the portion where the second semiconductor layer 36 is provided) can be reduced. Furthermore, the difference between the average refractive index in the in-plane direction of the stacked body 20 at the first position P1 and the average refractive index in the in-plane direction of the stacked body 20 at the second position P2 can be reduced. Therefore, as shown in FIG. 2, the peak of the light intensity in the stacking direction can be aligned with the position of the light emitting layer 34. In the illustrated example, the average refractive index in the in-plane direction of the stacked body 20 at the first position P1, the average refractive index in the in-plane direction of the stacked body 20 at the second position P2, and the average refractive index in the in-plane direction of the stacked body 20 at the second semiconductor layer 36 are equal to each other.

[0047] For example, as shown in Fig. 3, when the refractive index at the first position P1 of the first semiconductor layer 1032, the refractive index at the second position P2 of the first semiconductor layer 1032, and the refractive index of the second semiconductor layer 1036 are equal to each other, the average refractive index in the in-plane direction of the stack at the first position P1 is lower than the average refractive index in the in-plane direction of the stack at the second position P2 and the average refractive index in the in-plane direction of the stack at the second semiconductor layer 1036. Therefore, the peak of the light intensity in the stacking direction does not coincide with the position of the light emitting layer 1034, but shifts to the second electrode side. Note that Fig. 3 is a diagram showing a columnar section 1030 of a light emitting device 1000 according to a reference example.

[0048] As described above, in the light emitting device 100, light can be confined in the light emitting layer 34 and the light confinement coefficient can be improved compared to the light emitting device 1000. As a result, a semiconductor laser with high gain can be realized.

[0049] In the light emitting device 100, the diameter of the columnar portion 30 in the first semiconductor layer 32 is smallest at the first position P1, and the refractive index of the first semiconductor layer 32 is highest at the first position P1. Therefore, in the light emitting device 100, it is possible to reduce the difference between the average refractive index in the in-plane direction of the laminate 20 at the first position P1 and the average refractive index in the in-plane direction of the portion where the first semiconductor layer 32 is provided (the portion of the laminate 20) at positions other than the first position P1, compared to a case in which the refractive index of the first semiconductor layer is not highest at the first position P1.

[0050] In the light emitting device 100, the diameter of the columnar section 30 in the first semiconductor layer 32 decreases with increasing distance from the light emitting layer 34, and the refractive index of the first semiconductor layer 32 increases with increasing distance from the light emitting layer 34. Therefore, in the light emitting device 100, the average refractive index in the in-plane direction of the stacked body 20 in the first semiconductor layer 32 can be made constant, for example, in the stacking direction.

[0051] In the light emitting device 100, the first semiconductor layer 32 has an InGaN layer 50 and a GaN layer 52, with the InGaN layer 50 provided at a first position P1 and the GaN layer 52 provided at a second position P2. Therefore, in the light emitting device 100, the refractive index of the first semiconductor layer 32 at the first position P1 can be made higher than the refractive index of the first semiconductor layer 32 at the second position P2.

[0052] In the light emitting device 100, the diameter of the columnar portion 30 in the second semiconductor layer 36 and the refractive index of the second semiconductor layer 36 are not constant in the stacking direction, and the diameter of the columnar portion 30 in the second semiconductor layer 36 is smallest at a third position P3 in the stacking direction, and the refractive index of the second semiconductor layer 36 is highest at the third position P3. Therefore, in the light emitting device 100, as shown in Fig. 2, it is possible to reduce the difference between the average refractive index in the in-plane direction of the stacked body 20 at the third position P3 and the average refractive index in the in-plane direction of the stacked body 20 at positions other than the third position P3. In the example shown in Fig. 2, the difference is zero.

[0053] In the light emitting device 100, the diameter of the columnar portion 30 in the second semiconductor layer 36 increases with increasing distance from the light emitting layer 34, and the refractive index of the second semiconductor layer 36 decreases with increasing distance from the light emitting layer 34. Therefore, in the light emitting device 100, the average refractive index in the in-plane direction of the stacked body 20 in the second semiconductor layer 36 can be made constant, for example, in the stacking direction. For example, if the average refractive index in the in-plane direction of the stacked body 20 in the first semiconductor layer 32 and the average refractive index in the in-plane direction of the stacked body 20 in the second semiconductor layer 36 can be made constant in the stacking direction, the average refractive index in the in-plane direction of the stacked body 20 in the first semiconductor layer 32 and the average refractive index in the in-plane direction of the stacked body 20 in the second semiconductor layer 36 can be made symmetrical with respect to the light emitting layer 34. This can further improve the optical confinement coefficient.

[0054] In the light emitting device 100, the diameter of the columnar portion 30 in the second semiconductor layer 36 is maximum at a fourth position P4 different from the third position P3 in the stacking direction, and the second semiconductor layer 36 has a GaN layer 60 and an AlGaN layer 62, with the GaN layer 60 provided at the third position P3 and the AlGaN layer 62 provided at the fourth position P4. Therefore, in the light emitting device 100, the refractive index of the second semiconductor layer 36 at the fourth position P4 can be made lower than the refractive index of the second semiconductor layer 36 at the third position P3.

[0055] 1.2. Manufacturing method of light-emitting device Next, a method for manufacturing the light emitting device 100 according to the first embodiment will be described with reference to the drawings. Fig. 4 is a cross-sectional view that typically illustrates the manufacturing process of the light emitting device 100 according to the first embodiment.

[0056] 4, the buffer layer 22 is epitaxially grown on the substrate 10. Examples of the epitaxial growth method include a metal organic chemical vapor deposition (MOCVD) method and a molecular beam epitaxy (MBE) method.

[0057] Next, a mask layer 24 is formed on the buffer layer 22. The mask layer 24 is formed by, for example, film formation using an electron beam deposition method or a sputtering method, and patterning. The patterning is performed by photolithography and etching.

[0058] 1, a first semiconductor layer 32, a light emitting layer 34, and a second semiconductor layer 36 are epitaxially grown in this order on the buffer layer 22 using the mask layer 24 as a mask. Examples of the epitaxial growth method include the MOCVD method and the MBE method. By this process, a plurality of columnar sections 30 can be formed.

[0059] The first semiconductor layer 32 is grown, for example, by repeating epitaxial growth of InGaN one or two atomic layers at a time while appropriately selecting a predetermined film formation temperature and an opening time of a shutter for releasing In, so that the In composition decreases from the substrate 10 toward the light-emitting layer 34.

[0060] The second semiconductor layer 36 is grown, for example, by repeating epitaxial growth of AlGaN one or two atomic layers at a time, by appropriately selecting a predetermined film formation temperature and an open time of a shutter for releasing Al, so that the Al composition increases from the light emitting layer 34 toward the second electrode 42. Here, "high composition" means that the number of the element in question is large in the composition formula of the constituent material. For example, when the composition formula of AlGaN is Al x Ga 1-x In the case where N is used, the Al composition is high when the composition formula is Al x Ga 1-x This means that the value of x is large in N.

[0061] The columnar section 30 is grown at a film formation temperature and a film formation rate such that the diameter increases from the substrate 10 toward the second electrode .

[0062] 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 by, for example, a vacuum deposition method. The order in which the first electrode 40 and the second electrode 42 are formed is not particularly limited.

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

[0064] 2. Second embodiment 2.1. Light-emitting device Next, a light emitting device according to a second embodiment will be described with reference to the drawings. Fig. 5 is a cross-sectional view that shows a schematic diagram of a light emitting device 200 according to the second embodiment. Fig. 6 is an enlarged view of a region α of the first semiconductor layer 32 shown in Fig. 5. Fig. 7 is an enlarged view of a region β of the second semiconductor layer 36 shown in Fig. 5. For convenience, Fig. 5 shows a simplified view of the columnar section 30.

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

[0066] The light emitting device 200 differs from the above-described light emitting device 100 in that the first semiconductor layer 32 has a multilayer structure of an InGaN layer and a GaN layer, as shown in Fig. 6. Furthermore, the light emitting device 200 differs from the above-described light emitting device 100 in that the second semiconductor layer 36 has a multilayer structure of an AlGaN layer and a GaN layer, as shown in Fig. 7.

[0067] 6, the first semiconductor layer 32 includes, for example, a first InGaN layer 210 as a first layer, a second InGaN layer 212 as a second layer, a third InGaN layer 214, a fourth InGaN layer 216, and a first GaN layer 220 as a third layer, a second GaN layer 222, a third GaN layer 224, and a fourth GaN layer 226. The refractive indices of the InGaN layers 210, 212, 214, and 216 are higher than the refractive indices of the GaN layers 220, 222, 224, and 226.

[0068] The first InGaN layer 210 is provided between the substrate 10 and the second InGaN layer 212. The diameter of the columnar portion 30 in the first InGaN layer 210 is smaller than the diameter of the columnar portion 30 in the InGaN layers 212, 214, and 216. The diameter of the columnar portion 30 in the first InGaN layer 210 is smaller than the minimum diameter D3 of the columnar portion 30 in the second semiconductor layer 36.

[0069] The refractive index of the first InGaN layer 210 is higher than the refractive index of the second semiconductor layer 36. The refractive index of the first InGaN layer 210 is higher than the refractive index of the InGaN layers 212, 214, and 216. The In composition of the first InGaN layer 210 is higher than the In composition of the InGaN layers 212, 214, and 216. The refractive index of the first InGaN layer 210 is higher than the refractive index of the second semiconductor layer 36. The composition formula of the first InGaN layer 210 is In x Ga 1-x N, and the composition formula of the second InGaN layer 212 is In y Ga 1-y N, where x and y satisfy 0 < y < x < 1.

[0070] The second InGaN layer 212 is provided between the first InGaN layer 210 and the light-emitting layer 34. The second InGaN layer 212 is provided between the first InGaN layer 210 and the third InGaN layer 214. The second InGaN layer 212 is sandwiched between the first GaN layer 220 and the second GaN layer 222. The first GaN layer 220 is provided between the first InGaN layer 210 and the second InGaN layer 212. The diameter of the columnar portion 30 in the second InGaN layer 212 is smaller than the diameter of the columnar portion 30 in the InGaN layers 214 and 216. The refractive index of the second InGaN layer 212 is higher than the refractive index of the InGaN layers 214 and 216. The In composition of the second InGaN layer 212 is higher than the In composition of the InGaN layers 214 and 216.

[0071] The third InGaN layer 214 is provided between the second InGaN layer 212 and the fourth InGaN layer 216. The third InGaN layer 214 is sandwiched between the second GaN layer 222 and the third GaN layer 224. The diameter of the columnar portion 30 in the third InGaN layer 214 is smaller than the diameter of the columnar portion 30 in the fourth InGaN layer 216. The refractive index of the third InGaN layer 214 is higher than the refractive index of the fourth InGaN layer 216. The In composition of the third InGaN layer 214 is higher than the In composition of the fourth InGaN layer 216.

[0072] The fourth InGaN layer 216 is provided between the third InGaN layer 214 and the light emitting layer 34. The fourth InGaN layer 216 is sandwiched between the third GaN layer 224 and the fourth GaN layer 226.

[0073] As described above, the first semiconductor layer 32 has a plurality of InGaN layers in which the In composition decreases from the substrate 10 toward the light emitting layer 34. The number of InGaN layers is not particularly limited as long as it is two or more. The InGaN layers and GaN layers of the first semiconductor layer 32 may form a superlattice (SL) pseudo-alloyed crystal.

[0074] 7, the second semiconductor layer 36 has at least one of a GaN layer and an AlGaN layer. In the illustrated example, the second semiconductor layer 36 has a first AlGaN layer 230, a second AlGaN layer 232, a third AlGaN layer 234, a fourth AlGaN layer 236, a fifth GaN layer 240, a sixth GaN layer 242, a seventh GaN layer 244, and an eighth GaN layer 246. The refractive indices of the AlGaN layers 230, 232, 234, and 236 are lower than the refractive indices of the GaN layers 240, 242, 244, and 246.

[0075] The first AlGaN layer 230 is provided between the second AlGaN layer 232 and the second electrode 42. The diameter of the columnar portion 30 in the first AlGaN layer 230 is larger than the diameter of the columnar portion 30 in the AlGaN layers 232, 234, and 236. The refractive index of the first AlGaN layer 230 is lower than the refractive indexes of the AlGaN layers 232, 234, and 236. The Al composition of the first AlGaN layer 230 is higher than the Al composition of the AlGaN layers 232, 234, and 236.

[0076] The second AlGaN layer 232 is provided between the first AlGaN layer 230 and the light emitting layer 34. The second AlGaN layer 232 is provided between the first AlGaN layer 230 and the third AlGaN layer 234. The second AlGaN layer 232 is sandwiched between the fifth GaN layer 240 and the sixth GaN layer 242. The fifth GaN layer 240 is provided between the first AlGaN layer 230 and the second AlGaN layer 232. The diameter of the columnar portion 30 in the second AlGaN layer 232 is larger than the diameter of the columnar portion 30 in the AlGaN layers 234 and 236. The refractive index of the second AlGaN layer 232 is lower than the refractive index of the AlGaN layers 234 and 236. The Al composition of the second AlGaN layer 232 is higher than the Al composition of the AlGaN layers 234 and 236.

[0077] The third AlGaN layer 234 is provided between the second AlGaN layer 232 and the fourth AlGaN layer 236. The third AlGaN layer 234 is sandwiched between the sixth GaN layer 242 and the seventh GaN layer 244. The diameter of the columnar portion 30 in the third AlGaN layer 234 is larger than the diameter of the columnar portion 30 in the fourth AlGaN layer 236. The refractive index of the third AlGaN layer 234 is lower than the refractive index of the fourth AlGaN layer 236. The Al composition of the third AlGaN layer 234 is higher than the Al composition of the fourth AlGaN layer 236.

[0078] The fourth AlGaN layer 236 is provided between the third AlGaN layer 234 and the light emitting layer 34. The fourth AlGaN layer 236 is sandwiched between the seventh GaN layer 244 and the eighth GaN layer 246.

[0079] As described above, the second semiconductor layer 36 has a plurality of AlGaN layers in which the Al composition increases from the light emitting layer 34 toward the second electrode 42. The number of AlGaN layers is not particularly limited as long as it is two or more. The AlGaN layers and GaN layers of the second semiconductor layer 36 may form a superlattice (SL) pseudo-alloyed crystal.

[0080] The light emitting device 200 has, for example, the following advantages.

[0081] In the light emitting device 200, the first semiconductor layer 32 includes a first InGaN layer 210, a second InGaN layer 212 provided between the first InGaN layer 210 and the light emitting layer 34, and a first GaN layer 220 provided between the first InGaN layer 210 and the second InGaN layer 212. The diameter of the columnar portion 30 in the first InGaN layer 210 is smaller than the minimum diameter D3 of the columnar portion 30 in the second semiconductor layer 36 and the diameter of the columnar portion 30 in the second InGaN layer 212. The refractive index of the first InGaN layer 210 is higher than the refractive index of the second semiconductor layer 36 and the refractive index of the second InGaN layer 212, and the refractive index of the second InGaN layer 212 is higher than the refractive index of the first GaN layer 220.

[0082] Therefore, in the light emitting device 200, the difference between the average refractive index in the in-plane direction of the stack 20 in the first InGaN layer 210 and the average refractive index in the in-plane direction of the stack 20 in the second semiconductor layer 36 can be made smaller than when, for example, the refractive index of the first InGaN layer, the refractive index of the second semiconductor layer, and the refractive index of the second InGaN layer are equal to each other. Furthermore, the difference between the average refractive index in the in-plane direction of the stack 20 in the first InGaN layer 210 and the average refractive index in the in-plane direction of the stack 20 in the second InGaN layer 212 can be made smaller. This allows the peak of the light intensity in the stacking direction to be aligned with the position of the light emitting layer 34. As a result, light can be confined in the light emitting layer 34, and the light confinement coefficient can be improved.

[0083] In the light-emitting device 200, the first semiconductor layer 32 includes a second InGaN layer 212 provided between the first InGaN layer 210 and the light-emitting layer 34, and a first GaN layer 220 provided between the first InGaN layer 210 and the second InGaN layer 212. The diameter of the columnar portion 30 in the first InGaN layer 210 is smaller than the diameter of the columnar portion 30 in the second InGaN layer 212. The composition formula of the first InGaN layer 210 is In x Ga 1-x N, and the composition formula of the second InGaN layer 212 is In y Ga 1-y N, where x and y satisfy 0 < y < x < 1.

[0084] Therefore, in the light-emitting device 200, the refractive index of the first InGaN layer 210 can be made higher than the refractive index of the second InGaN layer 212. As a result, compared with the case where the refractive index of the first InGaN layer 210 is equal to the refractive index of the second InGaN layer 212, the difference between the in-plane average refractive index of the laminate 20 in the first InGaN layer 210 and the in-plane average refractive index of the laminate 20 in the second InGaN layer 212 can be reduced.

[0085] Furthermore, in the light-emitting device 200, since the first GaN layer 220 is provided between the first InGaN layer 210 and the second InGaN layer 212, the thickness of one InGaN layer can be reduced. Thereby, the possibility of defects occurring in the InGaN layer can be reduced.

[0086] In the light-emitting device 200, the second semiconductor layer 36 includes a first AlGaN layer 230, a second AlGaN layer 232 provided between the first AlGaN layer 230 and the light-emitting layer 34, and a fifth GaN layer 240 provided between the first AlGaN layer 230 and the second AlGaN layer 232. The diameter of the columnar portion 30 in the first AlGaN layer 230 is larger than the diameter of the columnar portion 30 in the second AlGaN layer 232, and the refractive index of the first AlGaN layer 230 is lower than the refractive index of the second AlGaN layer 232.

[0087] Therefore, in the light emitting device 200, the difference between the average refractive index in the in-plane direction of the stacked body 20 in the first AlGaN layer 230 and the average refractive index in the in-plane direction of the stacked body 20 in the second AlGaN layer 232 can be made smaller than when the refractive index of the first AlGaN layer 230 and the refractive index of the second AlGaN layer 232 are equal to each other. Furthermore, since one AlGaN layer can be made thinner, the possibility of defects occurring in the AlGaN layer can be reduced.

[0088] 2.2. Manufacturing method of light-emitting device Next, a method for manufacturing the light emitting device 200 according to the second embodiment will be described. In the method for manufacturing the light emitting device 200 according to the second embodiment, when the first semiconductor layer 32 is grown, the shutter is switched at short intervals to stack an InGaN layer and a GaN layer. Furthermore, when the second semiconductor layer 36 is grown, the shutter is switched at short intervals to stack an AlGaN layer and a GaN layer. Other than the above, the method for manufacturing the light emitting device 200 according to the second embodiment is basically the same as the method for manufacturing the light emitting device 100 according to the first embodiment described above.

[0089] 3. Third embodiment Next, a projector according to a third embodiment will be described with reference to the drawings. Fig. 8 is a diagram illustrating a projector 900 according to this embodiment.

[0090] The projector 900 includes, for example, a light emitting device 100 as a light source.

[0091] Projector 900 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. 8.

[0092] The projector 900 further includes a first optical element 902R, a second optical element 902G, a third optical element 902B, a first light modulation device 904R, a second light modulation device 904G, a third light modulation device 904B, and a projection device 908, which are provided in the housing. The first light modulation device 904R, the second light modulation device 904G, and the third light modulation device 904B are, for example, transmissive liquid crystal light valves. The projection device 908 is, for example, a projection lens.

[0093] The light emitted from red light source 100R is incident on first optical element 902R. The light emitted from red light source 100R is collected by first optical element 902R. Note that first optical element 902R may have a function other than collecting light. The same applies to second optical element 902G and third optical element 902B described later.

[0094] The light collected by the first optical element 902R is incident on the first light modulation device 904R. The first light modulation device 904R modulates the incident light in accordance with image information. The projection device 908 then enlarges the image formed by the first light modulation device 904R and projects it onto the screen 910.

[0095] The light emitted from green light source 100G is incident on second optical element 902G. The light emitted from green light source 100G is collected by second optical element 902G.

[0096] The light collected by the second optical element 902G is incident on the second light modulation device 904G. The second light modulation device 904G modulates the incident light in accordance with image information. The projection device 908 then enlarges the image formed by the second light modulation device 904G and projects it onto the screen 910.

[0097] The light emitted from blue light source 100B is incident on third optical element 902B. The light emitted from blue light source 100B is collected by third optical element 902B.

[0098] The light collected by the third optical element 902B enters the third light modulation device 904B. The third light modulation device 904B modulates the incident light in accordance with image information. The projection device 908 then enlarges the image formed by the third light modulation device 904B and projects it onto the screen 910.

[0099] The projector 900 may also have a cross dichroic prism 906 that combines the light emitted from the first light modulation device 904R, the second light modulation device 904G, and the third light modulation device 904B and guides the combined light to the projection device 908.

[0100] The three color lights modulated by the first light modulation device 904R, the second light modulation device 904G, and the third light modulation device 904B enter a cross dichroic prism 906. The cross dichroic prism 906 is formed by bonding four right-angle prisms together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are disposed on its inner surface. The three color lights are synthesized by these dielectric multilayer films to form light that represents a color image. The synthesized light is then projected by a projection device 908 onto a screen 910, and an enlarged image is displayed.

[0101] 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 904R, second light modulation device 904G, and third light modulation device 904B, by controlling light emitting device 100 as pixels of an image according to image information. Then, projection device 908 may enlarge and project the image formed by red light source 100R, green light source 100G, and blue light source 100B onto screen 910.

[0102] In the above example, a transmissive liquid crystal light valve is used as the light modulation device, but a light valve other than liquid crystal may be used, or a reflective light valve may be used. Examples of such light valves include a reflective liquid crystal light valve and a digital micro mirror device. The configuration of the projection device is changed as appropriate depending on the type of light valve used.

[0103] 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.

[0104] The light emitting devices according to the above-described embodiments can be used in applications other than projectors, such as indoor and outdoor lighting, displays, laser printers, scanners, car lights, sensing devices that use light, and light sources for communication devices.

[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 appropriately combined.

[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 in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

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

[0108] One aspect of the light emitting device is A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer; a diameter of the columnar portion in the first semiconductor layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer at a first position in a stacking direction of the stacked body, and is maximum at a second position different from the first position in the stacking direction; The refractive index of the first semiconductor layer at the first position is higher than the refractive index of the second semiconductor layer and the refractive index of the first semiconductor layer at the second position.

[0109] According to this light emitting device, the optical confinement coefficient can be improved.

[0110] In one embodiment of the light emitting device, the diameter of the columnar portion in the first semiconductor layer is smallest at the first position, The refractive index of the first semiconductor layer may be highest at the first location.

[0111] According to this light emitting device, it is possible to reduce the difference between the average refractive index in the in-plane direction of the laminate 20 at the first position and the average refractive index in the in-plane direction of the portion (laminar portion) in which the first semiconductor layer is provided at a position other than the first position.

[0112] In one embodiment of the light emitting device, The diameter of the columnar portion in the first semiconductor layer may decrease with increasing distance from the light emitting layer.

[0113] In one embodiment of the light emitting device, The refractive index of the first semiconductor layer may increase with increasing distance from the light emitting layer.

[0114] According to this light emitting device, the average refractive index in the in-plane direction of the stack in the first semiconductor layer can be made constant, for example, in the stacking direction.

[0115] In one embodiment of the light emitting device, the first semiconductor layer includes an InGaN layer and a GaN layer; The InGaN layer is provided at the first location; The GaN layer may be provided at the second location.

[0116] According to this light emitting device, the refractive index at the first position of the first semiconductor layer can be made higher than the refractive index at the second position of the first semiconductor layer.

[0117] In one embodiment of the light emitting device, In the stacking direction, a diameter of the columnar portion in the second semiconductor layer and a refractive index of the second semiconductor layer are not constant, a diameter of the columnar portion in the second semiconductor layer is smallest at a third position in the stacking direction, The refractive index of the second semiconductor layer may be highest at the third position.

[0118] According to this light emitting device, it is possible to reduce the difference between the average refractive index in the in-plane direction of the stack at the third position and the average refractive index in the in-plane direction of the stack at positions other than the third position.

[0119] In one embodiment of the light emitting device, The diameter of the columnar portion in the second semiconductor layer may increase with increasing distance from the light emitting layer.

[0120] In one embodiment of the light emitting device, The refractive index of the second semiconductor layer may decrease with increasing distance from the light emitting layer.

[0121] According to this light emitting device, the average refractive index in the in-plane direction of the stack in the second semiconductor layer can be made constant, for example, in the stacking direction.

[0122] In one embodiment of the light emitting device, a diameter of the columnar portion in the second semiconductor layer is maximum at a fourth position different from the third position in the stacking direction, the second semiconductor layer includes a GaN layer and an AlGaN layer; The GaN layer is provided at the third position; The AlGaN layer may be provided at the fourth position.

[0123] According to this light emitting device, the refractive index at the fourth position of the second semiconductor layer can be made lower than the refractive index at the third position of the second semiconductor layer.

[0124] One aspect of the light emitting device is A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer; The first semiconductor layer is The first layer, a second layer provided between the first layer and the light-emitting layer; a third layer disposed between the first layer and the second layer; and having a diameter of the columnar portion in the first layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer and a diameter of the columnar portion in the second layer; a refractive index of the first layer is higher than a refractive index of the second semiconductor layer and a refractive index of the second layer; A light emitting device, wherein the refractive index of the second layer is higher than the refractive index of the third layer.

[0125] According to this light emitting device, the optical confinement coefficient can be improved.

[0126] One aspect of the light-emitting device includes a laminate having a plurality of columnar portions, each of the plurality of columnar portions has 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 has a maximum diameter of the columnar portion in the first semiconductor layer is smaller than a maximum diameter of the columnar portion in the second semiconductor layer, the first semiconductor layer has a first InGaN layer, a diameter of the columnar portion in the first InGaN layer is smaller than a minimum diameter of the columnar portion in the second semiconductor layer, the second semiconductor layer has at least one of a GaN layer and an AlGaN layer.

[0127] According to this light-emitting device, the light confinement factor can be improved.

[0128] In one aspect of the light-emitting device, the first semiconductor layer has a second InGaN layer provided between the first InGaN layer and the light-emitting layer, and a GaN layer provided between the first InGaN layer and the second InGaN layer, and has a diameter of the columnar portion in the first InGaN layer is smaller than a diameter of the columnar portion in the second InGaN layer, a composition formula of the first InGaN layer is In x Ga 1-x N, a composition formula of the second InGaN layer is In y Ga 1-y N, where 0 < y < x < 1 for x and y. According to this light-emitting device, the refractive index of the first InGaN layer can be made higher than the refractive index of the second InGaN layer

[0129] In one embodiment of the light emitting device, The second semiconductor layer is a first AlGaN layer; a second AlGaN layer provided between the first AlGaN layer and the light emitting layer; a GaN layer provided between the first AlGaN layer and the second AlGaN layer; having a diameter of the columnar portion in the first AlGaN layer is larger than a diameter of the columnar portion in the second AlGaN layer; A light emitting device, wherein the first AlGaN layer has a lower refractive index than the second AlGaN layer.

[0130] According to this light emitting device, it is possible to reduce the difference between the average refractive index in the in-plane direction of the stack in the first AlGaN layer and the average refractive index in the in-plane direction of the stack in the second AlGaN layer.

[0131] One aspect of the projector is The present invention has one aspect of the light emitting device. [Explanation of symbols]

[0132] 10...substrate, 20...laminated body, 22...buffer layer, 24...mask layer, 30...columnar portion, 32...first semiconductor layer, 34...light emitting layer, 36...second semiconductor layer, 40...first electrode, 42...second electrode, 50...InGaN layer, 52...GaN layer, 60...GaN layer, 62...AlGaN layer, 100...light emitting device, 100R...red light source, 100G...green light source, 100B...blue light source, 200...light emitting device, 210...first InGaN layer, 212...second InGaN layer, 214...third InGaN layer, 216...fourth InGaN layer, 220...first GaN layer, 222...second GaN layer, 224...third GaN layer, 226...fourth GaN layer, 230...th 1AlGaN layer, 232...second AlGaN layer, 234...third AlGaN layer, 236...fourth AlGaN layer, 240...fifth GaN layer, 242...sixth GaN layer, 244...seventh GaN layer, 246...eighth GaN layer, 900...projector, 902R...first optical element, 902G...second optical element, 902B...third optical element, 904R...first optical modulation device, 904G...second optical modulation device, 904B...third optical modulation device, 906...cross dichroic prism, 908...projection device, 910...screen, 1000...light emitting device, 1030...columnar portion, 1032...first semiconductor layer, 1034...light emitting layer, 1036...second semiconductor layer

Claims

1. A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having The maximum diameter of the columnar portion in the first semiconductor layer is Smaller than the maximum diameter of the The diameter of the columnar portion in the first semiconductor layer is a first position in the stacking direction of the stacked body. and the diameter of the second semiconductor layer is smaller than the minimum diameter of the columnar portion in the stacking direction. the second position is different from the first position, The refractive index of the first semiconductor layer at the first position is equal to the refractive index of the second semiconductor layer and a refractive index higher than the refractive index at the second position of the first semiconductor layer, The diameter of the columnar portion in the first semiconductor layer decreases with increasing distance from the light emitting layer. And, A light emitting device, wherein the refractive index of the first semiconductor layer increases with increasing distance from the light emitting layer.

2. In claim 1, a diameter of the columnar portion in the first semiconductor layer is smallest at the first position, A light emitting device, wherein the refractive index of the first semiconductor layer is highest at the first location.

3. A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having The maximum diameter of the columnar portion in the first semiconductor layer is Smaller than the maximum diameter of the The diameter of the columnar portion in the first semiconductor layer is a first position in the stacking direction of the stacked body. and the diameter of the second semiconductor layer is smaller than the minimum diameter of the columnar portion in the stacking direction. the second position is different from the first position, The refractive index of the first semiconductor layer at the first position is equal to the refractive index of the second semiconductor layer and a refractive index higher than the refractive index at the second position of the first semiconductor layer, The first semiconductor layer includes an InGaN layer and a GaN layer, The InGaN layer is provided at the first position; The GaN layer is disposed at the second location.

4. In any one of claims 1 to 3, In the stacking direction, the diameter of the columnar portion in the second semiconductor layer and the The refractive index of the conductor layer is not constant, The diameter of the columnar portion in the second semiconductor layer is minimum at a third position in the stacking direction. can be, A light emitting device, wherein the refractive index of the second semiconductor layer is highest at the third position.

5. In claim 4, The diameter of the columnar portion in the second semiconductor layer increases with increasing distance from the light emitting layer. A light-emitting device.

6. In claim 5, A light emitting device, wherein the refractive index of the second semiconductor layer decreases with increasing distance from the light emitting layer.

7. In any one of claims 4 to 6, The diameter of the columnar portion in the second semiconductor layer is different from that at the third position in the stacking direction. and at a fourth position, the second semiconductor layer includes a GaN layer and an AlGaN layer; The GaN layer is provided at the third position; The AlGaN layer is provided at the fourth location.

8. A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having The maximum diameter of the columnar portion in the first semiconductor layer is Smaller than the maximum diameter of the The first semiconductor layer is A first layer; a second layer provided between the first layer and the light-emitting layer; a third layer disposed between the first layer and the second layer; having The diameter of the columnar portion in the first layer is the minimum diameter of the columnar portion in the second semiconductor layer. and smaller than the diameter of the columnar portion in the second layer, The refractive index of the first layer is higher than the refractive index of the second semiconductor layer and the refractive index of the second layer. Ku, A light emitting device, wherein the refractive index of the second layer is higher than the refractive index of the third layer.

9. A laminate having a plurality of columnar portions, Each of the plurality of columnar portions is A first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type different from the first conductivity type; a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; having The maximum diameter of the columnar portion in the first semiconductor layer is Smaller than the maximum diameter of the the first semiconductor layer comprises a first InGaN layer; The diameter of the columnar portion in the first InGaN layer is Smaller than the minimum diameter of the The second semiconductor layer has at least one of a GaN layer and an AlGaN layer. Place.

10. In claim 9, The first semiconductor layer is a second InGaN layer provided between the first InGaN layer and the light emitting layer; a GaN layer provided between the first InGaN layer and the second InGaN layer; having The diameter of the columnar portion in the first InGaN layer is Smaller than the diameter of the columnar part, The composition formula of the first InGaN layer is InxGa1-xN, The composition formula of the second InGaN layer is InGa1-yN, A light emitting device, wherein the x and y satisfy 0<y<x<1.

11. In any one of claims 8 to 10, The second semiconductor layer is a first AlGaN layer; a second AlGaN layer provided between the first AlGaN layer and the light emitting layer; a GaN layer provided between the first AlGaN layer and the second AlGaN layer; having The diameter of the columnar portion in the first AlGaN layer is Larger than the diameter of the columnar part, The refractive index of the first AlGaN layer is lower than the refractive index of the second AlGaN layer. Place.

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

Images