Patent ID: 12199408

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A preferable embodiment of the present disclosure will be described below in detail with reference to the drawings. It is not intended that the embodiment described below unduly limits the contents of the present disclosure set forth in the appended claims. Further, all configurations described below are not necessarily essential configuration requirements of the present disclosure.

1. Light Emitting Apparatus

A light emitting apparatus according to the present embodiment will first be described with reference to the drawings.FIG.1is a cross-sectional view diagrammatically showing a light emitting apparatus100according to the present embodiment. FIG. is a plan view diagrammatically showing the light emitting apparatus100according to the present embodiment.FIG.1is a cross-sectional view taken along the line I-I inFIG.2.

The light emitting apparatus100includes a substrate10, a laminated structure20, a first electrode50, and a second electrode52, as shown inFIGS.1and2. The second electrode52is omitted inFIG.2for convenience.

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

The laminated structure20is provided at the substrate10. In the illustrated example, the laminated structure20is provided on the substrate10. The laminated structure20includes, for example, a buffer layer22and columnar sections30.

The present specification will be described on the assumption that in a lamination direction of the laminated structure20(hereinafter also simply referred to as “lamination direction”), the direction from a light emitting layer33as a reference toward a second semiconductor layer35is called “upper”, and the direction from the light emitting layer33as the reference toward a first semiconductor layer31is called “lower”. The direction perpendicular to the lamination direction is also called an “in-plane direction”.

In the present disclosure, the “lamination direction of the laminated structure20” refers to the direction in which the first semiconductor layer31and the light emitting layer33of each of the columnar sections30are laminated structured on each other.

The buffer layer22is provided on the substrate10. The buffer layer22is, for example, an n-type GaN layer into which Si has been doped. A mask layer60for forming the columnar sections30is provided on the buffer layer22. The mask layer60is, for example, a silicon oxide layer, a titanium layer, a titanium oxide layer, or an aluminum oxide layer.

The columnar sections30are provided on the buffer layer22. The columnar sections30each have a columnar shape protruding upward from the buffer layer22. The columnar sections30are each also called, for example, a nano-column, a nano-wire, a nano-rod, and a nano-pillar. The columnar sections30each have, for example, a regular hexagonal planar shape or any other polygonal planar shape or a circular planar shape. In the example shown inFIG.2, the columnar sections30each have a regular hexagonal planar shape.

The columnar sections30each have a diameter, for example, greater than or equal to 50 nm but smaller than or equal to 500 nm. When the diameter of the columnar sections30is smaller than or equal to 500 nm, a high-quality-crystal light emitting layer33can be produced, and distortion intrinsically present in the light emitting layer33can be reduced. The light produced in the light emitting layer33can thus be efficiently amplified.

In a case where the columnar sections30each have a circular planar shape, “the diameter of the columnar sections” is the diameter of the circular shape, and when the columnar sections30each have a non-circular planar shape, the diameter of the columnar sections is the diameter of the smallest enclosing circle enclosing the non-circular shape. For example, when the columnar sections30each have a polygonal planar shape, the diameter of the columnar sections30is the diameter of the smallest circle enclosing the polygonal shape, and when the columnar sections30each have an elliptical planar shape, the diameter of the columnar sections30is the diameter of the smallest circle enclosing the elliptical shape. In the case where the columnar sections30each have a circular planar shape, “the centers of the columnar sections” are each the center of the circle, and when the columnar sections30each have a non-circular planar shape, the centers of the columnar sections are each the center of the smallest enclosing circle enclosing the non-circular shape. The “center of a columnar section assembly” is the center of the smallest circle enclosing the columnar section30that forms a columnar section assembly40, that is, the smallest enclosing circle in the plan view along the lamination direction.

The columnar sections30each include, for example, the first semiconductor layer31, a first guide layer32, the light emitting layer33, a second guide layer34, and the second semiconductor layer35, as shown inFIG.1.

The first semiconductor layers31are provided on the buffer layer22. The first semiconductor layer31is provided between the substrate10and the light emitting layer33. The first semiconductor layer31is, for example, an n-type GaN layer to which Si has been doped.

The first guide layer32is provided on the first semiconductor layer31. The first guide layer32has a diameter greater than the diameter of the first semiconductor layer31. The first guide layer32, for example, has a semiconductor superlattice (SL) structure formed of i-type GaN layers and i-type InGaN layers. The numbers of GaN layers and of InGaN layers that form the first guide layer32are each not limited to a specific number.

The light emitting layer33is provided on the first guide layer32. The light emitting layer33is provided between the first semiconductor layers31and the second semiconductor layer35. The light emitting layer33, for example, has a diameter greater than that of the first semiconductor layer31. The light emitting layer33produces light when a current is injected thereinto. The light emitting layer33, for example, has a quantum well (MQW) structure formed of i-type GaN layers and i-type InGaN layers. The numbers of GaN layers and InGaN layers that form the light emitting layer33are each not limited to a specific number.

The second guide layer34is provided on the light emitting layer33. The second guide layer34, for example, has a semiconductor superlattice (SL) structure formed of i-type GaN layers and i-type InGaN layers. The numbers of GaN layers and InGaN layers that form the second guide layer34are each not limited to a specific number. The first guide layer32and the second guide layer34are layers that increase the amount of overlap between the light emitting layer33and the light propagating in the in-plane direction. A light confinement coefficient can thus be increased.

The second semiconductor layer35is provided on the second guide layer34. The second semiconductor layer35, for example, has a diameter greater than that of the light emitting layer33. The second semiconductor layer35differs from the first semiconductor layers31in terms of conductivity type. The second semiconductor layer35is, for example, a p-type GaN layer to which Mg has been doped. The first semiconductor layers31and the second semiconductor layer35are each a cladding layer having the function of confining the light in the light emitting layer33.

In the light emitting apparatus100, the p-type second semiconductor layers35, the i-type light emitting layers33and guide layers32and34, into which no impurity has been doped, and the n-type first semiconductor layers31form pin diodes. In the light emitting apparatus100, when a forward bias voltage for the pin diodes is applied to the space between the first electrode50and the second electrode52, a current is injected into the light emitting layers33, whereby electrons and holes recombine with each other in the light emitting layers33. The recombination causes light emission. The photonic crystal effect provided by the plurality of columnar sections30causes the light produced in the light emitting layers33and propagated in the in-plane direction to form a standing wave, which receives gain in the light emitting layers33to achieve laser oscillation. The light emitting apparatus100then outputs positive first order diffracted light and negative first order diffracted light as laser light in the lamination direction.

Although not shown, a reflection layer may be provided between the substrate10and the buffer layer22or below the substrate10. The reflection layer is, for example, a distributed Bragg reflector (DBR) layer. The reflection layer can reflect the light generated in the light emitting layers33, and the light emitting apparatus100can emit light only via the side facing the second electrode52.

The columnar sections30form the columnar section assemblies40. The laminated structure20includes a plurality of columnar section assemblies40, as shown inFIG.2. In the illustrated example, the plurality of columnar section assemblies40are arranged in a triangular lattice. The distance between the centers of adjacent columnar section assemblies40is, for example, greater than or equal to 50 nm but smaller than or equal to 350 nm when viewed in the lamination direction.FIG.3is a plan view diagrammatically showing the columnar section assemblies40and illustrates the light emitting layers33and the second semiconductor layers35.

The columnar section assemblies40are each formed of p columnar sections30, as shown inFIGS.2and3. Parameter “p” is an integer greater than or equal to 2, for example, an integer greater than or equal to 3 but smaller than or equal to 15, preferably an integer greater than or equal to 3 but smaller than or equal to 7. In the illustrated example, “p” is 4, and the columnar section assemblies40are each formed of 4 columnar sections30. The columnar section assemblies40are each an assembly of columnar sections30that allow light oscillation in the red region. In each of the columnar section assemblies40, the distance between the centers of adjacent columnar sections30is, for example, greater than or equal to 50 nm but smaller than or equal to 150 nm when viewed in the lamination direction.

In the columnar section assembly40, for example, the figure F formed of the centers C of the p columnar sections30is rotationally symmetric when viewed in the lamination direction, as shown inFIG.3. That is, the figure F is n-fold symmetric, where n is an integer greater than or equal to 2. In the illustrated example, the figure F is four-fold symmetric. Since the figure F formed of three or more centers C, for example, is rotationally symmetric as described above, light that resonates in a plurality of directions is confined in the in-plane direction more isotropically than when the figure F is not rotationally symmetric, for example, when three or more columnar sections are arranged along a straight line. Columnar section assemblies40that allow light oscillation in the red region are therefore readily formed. In the illustrated example, the centers C of the columnar sections30are located at the vertices of a parallelogram that is not shown. In the present embodiment, the situation in which the figure F is rotationally symmetric means that the figure F is rotationally symmetric around a center Cf of the figure F. The center Cf of the figure F is the center of the smallest enclosing circle enclosing the figure F.

In each of the columnar section assemblies40, when viewed in the lamination direction, the ratio of the maximum width to the minimum width of the light emitting layer33in each of q first columnar sections30aout of the p columnar sections30(hereinafter also referred to as “width ratio”) is greater than the width ratio of the light emitting layer33in each of r second columnar sections30bout of the p columnar sections30. Parameter “q” is an integer greater than or equal to 1 but smaller than or equal to p and is 1 in the illustrated example. Parameter “r” is an integer that satisfies r=p−q and is 3 in the illustrated example.

The maximum width of each of the light emitting layers33is the maximum width of the portion passing through the center of the light emitting layer33. The minimum width of each of the light emitting layers33is the minimum width of the portion passing through the center of the light emitting layer33. In the example shown inFIG.3, the light emitting layers33each have a maximum width W1max and a minimum width W1min, and the direction of the maximum width W1max and the direction of the minimum width W1min are perpendicular to each other. The maximum width W1max of the light emitting layer33in each of the first columnar sections30ais greater than the maximum width W1max of the light emitting layer33in each of the second columnar sections30b. The minimum width W1min of the light emitting layer33in each of the first columnar sections30ais smaller than the minimum width W1min of the light emitting layer33in each of the second columnar sections30b.

In each of the columnar section assemblies40, since the width ratio of the light emitting layer33in each of the first columnar sections30ais greater than the width ratio of the light emitting layer33in each of the second columnar sections30b, the light emitting layers33of the p columnar sections30that form the columnar section assembly40each do not have a rotational symmetric shape when viewed in the lamination direction. That is, when m is an integer greater than or equal to 2, the light emitting layers33of the columnar section assemblies40each do not have an m-fold symmetric shape.

In each of the columnar section assemblies40, when viewed in the lamination direction, the area of the light emitting layer33in each of the first columnar sections30ais equal, for example, to the area of the light emitting layer33in each of the second columnar sections30b. In the illustrated example, the area of the second semiconductor layer35in each of the first columnar sections30ais smaller than the area of the second semiconductor layer35in each of the second columnar sections30b. Although not shown, the columnar sections30may each have a core-shell structure in which the light emitting layer33and the second semiconductor layer35are disposed also on the side facing the side surface of the first semiconductor layer31. In this case, the total area of the upper surface and side surface of the light emitting layer33in each of the first columnar sections30amay be equal to the total area of the upper surface and side surface of the light emitting layer33in each of the second columnar sections30b.

In each of the columnar section assemblies40, the width ratio of the light emitting layer33in each of the first columnar sections30ais greater than the width ratio of the second semiconductor layer35in each of the first columnar sections30aand the width ratio of the second semiconductor layer35in each of the second columnar sections30b. In the illustrated example, the width ratio of the light emitting layer33in each of the second columnar sections30bis equal to the width ratio of the second semiconductor layer35in each of the second columnar sections30b. The maximum width of each of the second semiconductor layers35is the maximum width of the portion passing through the center of the second semiconductor layer35. The minimum width of each of the second semiconductor layers35is the minimum width of the portion passing through the center of the second semiconductor layer35. In the example shown inFIG.3, the second semiconductor layers35each have a maximum width W2max and a minimum width W2min, and the direction of the maximum width W2max and the direction of the minimum width W2min are perpendicular to each other.

In each of the columnar section assemblies40, when viewed in the lamination direction, the difference in the width ratio between the second semiconductor layer35in each of the first columnar sections30aand the second semiconductor layer35in each of the second columnar sections30bis, for example, smaller than the difference in the width ratio between the light emitting layer33in each of the first columnar sections30aand the light emitting layer33in each of the second columnar sections30b. When viewed in the lamination direction, the difference in the width ratio between the light emitting layer33in each of the first columnar sections30aand the second semiconductor layer35in each of the first columnar sections30ais greater than the difference in the width ratio between the light emitting layer33in each of the second columnar sections30band the second semiconductor layer35in each of the second columnar sections30b.

In each of the columnar section assemblies40, the carrier concentration in the second semiconductor layer35in each of the first columnar sections30ais, for example, higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b. The carrier concentration in each of the second semiconductor layers35can be estimated, for example, by using an atom probe analysis method to measure the impurity concentration.

The first electrode50is provided on the buffer layer22. The buffer layer22may be in ohmic contact with the first electrode50. The first electrode50is electrically coupled to the first semiconductor layers31. In the illustrated example, the first electrode50is electrically coupled to the first semiconductor layers31via the buffer layer22. The first electrode50is one of the electrodes for injecting the current into the light emitting layers33. The first electrode50is, for example, a laminated structure of a Cr layer, an Ni layer, and an Au layer laminated structured in the presented order from the side facing the buffer layer22.

The second electrode52is provided on the second semiconductor layers35. The second electrode52is electrically coupled to the second semiconductor layers35. The second semiconductor layers35may be in ohmic contact with the second electrode52. The second electrode52is the other one of the electrodes for injecting the current into the light emitting layers33. The second electrode52is made, for example, of an indium tin oxide (ITO).

The above description has been made of the InGaN-based light emitting layers33, and the light emitting layers33can be made, in accordance with the wavelength of the light to be outputted therefrom, of any of a variety of other materials capable of emitting light when a current is injected thereinto. Examples of the material of the light emitting layers33may include an AlGaN-based, AlGaAs-based, InGaAs-based, InGaAsP-based, InP-based, GaP-based, and AlGaP-based semiconductor materials.

The light emitting apparatus100can provide, for example, the following effects and advantages.

The light emitting apparatus100includes the laminated structure20including a plurality of columnar section assemblies40each formed of p columnar sections30, and the p columnar sections30each have the light emitting layer33. When viewed in the lamination direction, the width ratio of the light emitting layer33in each of the q first columnar sections30aout of the p columnar sections30is greater than the width ratio of the light emitting layer33in each of the r second columnar sections30bout of the p columnar sections30, and the light emitting layer33in each of the p columnar sections30does not have a rotationally symmetric shape. The light emitted from the light emitting apparatus100is therefore linearly polarized. The light emitting apparatus100is therefore preferably used, for example, as the light source of a projector using a liquid crystal light valve. Further, the light emitting apparatus100can emit, for example, light having a single peak.

FIG.4describes the polarized light produced when the light emitting layer in each of the p columnar sections that form any of the columnar section assemblies has a rotationally symmetric shape.FIG.5shows a graph for describing the optical intensity along the line V-V shown inFIG.4.FIG.6describes the polarized light from the light emitting apparatus100. When the light emitting layer in each of the p columnar sections has a rotationally symmetric shape, the vibration directions of electric fields E of the emitted light L in a variety of positions therein are not aligned with one another, for example, as shown inFIG.4, and the electric fields E cancel with one another out in a central portion of the light L, as shown inFIGS.4and5. The emitted light L or beam therefore has a donut shape. On the other hand, in the light emitting apparatus100, the light emitting layer33in each of the p columnar sections30does not have a rotationally symmetrical shape, so that the vibration directions of the electric fields E are all aligned with one another, as shown inFIG.6, and the light emitted from the light emitting apparatus100is therefore linearly polarized. In the example shown inFIG.6, the emitted light L has a circular shape. That is, the emitted light L has a single peak.

In the light emitting apparatus100, when viewed in the lamination direction, the area of the light emitting layer33in each of the first columnar sections30ais equal to the area of the light emitting layer33in each of the second columnar section30b. Therefore, in the light emitting apparatus100, the light emission characteristics of the light emitting layer33in each of the first columnar sections30acan be made closer to the light emission characteristics of the light emitting layer33in each of the second columnar sections30bthan when the area of the light emitting layer in each of the first columnar sections differs from the area of the light emitting layer in each of the second columnar sections.

In the light emitting apparatus100, the p columnar sections30each include the n-type first semiconductor layer31and the p-type second semiconductor layer35, and the light emitting layer33is provided between the first semiconductor layer31and the second semiconductor layer35. When viewed in the lamination direction, the difference in the width ratio between the second semiconductor layer35in each of the first columnar sections30aand the second semiconductor layer35in each of the second columnar sections30b(hereinafter also referred to as “first difference”) is smaller than the difference in the width ratio between the light emitting layer33in each of the first columnar sections30aand the light emitting layer33in each of the second columnar sections30b(hereinafter also referred to as “second difference”). Therefore, in the light emitting apparatus100, the planar shape of the second semiconductor layer35in each of the first columnar sections30acan be made closer to the planar shape of the second semiconductor layer35in each of the second columnar sections30b, and the specific surface area of the second semiconductor layer35in each of the first columnar sections30acan be made closer to the specific surface area of the second semiconductor layer35in each of the second columnar sections30bthan in a case where the first difference is greater than the second difference. The difference in current-voltage (I-V) characteristics between the first columnar sections30aand the second columnar sections30bcan thus be reduced. A depletion region where no current flows is present in the vicinity of the surface of each of the second semiconductor layers35. The difference in the I-V characteristics between the first columnar sections30aand the second columnar sections30bcan therefore be reduced by making the specific surface area of the second semiconductor layer35in each of the first columnar sections30acloser to the specific surface area of the second semiconductor layer35in each of the second columnar sections30b. In particular, since the p-type second semiconductor layers35have higher resistance than the n-type first semiconductor layers31, the I-V characteristics are readily affected by controlling the second semiconductor layers35than controlling the first semiconductor layers31.

For example, when the amount of carriers injected into the columnar sections varies in accordance with the I-V characteristics thereof, the columnar sections into which a small amount of carriers has been injected will experience a relative decrease in gain and, in extreme cases, absorb the light, resulting in optical loss. In the columnar sections into which a large amount of carriers have been injected, the excessive carrier injection causes a decrease in differential gain and quantum efficiency. Different I-V characteristics of the columnar sections reduce the light emission efficiency, as described above. The light emitting apparatus100can avoid the problems described above and achieve a highly efficient laser that outputs linearly polarized light.

In the light emitting apparatus100, the carrier concentration in the second semiconductor layer35in each of the first columnar sections30ais higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b. Therefore, in the light emitting apparatus100in which, for example, the width ratio of the light emitting layer33in each of the first columnar sections30ais greater than the width ratio of the light emitting layer33in each of the second columnar sections30b, the resistance of the second semiconductor layer35in each of the first columnar sections30acan be made closer to the resistance of the second semiconductor layer35in each of the second columnar sections30beven when the area of the second semiconductor layer35in each of the first columnar sections30ais smaller than the area of the second semiconductor layer35in each of the second columnar sections30b.

2. Method for Manufacturing Light Emitting Apparatus

A method for manufacturing the light emitting apparatus100according to the present embodiment will next be described with reference to the drawings.FIG.7is a cross-sectional view diagrammatically showing one of the steps of manufacturing the light emitting apparatus100according to the present embodiment.

The buffer layer22is epitaxially grown on the substrate10, as shown inFIG.7. Examples of the epitaxial growth method may include a metal organic chemical vapor deposition (MOCVD) method and a molecular beam epitaxy (MBE) method.

The mask layer60is then formed on the buffer layer22. The mask layer60is formed, for example, by film deposition using an electron beam evaporation method or a plasma chemical vapor deposition (CVD) method and patterning using photolithography and etching.

The mask layer60is so patterned that the width ratio of openings62for forming the first columnar sections30ais greater than the width ratio of openings64for forming the second columnar sections30bwhen viewed in the lamination direction. The width ratio of the light emitting layer33in each of the first columnar sections30acan thus be greater than the width ratio of the light emitting layer33in each of the second columnar sections30b.

The mask layer60is further so patterned, for example, that the area of the light emitting layer33in each of the first columnar sections30ais equal to the area of the light emitting layer33in each of the second columnar sections30bwhen viewed in the lamination direction.

The mask layer60is used as a mask to epitaxially grow the first semiconductor layers31, the first guide layers32, the light emitting layers33, the second guide layers34, and the second semiconductor layer35in the presented order on the buffer layer22, as shown inFIG.1. Examples of the epitaxial growth method may include the MOCVD method and the MBE method.

The epitaxial growth of the second semiconductor layers35is performed under the conditions that the second semiconductor layers35each grow, for example, isotropically in the lateral direction (in-plane direction) from the center of the light emitting layer33when viewed in the lamination direction. The difference in the width ratio between the second semiconductor layer35in each of the first columnar sections30aand the second semiconductor layer35in each of the second columnar sections30bcan thus be smaller than the difference in the width ratio between the light emitting layer33in each of the first columnar sections30aand the light emitting layer33in each of the second columnar sections30b. Examples of the conditions include the film deposition temperature, the film deposition rate, the composition, and the positions of the columnar sections30.

Furthermore, the epitaxial growth of the second semiconductor layers35is so performed, for example, that the carrier concentration in the second semiconductor layer35in each of the first columnar sections30ais higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b. For example, when the semiconductor layers each have a c surface and a facet, the amount of dopant introduced via the c surface is greater than that introduced via the facet. Therefore, for example, the first columnar sections30aand the second columnar sections30bare grown under growth conditions that the proportion of the c surface in each of the first columnar sections30ais greater than the proportion of the c surface in each of the second columnar sections30b. The carrier concentration in the second semiconductor layer35in each of the first columnar sections30acan thus be higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b.

The columnar section assemblies40each formed of a plurality of columnar sections30can be formed by carrying out the steps described above.

Thereafter, the first electrode50is formed on the buffer layer22, and the second electrode52is formed on the second semiconductor layers35. The first electrode50and the second electrode52are formed, for example, by a vacuum evaporation method. The first electrode50and the second electrode52are not necessarily formed in a specific order.

The light emitting apparatus100can be manufactured by carrying out the steps described above.

3. Variation of Manufacturing Method

A variation of the method for manufacturing the light emitting apparatus100according to the present embodiment will next be described with reference to the drawings.FIGS.8to11are cross-sectional views diagrammatically showing the steps of manufacturing the light emitting apparatus100according to the present embodiment.

In “2. Method for manufacturing light emitting apparatus” described above, changing the ratio between the c surface and the facet has been described as an example of making the carrier concentration in the second semiconductor layer35in each of the first columnar sections30ahigher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b.

In contrast, an example in which the carrier concentration in the second semiconductor layer35in each of the first columnar sections30ais made higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30bby forming the columnar sections30in two steps will be described in the following sections. In the following description, the same portions as those in the manufacturing method described in “2. Method for manufacturing the light emitting apparatus” will not be described or will be described in a simplified manner.

After forming the mask layer60in the same manner as in “2. Method for manufacturing the light emitting apparatus” described above, first SAG layers70and second SAG layers72are formed, as shown inFIG.8. SAG means selective region growth and is also called selective area growth. The SAG layers70and72are formed, for example, by using a CVD (chemical vapor deposition) method or a sputtering method. The SAG layers70and72are each, for example, a silicon oxide layer, a silicon nitride layer, a titanium oxide layer, or an aluminum oxide layer. The second SAG layers72are thicker than the first SAG layers70.

Thereafter, the first SAG layers70are so patterned that openings71are formed, and the second SAG layers72are so patterned that openings73are formed. The patterning is performed, for example, by photolithography and etching. The openings71communicate with the openings64. The openings73communicate with the openings62.

The first semiconductor layer31, the first guide layer32, the light emitting layer33, and the second guide layer34are epitaxially grown on the buffer layer22in each of the openings71and73, as shown inFIG.9. In the illustrated example, the first SAG layers70are flush with the second guide layers34.

The first SAG layers70are removed, for example, by wet etching, as shown inFIG.10. Coating layers that are not shown may be formed on the second guide layers34located in the openings73to prevent the second guide layers34located in the openings73from being etched by the wet etching. The coating layers are removed when the second semiconductor layers35are grown. Furthermore, the second SAG layers72may each be covered with a coating layer that is not shown so that the second SAG layers72are not removed by the wet etching. The material of the first SAG layers70may be different from the material of the second SAG layers72so that the second SAG layers72are not removed by the wet etching.

The second semiconductor layers35are epitaxially grown on the second guide layers34as shown inFIG.11. The second semiconductor layers35are epitaxially grown under conditions that the second guide layers34that have no crystal surface exposed due to the wet etching for removing the first SAG layers70(second guide layers34located in the openings73) more readily capture the dopants than the second guide layers34that have crystal surfaces exposed due to the wet etching. The carrier concentration in the second semiconductor layer35in each of the first columnar sections30acan thus be higher than the carrier concentration in the second semiconductor layer35in each of the second columnar sections30b. In the illustrated example, the second SAG layers72are flush with the second semiconductor layers35.

Thereafter, the second SAG layers72are removed, for example, by wet etching, and the first electrode50and the second electrode52are formed.

The light emitting apparatus100can be manufactured by carrying out the steps described above.

4. Projector

A projector according to the present embodiment will next be described with reference to the drawings.FIG.12diagrammatically shows a projector900according to the present embodiment.

The projector900includes, for example, the light emitting apparatus100as a light source.

The projector900includes an enclosure that is not shown and a red light source100R, a green light source100G, and a blue light source100B, which are provided in the enclosure and emit red light, green light, and blue light, respectively. InFIG.12, the red light source100R, the green light source100G, and the blue light source100B are simplified for convenience.

The projector900further includes a first optical element902R, a second optical element902G, a third optical element902B, a first light modulator904R, a second light modulator904G, a third light modulator904B, and a projection apparatus908, which are provided in the enclosure. The first light modulator904R, the second light modulator904G, and the third light modulator904B are each, for example, a transmissive liquid crystal light valve. The projection apparatus908is, for example, a projection lens.

The light outputted from the red light source100R enters the first optical element902R. The light outputted from the red light source100R is collected by the first optical element902R. The first optical element902R may have another function in addition to the light collection function. The same holds true for the second optical element902G and the third optical element902B, which will be described later.

The light collected by the first optical element902R enters the first light modulator904R. The first light modulator904R modulates the light having entered it in accordance with image information. The projection apparatus908then enlarges an image formed by the first light modulator904R and projects the enlarged image on a screen910.

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

The light collected by the second optical element902G enters the second light modulator904G. The second light modulator904G modulates the light having entered it in accordance with image information. The projection apparatus908then enlarges an image formed by the second light modulator904G and projects the enlarged image on the screen910.

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

The light collected by the third optical element902B enters the third light modulator904B. The third light modulator904B modulates the light having entered it in accordance with image information. The projection apparatus908then enlarges an image formed by the third light modulator904B and projects the enlarged image on the screen910.

The projector900can further include a cross dichroic prism906, which combines the light fluxes outputted from the first light modulator904R, the second light modulator904G, and the third light modulator904B with one another and guides the combined light to the projection apparatus908.

The three color light fluxes modulated by the first light modulator904R, the second light modulator904G, and the third light modulator904B enter the cross dichroic prism906. The cross dichroic prism906is formed by bonding four right-angled prisms to each other, and a dielectric multilayer film that reflects the red light and a dielectric multilayer film that reflects the blue light are disposed at the inner surfaces of the combined prisms. The dielectric multilayer films combine the three color light fluxes with one another to form light representing a color image. The combined light is then projected by the projection apparatus908on the screen910. An enlarged image is thus displayed.

The red light source100R, the green light source100G, and the blue light source100B may instead directly form images without using of the first light modulator904R, the second light modulator904G, or the third light modulator904B but controlling the respective light emitting apparatuses100as the pixels of the images in accordance with image information. The projection apparatus908may then enlarge and project the images formed by the red light source100R, the green light source100G, and the blue light source100B on the screen910.

In the example described above, transmissive liquid crystal valves are used as the light modulators, and light valves not based on liquid crystal materials or reflective light valves may be used. Examples of such light valves may include reflective liquid crystal light valves and digital micromirror devices. The configuration of the projection apparatus is changed as appropriate in accordance with the type of the light valves used in the projector.

The present disclosure is also applicable to a light emitting apparatus of a scanning-type image display apparatus including a light source and a scanner that is an image formation apparatus that displays an image having a desired size on a display surface by scanning the screen with the light from the light source.

The light emitting apparatus according to the embodiment described above can be used in other applications in addition to a projector. Examples of the applications other than a projector may include an indoor or outdoor illuminator, a backlight of a display, a laser printer, a scanner, an in-vehicle light, a sensing instrument using light, and a light source of a communication instrument.

The present disclosure encompasses substantially the same configuration as the configuration described in the embodiment, for example, a configuration having the same function, using the same method, and providing the same result or a configuration having the same purpose and providing the same effect. Furthermore, the present disclosure encompasses a configuration in which an inessential portion of the configuration described in the embodiment is replaced. Moreover, the present disclosure encompasses a configuration that provides the same effects and advantages as those provided by the configuration described in the embodiment or a configuration that can achieve the same purpose as that achieved by the configuration described in the embodiment. Furthermore, the present disclosure encompasses a configuration in which a known technology is added to the configuration described in the embodiment.

The following contents are derived from the embodiment and variations described above.

A light emitting apparatus according to an aspect of the present disclosure includes a laminated structure including a plurality of columnar section assemblies each formed of p columnar sections. The p columnar sections each include a light emitting layer. When viewed in the lamination direction of the laminated structure, the ratio of the maximum width to the minimum width of the light emitting layer in each of q first columnar sections out of the p columnar sections is greater than the ratio of the light emitting layer in each of r second columnar sections out of the p columnar sections. The light emitting layer in each of the p columnar sections does not have a rotationally symmetrical shape. The parameter p is an integer greater than or equal to 2. The parameter q is an integer greater than or equal to 1 but smaller than p. The parameter r is an integer that satisfies r=p−q.

According to the light emitting apparatus described above, the light emitted from the light emitting apparatus is linearly polarized. The light emitting apparatus is therefore preferably used, for example, as the light source of a projector using a liquid crystal light valve.

In the light emitting apparatus according to the aspect, when viewed in the lamination direction, the area of the light emitting layer in each of the first columnar sections may be equal to the area of the light emitting layer in each of the second columnar sections.

According to the light emitting apparatus, the light emission characteristics of the light emitting layer in each of the first columnar sections can be made closer to the light emission characteristics of the light emitting layer in each of the second columnar sections.

In the light emitting apparatus according to the aspect, the p columnar sections may each include an n-type first semiconductor layer and a p-type second semiconductor layer. The light emitting layer may be provided between the first semiconductor layer and the second semiconductor layer. When viewed in the lamination direction, the difference in the ratio between the second semiconductor layer in each of the first columnar sections and the second semiconductor layer in each of the second columnar sections may be smaller than the difference in the ratio between the light emitting layer in each of the first columnar sections and the light emitting layer in each of the second columnar sections.

According to the light emitting apparatus described above, the difference in the I-V characteristics between the first columnar sections and the second columnar sections can be reduced.

In the light emitting apparatus according to the aspect, the carrier concentration in the second semiconductor layer in each of the first columnar sections may be higher than the carrier concentration in the second semiconductor layer in each of the second columnar sections.

According to the light emitting apparatus described above, for example, the resistance of the second semiconductor layer in each of the first columnar sections can be made closer to the resistance of the second semiconductor layer in each of the second columnar sections.

A projector according to another aspect of the present disclosure includes the light emitting apparatus according to the aspect of the present disclosure.