阅读说明：本技术 发光装置、投影仪以及显示器 (Light emitting device, projector, and display ) 是由 次六宽明 岸野克巳 于 2020-10-27 设计创作，主要内容包括：提供发光装置、投影仪以及显示器,能够降低由电极引起的光的损失并且能够提高光的取出效率。发光装置具有：基体；以及层叠体,其设置于基体,具有多个柱状部,柱状部具有：第1半导体层；第2半导体层,其导电类型与第1半导体层不同；以及发光层,其设置在所述第1半导体层与所述第2半导体层之间,所述层叠体具有第3半导体层,该第3半导体层连接在所述第2半导体层的与所述基体相反的一侧并且导电类型与所述第2半导体层相同,所述第2半导体层设置在所述发光层与所述第3半导体层之间,在所述第3半导体层设置有凹部,在所述第3半导体层的与所述基体侧相反的一侧的面设置有所述凹部的开口,所述凹部的底的直径比所述凹部的开口的直径小。(Provided are a light-emitting device, a projector, and a display, wherein light loss caused by an electrode can be reduced and light extraction efficiency can be improved. The light emitting device includes: a substrate; and a laminate provided on the base body and having a plurality of columnar portions, the columnar portions having: 1 st semiconductor layer; a 2 nd semiconductor layer having a conductivity type different from that of the 1 st semiconductor layer; and a light-emitting layer provided between the 1 st semiconductor layer and the 2 nd semiconductor layer, wherein the stacked body has a 3 rd semiconductor layer, the 3 rd semiconductor layer being connected to a side of the 2 nd semiconductor layer opposite to the base and having the same conductivity type as the 2 nd semiconductor layer, the 2 nd semiconductor layer is provided between the light-emitting layer and the 3 rd semiconductor layer, a recess is provided in the 3 rd semiconductor layer, an opening of the recess is provided on a surface of the 3 rd semiconductor layer opposite to the base, and a diameter of a bottom of the recess is smaller than a diameter of the opening of the recess.)

1. A light emitting device, comprising:

a substrate; and

a laminate provided on the base and having a plurality of columnar portions,

the columnar portion has:

1 st semiconductor layer;

a 2 nd semiconductor layer having a conductivity type different from that of the 1 st semiconductor layer; and

a light emitting layer disposed between the 1 st semiconductor layer and the 2 nd semiconductor layer,

the stacked body has a 3 rd semiconductor layer which is connected to a side of the 2 nd semiconductor layer opposite to the base body and has the same conductivity type as the 2 nd semiconductor layer,

the 2 nd semiconductor layer is disposed between the light emitting layer and the 3 rd semiconductor layer,

a recess is provided in the 3 rd semiconductor layer,

an opening of the recess is provided on a surface of the 3 rd semiconductor layer opposite to the substrate side,

the bottom of the recess has a diameter smaller than the diameter of the opening of the recess.

2. The light emitting device according to claim 1,

an electrode is provided on the side of the laminate opposite to the substrate side.

3. The light emitting device according to claim 2,

when viewed from the stacking direction of the stacked body, a through hole penetrating the electrode is provided at a position of the electrode overlapping the recess.

4. The light-emitting device according to any one of claims 1 to 3,

a plurality of said recesses are provided and,

a plurality of the columnar portions are arranged at a 1 st pitch in a 1 st direction,

a plurality of the concave portions are arranged at a 2 nd pitch in a 2 nd direction,

the 1 st direction is a direction in which the columnar portions are arranged at the shortest pitch,

the 2 nd direction is a direction in which the concave portions are arranged at the shortest pitch,

the 2 nd pitch is less than the 1 st pitch.

5. The light-emitting device according to any one of claims 1 to 4,

the opening of the recess has a diameter smaller than the diameter of the columnar portion.

6. The light-emitting device according to any one of claims 1 to 5,

the concave part is in the shape of a cone or a pyramid.

7. The light-emitting device according to any one of claims 1 to 6,

the diameter of the recess becomes smaller from the opening of the recess toward the bottom of the recess.

8. A projector having the light-emitting device according to any one of claims 1 to 7.

9. A display having the light-emitting device according to any one of claims 1 to 7.

Technical Field

The invention relates to a light emitting device, a projector, and a display.

Background

Semiconductor lasers are expected as next-generation light sources with high luminance. In particular, a semiconductor laser having a nanostructure such as a nanopillar (nanocolumn), a nanowire (nanowire), a nanorod (nanorod), or a nanopillar (nanopillar) is expected to realize a light-emitting device which can emit light at a high output at a narrow emission angle by a photonic crystal effect.

For example, patent document 1 discloses a light emitting diode in which an n-type GaN nanorod layer and a light emitting layer are formed on a silicon substrate, and a p-type electrode is formed to be semi-transparent after a p-type GaN contact layer is epitaxially grown while enlarging the diameter of the nanorod, wherein an absorption/re-emission layer realized by a multiple quantum well structure or a double hetero structure is provided on the n-type GaN nanorod layer, thereby improving light extraction efficiency.

Patent document 1: japanese patent laid-open publication No. 2007 and 49062

In the light-emitting device having the nanopillars as described above, conditions such as lattice matching need to be considered depending on the material of the light-emitting layer or the material of the substrate, and the selection of the material is greatly limited. Therefore, it is difficult to obtain a difference in refractive index between the active layer and the cover layer, and for example, light generated in the active layer leaks to the electrode side and is absorbed in the electrode to cause a loss. In such a light emitting device, as disclosed in patent document 1, improvement in light extraction efficiency is required.

Disclosure of Invention

One embodiment of a light-emitting device of the present invention includes: a substrate; and a laminate provided on the base body, the laminate having a plurality of columnar portions, the columnar portions having: 1 st semiconductor layer; a 2 nd semiconductor layer having a conductivity type different from that of the 1 st semiconductor layer; and a light-emitting layer provided between the 1 st semiconductor layer and the 2 nd semiconductor layer, wherein the stacked body has a 3 rd semiconductor layer, the 3 rd semiconductor layer being connected to a side of the 2 nd semiconductor layer opposite to the base and having the same conductivity type as the 2 nd semiconductor layer, the 2 nd semiconductor layer is provided between the light-emitting layer and the 3 rd semiconductor layer, the 3 rd semiconductor layer is provided with a recess, a surface of the 3 rd semiconductor layer opposite to the base is provided with an opening of the recess, and a diameter of a bottom of the recess is smaller than a diameter of the opening of the recess.

In one embodiment of the light-emitting device, an electrode may be provided on a side of the laminate opposite to the substrate side.

In one embodiment of the light-emitting device, a through hole penetrating the electrode may be provided at a position of the electrode overlapping the concave portion when viewed from a stacking direction of the stacked body.

In one aspect of the light emitting device, a plurality of the concave portions may be provided, the plurality of the columnar portions may be arranged at a 1 st pitch in a 1 st direction, the plurality of the concave portions may be arranged at a 2 nd pitch in a 2 nd direction, the 1 st direction may be a direction in which the columnar portions are arranged at a shortest pitch, the 2 nd direction may be a direction in which the concave portions are arranged at a shortest pitch, and the 2 nd pitch may be smaller than the 1 st pitch.

In one aspect of the light-emitting device, an opening of the recess may have a diameter smaller than a diameter of the columnar portion.

In one embodiment of the light-emitting device, the recess may have a conical or pyramidal shape.

In one aspect of the light-emitting device, the diameter of the recess may be smaller from the opening of the recess toward the bottom of the recess.

One embodiment of the projector according to the present invention includes the light-emitting device.

One embodiment of the display device of the present invention includes the light-emitting device.

Drawings

Fig. 1 is a sectional view schematically showing a light-emitting device of embodiment 1.

Fig. 2 is a plan view schematically showing a light-emitting device of embodiment 1.

Fig. 3 is a cross-sectional view schematically showing the 3 rd semiconductor layer of the light-emitting device of embodiment 1.

Fig. 4 is a sectional view schematically showing the 3 rd semiconductor layer of the light emitting device of reference example 1.

Fig. 5 is a sectional view schematically showing the 3 rd semiconductor layer of the light emitting device of the 2 nd reference example.

Fig. 6 is a sectional view schematically showing a manufacturing process of a light-emitting device according to embodiment 1.

Fig. 7 is a sectional view schematically showing a light-emitting device of embodiment 2.

Fig. 8 is a cross-sectional view schematically showing the 3 rd semiconductor layer of the light-emitting device of embodiment 2.

Fig. 9 is a diagram schematically showing a projector of embodiment 3.

Description of the reference symbols

2: an area; 4: an area; 10: a substrate; 20: a laminate; 22: a buffer layer; 30: a columnar portion; 32: 1 st semiconductor layer; 34: a light emitting layer; 36: a 2 nd semiconductor layer; 38: a 3 rd semiconductor layer; 38 a: the 1 st surface; 38 b: the 2 nd surface; 40: a recess; 41: an opening; 42: a bottom; 50: a 1 st electrode; 52: a 2 nd electrode; 53: a through hole; 100: a light emitting device; 100R: a red light source; 100G: a green light source; 100B: a blue light source; 200: a light emitting device; 900: a projector; 902R: 1 st optical element; 902G: a 2 nd optical element; 902B: a 3 rd optical element; 904R: 1 st light modulation device; 904G: a 2 nd light modulation device; 904B: a 3 rd light modulation device; 906: a cross dichroic prism; 908: a projection device; 910: and (6) a screen.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below do not limit the contents of the present invention described in the claims. Moreover, not all of the structures described below are essential components of the present invention.

1. Embodiment 1

1.1. Light emitting device

First, a light-emitting device according to embodiment 1 will be described with reference to the drawings. Fig. 1 is a sectional view schematically showing a light-emitting device 100 of embodiment 1. Fig. 2 is a plan view schematically showing light-emitting device 100 of embodiment 1. In addition, fig. 1 is a sectional view taken along line I-I of fig. 2.

The light-emitting device 100 includes a substrate 10, a laminate 20, a 1 st electrode 50, and a 2 nd electrode 52.

The substrate 10 has, for example, a plate-like shape. The substrate 10 is, for example, a Si substrate, a GaN substrate, a sapphire substrate, or the like.

The laminated body 20 is provided on the base body 10. The laminate 20 includes a buffer layer 22 and a plurality of columnar portions 30.

In the present specification, when the light-emitting layer 34 is used as a reference in the stacking direction of the stacked body 20 (hereinafter, also simply referred to as "stacking direction"), the direction from the light-emitting layer 34 to the 2 nd semiconductor layer 36 is referred to as "upper" and the direction from the light-emitting layer 34 to the 1 st semiconductor layer 32 is referred to as "lower". The "lamination direction of the laminate" refers to the lamination direction of the 1 st semiconductor layer 32 and the light-emitting layer 34.

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.

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. The pillar portion 30 is also referred to as a nanopillar, a nanowire, a nanorod, or a nanopillar, for example. The columnar portion 30 has a cross-sectional shape in a direction perpendicular to the stacking direction, for example, a polygon, a circle, or the like.

The diameter of the columnar portion 30 is, for example, 50nm or more and 250nm or less. By setting the diameter of the columnar portion 30 to 250nm or less, a high-quality crystalline light-emitting layer 34 can be obtained, and deformation in the light-emitting layer 34 can be reduced. This enables efficient amplification of light generated in the light-emitting layer 34. The plurality of columnar portions 30 are, for example, equal in diameter to each other.

The "diameter of the columnar portion" is a diameter when the planar shape of the columnar portion 30 is a circle, and is a diameter of a minimum including 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 a polygon when the planar shape of the columnar portion 30 is polygonal, and the diameter of the smallest circle that includes an ellipse when the planar shape of the columnar portion 30 is elliptical.

The columnar portion 30 is provided in plurality. The interval between adjacent columnar portions 30 is, for example, 1nm or more and 250nm or less. The plurality of columnar portions 30 are arranged at a 1 st pitch P1 in the 1 st direction in a plan view seen from the stacking direction (hereinafter, also simply referred to as "in plan view"). The 1 st direction is a direction in which the columnar portions 30 are arranged at the shortest pitch. The plurality of columnar portions 30 are arranged in a triangular lattice shape, a tetragonal lattice shape, or the like, for example. The plurality of columnar portions 30 can exhibit the effect of photonic crystals.

The "pitch of the columnar portions" refers to a distance between centers of the columnar portions 30 adjacent to each other along the 1 st direction. The "center of the columnar portion" is the center of a circle when the planar shape of the columnar portion 30 is the circle, and is the center of a minimum inclusion circle when the planar shape of the columnar portion 30 is not the 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 including the polygon therein, and when the planar shape of the columnar portion 30 is an ellipse, the center of the columnar portion 30 is the center of the smallest circle including the ellipse therein.

The columnar portion 30 has a 1 st semiconductor layer 32, a light-emitting layer 34, and a 2 nd semiconductor layer 36.

The 1 st semiconductor layer 32 is disposed on the buffer layer 22. The 1 st semiconductor layer 32 is disposed between the substrate 10 and the light emitting layer 34. The 1 st semiconductor layer 32 is an n-type semiconductor layer. The 1 st semiconductor layer 32 is, for example, an n-type GaN layer doped with Si.

The light emitting layer 34 is disposed on the 1 st semiconductor layer 32. The light emitting layer 34 is disposed between the 1 st semiconductor layer 32 and the 2 nd semiconductor layer 36. The light emitting layer 34 generates light by being injected with current. The light emitting layer 34 has, for example, a multiple quantum well structure in which a quantum well structure composed of an i-type GaN layer and an i-type InGaN layer are stacked.

The 2 nd semiconductor layer 36 is provided on the light emitting layer 34. The 2 nd semiconductor layer 36 is disposed between the light emitting layer 34 and the 3 rd semiconductor layer 38. The 2 nd semiconductor layer 36 is a layer having a different conductivity type from the 1 st semiconductor layer 32. The 2 nd semiconductor layer 36 is a p-type semiconductor layer. The 2 nd semiconductor layer 36 is, for example, a p-type GaN layer doped with Mg. The 1 st semiconductor layer 32 and the 2 nd semiconductor layer 36 are cladding layers having a function of confining light to the light-emitting layer 34.

The adjacent columnar portions 30 are, for example, spaced apart from each other. Further, a light propagation layer may be provided between adjacent columnar portions 30. The light transmitting layer is, for example, a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, or the like. The light generated in the light emitting layer 34 can propagate in the plurality of columnar portions 30 in the direction perpendicular to the lamination direction through the light propagation layer.

The stack 20 also has a 3 rd semiconductor layer 38. The 3 rd semiconductor layer 38 is disposed on the 2 nd semiconductor layer 36. The 3 rd semiconductor layer 38 is connected to the 2 nd semiconductor layer 36 on the side opposite to the substrate 10. The 3 rd semiconductor layer 38 is a layer of the same conductivity type as the 2 nd semiconductor layer 36. The 3 rd semiconductor layer 38 is a p-type semiconductor layer. The 3 rd semiconductor layer 38 is, for example, a p-type GaN layer doped with Mg. The 3 rd semiconductor layer 38 is, for example, a contact layer, and the 2 nd electrode 52 is in contact with the 3 rd semiconductor layer 38. The material of the 3 rd semiconductor layer 38 may be the same as that of the 2 nd semiconductor layer 36.

The 3 rd semiconductor layer 38 is one layer provided across the plurality of columnar portions 30. That is, the 3 rd semiconductor layer 38 does not constitute the columnar portion 30.

Fig. 3 is a cross-sectional view schematically showing the 3 rd semiconductor layer 38 of the light emitting device 100. Fig. 3 also shows a graph showing the distribution of the average refractive index of the 3 rd semiconductor layer 38 in the stacking direction. The average refractive index is an average of the refractive indices in the in-plane direction of the 3 rd semiconductor layer 38.

The 3 rd semiconductor layer 38 has a 1 st surface 38a on the substrate 10 side and a 2 nd surface 38b on the opposite side of the 1 st surface 38 a. The 2 nd surface 38b of the 3 rd semiconductor layer 38 is a flat surface. A plurality of recesses 40 are provided in the 3 rd semiconductor layer 38.

As shown in fig. 2, the planar shape of the recess 40 is a circle. That is, the opening 41 of the recess 40 is circular in shape. The planar shape of the recess 40 is not particularly limited, and may be a polygon, an ellipse, or the like. The planar shape of the recess 40 is the shape of the recess 40 when viewed from the stacking direction.

As shown in fig. 3, the diameter B of the bottom 42 of the recess 40 is smaller than the diameter T of the opening 41 of the recess 40. The diameter T of the recess 40 is the diameter of the recess 40 in the 2 nd face 38 b. The diameter T of the recess 40 is, for example, 5nm or more and 100nm or less. The diameter of the recess 40 becomes smaller from the opening 41 toward the bottom 42. The concave portion 40 is, for example, a truncated cone or a truncated pyramid. The diameter T of the concave portion 40 is smaller than the diameter of the columnar portion 30, for example.

The "diameter of the concave portion" is a diameter when the planar shape of the concave portion 40 is a circle, and is a diameter of a minimum including circle when the planar shape of the concave portion 40 is not a circle. For example, the diameter of the recess is the diameter of the smallest circle including the polygon when the planar shape of the recess 40 is a polygon, and the diameter of the smallest circle including the ellipse when the planar shape of the recess 40 is an ellipse.

As shown in fig. 1, the recesses 40 are arranged at a 2 nd pitch P2 in the 2 nd direction. The 2 nd direction is a direction in which the concave portions 40 are arranged at the shortest pitch. The 2 nd pitch P2 is less than the 1 st pitch P1. The interval between adjacent recesses 40 is, for example, 5nm to 500 nm. The plurality of concave portions 40 are arranged in, for example, a triangular lattice shape, a tetragonal lattice shape, or the like.

"pitch of the concave portions" means a distance between centers of the concave portions 40 adjacent in the 2 nd direction. The "center of the concave portion" is the center of a circle when the planar shape of the concave portion 40 is a circle, and is the center of a minimum inclusion circle when the planar shape of the concave portion 40 is not a circle. For example, the center of the concave portion 40 is the center of the smallest circle including the polygon when the planar shape of the concave portion 40 is a polygon, and is the center of the smallest circle including the ellipse when the planar shape of the concave portion 40 is an ellipse.

In addition, the recesses 40 may also be randomly provided in the 3 rd semiconductor layer 38. This can prevent the recess 40 from exhibiting the effect of the photonic crystal.

The depth of the recess 40 is smaller than the thickness of the 3 rd semiconductor layer 38, for example. The depth of the recess 40 is the size of the recess 40 in the stacking direction, and is the distance between the opening 41 and the bottom 42. The depth of the recess 40 may be 5 times or more the diameter T of the recess 40.

The inside of the recess 40 is, for example, a void. The inside of the recess 40 may be a low refractive index portion made of a low refractive index material having a lower refractive index than the 3 rd semiconductor layer 38.

The 1 st electrode 50 is disposed on the buffer layer 22. The buffer layer 22 may also make ohmic contact with the 1 st electrode 50. The 1 st electrode 50 is electrically connected to the 1 st semiconductor layer 32. In the illustrated example, the 1 st electrode 50 is electrically connected to the 1 st semiconductor layer 32 via the buffer layer 22. The 1 st electrode 50 is one electrode for injecting current into the light-emitting layer 34. As the 1 st electrode 50, for example, an electrode in which a Cr layer, a Ni layer, and an Au layer are laminated in this order from the buffer layer 22 side is used.

The 2 nd electrode 52 is provided on the opposite side of the laminated body 20 from the base 10 side. In the illustrated example, the 2 nd electrode 52 is provided on the 2 nd surface 38b of the 3 rd semiconductor layer 38. The 2 nd electrode 52 is provided with a through hole 53 at a position overlapping the recess 40 when viewed from the stacking direction. That is, the opening 41 of the recess 40 is not blocked by the 2 nd electrode 52. The 2 nd electrode 52 is not disposed inside the recess 40. The 2 nd electrode 52 is not provided on the surface of the 3 rd semiconductor layer 38 defining the recess 40.

The 2 nd electrode 52 is electrically connected to the 3 rd semiconductor layer 38. The 2 nd electrode 52 is electrically connected to the 2 nd semiconductor layer 36 via the 3 rd semiconductor layer 38. The 2 nd electrode 52 is another electrode for injecting current into the light-emitting layer 34. For example, ITO (indium tin oxide) is used as the 2 nd electrode 52. The film thickness of the 2 nd electrode 52 is, for example, 100nm to 300 nm.

Although not shown, a metal film for reducing contact resistance may be provided between the 3 rd semiconductor layer 38 and the 2 nd electrode 52.

In the light-emitting device 100, the p-type 2 nd semiconductor layer 36, the light-emitting layer 34, and the n-type 1 st semiconductor layer 32 constitute a pin diode. In the light emitting device 100, when a forward bias voltage of the pin diode is applied between the 1 st electrode 50 and the 2 nd electrode 52, a current is injected into the light emitting layer 34, causing recombination of electrons and holes in the light emitting layer 34. Luminescence is generated by this recombination. The light generated in the light emitting layer 34 propagates through the 1 st semiconductor layer 32 and the 2 nd semiconductor layer 36 in a direction perpendicular to the stacking direction, forms a standing wave by the effect of the photonic crystals of the plurality of columnar portions 30, and receives a gain in the light emitting layer 34 to perform laser oscillation. Then, the light emitting device 100 emits the +1 st order diffracted light and the-1 st order diffracted light as laser light in the stacking direction.

Here, in the light-emitting device 100, the recess 40 is provided in the 3 rd semiconductor layer 38. Therefore, in the light-emitting device 100, the loss of light due to the 2 nd electrode 52 can be reduced. Further, in the light emitting device 100, the diameter B of the bottom 42 of the recess 40 is smaller than the diameter T of the recess 40 on the 2 nd surface 38B. Therefore, the light-emitting device 100 can improve the light extraction efficiency. The reason for this will be explained below.

Fig. 4 is a sectional view schematically showing the 3 rd semiconductor layer 38 of the light emitting device of the 1 st reference example. Fig. 4 corresponds to fig. 3, and is different from the example shown in fig. 3 in that the recess 40 is not provided in the 3 rd semiconductor layer 38 in the 1 st reference example shown in fig. 4.

In the light-emitting device 100, as shown in fig. 3, by providing the recessed portion 40 in the 3 rd semiconductor layer 38, the average refractive index in the vicinity of the 2 nd electrode 52 of the 3 rd semiconductor layer 38 can be reduced as compared with the case where the recessed portion 40 is not provided in the 3 rd semiconductor layer 38 shown in fig. 4. Therefore, in the light-emitting device 100, the effect of confining light in the vicinity of the light-emitting layer 34 can be improved, and leakage of light generated in the light-emitting layer 34 to the 2 nd electrode 52 side can be reduced. Therefore, in the light-emitting device 100, the absorption of light by the 2 nd electrode 52 can be reduced, and the loss of light by the 2 nd electrode 52 can be reduced. As a result, in the light-emitting device 100, as shown in fig. 1, the peak of the light intensity can be positioned in the light-emitting layer 34.

Fig. 5 is a sectional view schematically showing the 3 rd semiconductor layer 38 of the light emitting device of the 2 nd reference example. Fig. 5 corresponds to fig. 3, and differs from the example shown in fig. 3 in that in the 2 nd reference example shown in fig. 5, the diameter B of the bottom 42 of the concave portion 40 is equal to the diameter T of the concave portion 40 on the 2 nd surface 38B.

As shown in fig. 5, in the case where the diameter B at the bottom 42 of the recess 40 is equal to the diameter T at the 2 nd surface 38B of the recess 40, that is, in the case where the diameter of the recess 40 is constant in the range from the opening 41 to the bottom 42, in the 3 rd semiconductor layer 38, the variation in the average refractive index at the boundary between the region 2 where the recess 40 is provided and the region 4 where the recess 40 is not provided is large. Therefore, the reflectance at the boundary becomes high, and the efficiency of extracting light generated in the light-emitting layer 34 and emitted in the stacking direction is reduced.

In contrast, in light-emitting device 100, as shown in fig. 3, diameter B of bottom 42 of recess 40 is smaller than diameter T of recess 40 at 2 nd surface 38B. Therefore, in the light-emitting device 100, the change in the average refractive index at the boundary between the region 2 where the concave portion 40 is provided and the region 4 where the concave portion 40 is not provided can be reduced as compared with the case where the diameter B at the bottom 42 of the concave portion 40 and the diameter T at the 2 nd surface 38B of the concave portion 40 are equal as shown in fig. 5.

Specifically, in light-emitting device 100, as shown in fig. 3, the diameter of concave portion 40 decreases from opening 41 toward bottom 42. Therefore, the average refractive index gradually becomes larger from the opening 41 toward the bottom 42. Therefore, the variation in average refractive index at the boundary between the region 2 where the concave portion 40 is provided and the region 4 where the concave portion 40 is not provided is small.

In this way, in the light-emitting device 100, since the change in the average refractive index at the boundary between the region 2 where the concave portion 40 is provided and the region 4 where the concave portion 40 is not provided can be reduced, the reflectance of the 3 rd semiconductor layer 38 with respect to light generated in the light-emitting layer 34 and emitted in the stacking direction can be reduced. Therefore, in the light-emitting device 100, the light generated in the light-emitting layer 34 can be efficiently emitted in the stacking direction.

Further, in the light-emitting device 100, since the diameter of the concave portion 40 becomes smaller from the opening 41 toward the bottom 42, the average refractive index gradually becomes larger from the opening 41 toward the bottom 42. This can reduce the reflectance of the 3 rd semiconductor layer 38 with respect to light generated in the light-emitting layer 34 and emitted in the stacking direction. That is, by providing the concave portion 40 in the 3 rd semiconductor layer 38, a moth-eye structure in which the reflectance is reduced by continuously changing the refractive index can be realized. Therefore, in the light-emitting device 100, the light generated in the light-emitting layer 34 can be efficiently emitted in the stacking direction.

In addition, although the InGaN-based light emitting layer 34 is described above, various material systems capable of emitting light by injecting current may be used as the light emitting layer 34 according to the wavelength of light to be emitted. For example, semiconductor materials such as AlGaN, AlGaAs, InGaAs, InGaAsP, InP, GaP, and AlGaP can be used.

1.2. Effect

In the light-emitting device 100, the recess 40 is provided in the 3 rd semiconductor layer 38, and the diameter B at the bottom 42 of the recess 40 is smaller than the diameter T at the opening 41 of the recess 40. Therefore, in the light-emitting device 100, as described above, the loss of light due to the 2 nd electrode 52 can be reduced, and the light extraction efficiency can be improved.

In the light-emitting device 100, the through-hole 53 penetrating the 2 nd electrode 52 is provided at a position overlapping the recess 40 of the 2 nd electrode 52 when viewed from the stacking direction. Therefore, in the light-emitting device 100, the light extraction efficiency can be improved as compared with the case where the through hole 53 is not provided in the 2 nd electrode 52.

In the light emitting device 100, the plurality of columnar portions 30 are arranged at a 1 st pitch P1 in the 1 st direction, the plurality of concave portions 40 are arranged at a 2 nd pitch P2 in the 2 nd direction, and the 2 nd pitch P2 is smaller than the 1 st pitch P1. This can reduce the influence of the plurality of concave portions 40 on the effect of the photonic crystal exhibited by the plurality of columnar portions 30. For example, when the 1 st pitch P1 and the 2 nd pitch P2 are equal, the effect of the plurality of concave portions 40 on the photonic crystal exhibited by the plurality of columnar portions 30 becomes large.

In the light emitting device 100, the diameter T at the opening 41 of the recess 40 is smaller than the diameter of the columnar portion 30. This can reduce the influence of the plurality of concave portions 40 on the effect of the photonic crystal exhibited by the plurality of columnar portions 30. For example, when the diameter T is equal to the diameter of the columnar portion 30, the effect of the plurality of concave portions 40 on the photonic crystal effect exhibited by the plurality of columnar portions 30 becomes large.

In the light emitting device 100, the diameter of the recess 40 becomes smaller from the opening 41 toward the bottom 42. Thus, as described above, the average refractive index can be gradually changed from the opening 41 of the recess 40 to the bottom 42 of the recess 40, and therefore the reflectance of the 3 rd semiconductor layer 38 can be reduced, and the light extraction efficiency can be further improved.

1.3. Manufacturing method

Next, a method for manufacturing the light-emitting device 100 according to embodiment 1 will be described with reference to the drawings. Fig. 6 is a sectional view schematically showing a manufacturing process of the light emitting device 100 according to embodiment 1.

As shown in fig. 6, the buffer layer 22 is epitaxially grown on the substrate 10. Examples of the method of epitaxial growth include the MOCVD (Metal Organic Chemical Vapor Deposition) method and the MBE (Molecular Beam Epitaxy) method.

Next, a mask layer is formed on the buffer layer 22, and the 1 st semiconductor layer 32, the light-emitting layer 34, and the 2 nd semiconductor layer 36 are epitaxially grown on the buffer layer 22 using the mask layer as a mask. Examples of the method of epitaxial growth include MOCVD method and MBE method. Thereby, the columnar portion 30 is formed.

Next, the 3 rd semiconductor layer 38 is epitaxially grown on the columnar portion 30. At this time, the 3 rd semiconductor layer 38 is formed so as to be a layer spanning over the plurality of columnar portions 30.

For example, the 2 nd semiconductor layer 36 and the 3 rd semiconductor layer 38 may be epitaxially grown continuously. In this case, by adjusting the growth temperature, the distance between the adjacent columnar portions 30 is reduced as the 2 nd semiconductor layer 36 grows, and finally the adjacent columnar portions 30 are connected to each other, thereby forming the 3 rd semiconductor layer 38.

Next, as shown in fig. 1, a 1 st electrode 50 is formed on the buffer layer 22, and a 2 nd electrode 52 is formed on the 3 rd semiconductor layer 38. The 1 st electrode 50 and the 2 nd electrode 52 are formed by, for example, a vacuum evaporation method. The order of formation of the 1 st electrode 50 and the 2 nd electrode 52 is not particularly limited.

Next, a mask layer is formed on the 2 nd electrode 52, the 2 nd electrode 52 and the 3 rd semiconductor layer 38 are etched using the mask layer as a mask, a through hole 53 is formed in the 2 nd electrode 52, and a recess 40 is formed in the 3 rd semiconductor layer 38. At this time, the etching conditions are set such that the diameter of the recess 40 becomes smaller from the opening 41 toward the bottom 42. The etching of the 2 nd electrode 52 and the 3 rd semiconductor layer 38 is performed by, for example, dry etching.

Through the above steps, the light-emitting device 100 can be manufactured.

2. Embodiment 2

Next, a light-emitting device according to embodiment 2 will be described with reference to the drawings. Fig. 7 is a sectional view schematically showing a light-emitting device 200 of embodiment 2. Fig. 8 is a cross-sectional view schematically showing the 3 rd semiconductor layer 38 of the light emitting device 200. Fig. 8 also shows a graph showing the distribution of the average refractive index of the 3 rd semiconductor layer 38 in the stacking direction.

Hereinafter, in the light-emitting device 200 of embodiment 2, the same reference numerals are given to components having the same functions as those of the components of the light-emitting device 100 of embodiment 1, and detailed descriptions thereof are omitted.

In the light emitting device 200, as shown in fig. 7 and 8, the recess 40 has a conical shape, and the bottom 42 of the recess 40 is the apex of the cone. Therefore, as shown in fig. 8, the variation in average refractive index at the boundary between the region 2 where the concave portion 40 is provided and the region 4 where the concave portion 40 is not provided can be further reduced. Therefore, the light-emitting device 200 can further improve the light extraction efficiency as compared with the light-emitting device 100.

In the above description, the case where the shape of the concave portion 40 is a cone has been described, but the shape of the concave portion 40 may be a pyramid, and the bottom 42 of the concave portion 40 may be the apex of the pyramid. In this case, the same operational effect as in the case where the shape of the concave portion 40 is a cone can be obtained.

3. Embodiment 3

Next, a projector according to embodiment 3 will be described with reference to the drawings. Fig. 9 is a diagram schematically illustrating a projector 900 according to embodiment 3.

The projector 900 has, for example, the light-emitting device 100 as a light source.

The projector 900 includes a casing, not shown, and a red light source 100R, a green light source 100G, and a blue light source 100B that emit red light, green light, and blue light, respectively, and are disposed in the casing. For convenience, in fig. 9, the red light source 100R, the green light source 100G, and the blue light source 100B are simplified.

The projector 900 further includes a 1 st optical element 902R, a 2 nd optical element 902G, a 3 rd optical element 902B, a 1 st light modulation device 904R, a 2 nd light modulation device 904G, a 3 rd light modulation device 904B, and a projection device 908 provided in the housing. The 1 st, 2 nd, and 3 rd optical modulation devices 904R, 904G, and 904B are, for example, transmissive liquid crystal light valves. The projection device 908 is, for example, a projection lens.

Light emitted from the red light source 100R enters the 1 st optical element 902R. The light emitted from the red light source 100R is condensed by the 1 st optical element 902R. The 1 st optical element 902R may have a function other than light collection. The same applies to the 2 nd optical element 902G and the 3 rd optical element 902B which will be described later.

The light condensed by the 1 st optical element 902R is incident on the 1 st light modulation device 904R. The 1 st light modulation device 904R modulates the incident light according to the image information. Then, the projection device 908 enlarges and projects an image formed by the 1 st light modulation device 904R onto the screen 910.

Light emitted from the green light source 100G enters the 2 nd optical element 902G. Light emitted from green light source 100G is condensed by 2 nd optical element 902G.

The light condensed by the 2 nd optical element 902G is incident on the 2 nd light modulation device 904G. The 2 nd light modulation device 904G modulates the incident light according to the image information. Then, the projection device 908 enlarges and projects the image formed by the 2 nd light modulation device 904G onto the screen 910.

Light emitted from the blue light source 100B enters the 3 rd optical element 902B. Light emitted from the blue light source 100B is condensed by the 3 rd optical element 902B.

The light condensed by the 3 rd optical element 902B is incident on the 3 rd light modulation device 904B. The 3 rd light modulation device 904B modulates the incident light according to the image information. Then, the projection device 908 enlarges and projects an image formed by the 3 rd light modulation device 904B onto the screen 910.

The projector 900 may further include a cross dichroic prism 906, and the cross dichroic prism 906 may combine the light emitted from the 1 st light modulation device 904R, the 2 nd light modulation device 904G, and the 3 rd light modulation device 904B and guide the combined light to the projector 908.

The 3 color lights modulated by the 1 st light modulation device 904R, the 2 nd light modulation device 904G, and the 3 rd light modulation device 904B are incident on the cross dichroic prism 906. The cross dichroic prism 906 is formed by bonding 4 rectangular prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged on the inner surface thereof. The 3 color lights are combined by the dielectric multilayer films to form light representing a color image. The combined light is then projected onto a screen 910 by a projection device 908, displaying the magnified image.

Note that the red light source 100R, the green light source 100G, and the blue light source 100B may be configured such that the 1 st light modulation device 904R, the 2 nd light modulation device 904G, and the 3 rd light modulation device 904B are not used, by controlling the light emitting device 100 as a pixel of a video based on image information to directly form a video. Then, the projector 908 magnifies and projects the image formed by the red light source 100R, the green light source 100G, and the blue light source 100B onto the screen 910.

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 or a reflective light valve may be used. Examples of such a light valve include a reflective liquid crystal light valve and a Digital Micro Mirror Device (dmd). The configuration of the projection device may be appropriately changed according to the type of light valve used.

The light source may be applied to a light source device of a scanning type image display device having a scanning unit as an image forming device that scans light from the light source on a screen to display an image of a desired size on a display surface.

The light-emitting device of the above embodiment can be used for applications other than a projector. In applications other than projectors, there are light sources such as indoor and outdoor lighting, backlights of displays, laser printers, scanners, in-vehicle lamps, sensor devices using light, and communication devices.

The present invention may omit a part of the configuration or combine the embodiments and the modifications within the scope of the features and effects described in the present application.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes substantially the same structure as that described in the embodiment. Substantially the same structure means, for example, a structure having the same function, method, and result, or a structure having the same purpose and effect. The present invention includes a structure in which an immaterial part of the structure described in the embodiment is replaced. The present invention includes a structure that achieves the same operational effects as the structures described in the embodiments or a structure that can achieve the same object. The present invention includes a configuration in which a known technique is added to the configurations described in the embodiments.