Patent ID: 12224556

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

A preferred embodiment of the present disclosure will hereinafter be described in detail using the drawings. It should be noted that the embodiment described hereinafter does not unreasonably limit the contents of the present disclosure as set forth in the appended claims. Further, all of the constituents described hereinafter are not necessarily essential elements of the present disclosure.

1. Light Emitting Device

1.1. Overall Configuration

First, a light emitting device according to the present embodiment will be described with reference to the drawings.FIG.1is a cross-sectional view schematically showing a light emitting device100according to the present embodiment.

As shown inFIG.1, the light emitting device100has a substrate10, a laminated structure20, a first electrode40, and a second electrode42. The light emitting device100is, for example, a semiconductor laser.

The substrate10is, for example, an Si substrate, a GaN substrate, a sapphire substrate, or an SiC substrate.

The laminated structure20is provided to the substrate10. In the illustrated example, the laminated structure20is disposed on the substrate10. The laminated structure20has, for example, a buffer layer22and columnar parts30.

In the present specification, when taking a light emitting layer34as a reference in a stacking direction of a first semiconductor layer32and the light emitting layer (hereinafter also referred to simply as a “stacking direction”), the description will be presented assuming a direction from the light emitting layer34toward a second semiconductor layer36as an “upward direction,” and a direction from the light emitting layer34toward the first semiconductor layer32as a “downward direction.” Further, a direction perpendicular to the stacking direction is also referred to as an “in-plane direction.”

The buffer layer22is disposed on the substrate10. The buffer layer22is, for example, an Si-doped n-type GaN layer. On the buffer layer22, there is disposed an insulating layer24.

The insulating layer24functions as a mask layer for forming the columnar parts30. The insulating layer24has a plurality of opening parts25. The opening parts25are each a hole penetrating the insulating layer24. The insulating layer24is, for example, a silicon oxide layer, a silicon nitride layer, a silicon layer, a titanium oxide layer, a titanium nitride layer, an aluminum oxide layer, a tantalum oxide layer, a hafnium oxide layer, or a germanium layer.

The columnar parts30are disposed on the buffer layer22. The columnar parts30each have a columnar shape protruding upward from the buffer layer22. In other words, the columnar parts30protrude upward from the substrate10via the buffer layer22. The columnar part30is also referred to as, for example, a nano-column, a nano-wire, a nano-rod, or a nano-pillar. The planar shape of the columnar part30is, for example, a polygon or a circle.

The diametrical size of the columnar part30is, for example, no smaller than 50 nm and no larger than 500 nm. By setting the diametrical size of the columnar part30to be no larger than 500 nm, it is possible to obtain the light emitting layer34made of crystal high in quality, and at the same time, it is possible to reduce a distortion inherent in the light emitting layer34. Thus, it is possible to amplify the light generated in the light emitting layer34with high efficiency.

It should be noted that when the planar shape of the columnar part30is a circle, the “diametrical size of the columnar part” means the diameter of the circle, and when the planar shape of the columnar part30is not a circular shape, the “diametrical size of the columnar part” means the diameter of the minimum bounding circle. For example, when the planar shape of the columnar part30is a polygonal shape, the diametrical size of the columnar part is the diameter of a minimum circle including the polygonal shape inside, and when the planar shape of the columnar part30is an ellipse, the diametrical size of the columnar part30is the diameter of a minimum circle including the ellipse inside. Further, regarding a diametrical size of each of the layers constituting the columnar part, similarly, when the planar shape of each of the layers is a circle, the diametrical size means the diameter of the circle, and when the planar shape of each of the layers is not a circular shape, the diametrical size means the diameter of the minimum bounding circle.

The number of the columnar parts30disposed is two or more. An interval between the columnar parts30adjacent to each other is, for example, no smaller than 1 nm and no larger than 500 nm. The plurality of columnar parts30is arranged at a predetermined pitch in a predetermined direction when viewed from the stacking direction. The plurality of columnar parts30is arranged so as to form, for example, a triangular lattice or a square lattice. The plurality of columnar parts30can develop an effect of a photonic crystal.

It should be noted that the “pitch of the columnar parts” means a distance between the centers of the columnar parts30adjacent to each other along the predetermined direction. When the planar shape of the columnar part30is a circle, the “center of the columnar part” means the center of the circle, and when the planar shape of the columnar part30is not a circular shape, the “center of the columnar part” means the center of the minimum bounding circle. For example, when the planar shape of the columnar part30is a polygonal shape, the center of the columnar part30is the center of a minimum circle including the polygonal shape inside, and when the planar shape of the columnar part30is an ellipse, the center of the columnar part30is the center of a minimum circle including the ellipse inside.

The columnar parts30each have the first semiconductor layer32, the light emitting layer34, and the second semiconductor layer36. It should be noted that the detailed shape and so on of the columnar parts30will be described later.

The first semiconductor layer32is disposed on the buffer layer22. The first semiconductor layer32is disposed between the substrate10and the light emitting layer34. The first semiconductor layer32is, for example, an Si-doped n-type GaN layer.

The light emitting layer34is disposed on the first semiconductor layer32. The light emitting layer34is disposed between the first semiconductor layer32and the second semiconductor layer36. The light emitting layer34generates light in response to injection of an electrical current. The light emitting layer34has, for example, well layers33and barrier layers35. The well layers33and the barrier layers35are each an i-type semiconductor layer which is not intentionally doped with any impurity. The well layers33are each, for example, an InGaN layer. The barrier layers35are each, for example, a GaN layer. The light emitting layer34has an MQW (Multiple Quantum Well) structure constituted by the well layers33and the barrier layers35.

It should be noted that the number of the well layers33and the barrier layers35constituting the light emitting layer34is not particularly limited. For example, the number of the well layers33disposed can be one, and in this case, the light emitting layer34has an SQW (Single Quantum Well) structure.

The second semiconductor layer36is disposed on the light emitting layer34. The second semiconductor layer36is a layer different in conductivity type from the first semiconductor layer32. The second semiconductor layer36is, for example, an Mg-doped p-type GaN layer. The first semiconductor layer32and the second semiconductor layer36are cladding layers having a function of confining the light in the light emitting layer34.

It should be noted that although not shown in the drawings, an OCL (Optical Confinement Layer) made of an i-type InGaN layer can be disposed between the first semiconductor layer32and the light emitting layer34. Further, although not shown in the drawings, the OCL made of the i-type InGaN layer can be disposed between the light emitting layer34and the second semiconductor layer36. Further, the second semiconductor layer36can be provided with an EBL (Electron Blocking Layer) made of a p-type AlGaN layer.

In the light emitting device100, there is constituted a pin diode by the second semiconductor layer36of the p-type, the light emitting layer34of the i-type doped with no impurity, and the first semiconductor layer32of the n-type. In the light emitting device100, when a forward bias voltage of the pin diode is applied between the first electrode40and the second electrode42, an electrical current is injected into the light emitting layer34, and recombination of electrons and holes occurs in the light emitting layer34. The recombination causes light emission. The light generated in the light emitting layer34propagates in an in-plane direction to form a standing wave due to the effect of the photonic crystal caused by the plurality of columnar parts30, and is then gained by the light emitting layer34to cause laser oscillation. Then, the light emitting device100emits positive first-order diffracted light and negative first-order diffracted light as a laser beam in the stacking direction.

It should be noted that it is also possible to dispose a reflecting layer between the substrate10and the buffer layer22, or below the substrate10although not shown in the drawings. The reflecting layer is, for example, a DBR (Distributed Bragg Reflector) layer. Due to the reflecting layer, it is possible to reflect the light generated in the light emitting layer34, and thus, it is possible for the light emitting device100to emit the light only from the second electrode42side.

The first electrode40is disposed on the buffer layer22. It is also possible for the buffer layer22to have ohmic contact with the first electrode40. The first electrode40is electrically coupled to the first semiconductor layer32. In the illustrated example, the first electrode40is electrically coupled to the first semiconductor layer32via the buffer layer22. The first electrode40is one of electrodes for injecting the electrical current into the light emitting layer34. As the first electrode40, there is used, for example, what is obtained by stacking a Cr layer, an Ni layer, and an Au layer in this order from the buffer layer22side.

The second electrode42is disposed on the second semiconductor layer36. The second electrode42is disposed at the opposite side to the substrate10of the laminated structure20. The second electrode42is electrically coupled to the second semiconductor layer36. It is also possible for the second semiconductor layer36to have ohmic contact with the second electrode42. The second electrode is the other of the electrodes for injecting the electrical current into the light emitting layer34. As the second electrode42, there is used, for example, ITO (indium tin oxide).

1.2. Detailed Shape etc. of Columnar Part

FIG.2is a cross-sectional view schematically showing the columnar part30.FIG.3is a plan view schematically showing the columnar part30. It should be noted thatFIG.3illustrates only a second portion32bof the first semiconductor layer32, the light emitting layer34, and a c-plane35aof the light emitting layer34for the sake of convenience.

The first semiconductor layer32, the light emitting layer34, and the second semiconductor layer36are made of, for example, a group-III nitride semiconductor, and have a wurtzite crystal structure.

As shown inFIG.2, the first semiconductor layer32has a first portion32aand the second portion32b.

The first portion32ais disposed between the second portion32band the light emitting layer34. The first portion32ais disposed on the second portion32band the insulating layer24. The first portion32ahas the c-plane33aand a facet plane33b. The c-plane33ais parallel to a principal surface of the substrate10, and the facet surface33bare tilted with respect to the principal surface of the substrate10. The principal surface of the substrate10is a surface on which the buffer layer22is formed.

The second portion32bis disposed between the substrate10and the first portion32a. In the example shown inFIG.1, the second portion32bis disposed on the buffer layers22. As shown inFIG.1, the second portion32bis provided to each of the opening parts25of the insulating layer24. The insulating layer24is disposed between the substrate10and the first portion32a.

In the plan view from the stacking direction (hereinafter also referred to simply as “in the plan view”), the first portion32aand the second portion32boverlap each other. In the plan view, the second portion32bis disposed only inside the outer edge of the first portion32a. The diametrical size D2of the second portion32bis smaller than the diametrical size D1of the first portion32a. Since the diametrical size D1of the first portion32aand the diametrical size D2of the second portion32bare different from each other, a step2is formed at a boundary between the first portion32aand the second portion32b.

It should be noted that when the planar shape of the first portion32ais a circle, the “diametrical size of the first portion” means the diameter of the circle, and when the planar shape of the first portion32ais not a circular shape, the “diametrical size of the first portion” means the diameter of the minimum bounding circle. Similarly, when the planar shape of the second portion32bis a circle, the “diametrical size of the second portion” means the diameter of the circle, and when the planar shape of the second portion32bis not a circular shape, the “diametrical size of the second portion” means the diameter of the minimum bounding circle.

The light emitting layer34has the c-plane35aand the facet plane35b. In the plan view, the c-plane35ais surrounded by the facet plane35b. As shown inFIG.3, in the plan view, the c-plane35aand the second portion32boverlap each other, and the diametrical size D3of the c-plane35ais smaller than the diametrical size D2of the second portion32b. For example, in the plan view, the c-plane35ais disposed only inside the outer edge of the second portion32b. In the plan view, the area of the c-plane35aentirely overlaps the second portion32b.

It should be noted that when the shape of the c-plane35ais a circle, the “diametrical size of the c-plane” means the diameter of the circle, and when the shape of the c-plane35ais not a circular shape, the “diametrical size of the c-plane” means the diameter of the minimum bounding circle.

The second semiconductor layer36is disposed on the c-plane35aand the facet plane35bof the light emitting layer34. It should be noted that although not shown in the drawings, when another layer such as the OCL exists between the light emitting layer34and the second semiconductor layer36, it is possible for the second semiconductor layer36to be disposed on the c-plane35aand the facet plane35bvia the another layer.

In the plan view, the impurity concentration of the second semiconductor layer36overlapping the c-plane35ais higher than the impurity concentration of the second semiconductor layer36overlapping the facet plane35bin the plan view. In other words, the second semiconductor layer36has a high concentration portion36ahigh in impurity concentration and a low concentration portion36blower in impurity concentration than the high concentration portion36a, wherein the high concentration portion36aoverlaps the c-plane35ain the plan view, and the low concentration portion36boverlaps the facet plane35bin the plan view. When growing the second semiconductor layer36epitaxially, the impurity concentration of the second semiconductor layer36growing on the c-plane35abecomes higher than the impurity concentration of the second semiconductor layer36growing on the facet plane35b. Thus, there is formed the second semiconductor layer36having the high concentration portion36aand the low concentration portion36b.

The high concentration portion36ais formed along, for example, a central axis of the columnar part30, and the low concentration portion36bsurrounds the high concentration portion36ain the plan view. The impurity concentration of the high concentration portion36ais, for example, about 5×1019cm−3. The impurity concentration of the low concentration portion36bis, for example, equal to or less than 2×1019cm−3. When the impurity concentration of the second semiconductor layer36becomes high, namely when the concentration of Mg doped in GaN becomes high, the electrical resistance becomes low.

The diametrical size D4of the light emitting layer34is larger than the diametrical size D3of the c-plane35aand the diametrical size D2of the second portion32b. For example, in the plan view, the second portion32bis disposed only inside the outer edge of the light emitting layer34.

It should be noted that when the planar shape of the light emitting layer34is a circle, the “diametrical size of the light emitting layer” means the diameter of the circle, and when the planar shape of the light emitting layer34is not a circular shape, the “diametrical size of the light emitting layer” means the diameter of the minimum bounding circle.

Although the light emitting layer34of the InGaN type is described above, as the light emitting layer34, there can be used a variety of types of material system capable of emitting light in response to injection of an electrical current in accordance with the wavelength of the light to be emitted. It is possible to use semiconductor materials of, for example, an AlGaN type, an AlGaAs type, an InGaAs type, an InGaAsP type, an InP type, a GaP type, or an AlGaP type.

Further, although there is described above when the light emitting device100is a vertical cavity surface emitting laser using the effect of the photonic crystal, the light emitting device100can be a light emitting device such as an LED (light emitting diode) or a resonant light emitting diode.

Further, in the above description, the first portion32aof the first semiconductor layer32, the light emitting layer34, and the second semiconductor layer36are the same in diametrical size inFIG.2, but this is not a limitation, and the diametrical size of the first portion32aand the diametrical size of the light emitting layer34can be different form each other, the diametrical size of the first portion32aand the diametrical size of the second semiconductor layer36can be different from each other, and the diametrical size of the light emitting layer34and the diametrical size of the second semiconductor layer36can be different from each other. Further, the diametrical size of the first portion32aof the first semiconductor layer32can vary in the stacking direction. For example, the diametrical size of the first portion32acan gradually increase upward in the stacking direction. Further, the diametrical size of the light emitting layer34can vary in the stacking direction. For example, the diametrical size of the light emitting layer34can gradually increase upward in the stacking direction. Further, the diametrical size of the second semiconductor layer36can vary in the stacking direction. For example, the diametrical size of the second semiconductor layer36can gradually increase upward in the stacking direction, or the diametrical size of the second semiconductor layer36can gradually decrease upward in the stacking direction.

1.3. Functions and Advantages

In the light emitting device100, the first semiconductor layer32has the first portion32a, and the second portion32bsmaller in diametrical size than the first portion32a, and in the plan view, the c-plane35aof the light emitting layer34and the second portion32boverlap each other, and the diametrical size D3of the c-plane35ais smaller than the diametrical size D2of the second portion32b. Therefore, in the light emitting device100, it is possible to reduce the electrical current flowing on the side surface of the columnar part30where the crystal defect is apt to occur. Thus, it is possible to reduce the leakage of the electrical current between the first semiconductor layer32and the second semiconductor layer36. As a result, in the light emitting device100, it is possible to efficiently inject the electrical current into the light emitting layer34.

Specifically, in the light emitting device100, since the first semiconductor layer32has the second portion32bsmaller in diametrical size than the first portion32a, it is possible to reduce the spread of the electrical current in an area below the light emitting layer34, namely the spread of the electrical current in the first semiconductor layer32, in the path of the electrical current flowing through the columnar part30.

Further, in the light emitting device100, the diametrical size D3of the c-plane35aof the light emitting layer34is smaller than the diametrical size D2of the second portion32b. Here, the electrical resistance of the high concentration portion36aoverlapping the c-plane35ain the plan view is lower than the electrical resistance of the low concentration portion36boverlapping the facet plane35bin the plan view. Therefore, it is possible to reduce the spread of the electrical current in an area above the light emitting layer34, namely the spread of the electrical current in the second semiconductor layer36, in the path of the electrical current flowing through the columnar part30.

As described above, in the light emitting device100, since the spread of the electrical current flowing through the columnar part30can be reduced, it is possible to reduce the electrical current flowing on the side surface of the columnar part30.

Further, in the light emitting device100, the diametrical size D3of the c-plane35aof the light emitting layer34is smaller than the diametrical size D2of the second portion32b. Therefore, in the light emitting device100, it is possible to reduce the electrical current which straddles the crystal defect generated from the step2, and which does not make a contribution to the light emission compared to when, for example, the diametrical size D3of the c-plane35aof the light emitting layer34is no smaller than the diametrical size D2of the second portion32b. Thus, it is possible to improve the luminous efficiency.

Here, the crystal defect is apt to occur in the step2formed at the boundary between the first portion32aand the second portion32b. Further, the electrical current straddling the crystal defect does not make a contribution to the light emission. Since in the light emitting device100, the diametrical size D3is smaller than the diametrical size D2, it is possible to concentrate the electrical current on the central portion of the first semiconductor layer32compared to when, for example, the diametrical size D3is no smaller than the diametrical size D2, and thus, it is possible to reduce the electrical current straddling the crystal defect generated from the step2.

In the light emitting device100, the diametrical size D4of the light emitting layer34is larger than the diametrical size D3of the c-plane35aand the diametrical size D2of the second portion32b. Therefore, in the light emitting device100, it is possible to reduce the electrical current flowing on the side surface of the light emitting layer34. Thus, it is possible to reduce the leakage of the electrical current between the first semiconductor layer and the second semiconductor layer36. Further, by reducing the electrical current flowing on the side surface of the light emitting layer34, it is possible to reduce non-radiative recombination on the side surface of the light emitting layer34.

In the light emitting device100, the step2is formed at the boundary between the first portion32aand the second portion32b. Therefore, in the light emitting device100, the diametrical size D2of the second portion32bcan be made smaller than the diametrical size D1of the first portion32a.

In the light emitting device100, the substrate10is provided with the insulating layer24having the opening parts25, and the second portion32bis provided to each of the opening parts25. Therefore, in the light emitting device100, it is possible to easily form the first semiconductor layer32having the first portion32aand the second portion32bsmaller in diametrical size than the first portion32a.

In the light emitting device100, the insulating layer24is disposed between the substrate10and the first portion32a. Therefore, in the light emitting device100, it is possible to easily form the first semiconductor layer32having the first portion32aand the second portion32b.

In the light emitting device100, the impurity concentration of the second semiconductor layer36overlapping the c-plane35ais higher than the impurity concentration of the second semiconductor layer36overlapping the facet plane35bin the plan view. Therefore, in the light emitting device100, it is possible to reduce the spread of the electrical current flowing through the second semiconductor layer36.

2. Method of Manufacturing Light Emitting Device

Then, a method of manufacturing the light emitting device100according to the present embodiment will be described with reference to the drawings.FIG.4andFIG.5are cross-sectional views schematically showing a manufacturing process of the light emitting device100according to the present embodiment.

As shown inFIG.4, the buffer layer22is grown epitaxially on the substrate10. As the method of achieving the epitaxial growth, there can be cited an MOCVD (Metal Organic Chemical Vapor Deposition) method, an MBE (Molecular Beam Epitaxy) method, and so on.

Then, the insulating layer24having the plurality of opening parts25is formed on the buffer layer22. The insulating layer24is formed by deposition using, for example, an electron beam evaporation method or a spattering method, and patterning. The patterning is performed using, for example, photolithography and etching. The diametrical size D2of the second portion32bis decided by the diametrical size of the opening part25.

As shown inFIG.5, the first semiconductor layer32is grown epitaxially on the buffer layer22using the insulating layer24as a mask. As the method of achieving the epitaxial growth, there can be cited the MOCVD method, the MBE method, and so on.

By epitaxially growing the first semiconductor layer32using the insulating layer24as a mask, the second portion32bis formed in each of the opening parts25, and the first portion32ais formed on the second portion32band the insulating layer24. In such a manner, there is formed the first semiconductor layer32having the first portion32aand the second portion32bsmaller in diametrical size than the first portion32a. In this step, growth conditions such as a growth temperature and a growth speed are adjusted so that the c-plane33aand the facet plane33bare provided to the first semiconductor layer32.

Then, the light emitting layer34is grown epitaxially on the first semiconductor layer32. As the method of achieving the epitaxial growth, there can be cited the MOCVD method, the MBE method, and so on. In this step, growth conditions such as a growth temperature and a growth speed are adjusted so that the c-plane35aand the facet plane35bare provided to the light emitting layer34.

Then, the second semiconductor layer36is grown epitaxially on the light emitting layer34. As the method of achieving the epitaxial growth, there can be cited the MOCVD method, the MBE method, and so on. By epitaxally growing the second semiconductor layer36on the light emitting layer34having the c-plane35aand the facet plane35b, the high concentration portion36ahigh in impurity concentration is formed on the c-plane35a, and the low concentration portion36blow in impurity concentration is formed on the facet plane35b.

Due to the steps described hereinabove, it is possible to form the laminated structure20having the columnar parts30.

Then, the first electrode40is formed on the buffer layer22, and the second electrode42is formed on the second semiconductor layer36. The first electrode40and the second electrode42are formed using, for example, a vacuum deposition method. It should be noted that the order of the formation of the first electrode40and the formation of the second electrode42is not particularly limited. Subsequently, the substrate10is cut into a predetermined shape.

Due to the steps described hereinabove, it is possible to manufacture the light emitting device100.

3. Projector

Then, a projector according to the present embodiment will be described with reference to the drawings.FIG.6is a diagram schematically showing the projector900according to the present embodiment.

The projector900has, for example, the light emitting devices100as light sources.

The projector900includes a housing not shown, a red light source100R, a green light source100G, and a blue light source100B which are disposed inside the housing, and respectively emit red light, green light, and blue light. It should be noted that inFIG.6, the red light source100R, the green light source100G, and the blue light source100B are simplified for the sake of convenience.

The projector900further includes a first optical element902R, a second optical element902G, a third optical element902B, a first light modulation device904R, a second light modulation device904G, a third light modulation device904B, and a projection device908all installed inside the housing. The first light modulation device904R, the second light modulation device904G, and the third light modulation device904B are each, for example, a transmissive liquid crystal light valve. The projection device908is, for example, a projection lens.

The light emitted from the red light source100R enters the first optical element902R. The light emitted from the red light source100R is collected by the first optical element902R. It should be noted that the first optical element902R can be provided with other functions than the light collection. The same applies to the second optical element902G and the third optical element902B described later.

The light collected by the first optical element902R enters the first light modulation device904R. The first light modulation device904R modulates the incident light in accordance with image information. Then, the projection device908projects an image formed by the first light modulation device904R on a screen910in an enlarged manner.

The light emitted from the green light source100G enters the second optical element902G. The light emitted from the green light source100G is collected by the second optical element902G.

The light collected by the second optical element902G enters the second light modulation device904G. The second light modulation device904G modulates the incident light in accordance with the image information. Then, the projection device908projects an image formed by the second light modulation device904G on the screen910in an enlarged manner.

The light emitted from the blue light source100B enters the third optical element902B. The light emitted from the blue light source100B is collected by the third optical element902B.

The light collected by the third optical element902B enters the third light modulation device904B. The third light modulation device904B modulates the incident light in accordance with the image information. Then, the projection device908projects an image formed by the third light modulation device904B on the screen910in an enlarged manner.

Further, it is possible for the projector900to include a cross dichroic prism906for combining the light emitted from the first light modulation device904R, the light emitted from the second light modulation device904G, and the light emitted from the third light modulation device904B with each other to guide the light thus combined to the projection device908.

The three colors of light respectively modulated by the first light modulation device904R, the second light modulation device904G, and the third light modulation device904B enter the cross dichroic prism906. The cross dichroic prism906is formed by bonding four rectangular prisms to each other, and is provided with a dielectric multilayer film for reflecting the red light and a dielectric multilayer film for reflecting the blue light disposed on the inside surfaces. The three colors of light are combined with each other by these dielectric multilayer films, and thus, the light representing a color image is formed. Then, the light thus combined is projected on the screen910by the projection device908, and thus, an enlarged image is displayed.

It should be noted that it is possible for the red light source100R, the green light source100G, and the blue light source100B to directly form the images by controlling the light emitting devices100as the pixels of the image in accordance with the image information without using the first light modulation device904R, the second light modulation device904G, and the third light modulation device904B. Then, it is also possible for the projection device908to project the images formed by the red light source100R, the green light source100G, and the blue light source100B on the screen910in an enlarged manner.

Further, although the transmissive liquid crystal light valves are used as the light modulation devices in the example described above, it is also possible to use light valves other than the liquid crystal light valves, or to use reflective light valves. As such light valves, there can be cited, for example, reflective liquid crystal light valves and Digital Micromirror Device™. Further, the configuration of the projection device is appropriately modified in accordance with the type of the light valves used.

Further, it is also possible to apply the light source to a light source device of a scanning type image display device having a scanning unit as an image forming device which scans the surface of the screen with the light from the light source to thereby display an image with a desired size on the display surface.

4. Display

Then, a display according to the present embodiment will be described with reference to the drawings.FIG.7is a plan view schematically showing the display1000according to the present embodiment.FIG.8is a cross-sectional view schematically showing the display1000according to the present embodiment. InFIG.7, the X axis and the Y axis are illustrated as two axes perpendicular to each other for the sake of convenience.

The display1000has, for example, the light emitting devices100as light sources.

The display1000is a display device for displaying an image. The image includes what displays only character information. The display1000is a self-luminous type display. The display1000has a circuit board1010, a lens array1020, and a heatsink1030as shown inFIG.7andFIG.8.

On the circuit board1010, there is mounted a drive circuit for driving the light emitting devices100. The drive circuit is a circuit including, for example, a CMOS (Complementary Metal Oxide Semiconductor). The drive circuit drives the light emitting devices100based on, for example, the image information input thereto. Although not shown in the drawings, on the circuit board1010, there is disposed a light transmissive substrate for protecting the circuit board1010.

The circuit board1010has a display area1012, a data line drive circuit1014, a scanning line drive circuit1016, and a control circuit1018.

The display area1012is formed of a plurality of pixels P. The pixels P are arranged along the X axis and the Y axis in the illustrated example.

Although not shown in the drawings, the circuit board1010is provided with a plurality of scanning lines and a plurality of data lines. For example, the scanning lines extend along the X axis, and the data lines extend along the Y axis. The scanning lines are coupled to the scanning line drive circuit1016. The data lines are coupled to the data line drive circuit1014. The pixels P are disposed so as to correspond to the respective intersections between the scanning lines and the data lines.

Each of the pixels P has, for example one of the light emitting devices100, a single lens1022, and a pixel circuit not shown. The pixel circuit includes a switching transistor functioning as a switch for the pixel P, wherein the gate of the switching transistor is coupled to the scanning line, and one of the source and the drain thereof is coupled to the data line.

The data line drive circuit1014and the scanning line drive circuit1016are circuits for controlling the drive of the light emitting devices100respectively constituting the pixels P. The control circuit1018controls the display of the image.

The control circuit1018is supplied with image data from a higher-level circuit. The control circuit1018supplies a variety of signals based on the image data to the data line drive circuit1014and the scanning line drive circuit1016.

When the scanning line drive circuit1016activates a scanning signal to thereby select the scanning line, the switching transistor of the pixel P thus selected is set to an ON state. On this occasion, by the data line drive circuit1014supplying the pixel P thus selected with the data signal from the data line, the light emitting device100of the pixel P thus selected emits light in accordance with the data signal.

The lens array1020has a plurality of lenses1022. The lenses1022are disposed, for example, so as to correspond one-to-one to the light emitting devices100. The light emitted from the light emitting device100enters corresponding one of the lenses1022.

The heatsink1030has contact with the circuit board1010. The material of the heatsink1030is metal such as copper or aluminum. The heatsink1030releases heat generated in the light emitting devices100.

The light emitting device according to the embodiment described above can also be used for other devices than the projector and the display. As the applications other than the projector and the display, there can be cited a light source of, for example, indoor and outdoor illumination, a laser printer, a scanner, an in-car light, sensing equipment using light, or communication equipment. Further, the light emitting device according to the embodiment described above can also be used for a display device of a head-mounted display.

The present disclosure includes configurations substantially the same as the configuration described as the embodiment such as configurations having the same function, the same way, and the same result, or configurations having the same object and the same advantage. Further, the present disclosure includes configurations obtained by replacing a non-essential part of the configuration described as the embodiment. Further, the present disclosure includes configurations providing the same functions and advantages, and configurations capable of achieving the same object as those of the configuration described as the embodiment. Further, the present disclosure includes configurations obtained by adding a known technology to the configuration described as the embodiment.

The following contents derive from the embodiment and the modified example described above.

A light emitting device according to an aspect includes a substrate, and a laminated structure provided to the substrate, and including a plurality of columnar parts, wherein the columnar part includes 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 disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer is disposed between the substrate and the light emitting layer, the light emitting layer has a c-plane and a facet plane, the second semiconductor layer is disposed on the c-plane and the facet plane, the first semiconductor layer has a first portion and a second portion smaller in diametrical size than the first portion, the second portion is disposed between the substrate and the first portion, and the c-plane and the second portion overlap each other, and the c-plane is smaller in diametrical size than the second portion in a plan view from a stacking direction of the first semiconductor layer and the light emitting layer.

According to this light emitting device, it is possible to reduce the electrical current flowing on the side surface of the columnar part where the crystal defect is apt to occur. Thus, it is possible to reduce the leakage of the electrical current between the first semiconductor layer and the second semiconductor layer.

In the light emitting device according to the aspect, the light emitting layer may be larger in diametrical size than the c-plane and the second portion.

According to this light emitting device, it is possible to reduce the current which straddles the crystal defect generated from the step at the boundary between the first portion and the second portion of the first semiconductor layer, and which does not make a contribution to the light emission.

In the light emitting device according to the aspect, a step may be formed at a boundary between the first portion and the second portion.

According to this light emitting device, it is possible to make the diametrical size of the second portion smaller than the diametrical size of the first portion.

In the light emitting device according to the aspect, the substrate may be provided with an insulating layer having an opening part, and the second portion may be disposed in the opening part.

According to this light emitting device, it is possible to easily form the first semiconductor layer having the first portion and the second portion smaller in diametrical size than the first portion.

In the light emitting device according to the aspect, the insulating layer may be disposed between the substrate and the first portion.

According to this light emitting device, it is possible to easily form the first semiconductor layer having the first portion and the second portion smaller in diametrical size than the first portion.

In the light emitting device according to the aspect, in the plan view, a portion of the second semiconductor layer overlapping the c-plane may be higher in impurity concentration than a portion of the second semiconductor layer overlapping the facet plane.

According to this light emitting device, it is possible to reduce the spread of the electrical current flowing through the second semiconductor layer.

A projector according to an aspect includes the light emitting device according to the above aspect.

A display according to an aspect includes the light emitting device according to the above aspect.