JP2011035275A - Nitride semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting element for achieving high conversion efficiency of a wavelength of a phosphor in a phosphor layer and white light emission with superior color rendering properties. <P>SOLUTION: The nitride semiconductor light-emitting element includes: a nitride semiconductor light-emitting layer composed of an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light-emitting part sandwiched by the n-type nitride semiconductor layer and the p-type nitride layer; a dielectric layer formed on the nitride semiconductor light-emitting layer; a metal layer formed on the dielectric layer; and the phosphor layer, which is formed either between the metal layer and the dielectric layer, or on the metal layer, and absorbs a light emitted by the nitride semiconductor light-emitting layer to emit fluorescence. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor light emitting device.

  For example, a white light source is used as a backlight source of a lighting fixture or a liquid crystal display device. In recent years, white light emitting elements using light emitting diodes (LEDs) have been actively researched in order to reduce the power consumption of white light sources. Among them, in particular, light emitting diodes using wide band gap semiconductors such as nitride semiconductors have been actively developed as light sources for white light emitting elements that emit white light. This is because the light emitting diode can emit ultraviolet light or blue light. In addition, as a configuration for realizing a white light emitting element, a light emitting diode that emits ultraviolet light (hereinafter referred to as “ultraviolet light emitting diode”) or a light emitting diode that emits blue light (hereinafter referred to as “blue light emitting diode”). The following configurations (1) to (3) are mainly used.

(1) Configuration combining blue light emitting diode and yellow phosphor (2) Configuration combining ultraviolet light emitting diode and blue, green, and red phosphor (3) Configuration combining blue, green, and red light emitting diode

  In the configurations (1) to (3), the configuration (3) has a problem of high cost and a problem of poor color mixing. Therefore, at present, the development of the constitutions (1) and (2), that is, the constitution combining the light emitting diode and the phosphor is proceeding. Among them, the development of a white light emitting element in which the structure (1), that is, a combination of a blue light emitting diode and a yellow phosphor, is progressing particularly because high luminous efficiency can be obtained.

  In a white light emitting element in which yellow and other phosphors are combined, a light emitting diode in which phosphors are integrated is being developed in order to reduce the size and thickness of the white light emitting element (for example, Patent Document 1). Patent Document 1 proposes a shape of a white light emitting element for reducing the size and thickness of the white light emitting element.

  Hereinafter, the structure and manufacturing method of the light emitting element of the prior art disclosed in Patent Document 1 will be described. FIG. 17 is a diagram for explaining a configuration and a manufacturing method of a conventional light emitting device.

  A conventional white light emitting device includes a first electrode 1001, a second electrode 1002, a phosphor thin film 1003, an epitaxial layer 1004, and a substrate 1005. In FIG. 17, the conventional white light emitting element is an LED chip (light emitting element) obtained by cutting the LED wafer 1000 along a cutting surface 1006 into individual pieces. Specifically, a conventional white light-emitting element includes a substrate 1005, an epitaxial layer 1004 formed on the substrate 1005, a surface on the epitaxial layer 1004, and a lower surface of the substrate 1005 (that is, a surface opposite to the surface on which the epitaxial layer 1004 is formed). ) Formed on the phosphor thin film 1003. Further, the conventional white light emitting element is formed with a first electrode 1001 and a second electrode 1002.

And the conventional white light emitting element is manufactured as follows.
First, an epitaxial layer 1004 in which a plurality of semiconductor layers are stacked is formed on a substrate 1005 by epitaxial growth. Thereafter, unnecessary portions of the epitaxial layer 1004 are removed by etching, and recesses are formed in the epitaxial layer 1004. Here, the epitaxial layer 1004 includes a semiconductor layer composed of a plurality of semiconductor layers positioned on the upper side and a semiconductor layer composed of a plurality of semiconductor layers positioned on the lower side. Further, the recess is formed in the recess so that the upper surface of a semiconductor layer (hereinafter referred to as “lower semiconductor layer”) located below among the plurality of semiconductor layers constituting the epitaxial layer 1004 is exposed. Has been.

  Next, a phosphor thin film (or a phosphor film made of a phosphor) 1003 mainly containing a phosphor is formed on the lower surface of the substrate 1005 by using a semiconductor technique such as coating, vapor deposition, or sputtering.

  Next, a phosphor thin film 1003 mainly containing a phosphor is formed on the epitaxial layer 1004 using a semiconductor technique such as coating, vapor deposition, or sputtering. Here, the phosphor thin film 1003 is also formed on the lower semiconductor layer of the epitaxial layer 1004 so as to fill the recess. Thereafter, unnecessary portions of the phosphor thin film 1003 are removed by etching to form a first recess and a second recess in the phosphor thin film 1003. Here, the first recess is formed in the first recess so as to expose the upper surface of the epitaxial layer 1004, and the second recess is exposed in the second recess so as to expose the upper surface of the lower semiconductor layer. Formed.

  Next, the first electrode 1001 is formed on the upper surface of the epitaxial layer 1004 exposed in the first recess by sputtering or vapor deposition, and the second electrode 1002 is formed on the upper surface of the lower semiconductor layer exposed in the second recess. Form.

  Next, the LED wafer 1000 formed by combining the plurality of LED chips (light emitting elements) formed in this manner is cut at the cutting surface 1006, so that each LED chip, that is, a conventional white light emitting element is separated. Tidy up.

  As described above, the white light emitting element of the prior art is manufactured.

JP 2005-332858 A

However, the conventional white light emitting device has the following problems.
That is, the conventional white light emitting device has a problem that the wavelength conversion efficiency is poor because the phosphor thin film 1003 formed by vapor deposition or sputtering has low crystallinity. Therefore, it is necessary to increase the thickness of the phosphor thin film 1003 in order to obtain a sufficient amount of light from the phosphor, and the cost increases as the thickness of the white light emitting element increases.

  In the structure of the conventional white light emitting device, the number of times that the blue light generated in the epitaxial layer 1004 passes through the phosphor thin film 1003 is small. Therefore, there is a problem that it is difficult to obtain sufficient yellow light from the phosphor thin film 1003 to achieve white color combined with blue light.

  Accordingly, the present invention has been made in view of the above-described circumstances, and provides a nitride semiconductor light-emitting device that has high phosphor wavelength conversion efficiency in the phosphor layer and enables white light emission excellent in color rendering. For the purpose.

  In order to achieve the above object, a nitride semiconductor light emitting device according to the present invention includes an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, the n-type nitride semiconductor layer, and the p-type nitride semiconductor layer. A nitride semiconductor light emitting layer composed of a light emitting portion sandwiched between, a dielectric layer formed on the nitride semiconductor light emitting layer, a metal layer formed on the dielectric layer, and the metal layer And a phosphor layer which is formed between the dielectric layers or on the metal layer and emits fluorescence by absorbing light emitted from the nitride semiconductor light emitting layer.

  With this configuration, it is possible to realize a nitride semiconductor light-emitting element that has high phosphor wavelength conversion efficiency in the phosphor layer and enables white light emission with excellent color rendering.

  Specifically, by adjusting the structure, material, and film thickness of the metal layer, part of the light emitted from the light emitting portion is transmitted and extracted outside the device. On the other hand, surface plasmons are excited in the metal by the evanescent light generated when the light emitted from the light emitting part is totally reflected at the interface between the nitride semiconductor light emitting layer and the dielectric layer. The generated surface plasmon is coupled with the carrier in the phosphor layer. Thereby, since the light emission recombination in the phosphor layer is promoted, the wavelength conversion efficiency in the phosphor is improved. As a result, it is possible to realize a nitride semiconductor light emitting device that has high phosphor wavelength conversion efficiency in the phosphor layer and enables white light emission with excellent color rendering.

  Here, the dielectric layer, the metal layer, and the phosphor layer may be sequentially formed on the nitride semiconductor light emitting layer.

  The dielectric layer, the phosphor layer, and the metal layer may be sequentially formed on the nitride semiconductor light emitting layer.

  The dielectric layer may be transparent to light emitted from the nitride semiconductor light emitting layer.

  With this configuration, the light emitted from the nitride semiconductor light emitting layer can be extracted outside the white light emitting element without absorbing light.

The dielectric layer may be made of an undoped nitride semiconductor.
With this configuration, since carrier diffusion from the metal layer is suppressed, the strength of the surface plasmon can be improved, and the conversion efficiency of the phosphor in the phosphor layer can be improved. Here, the surface plasmon is excited by evanescent light generated when the light emitted from the light emitting part is totally reflected at the interface between the dielectric layer and the metal layer.

  The dielectric layer, the metal layer, and the phosphor layer may be provided on the n-type nitride semiconductor layer side that constitutes the nitride semiconductor light emitting layer.

  With this configuration, since it is provided on the n-type side, it is not necessary to provide a transparent conductive layer, and a configuration for easily exciting surface plasmons can be realized.

  Further, the thickness of the dielectric layer is not more than a penetration depth of evanescent light generated when the light emitted from the nitride semiconductor light emitting layer is totally reflected at the interface between the nitride semiconductor light emitting layer and the dielectric layer. There may be.

With this configuration, surface plasmons can be effectively excited in the metal layer.
The metal layer may be made of a metal containing Al or Ag.

  With this configuration, since surface plasmon is effectively excited in Al and Ag, the conversion efficiency of the phosphor layer can be improved.

  The phosphor layer may be made of an oxide containing at least one of Y (yttrium), Ce (cerium), Al, Si, Ca, and Eu (eurobium).

  According to this configuration, the wavelength conversion efficiency can be improved by using surface plasmons in these oxide phosphor layers formed by vapor deposition or sputtering. Therefore, a low-cost white light-emitting element having a phosphor layer with high conversion efficiency can be realized by using a conventional semiconductor process technology such as vapor deposition or sputtering.

  The nitride semiconductor light emitting layer may have an uneven shape on the side where the dielectric layer is formed.

  With this configuration, the light emitted from the light emitting portion is repeatedly reflected in the concavo-convex portion, and surface plasmons can be effectively excited.

The metal layer may be composed of metal fine particles.
With such a configuration, the surface plasmon can be efficiently excited by the metal fine particles, and at the same time, the coverage of the nitride semiconductor surface can be reduced. Thereby, compared with the case where it is coat | covered with the metal thin film, blue light can be taken out outside a light emitting element effectively, and color rendering property can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the nitride semiconductor light-emitting device which has high conversion efficiency of the wavelength of the fluorescent substance in a fluorescent substance layer, and enables white light emission excellent in color rendering property is realizable.

1 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a first embodiment. It is a figure for demonstrating the recombination of the carrier in a fluorescent substance layer. It is a figure for demonstrating the recombination of the carrier in a fluorescent substance layer. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 6 is a diagram for explaining operations and effects in the first embodiment. FIG. 5 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the first embodiment. FIG. 5 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the first embodiment. FIG. 5 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the first embodiment. FIG. 5 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a second embodiment. FIG. 10 is a diagram for explaining an operation and an effect in the second embodiment. FIG. 10 is a diagram for explaining an operation and an effect in the second embodiment. FIG. 10 is a diagram for explaining an operation and an effect in the second embodiment. FIG. 10 is a diagram for explaining an operation and an effect in the second embodiment. FIG. 5 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the third embodiment. FIG. 6 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the fourth embodiment. FIG. 10 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a fifth embodiment. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. FIG. FIG. 10 is a cross-sectional view showing a configuration of a nitride semiconductor light emitting element in a sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment. It is sectional drawing explaining the structure and manufacturing method of a light emitting element of a prior art.

  Hereinafter, a nitride semiconductor light emitting device and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
First, the first embodiment will be described. FIG. 1 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the first embodiment. 2A and 2B are diagrams for explaining carrier recombination in a phosphor. FIGS. 3A to 3C and FIGS. 4A to 4C are diagrams for explaining operations and effects in the first embodiment. 5A to 5C are diagrams for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the first embodiment. Hereinafter, the present embodiment will be described in detail.

(Construction)
A nitride semiconductor light emitting device 100 shown in FIG. 1 includes a nitride semiconductor light emitting layer 10, a metal layer 50, and a phosphor layer 60 stacked on a substrate 2. The nitride semiconductor light emitting device 100 includes an n-type electrode 20 and a p-type electrode 30.

  The substrate 2 is made of, for example, a Si substrate having a plane orientation of <111>, a sapphire substrate having a plane orientation of <0001>, or a 6H-SiC substrate having a plane orientation of <0001>.

The nitride semiconductor light emitting layer 10 includes an n-type nitride semiconductor layer 5a, a light emitting portion 5b, a p-type nitride semiconductor layer 5c, a high-concentration n-type nitride semiconductor layer 5d, and an undoped nitride semiconductor layer 6 stacked in this order. Yes. The nitride semiconductor light emitting layer 10 may be formed of a transparent electrode such as ITO (Indium Tin Oxide) instead of the high concentration n-type nitride semiconductor layer 5d. In addition, the nitride semiconductor light emitting layer 10 may be composed of a dielectric layer made of SiO ₂ or the like having a thickness of about 150 nm, for example, instead of the undoped nitride semiconductor layer 6.

  The n-type nitride semiconductor layer 5a is formed on the substrate 2 via a buffer layer and is made of, for example, GaN doped with Si.

The light emitting portion 5b is formed on the n-type nitride semiconductor layer 5a and is composed of, for example, InGaN and GaN multiple quantum wells adjusted to exhibit blue light emission centered on a wavelength of 470 nm. That is, the light emitting portion 5b has a multiple quantum well structure in which a plurality of In _x Ga _1-x N well layers and GaN barrier layers are alternately formed, and emits light.

  The p-type nitride semiconductor layer 5c is formed on the light emitting portion 5b and is made of, for example, p-type GaN doped with Mg.

The high concentration n-type nitride semiconductor layer 5d is made of high concentration n-type GaN and is formed on the p-type nitride semiconductor layer 5c. The high-concentration n-type nitride semiconductor layer 5d has conductivity and functions to supply carriers to the p-type nitride semiconductor by a tunnel current. Therefore, the high-concentration n-type nitride semiconductor layer 5d preferably contains 1 × 10 ¹⁹ cm ⁻³ or more of, for example, Si as a dopant.

  The undoped nitride semiconductor layer 6 is made of undoped GaN and is formed on the high-concentration n-type nitride semiconductor layer 5d. The undoped nitride semiconductor layer 6 is formed in contact with the high-concentration n-type nitride semiconductor layer 5d.

  The metal layer 50 is a metal thin film formed on the nitride semiconductor light emitting layer 10 and made of a metal such as Al or Ag. Specifically, the metal layer 50 is formed in contact with the undoped nitride semiconductor layer 6 of the nitride semiconductor light emitting layer 10, and is a thin metal film of, for example, 5 to 25 nm. The metal layer 50 may be composed of metal fine particles, and may further have an opening. The thickness of the metal layer 50 is preferably 5 to 25 nm, but is not limited thereto. Any thickness that can generate surface plasmons at the interface between the metal layer 50 and the phosphor layer 60 may be used.

  The phosphor layer 60 is formed on the metal layer 50 so as to be in contact with the metal layer 50. Here, the phosphor layer 60 is made of a material that absorbs light generated in the light emitting portion 5b and generates fluorescence that is complementary to the light, such as YAG (Yttrium Aluminum Garnet) or sialon phosphor. That is, the phosphor layer 60 may be configured to be at least one oxide of Y (yttrium), Ce (cerium), Al, Si (silicon), Ca (calcium), and Eu (eurobium).

  The n-type electrode 20 is composed of a multilayer film of a metal such as Ti, Al, Ni, Au, etc., and is formed so as to be electrically connected to the n-type nitride semiconductor layer 5a. Specifically, the n-type electrode 20 is formed in contact with the p-type nitride semiconductor layer 5c and the n-type nitride semiconductor layer 5a exposed by selectively removing a part of the light emitting portion 5b.

  The p-type electrode 30 is formed on the nitride semiconductor light emitting layer 10, that is, on the high-concentration n-type nitride semiconductor layer 5 d, and is composed of a multilayer film of a metal such as Ti, Al, Ni, or Au.

  As described above, nitride semiconductor light emitting element 100 in the first embodiment is configured.

(Operation and effect)
Next, the operation of the nitride semiconductor light emitting device 100 according to the first embodiment will be described.

  First, the light emitting unit 5b emits light. Here, it is assumed that the light emitting unit 5b generates, for example, outgoing light 70a and outgoing light 70b. The emitted light 70a and the emitted light 70b are incident on the metal layer 50 at a certain angle, and are transmitted (emitted light 70a) and reflected (emitted light 70b) at the interface between the nitride semiconductor light emitting layer 10 and the metal layer 50. ), Resulting in either absorption.

  As shown in FIG. 1, the outgoing light 70 a passes through the interface between the nitride semiconductor light emitting layer 10 and the metal layer 50, further passes through the metal layer 50, and enters the phosphor layer 60. Then, a part of the outgoing light 70a incident on the phosphor layer 60 excites the phosphor in the phosphor layer 60, so that carriers are generated in the phosphor. In this way, the phosphor layer 60 emits yellow light by recombination of carriers generated by the emitted light 70a.

  In addition, when the metal layer 50 is sufficiently thin as described above, a part of the outgoing light 70 a incident on the metal layer 50 passes through the metal layer 50 and the phosphor layer 60 and is output to the outside of the nitride semiconductor light emitting device 100. To do. That is, part of the outgoing light 70a incident on the metal layer 50 passes through the phosphor layer 60 and is output to the outside as blue light.

  On the other hand, the emitted light 70b is reflected at the interface between the nitride semiconductor light emitting layer 10 and the metal layer 50, as shown in FIG. When the outgoing light 70 b is totally reflected, evanescent light propagating along the interface is generated at the interface between the undoped nitride semiconductor layer 6 and the metal layer 50. This evanescent light excites surface plasmons at the interface between the undoped nitride semiconductor layer 6 and the metal layer 50. Here, when the metal layer 50 is sufficiently thin, for example, having a thickness of 5 nm to 25 nm, surface plasmons are also excited at the interface between the metal layer 50 and the phosphor layer 60. Then, surface plasmons excited on the surface of the metal layer 50 and carriers in the phosphor layer 60 generated by the emitted light 70a are coupled (linked), thereby enhancing light emission (fluorescence) from the phosphor layer 60. can do. In this manner, in the nitride semiconductor light emitting device 100, the wavelength conversion efficiency in the phosphor layer 60 can be improved.

  Thus, in Embodiment 1, the wavelength of the phosphor in the phosphor layer 60 is converted by mixing the blue light transmitted through the phosphor layer 60 and the yellow light converted in the phosphor layer 60. The nitride semiconductor light emitting device 100 that can emit white light with high efficiency and excellent color rendering can be realized.

  Next, the effect of surface plasmons on carrier recombination in the phosphor layer 60 will be described. FIG. 2A is a diagram for explaining recombination of carriers in the phosphor layer when surface plasmons are not excited. FIG. 2B is a diagram for explaining recombination of carriers in the phosphor layer when surface plasmons are excited.

As shown in FIG. 2A, in the absence of surface plasmon, carriers generated in the phosphor layer by the excitation light recombine by emitting light or not emitting light. Here, assuming that the emission recombination probability is k _r and the non-light emission recombination probability is k _nr , the wavelength conversion efficiency η _int in the phosphor layer is expressed as shown in Equation 1.

_{η int = k r / (k} r + k nr) ( Equation 1)

On the other hand, as shown in FIG. 2B, when surface plasmon exists, in addition to the carrier recombination in the phosphor layer described in FIG. 2A, the surface plasmon and the carrier in the phosphor layer are coupled. As a result, luminescence recombination occurs. Here, if the emission recombination probability due to the coupling between the surface plasmon and the carrier is k _SP , η _int changes as shown in Equation 2.

_{η int = (k r + k} SP) / (k r + k SP + k nr) ( Equation 2)

As described above, since the value of k _SP can be increased by generating surface plasmons, it can be seen that the wavelength conversion efficiency in the phosphor layer is improved.

  Next, it will be described that the undoped nitride semiconductor layer 6, the metal layer 50, and the phosphor layer 60 constituting the nitride semiconductor light emitting device 100 generate surface plasmons. Specifically, the relationship between the angle of light incident on the metal layer 50 (incident angle) and the absorptance will be described using calculation results using a model structure of a nitride semiconductor light emitting device. Here, FIGS. 3A to 3C show the structures and parameters used in the calculation. 4A to 4C show the calculation results.

  FIG. 3A shows a model structure of a nitride semiconductor light emitting device in which a nitride semiconductor layer 6a, a metal layer 50a, and a phosphor layer 60a are sequentially stacked. FIG. 3B shows a model structure of a nitride semiconductor light emitting device in which a nitride semiconductor layer 6a, a dielectric layer 40a, a metal layer 50a, and a phosphor layer 60a are sequentially stacked. FIG. 3C shows calculation parameters of materials used in the model structure shown in FIGS. 3A and 3B.

Specifically, in the nitride semiconductor layer 6a made of undoped GaN, the complex refractive index is n = 2.42 and k = 0 at the setting wavelength of 470 nm. In the nitride semiconductor layer 6a made of doped GaN, the complex refractive index is n = 2.42 and k = 0.004 at the setting wavelength of 470 nm. In the dielectric layer 40a made of SiO ₂ , the complex refractive index is n = 1.40 and k = 0 at the setting wavelength of 470 nm. In the dielectric layer 40a made of SiO ₂ , the complex refractive index is n = 1.40 and k = 0 at the setting wavelength of 470 nm. In the metal layer 50a made of Al, the complex refractive index is n = 0.675 and k = 5.60 at the setting wavelength of 470 nm. Further, in the phosphor layer 60a made of YAG, the complex refractive index is n = 1.83 and k = 0 at the setting wavelength of 470 nm.

  First, FIG. 4A shows a calculation result when the nitride semiconductor layer 6a is made of undoped GaN in the model structure shown in FIG. 3A without the dielectric layer 40a. FIG. 4A shows the calculation results when the thickness of the metal layer 50a made of Al is 0 nm (described as “without Al thin film” in the figure), 5 nm, 15 nm, and 25 nm.

  As shown in the calculation result of FIG. 4A, that is, as indicated by the absorptance of the metal layer 50a when incident light passes through the nitride semiconductor layer 6a and enters the metal layer 50a, the surface plasmon is applied to the metal layer 50a. No absorption due to excitation is observed. This is because carrier diffusion from the metal layer 50a to the doped nitride semiconductor layer 6a occurs.

  On the other hand, FIG. 4B shows the calculation result when the nitride semiconductor layer 6a is made of doped GaN in the model structure shown in FIG. 3A without the dielectric layer 40a. FIG. 4B shows calculation results when the metal layer 50a made of Al has a film thickness of 0 nm (no Al thin film), 5 nm, 15 nm, and 25 nm.

  As shown in the calculation result of FIG. 4B, that is, as indicated by the absorptance of the metal layer 50a when incident light passes through the nitride semiconductor layer 6a and enters the metal layer 50a, the surface plasmon is applied to the metal layer 50a. Absorption due to excitation is observed. Specifically, a steep absorption peak accompanying excitation of surface plasmons occurs in the metal layer 50a near an incident angle of 54 degrees. This is because the diffusion of carriers from the metal layer 50a to the nitride semiconductor layer 6a is suppressed.

FIG. 4C shows a calculation result when the nitride semiconductor layer 6a is made of GaN with doping in the model structure shown in FIG. 3B having the dielectric layer 40a. FIG. 4C shows calculation results when the thickness of the metal layer 50a made of Al is 0 nm (no Al thin film), 5 nm, 15 nm, and 25 nm. Here, the dielectric layer 40a is set to be made of SiO ₂ having a thickness of 150 nm.

  As shown in the calculation result of FIG. 4B, that is, as indicated by the absorptance of the metal layer 50a when incident light passes through the nitride semiconductor layer 6a and enters the dielectric layer 40a and the metal layer 50a, Absorption accompanying excitation of surface plasmons in the metal layer 50a is observed. Specifically, a steep absorption peak accompanying the excitation of surface plasmon occurs in the metal layer 50a near an incident angle of 40 degrees. This is because the diffusion of carriers from the metal layer 50a to the nitride semiconductor layer 6a is suppressed due to the dielectric layer 40a. Also, absorption is hardly observed at an incident angle of 45 degrees or more. This is because the incident light reflected by the metal layer 50a is totally reflected at the interface between the nitride semiconductor layer 6a and the dielectric layer 40a when the light enters the metal layer 50a from the dielectric layer 40a. As a result, the loss of incident light due to reflection can be suppressed.

  As described above, the nitride semiconductor light emitting device 100 including the undoped nitride semiconductor layer 6, the metal layer 50, and the phosphor layer 60 or including the undoped nitride semiconductor layer 6, the dielectric layer, the metal layer 50, and the phosphor layer 60 is It can be seen that surface plasmons can be generated.

  At this time, from the results of FIGS. 4B and 4C, when the material of the metal layer 50 is Al, the film thickness is desirably 5 nm to 25 nm. By setting the film thickness within the range of the metal layer 50, the transmittance of blue light emitted from the light emitting portion 5b can be increased simultaneously with exciting the surface plasmon.

(Production method)
Next, a method for manufacturing the nitride semiconductor light emitting device 100 configured as described above will be described.

First, for example, a buffer layer such as AlN or a low-temperature growth GaN layer is formed on the main surface of the substrate 2 made of a Si substrate having a plane orientation of <111> by epitaxial growth using a MOCVD (Metal Organic Chemical Vapor Deposition) method (see FIG. The nitride semiconductor light emitting layer 10 is formed with a not-shown interposition (FIG. 5A). Here, the nitride semiconductor light emitting layer 10 includes an n-type nitride semiconductor layer 5a made of n-type GaN, an In _x Ga _1-x N well layer, and a GaN barrier on the main surface of the substrate 2 via a buffer layer. A light emitting portion 5b having a multiple quantum well structure in which a plurality of layers are alternately formed, a p-type nitride semiconductor layer 5c made of p-type GaN, and a high-concentration n-type nitride semiconductor layer 5d made of high-concentration n-type GaN, The undoped nitride semiconductor layer 6 made of undoped GaN is sequentially stacked. The substrate 2 is not limited to a Si substrate having a surface orientation of <111>, but may be a sapphire substrate having a surface orientation of <0001> or a 6H-SiC substrate having a surface orientation of <0001>. Good.

  Next, the metal layer 50 and the phosphor layer 60 are sequentially formed on the nitride semiconductor light emitting layer 10 by vacuum deposition. Then, the phosphor layer 60, the metal layer 50, and a part of the nitride semiconductor light emitting layer 10 are selectively etched by using a photolithography technique and a dry etching method, and the n-type nitride semiconductor layer 5a made of n-type GaN. A first opening 15 exposing a part of the first opening 15 is formed. Subsequently, the phosphor layer 60, the metal layer 50, and a part of the nitride semiconductor light emitting layer 10 are selectively etched using a photolithography technique and a dry etching method, and a high-concentration n-type composed of a high-concentration n-type GaN layer. A second opening 25 exposing a part of the nitride semiconductor layer 5d is formed (FIG. 5B).

  Next, the n-type electrode 20 is selectively formed on a part of the upper surface of the first opening 15 by photolithography and vacuum deposition. Subsequently, the p-type electrode 30 is selectively formed on a part of the upper surface of the second opening 25 by photolithography and vacuum deposition. Finally, the nitride semiconductor light emitting device 100 is formed by performing chip separation by dicing using a blade (FIG. 5C).

As described above, the nitride semiconductor light emitting device 100 is formed.
As described above, in the nitride semiconductor light emitting device 100 of the first embodiment, by adjusting the configuration, material, and film thickness of the metal layer 50, a part of the light emitted from the light emitting portion 5b is transmitted. Thus, the nitride semiconductor light emitting device 100 is taken out. On the other hand, surface plasmons are excited in the metal layer 50 by evanescent light generated when the light emitted from the light emitting part is totally reflected at the interface between the undoped nitride semiconductor layer 6 and the metal layer 50 of the nitride semiconductor light emitting layer 10. Is done. Then, the generated surface plasmon and the carrier in the phosphor layer 60 are coupled. Thereby, since the light emission recombination in the phosphor layer 60 is promoted, the wavelength conversion efficiency in the phosphor is improved.

  In the nitride semiconductor light emitting device 100 of the first embodiment, the undoped nitride semiconductor layer 6 is formed in the nitride semiconductor light emitting layer 10 that is in contact with the metal layer 50, thereby suppressing carrier diffusion from the metal layer. Therefore, the intensity of the surface plasmon can be improved, and the phosphor conversion efficiency in the phosphor layer 60 can be improved.

  In the nitride semiconductor light emitting device 100 of the first embodiment, the undoped nitride semiconductor layer 6 is transparent and does not absorb the light emitted by the nitride semiconductor light emitting layer 10. The light emitted from the portion 5b can be extracted outside the nitride semiconductor light emitting device 100 without absorbing light.

  In the nitride semiconductor light emitting device 100 of the first embodiment, the metal layer 50 is made of Al or Ag, and the surface plasmon is effectively excited in Al and Ag, so that the conversion efficiency of the phosphor layer 60 is increased. Can be improved.

  In the nitride semiconductor light emitting device 100 of the first embodiment, the phosphor layer 60 is made of at least one oxide of Y, Ce, Al, Si, Ca, Eu. Thereby, the wavelength conversion efficiency can be improved by using the surface plasmon even in the phosphor layer 60 composed of these oxides formed by vapor deposition or sputtering. Therefore, the nitride semiconductor light emitting device 100 having the phosphor layer 60 with a high conversion rate and enabling white light emission at a low cost can be realized by using a conventional semiconductor process technology such as vapor deposition or sputtering.

  As described above, according to the first embodiment, it is possible to realize a nitride semiconductor light emitting element that has high phosphor wavelength conversion efficiency in the phosphor layer 60 and enables white light emission excellent in color rendering.

As described above, the nitride semiconductor light emitting device 100 may be configured by a transparent electrode such as ITO (Indium Tin Oxide) instead of the high-concentration n-type nitride semiconductor layer 5d. Further, instead of the undoped nitride semiconductor layer 6, it may be composed of a dielectric layer made of SiO ₂ having a thickness of about 150 nm, for example.

(Embodiment 2)
Next, a second embodiment will be described. In the second embodiment, an example in which a dielectric layer is formed between a nitride semiconductor light emitting layer and a metal layer will be described.

  FIG. 6 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the second embodiment. Elements similar to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. 7A, 7B, 8A and 8B are diagrams for explaining the operation and effect of the second embodiment.

(Construction)
A nitride semiconductor light emitting device 101 shown in FIG. 6 includes a nitride semiconductor light emitting layer 110, a dielectric layer 140, a metal layer 150, and a phosphor layer 60 stacked on the substrate 2. The nitride semiconductor light emitting device 101 includes an n-type electrode 20 and a p-type electrode 30. The nitride semiconductor light emitting device 101 shown in FIG. 6 differs from the nitride semiconductor light emitting device 100 according to the first embodiment in the configuration of the nitride semiconductor light emitting layer 110 and the metal layer 150, and includes a dielectric layer 140. ing.

  Specifically, the nitride semiconductor light emitting layer 110 does not include the undoped nitride semiconductor layer 6 included in the nitride semiconductor light emitting layer 10 according to the first embodiment. That is, in the nitride semiconductor light emitting layer 110, the n-type nitride semiconductor layer 5a, the light emitting portion 5b, the p-type nitride semiconductor layer 5c, and the high-concentration n-type nitride semiconductor layer 5d are sequentially stacked.

The dielectric layer 140 is made of SiO ₂ or the like having a lower refractive index than GaN, and is formed on the nitride semiconductor light emitting layer 110, that is, in contact with the high-concentration n-type nitride semiconductor layer 5d. Therefore, in the dielectric layer 140, part of the light incident on the dielectric layer 140 from the high-concentration n-type nitride semiconductor layer 5d is transferred to the dielectric layer 140 and the high-concentration n-type nitride semiconductor layer 5d. It is totally reflected without being absorbed.

  The dielectric layer 140 is formed with a sufficiently thin thickness, for example, 150 nm. Note that the thickness of the dielectric layer 140 is not limited to 150 nm. At the interface between the nitride semiconductor light emitting layer 110 and the dielectric layer 140, the thickness should be equal to or less than the penetration depth of the evanescent light generated when the light emitted from the nitride semiconductor light emitting layer 110 is totally reflected by the dielectric layer 140. That's fine.

  The metal layer 150 is made of a metal such as Al or Ag, and is formed in contact with the dielectric layer 140. At this time, the metal layer 150 is provided with periodic openings. Further, the metal layer 150 is formed with a sufficiently thin thickness of, for example, 20 nm.

  As described above, nitride semiconductor light emitting element 101 in the second embodiment is configured.

(Operation and effect)
Next, the operation and effect of nitride semiconductor light emitting element 101 in the second embodiment will be described.

  First, light generated in the light emitting unit 5b is incident on the dielectric layer 140 at a certain angle. Here, the dielectric layer 140 has a refractive index lower than that of the nitride semiconductor light emitting layer 110. Therefore, a part of the light incident on the dielectric layer 140 from the high-concentration n-type nitride semiconductor layer 5d is not absorbed by the dielectric layer 140 and the high-concentration n-type nitride semiconductor layer 5d. Reflected.

  Therefore, a part of the light incident at a certain angle with respect to the dielectric layer 140 is totally reflected at the interface between the high-concentration n-type nitride semiconductor layer 5d and the dielectric layer 140. When a part of the incident light is totally reflected, evanescent light propagating along the interface is generated at the interface between the high-concentration n-type nitride semiconductor layer 5d and the dielectric layer 140.

  Here, when the dielectric layer 140 is sufficiently thin so as to have a thickness of, for example, 150 nm, evanescent light generated at the interface between the high-concentration n-type nitride semiconductor layer 5d and the dielectric layer 140 is generated in the dielectric layer 140. If so, surface plasmons are excited at the interface between the dielectric layer 140 and the metal layer 150. Further, when the metal layer 150 is sufficiently thin so as to have a thickness of, for example, 20 nm, surface plasmons are also excited at the interface between the metal layer 150 and the phosphor layer 60.

  By coupling the excited surface plasmon and the carrier in the phosphor layer 60, light emission (fluorescence) from the phosphor layer 60 can be enhanced. That is, in the nitride semiconductor light emitting device 101, the conversion efficiency in the phosphor layer 60 can be improved. Furthermore, by providing periodic openings in the metal layer 150, surface plasmons can be effectively excited in the metal layer 150. Thereby, the conversion efficiency of the phosphor layer 60 can be further improved.

  On the other hand, since the metal layer 150 is sufficiently thin, for example, to have a thickness of 20 nm, a part of the blue light incident on the metal layer 150 is transmitted through the metal layer 150 or the opening thereof, and is effective to the outside of the light emitting element. Blue light can be extracted.

  Thus, in Embodiment 2, the wavelength of the phosphor in the phosphor layer 60 is converted by mixing the blue light transmitted through the phosphor layer 60 and the yellow light converted in the phosphor layer 60. The nitride semiconductor light emitting device 101 that can emit white light with high efficiency and excellent color rendering can be realized.

  Next, it will be described that the nitride semiconductor light emitting layer 110, the dielectric layer 140, the metal layer 150, and the phosphor layer 60 constituting the nitride semiconductor light emitting element 101 generate surface plasmons. Specifically, the relationship between the angle of light incident on the metal layer 150 (incident angle) and the absorptance will be described using calculation results using a model structure of a nitride semiconductor light emitting device. 7A, 7B, 8A, and 8B are diagrams for explaining operations and effects in the second embodiment.

  FIG. 7A shows a model structure of a nitride semiconductor light emitting device in which a nitride semiconductor layer 110a, a dielectric layer 140a, a metal layer 150a, and a phosphor layer 60a are sequentially stacked. FIG. 7B shows calculation parameters of materials used in the model structure shown in FIG. 7A.

8A and 8B, a nitride semiconductor layer 110a made of doped GaN, a dielectric layer 140a made of 150 nm of SiO _2, a metal layer 150a made of 20 nm of Al, and a phosphor layer 60a made of YAG are sequentially laminated. The calculation results of the model structure of the nitride semiconductor light emitting device are shown. In this model structure, incident light passes through the nitride semiconductor layer 110a and enters the dielectric layer 140a, the metal layer 150a having the opening, and the phosphor layer 60a. FIG. 8A shows calculation results when the metal layer 150a has an aperture ratio of 50% and the period is 0.5 μm, 1 μm, and 1.5 μm. FIG. 8B shows calculation results when the metal layer 150a has a period of 1 μm and the aperture ratio is 25%, 50%, and 75%.

  As shown in the calculation results of FIGS. 8A and 8B, when the metal layer 150a has a periodic structure with a period of 1 μm and an aperture ratio of 50% or more, surface plasmons are effectively excited in the metal layer 150a. Due to the excitation of the surface plasmon, a steep absorption peak is generated in the vicinity of an incident angle of 37.5 degrees. As a result, by providing an opening in the metal layer 150a, it is possible to effectively extract blue light to the outside of the light emitting element and improve the conversion efficiency of the phosphor layer 60a by the excited surface plasmon.

  As described above, in the nitride semiconductor light emitting device 101 of the second embodiment, by adjusting the configuration, material, and film thickness of the metal layer 150, a part of the light emitted from the light emitting portion 5b is transmitted. Thus, the nitride semiconductor light emitting device 101 is taken out. On the other hand, surface plasmons are excited in the metal layer 150 by evanescent light generated when the light emitted from the light emitting part is totally reflected at the interface between the nitride semiconductor light emitting layer 110 and the dielectric layer 140. Then, the generated surface plasmon and the carrier in the phosphor layer 60 are coupled. Thereby, since the light emission recombination in the phosphor layer 60 is promoted, the wavelength conversion efficiency in the phosphor is improved.

  In the nitride semiconductor light emitting device 101 of the second embodiment, the dielectric layer 140 is transparent and does not absorb the light emitted by the nitride semiconductor light emitting layer 110, so that the light emitting portion 5b of the nitride semiconductor light emitting layer 110 is used. Can be extracted to the outside of the nitride semiconductor light emitting device 101 without absorbing the light emitted.

  Moreover, in the nitride semiconductor light emitting device 101 of the second embodiment, the dielectric layer 140 is configured with a sufficiently thin thickness of, for example, 150 nm. That is, the dielectric layer 140 has a depth of evanescent light generated when light emitted from the nitride semiconductor light emitting layer 110 is totally reflected by the dielectric layer 140 at the interface between the nitride semiconductor light emitting layer 110 and the dielectric layer 140. The thickness is less than that. With this configuration, surface plasmons can be effectively excited on the metal layer 150.

  In the nitride semiconductor light emitting device 101 of the first embodiment, the metal layer 150 is made of Al or Ag, and the surface plasmon is effectively excited in Al and Ag. Therefore, the conversion efficiency of the phosphor layer 60 Can be improved.

  In the nitride semiconductor light emitting device 101 of the first embodiment, the metal layer 150 is provided with periodic openings. Thereby, blue light can be effectively extracted outside the nitride semiconductor light emitting device 101, and the conversion efficiency of the phosphor layer 60 can be improved by the excited surface plasmon.

  In the nitride semiconductor light emitting device 101 of the first embodiment, the phosphor layer 60 is composed of at least one oxide of Y, Ce, Al, Si, Ca, and Eu. Thereby, the wavelength conversion efficiency can be improved by using the surface plasmon even in the phosphor layer 60 composed of these oxides formed by vapor deposition or sputtering. Therefore, the nitride semiconductor light emitting device 101 that has the phosphor layer 60 with a high conversion rate and enables white light emission at a low cost can be realized by using a conventional semiconductor process technology such as vapor deposition or sputtering.

  As described above, according to the second embodiment, it is possible to realize the nitride semiconductor light emitting device 101 that has high phosphor wavelength conversion efficiency in the phosphor layer 60 and enables white light emission with excellent color rendering.

(Embodiment 3)
Subsequently, Embodiment 3 will be described.

  FIG. 9 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the third embodiment. Elements similar to those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted. 10A to 10F are diagrams for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the third embodiment. Hereinafter, this embodiment will be described in detail.

(Construction)
A nitride semiconductor light emitting device 200 shown in FIG. 9 includes a reflective film 216, a nitride semiconductor light emitting layer 210, a dielectric layer 240, a metal layer 250, and a phosphor layer 260 stacked on a support substrate 217. The nitride semiconductor light emitting device 200 includes an n-type electrode 220 and a p-type electrode 230.

  The nitride semiconductor light emitting device 200 shown in FIG. 9 is different from the nitride semiconductor light emitting device 101 according to the second embodiment in the configuration of the nitride semiconductor light emitting layer 210, and has a dielectric layer 240, a metal layer 150, and a phosphor. The shape of the layer 260 is different. Nitride semiconductor light emitting element 200 differs from nitride semiconductor light emitting element 101 according to Embodiment 2 in that it includes a reflective film 216 and a support substrate 217, and the configuration of p-type electrode 230 is different.

  In the nitride semiconductor light emitting layer 210, a p-type nitride semiconductor layer 5c, a light emitting portion 5b, and an n-type nitride semiconductor layer 205a are sequentially stacked.

  The n-type nitride semiconductor layer 205a is made of, for example, GaN doped with Si. In addition, the n-type nitride semiconductor layer 205a has irregularities formed on the side opposite to the light emitting portion 5b, that is, the side on which the dielectric layer 240 is laminated.

The light-emitting portion 5b is formed under the n-type nitride semiconductor layer 205a, and is composed of, for example, InGaN and GaN multiple quantum wells adjusted to exhibit blue light emission centered on a wavelength of 470 nm. That is, the light emitting portion 5b has a multiple quantum well structure in which a plurality of In _x Ga _1-x N well layers and GaN barrier layers are alternately formed, and emits light.

  The p-type nitride semiconductor layer 5c is formed under the light emitting portion 5b and is made of, for example, GaN doped with Mg.

  The reflective film 216 is formed of a multilayer film of a metal such as Pt, Ag, Ni, or Cu, for example, and is formed so as to be electrically connected to the p-type nitride semiconductor layer 5c. Further, the reflective film 216 is electrically connected to the support substrate 217.

  The support substrate 217 is a substrate configured by metal plating such as Au or Cu, and is formed so as to be electrically connected to the reflective film 216.

  The p-type electrode 230 is formed of a multilayer film of a metal such as Ti, Al, Ni, and Au, for example, and is formed so as to be electrically connected to the surface of the support substrate 217 opposite to the reflective film 216.

The dielectric layer 240 is made of a dielectric material such as SiO ₂ or MgF ₂ having a refractive index lower than that of the nitride semiconductor light emitting layer 210, and is formed in contact with the n-type nitride semiconductor layer 205a. . The dielectric layer 240 is a dielectric having a thickness of about 150 nm, for example. The dielectric layer 240 is formed in a concavo-convex shape along the concavo-convex shape formed on the dielectric layer 240 side of the n-type nitride semiconductor layer 205a.

  The metal layer 250 is made of a metal such as Al or Ag, and is formed in contact with the dielectric layer 240. The metal layer 250 is a thin metal film having a thickness of 5 to 25 nm, for example. The metal layer 250 is formed in a concavo-convex shape along the shape of the dielectric layer 240.

  The phosphor layer 260 is made of, for example, YAG or sialon phosphor, and is formed in contact with the metal layer 250. The phosphor layer 260 is formed in a concavo-convex shape along the shape of the metal layer 250.

  The n-type electrode 220 is composed of, for example, a multilayer film of a metal such as Ti, Al, Ni, and Au, and is formed so as to be electrically connected to the n-type nitride semiconductor layer 205a. Specifically, the n-type electrode 220 is formed in contact with the n-type nitride semiconductor layer 205a exposed by selectively removing a part of the phosphor layer 260, the metal layer 250, and the dielectric layer 240. Yes.

As described above, nitride semiconductor light emitting element 200 in the third embodiment is configured.
In the nitride semiconductor light emitting device 200, as described above, the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240 and the interface between the n-type nitride semiconductor layer 205a and the n-type electrode 220 are Unevenness is formed.

(Operation and effect)
Next, the operation and effect of nitride semiconductor light emitting device 200 in the third embodiment will be described.

  First, the light generated in the light emitting unit 5b is incident on the dielectric layer 240 at a certain angle. Here, the dielectric layer 240 has a refractive index lower than that of the nitride semiconductor light emitting layer 210. Therefore, a part of the light incident on the dielectric layer 240 from the n-type nitride semiconductor layer 205a is totally reflected without being absorbed.

  Therefore, part of the light incident at a certain angle with respect to dielectric layer 240 is totally reflected at the interface between n-type nitride semiconductor layer 205a and dielectric layer 240. When a part of the incident light is totally reflected, evanescent light propagating along the interface is generated at the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240.

  Here, when the dielectric layer 240 is sufficiently thin so as to have a thickness of, for example, about 150 nm, evanescent light generated at the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240 also enters the dielectric layer 240. The surface plasmon is excited at the interface between the dielectric layer 240 and the metal layer 250. Further, when the metal layer 250 is sufficiently thin so as to have a thickness of, for example, about 5 to 25 nm, surface plasmons are also excited at the interface between the metal layer 250 and the phosphor layer 260.

  By coupling the excited surface plasmon and the carrier in the phosphor layer 260 in this way, light emission (fluorescence) from the phosphor layer 260 can be enhanced. That is, in the nitride semiconductor light emitting device 101, the wavelength conversion efficiency in the phosphor layer 260 can be improved.

  On the other hand, since the metal layer 250 is sufficiently thin, for example, to have a thickness of about 5 to 25 nm, a part of incident light (blue light) incident on the metal layer 250 is transmitted through the metal layer 250, and the nitride semiconductor It is taken out of the light emitting element 200.

  As described above, the nitride semiconductor light emitting device 200 according to the third embodiment mixes the incident light (blue light) transmitted through the metal layer 250 and the yellow light converted by the phosphor layer 260, thereby producing white light. Can be realized.

  In addition, unevenness is provided at the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240, and incident light is reflected many times by the unevenness, so that surface plasmons can be excited efficiently.

  Further, since total reflection occurs at the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240, no reflection loss occurs at the time of reflection at the metal interface, and blue light is efficiently transmitted to the outside of the nitride semiconductor light emitting device 200. Can be taken out well.

  Furthermore, in the nitride semiconductor light emitting device 200, the n-type nitride semiconductor layer 205a can easily obtain conductivity. Therefore, as shown in FIG. 9, the n-type electrode 220 and the n-type nitride semiconductor layer 205a are electrically connected to diffuse carriers into the n-type nitride semiconductor layer 205a without using a transparent conductive layer or the like. be able to. That is, light absorption by the transparent conductive layer can be suppressed, and blue light can be efficiently extracted outside the light emitting element.

  In this way, the blue light transmitted through the nitride semiconductor light emitting layer 210, the dielectric layer 240, the metal layer 250, and the phosphor layer 260 and the yellow light converted by the phosphor layer 260 are mixed to produce fluorescence. The nitride semiconductor light emitting device 200 that has high phosphor wavelength conversion efficiency in the body layer 260 and can emit white light with excellent color rendering can be realized.

(Production method)
Next, a method for manufacturing the nitride semiconductor light emitting device 200 configured as described above will be described.

First, a buffer layer (not shown) such as AlN or a low-temperature growth GaN layer is interposed on the main surface of the substrate 2 made of a Si substrate having a plane orientation of <111>, for example, by epitaxial growth using MOCVD. A nitride semiconductor light emitting layer 210 is formed (FIG. 10A). Here, the nitride semiconductor light emitting layer 210 includes an n-type nitride semiconductor layer 205a made of n-type GaN, a In _x Ga _1-x N well layer, and a GaN barrier on the main surface of the substrate 2 via a buffer layer. A light emitting portion 5b having a multiple quantum well structure in which a plurality of layers are alternately formed and a p-type nitride semiconductor layer 5c made of p-type GaN are sequentially stacked. The substrate 2 is not limited to a Si substrate having a plane orientation of <111>, but may be a sapphire substrate having a plane orientation of <0001> or a 6H-SiC substrate having a plane orientation of <0001>. Good.

  Next, a reflective film 216 made of Ni, Ti, Al, Pt, Ag, and Cu is formed on the nitride semiconductor light emitting layer 210 by vacuum deposition. Subsequently, a support substrate 217 is formed on the reflective film 216 by electroplating Cu. Subsequently, a p-type electrode 230 made of Ni and Au is formed on the support substrate 217 (FIG. 10B).

  Next, an adhesive layer (not shown) is applied so as to cover the surface of nitride semiconductor light emitting device 200 on which p-type electrode 230 is formed, and second nitride semiconductor light emitting device 200 is applied to nitride semiconductor light emitting device 200 through the adhesive layer. A support substrate (not shown) is bonded. Here, as the adhesive constituting the adhesive layer, for example, a silicone resin adhesive that is resistant to a strong alkaline solution such as potassium hydroxide (KOH) is used. Then, after the nitride semiconductor light emitting element 200 is bonded onto the second support substrate, the substrate 2 is removed. Thereby, the n-type nitride semiconductor layer 205a made of n-type GaN is exposed (FIG. 10C).

  When the substrate 2 is a Si substrate, the substrate 2 can be removed by wet etching using a mixed solution of hydrofluoric acid and nitric acid. If the substrate 2 is a sapphire substrate, the substrate can be removed by a laser lift-off method.

  Next, the exposed n-type nitride semiconductor layer 205a made of n-type GaN is wet-etched using a PEC (Photoelectrochemical) etching method using a combination of KOH aqueous solution and ultraviolet light irradiation. Specifically, the nitride semiconductor light-emitting element 200 bonded onto the second support substrate is immersed in a container containing a potassium hydroxide (KOH) aqueous solution, and wet etching is performed in a state where ultraviolet light is irradiated. Thereby, an uneven surface (FIG. 10D) having a slope is formed in the n-type nitride semiconductor layer 205a.

  This nitride semiconductor etching by PEC etching has anisotropy in the plane orientation, and the plane orientation is a kind of crystal orientation plane of the n-type nitride semiconductor layer 205a made of n-type GaN, and is one of the semipolar planes. A certain {1-101} plane is formed. Thereby, it is possible to form an uneven surface having a slope composed of {1-101} planes in the n-type nitride semiconductor layer 205a.

  Next, an n-type electrode 220 is selectively formed on a part of the concavo-convex surface of the n-type nitride semiconductor layer 205a by a photolithography technique and a vacuum deposition method (FIG. 10E).

  Next, a dielectric layer 240, a metal layer 250, and a phosphor layer 260 are sequentially formed on the concavo-convex surface of the n-type nitride semiconductor layer 205a by using a photolithography technique and a vacuum deposition method. Subsequently, the second support substrate is separated by removing the adhesive layer using an adhesive remover. Finally, chip separation is performed by dicing using a blade (not shown) to form the nitride semiconductor light emitting device 200 (FIG. 10F).

As described above, the nitride semiconductor light emitting device 200 is formed.
As described above, in the nitride semiconductor light emitting device 200 of the third embodiment, by adjusting the configuration, material, and film thickness of the metal layer 250, a part of the light emitted from the light emitting portion 5b is transmitted. Thus, the nitride semiconductor light emitting device 200 is taken out. On the other hand, surface plasmons are excited in the metal layer 250 by evanescent light generated when the light emitted from the light emitting part is totally reflected at the interface between the nitride semiconductor light emitting layer 210 and the dielectric layer 240. Then, the generated surface plasmon is coupled with the carrier in the phosphor layer 260. Thereby, since the light emission recombination in the phosphor layer 260 is promoted, the wavelength conversion efficiency in the phosphor is improved.

  In the nitride semiconductor light emitting device 200 of the third embodiment, the dielectric layer 240 is transparent and does not absorb the light emitted from the nitride semiconductor light emitting layer 210. Therefore, the light emitting portion 5b of the nitride semiconductor light emitting layer 210 is used. Can be extracted to the outside of the nitride semiconductor light emitting device 200 without absorbing the light emitted by.

  In the nitride semiconductor light emitting device 200 of the third embodiment, the metal layer 250 is made of Al or Ag, and the surface plasmon is effectively excited in Al and Ag, so that the conversion efficiency of the phosphor layer 260 is increased. Can be improved.

  In the nitride semiconductor light emitting device 101 of the second embodiment, the phosphor layer 260 is made of at least one oxide of Y, Ce, Al, Si, Ca, and Eu. Accordingly, the wavelength conversion efficiency can be improved by using the surface plasmon even in the phosphor layer 260 formed of these oxides formed by vapor deposition or sputtering. In other words, the effect of improving the conversion efficiency of the phosphor layer 260 using surface plasmons is significant in a phosphor having a defect level or a surface level. Therefore, the phosphor layer 260 can be formed using a general semiconductor process technology such as vapor deposition or sputtering, and the cost of the white light emitting element can be reduced. Therefore, the nitride semiconductor light emitting device 200 which has the phosphor layer 260 with a high conversion rate and enables white light emission at a low cost can be realized by using a conventional semiconductor process technology such as vapor deposition or sputtering.

  In the nitride semiconductor light emitting device 101 of the second embodiment, the dielectric layer 240 and the nitride semiconductor light emitting layer 210 provided with the dielectric layer 240 have an uneven shape. With this configuration, the light emitted from the light-emitting portion 5b of the nitride semiconductor light-emitting layer 210 is repeatedly totally reflected in the unevenness formed in the dielectric layer 240 and the nitride semiconductor light-emitting layer 210, and the surface plasmon is effectively obtained. Can be excited.

  As described above, according to the third embodiment, it is possible to realize the nitride semiconductor light emitting device 100 that has high phosphor wavelength conversion efficiency in the phosphor layer 260 and enables white light emission excellent in color rendering.

(Embodiment 4)
Next, a fourth embodiment will be described. In the fourth embodiment, an example in which the configuration is the same as that of the third embodiment but the manufacturing method is different will be described.

  FIG. 11 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the fourth embodiment. Elements similar to those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted. 12A to 12F are diagrams for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fourth embodiment.

(Construction)
A nitride semiconductor light emitting device 300 shown in FIG. 11 includes a reflective film 216, a nitride semiconductor light emitting layer 310, a dielectric layer 340, a metal layer 250, and a phosphor layer 260 stacked on a support substrate 217. The nitride semiconductor light emitting device 300 includes an n-type electrode 220 and a p-type electrode 230. The nitride semiconductor light emitting device 300 shown in FIG. 11 is different from the nitride semiconductor light emitting device 200 according to the third embodiment in the manufacturing method of the nitride semiconductor light emitting layer 310 and the dielectric layer 340 that have the same configuration.

  In the nitride semiconductor light emitting layer 310, an n-type nitride semiconductor layer 305a, a light emitting portion 5b, and a p-type nitride semiconductor layer 5c are stacked. The nitride semiconductor light emitting layer 310 has crystal growth along a plane other than the (0001) plane of the GaN crystal, for example, along the {1-101} plane.

  The dielectric layer 340 is made of a nitride such as AlN, for example, and is formed in contact with the n-type nitride semiconductor layer 305a. The dielectric layer 340 is a thin dielectric material having a thickness of about 150 nm, for example.

As described above, nitride semiconductor light emitting element 300 in the fourth embodiment is configured.
Since the operation and effect of nitride semiconductor light emitting element 300 in the fourth embodiment are the same as those of nitride semiconductor light emitting element 200 in the third embodiment, description thereof will be omitted.

  In the nitride semiconductor light emitting device 300, the growth surface of the nitride semiconductor light emitting layer 310 is inclined with respect to the C plane. For this reason, it has the effect that the recombination probability of the electron and the hole in the light emission part 5b improves, and the luminous efficiency in the light emission part 5b becomes high.

  As described above, by mixing the blue light transmitted through the nitride semiconductor light emitting layer 310, the dielectric layer 340, the metal layer 250 and the phosphor layer 260 with the yellow light converted by the phosphor layer 260, The nitride semiconductor light emitting device 300 that has high phosphor wavelength conversion efficiency in the phosphor layer 260 and can emit white light with excellent color rendering properties can be realized.

(Production method)
Next, a method for manufacturing the nitride semiconductor light emitting device 300 configured as described above will be described.

First, an oxide film (not shown) made of SiO ₂ is formed on a main surface of a substrate 302 made of an Si substrate having a surface orientation of <100> whose surface orientation is 7 ° off, for example. Subsequently, the formed oxide film is patterned by a photolithography technique and dry etching using, for example, CHF 3 gas to expose Si.

  Subsequently, the substrate 302 is immersed in an alkaline aqueous solution such as heated TMAH (Tetramethylammonium Hydroxide) or KOH, so that the substrate 302 is subjected to anisotropic etching. Here, for example, the concentration of TMAH is 2.38%, the temperature is 80 ° C., and the wet etching time is 20 minutes. Thus, since Si (111) is exposed by anisotropic etching performed on the substrate 302, irregularities are formed on the main surface of the substrate 302.

Subsequently, by using a semiconductor process technology such as vacuum deposition or photolithography, one inclined surface of the unevenness formed on the main surface of the substrate 302 is formed with a dielectric film such as SiO ₂ (not shown). ) Subsequently, a nitride semiconductor light emitting layer 310 is formed on the substrate 302 by epitaxial growth using MOCVD, with a dielectric layer 340 made of AlN and a buffer layer (not shown) such as a low temperature growth GaN layer interposed. (FIG. 12A). Here, the nitride semiconductor light emitting layer 310 includes an n-type nitride semiconductor layer 305a made of n-type GaN, an In _x Ga _1-x N well layer, and a GaN barrier layer on a substrate 302 via a buffer layer. A plurality of light emitting portions 5b having a multiple quantum well structure and a p-type nitride semiconductor layer 5c made of p-type GaN are sequentially stacked.

  Next, a reflective film 216 made of Ni, Ti, Al, Pt, Ag, and Cu is formed on the nitride semiconductor light emitting layer 310 by vacuum deposition. Subsequently, the support substrate 217 is formed on the reflective film 216 by electroplating Cu. Subsequently, a p-type electrode 230 made of Ni and Au is formed on the support substrate 217 (FIG. 12B).

  Next, an adhesive layer (not shown) is applied so as to cover the surface of the nitride semiconductor light emitting device 300 on which the p-type electrode 230 is formed, and the second layer is applied to the nitride semiconductor light emitting device 300 through the adhesive layer. A support substrate (not shown) is adhered. Here, as the adhesive constituting the adhesive layer, for example, a silicone resin adhesive that is resistant to a strong alkaline solution such as potassium hydroxide (KOH) is used. Then, after the nitride semiconductor light emitting device 300 is bonded onto the second support substrate, the substrate 302 is removed. This exposes the dielectric layer 340 (FIG. 12C).

  Note that if the substrate 302 is a Si substrate, the substrate 302 can also be removed by wet etching using a mixed solution of hydrofluoric acid and nitric acid. If the substrate 302 is a sapphire substrate, the substrate can be removed by a laser lift-off method.

Next, an opening 325 is formed in the dielectric layer 340 using a photolithography technique and a dry etching technique using CHF ₃ gas. Thereby, the n-type nitride semiconductor layer 305a is exposed (FIG. 12D).

  Next, the n-type electrode 220 is selectively formed on a part of the concavo-convex surface of the n-type nitride semiconductor layer 305a by photolithography and vacuum deposition (FIG. 12D).

  Next, the metal layer 250 and the phosphor layer 260 are sequentially formed on the uneven surface of the dielectric layer 340 by using a photolithography technique and a vacuum deposition method. Subsequently, the second support substrate is separated by removing the adhesive layer using an adhesive remover. Finally, the nitride semiconductor light emitting device 300 is formed by performing chip separation by dicing using a blade (not shown) (FIG. 12F).

  As described above, the nitride semiconductor light emitting device 300 is manufactured. In the nitride semiconductor light emitting device 300, the shape of the substrate 302 can be inherited to form irregularities, so that the manufacturing process can be simplified.

  As described above, according to the fourth embodiment, it is possible to realize the nitride semiconductor light emitting device 300 that has high phosphor wavelength conversion efficiency in the phosphor layer 260 and enables white light emission excellent in color rendering.

(Embodiment 5)
Next, a fifth embodiment will be described.

  FIG. 13 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the fifth embodiment. Elements similar to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. 14A to 14F are diagrams for illustrating the method for manufacturing the nitride semiconductor light-emitting element in the fifth embodiment. Hereinafter, this embodiment will be described in detail.

(Construction)
A nitride semiconductor light emitting device 400 shown in FIG. 13 includes a metal layer 460, a phosphor layer 450, a dielectric layer 440, a nitride semiconductor light emitting layer 410, and a transparent conductive layer 415 stacked on a support substrate 470. The nitride semiconductor light emitting device 400 includes an n-type electrode 20 and a p-type electrode 30. The nitride semiconductor light emitting device 400 shown in FIG. 13 differs from the nitride semiconductor light emitting device 100 according to the first embodiment in the configuration of the nitride semiconductor light emitting layer 410, and includes a dielectric layer 440, a metal layer 460, and a phosphor. The stacking direction and stacking order of the layers 450 are different. The nitride semiconductor light emitting device 400 is different from the nitride semiconductor light emitting device 100 according to the first embodiment in that the configuration of the transparent conductive layer 415 and the support substrate 470 is added.

  In the nitride semiconductor light emitting layer 410, an n-type nitride semiconductor layer 405a, a light emitting portion 5b, and a p-type nitride semiconductor layer 5c are stacked. Nitride semiconductor light emitting layer 410 does not include high-concentration n-type nitride semiconductor layer 5d and undoped nitride semiconductor layer 6 included in nitride semiconductor light emitting layer 10 according to the first embodiment.

  The n-type nitride semiconductor layer 405a is made of, for example, GaN doped with Si. The n-type nitride semiconductor layer 405a has irregularities on the side opposite to the light emitting portion 5b, that is, the side on which the dielectric layer 440 is laminated.

  The transparent conductive layer 415 is made of, for example, ITO and is formed on the nitride semiconductor light emitting layer 410. The transparent conductive layer 415 is formed so as to be electrically connected to the p-type nitride semiconductor layer 5c.

The dielectric layer 440 is made of, for example, SiO ₂ and is formed along the uneven surface of the n-type nitride semiconductor layer 405a. That is, unevenness is formed at the interface between the n-type nitride semiconductor layer 405a and the dielectric layer 440. The dielectric layer 440 is a dielectric having a thickness of about 150 nm, for example.

  The phosphor layer 450 is made of, for example, YAG, sialon phosphor, or the like, and is formed along the uneven surface of the dielectric layer 440.

  The metal layer 460 is formed of a metal multilayer film such as Al, Ag, or Cu, for example, and is formed along the uneven surface of the phosphor layer 450. The metal layer 460 is formed with a thickness of about 5 to 25 nm, for example.

  The n-type electrode 20 is composed of, for example, a multilayer film of metal such as Ti, Al, Ni, and Au, and is formed so as to be electrically connected to the n-type nitride semiconductor layer 405a.

  The p-type electrode 30 is composed of, for example, a multilayer film of metal such as Ti, Al, Ni, and Au, and is formed so as to be electrically connected to the transparent conductive layer 415.

The support substrate 470 is a substrate configured by metal plating such as Au or Cu.
As described above, nitride semiconductor light emitting element 400 in the fifth embodiment is configured.

(Operation and effect)
Next, the operation and effect of nitride semiconductor light emitting device 400 in the fifth embodiment will be described.

  First, the light emitting unit 5b emits light to generate light. Part of the generated light is totally reflected at the interface between the n-type nitride semiconductor layer 405a and the dielectric layer 440. The evanescent light generated at this time propagates through the dielectric layer 440 and the phosphor layer 450 and excites surface plasmons on the surface of the metal layer 460. On the other hand, in the dielectric layer 440, that is, at the interface between the n-type nitride semiconductor layer 405a and the dielectric layer 440, light that has not been totally reflected is transmitted through the dielectric layer 440 and excites carriers in the phosphor layer 450. .

  Then, by coupling the surface plasmon excited on the surface of the metal layer 460 and the carrier excited on the phosphor layer 450, the carriers are efficiently recombined and the conversion efficiency of the phosphor layer 450 is improved. .

  In this way, the blue light transmitted through the transparent conductive layer 415 is mixed with the yellow light converted by the phosphor layer 450 and transmitted through the dielectric layer 440, the nitride semiconductor light emitting layer 410, and the transparent conductive layer 415. As a result, the nitride semiconductor light emitting device 400 that has high phosphor wavelength conversion efficiency in the phosphor layer 450 and that can emit white light with excellent color rendering can be realized.

(Production method)
Next, a method for manufacturing the nitride semiconductor light emitting device 400 configured as described above will be described.

First, a buffer layer (not shown) such as AlN or a low-temperature growth GaN layer is interposed on the main surface of a substrate 402 made of a Si substrate having a plane orientation of <111>, for example, by epitaxial growth using MOCVD. A nitride semiconductor light emitting layer 410 is formed (FIG. 14A). Here, the nitride semiconductor light emitting layer 410 includes an n-type nitride semiconductor layer 405a made of n-type GaN, an In _x Ga _1-x N well layer, and a GaN barrier on the main surface of the substrate 402 via a buffer layer. A light emitting portion 5b having a multiple quantum well structure in which a plurality of layers are alternately formed and a p-type nitride semiconductor layer 5c made of p-type GaN are sequentially stacked. Note that the substrate 402 is not limited to a Si substrate having a plane orientation of <111>, but may be a sapphire substrate having a plane orientation of <0001>, a 6H-SiC substrate having a plane orientation of <0001>, or the like. Good.

Next, a first opening 425 is formed in the nitride semiconductor light emitting layer 410 by photolithography and dry etching using, for example, Cl ₂ gas (FIG. 14B).

  Next, a transparent conductive layer 415 made of, for example, ITO is formed by a photolithography technique and a vacuum deposition method so as to be electrically connected to the p-type nitride semiconductor layer 5c made of p-type GaN. Further, the p-type electrode 30 made of, for example, a multilayer film of Ti, Al, Ni, or Au is formed in a form that is electrically connected to the transparent conductive layer 415 by photolithography and vacuum deposition. Further, an n-type nitride semiconductor made of n-type GaN exposed from the first opening 425 by an n-type electrode 20 made of, for example, a multilayer film of Ti, Al, Ni, or Au, by a photolithography technique and a vacuum deposition method. It is formed so as to be electrically connected to the layer 405a (FIG. 14C).

  Next, an adhesive layer (not shown) is applied so as to cover the surface of the nitride semiconductor light emitting device 400 on which the p-type electrode 30 is formed, and the second layer is applied to the nitride semiconductor light emitting device 400 via the adhesive layer. A substrate (not shown) is adhered. Here, as the adhesive constituting the adhesive layer, for example, a silicone resin adhesive that is resistant to a strong alkaline solution such as potassium hydroxide (KOH) is used. Then, after bonding the nitride semiconductor light emitting device 400 onto the second substrate, the substrate 402 is removed. Thereby, the n-type nitride semiconductor layer 405a made of n-type GaN is exposed (FIG. 14D).

  Note that in the case where the substrate 402 is a Si substrate, the substrate 402 can be removed by wet etching using a mixed solution of hydrofluoric acid and nitric acid. When the substrate 402 is a sapphire substrate, the substrate can be removed by a laser lift-off method.

  Next, the exposed n-type nitride semiconductor layer 405a made of n-type GaN is wet-etched using a PEC (Photoelectrochemical) etching method using a combination of KOH aqueous solution and ultraviolet light irradiation. Specifically, the nitride semiconductor light-emitting element 400 adhered on the second substrate formed in FIG. 14C is immersed in a container containing an aqueous potassium hydroxide (KOH) solution, and wet etching is performed in a state irradiated with ultraviolet light. I do. Thereby, an uneven surface having a slope is formed in the n-type nitride semiconductor layer 405a (FIG. 14E).

  The etching of the nitride semiconductor by this PEC etching has a plane orientation anisotropy, which is a kind of crystal orientation plane of the n-type nitride semiconductor layer 405a made of n-type GaN, and is one of the semipolar planes. A certain {1-101} plane is formed. Thereby, an uneven surface having an inclined surface constituted by the {1-101} plane can be formed in the n-type nitride semiconductor layer 405a.

Next, a dielectric layer 440 made of, for example, SiO _2, a phosphor layer 450 made of, for example, YAG, and Al, for example, on the concavo-convex surface of the n-type nitride semiconductor layer 405a by photolithography and vacuum deposition. A metal layer 460 made of a multilayer film of a metal such as Ag or Cu is sequentially formed. Further, the support substrate 470 is formed on the metal layer 460 by, for example, Au or Cu plating. Then, the second substrate is separated by removing the adhesive layer using an adhesive stripping solution. Finally, chip separation is performed by dicing using a blade (not shown) to form the nitride semiconductor light emitting device 400 (FIG. 14F).

As described above, the nitride semiconductor light emitting device 400 is formed.
As described above, according to the fifth embodiment, it is possible to realize the nitride semiconductor light emitting element 400 that has high phosphor wavelength conversion efficiency in the phosphor layer 450 and enables white light emission excellent in color rendering.

(Embodiment 6)
Next, a sixth embodiment will be described.

  FIG. 15 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting device in the sixth embodiment. Elements similar to those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted. 16A to 16F are views for explaining the method for manufacturing the nitride semiconductor light emitting element in the sixth embodiment.

(Construction)
A nitride semiconductor light emitting device 500 shown in FIG. 15 includes a dielectric layer 240, a metal layer 250, and a phosphor layer 260 stacked on the nitride semiconductor light emitting layer 210. The nitride semiconductor light emitting device 500 includes a reflective film 516, an n-type electrode 520, and a p-type electrode 530. A nitride semiconductor light emitting device 500 shown in FIG. 15 differs from the nitride semiconductor light emitting device 200 according to the third embodiment in the configuration of a reflective film 516, an n-type electrode 520, and a p-type electrode 530.

  The reflective film 516 is made of, for example, Ni or Ag, and is formed so as to be electrically connected to the p-type nitride semiconductor layer 5 c of the nitride semiconductor light emitting layer 210.

  The p-type electrode 530 is formed of a multilayer film of a metal such as Ti, Al, Ni, Au, etc., and is formed so as to be electrically connected to the reflective film 516. The p-type electrode 530 is formed on the surface opposite to the surface on which the nitride semiconductor light emitting layer 210 of the reflective film 516 is laminated so as to be lower than the nitride semiconductor light emitting layer 210, and the support substrate (FIG. (Not shown). In this way, the p-type electrode 530 is installed so that wiring is possible to the outside.

  The n-type electrode 520 is composed of, for example, a multilayer film of a metal such as Ti, Al, Ni, and Au, and is formed so as to be electrically connected to the n-type nitride semiconductor layer 205a. The n-type electrode 520 is formed on the surface opposite to the surface on which the dielectric layer 240 of the nitride semiconductor light-emitting layer 210 is laminated so as to be lower than the nitride semiconductor light-emitting layer 210, and a support substrate ( (Not shown). In this way, it is installed so that wiring is possible to the outside.

As described above, nitride semiconductor light emitting element 500 in the sixth embodiment is configured.
As shown in FIG. 15, in the nitride semiconductor light emitting device 500, similarly to the nitride semiconductor light emitting device 400, the interface between the n-type nitride semiconductor layer 205 a and the dielectric layer 240, and the n-type nitride semiconductor Irregularities are formed at the interface between the layer 205a and the n-type electrode 520.

(Operation and effect)
Next, the operation and effect of nitride semiconductor light emitting element 500 in the sixth embodiment will be described.

  First, the light emitting unit 5b emits light to generate light. Part of the generated light is totally reflected at the interface between the n-type nitride semiconductor layer 205a and the dielectric layer 240. The evanescent light generated at this time propagates through the dielectric layer 240 and excites surface plasmons on the surface of the metal layer 250. On the other hand, light that has not been totally reflected in dielectric layer 240, that is, at the interface between n-type nitride semiconductor layer 205 a and dielectric layer 240, passes through dielectric layer 240 and metal layer 250 and is transferred to phosphor layer 260 as a carrier. Excited.

  Thus, by coupling the surface plasmon excited on the surface of the metal layer 250 and the carrier excited on the phosphor layer 260, the carriers are efficiently recombined and the conversion efficiency of the phosphor layer 260 is improved. To do.

  In this way, by mixing the blue light transmitted through the nitride semiconductor light emitting layer 210, the dielectric layer 240, the metal layer 250 and the phosphor layer 260 with the yellow light converted by the phosphor layer 260, The nitride semiconductor light emitting device 500 that has high phosphor wavelength conversion efficiency in the phosphor layer 260 and can emit white light with excellent color rendering.

(Production method)
Next, a method for manufacturing the nitride semiconductor light emitting device 500 configured as described above will be described.

First, a buffer layer (not shown) such as AlN or a low-temperature growth GaN layer is interposed on the main surface of a substrate 502 made of a Si substrate having a plane orientation of <111>, for example, by epitaxial growth using MOCVD. A nitride semiconductor light emitting layer 210 is formed (FIG. 16A). Here, the nitride semiconductor light emitting layer 210 includes an n-type nitride semiconductor layer 205a made of n-type GaN, a In _x Ga _1-x N well layer, and a GaN barrier on the main surface of the substrate 502 via a buffer layer. A light emitting portion 5b having a multiple quantum well structure in which a plurality of layers are alternately formed and a p-type nitride semiconductor layer 5c made of p-type GaN are sequentially stacked. Note that the substrate 502 is not limited to a Si substrate having a surface orientation of <111>, but may be a sapphire substrate having a surface orientation of <0001> or a 6H-SiC substrate having a surface orientation of <0001>. Good.

Next, a first opening 525 is formed on the nitride semiconductor light emitting layer 210 by photolithography and dry etching using, for example, Cl ₂ gas (FIG. 16B).

  Next, a reflective film 516 made of, for example, Ni or Ag is formed by a photolithography technique and a vacuum deposition method so as to be electrically connected to the p-type nitride semiconductor layer 5c made of p-type GaN. Subsequently, a p-type electrode 530 made of, for example, a multilayer film of Ti, Al, Ni, and Au is formed in a form that is electrically connected to the reflective film 516 by photolithography and vacuum deposition. Then, by photolithography and vacuum deposition, for example, an n-type electrode 520 made of a multilayer film of Ti, Al, Ni, or Au is converted into an n-type nitride made of n-type GaN exposed through the first opening 525. An electrical contact with the semiconductor layer 205a is formed (FIG. 16C).

  Next, the p-type electrode 530 and the n-type electrode 520 of the nitride semiconductor light emitting device 500 are bonded to a second substrate (not shown) so that wirings can be electrically connected to the outside. Then, after bonding the p-type electrode 530 and the n-type electrode 520 of the nitride semiconductor light emitting device 500 onto the second substrate, the substrate 502 is removed. This exposes the n-type nitride semiconductor layer 205a made of n-type GaN (FIG. 16D).

  Note that in the case where the substrate 502 is a Si substrate, the substrate 502 can be removed by wet etching using a mixed solution of hydrofluoric acid and nitric acid. When the substrate 502 is a sapphire substrate, the substrate can be removed by a laser lift-off method. Thereby, the n-type nitride semiconductor layer 205a made of n-type GaN is exposed.

  Next, the n-type nitride semiconductor layer 205a composed of the n-type GaN layer exposed in FIG. 16D is wet-etched by using a PEC (Photoelectrochemical) etching method using a combination of KOH aqueous solution and ultraviolet light irradiation. Specifically, the nitride semiconductor light-emitting element 500 bonded on the second substrate formed in FIG. 16C is immersed in a container containing a potassium hydroxide (KOH) aqueous solution, and wet etching is performed in a state irradiated with ultraviolet light. I do. Thereby, an uneven surface having a slope is formed in the n-type nitride semiconductor layer 205a (FIG. 16E).

  Note that nitride semiconductor etching by PEC etching has anisotropy in the plane orientation, and is a kind of crystal orientation plane of the n-type nitride semiconductor layer 205a made of n-type GaN, and one of the semipolar planes. A {1-101} plane is formed. Thereby, it is possible to form an uneven surface having a slope composed of {1-101} planes in the n-type nitride semiconductor layer 205a.

Next, a dielectric layer 240 made of, for example, SiO ₂ and a multilayer film made of a metal, for example, Al, Ag, or Cu, are formed on the uneven surface of the n-type nitride semiconductor layer 205a by photolithography and vacuum deposition. A metal layer 250 and a phosphor layer 260 made of, for example, YAG are sequentially formed. Finally, chip separation is performed by dicing using a blade (not shown) to form a nitride semiconductor light emitting device 500 (FIG. 16F).

As described above, the nitride semiconductor light emitting device 500 is formed.
As described above, according to the fifth embodiment, it is possible to realize the nitride semiconductor light emitting device 100 that has high phosphor wavelength conversion efficiency in the phosphor layer 260 and enables white light emission excellent in color rendering.

  As described above, according to the present invention, in the nitride semiconductor light emitting device, by adjusting the configuration, material, and film thickness of the metal layer, a part of the light emitted from the light emitting portion 5b is transmitted and nitride semiconductor light emitting is achieved. It is taken out of the element. On the other hand, at the interface between the undoped nitride semiconductor layer 6 or dielectric layer of the nitride semiconductor light emitting layer and the metal layer, the evanescent light generated when the light emitted from the light emitting part is totally reflected in the metal layer. Surface plasmons are excited. Then, the generated surface plasmon is coupled with the carrier in the phosphor layer. Thereby, since the light emission recombination in the phosphor layer is promoted, the wavelength conversion efficiency in the phosphor is improved.

  In the nitride semiconductor light emitting device of the present invention, the undoped nitride semiconductor layer and the dielectric layer film are transparent and do not absorb the light emitted by the nitride semiconductor light emitting layer. Can be taken out of the nitride semiconductor light emitting device without absorbing the light emitted from it.

  In the nitride semiconductor light emitting device of the present invention, the dielectric layer is formed with a sufficiently thin thickness of, for example, 150 nm. That is, the dielectric layer has a thickness equal to or less than the penetration depth of evanescent light generated when, for example, the light emitted from the nitride semiconductor light emitting layer is totally reflected by the dielectric layer at the interface between the nitride semiconductor light emitting layer and the dielectric layer. It is composed of. With this configuration, surface plasmons can be effectively excited in the metal layer.

  In the nitride semiconductor light emitting device of the present invention, the metal layer is made of Al or Ag, and surface plasmons are effectively excited in Al and Ag, so that the conversion efficiency of the phosphor layer can be improved. .

  In the nitride semiconductor light emitting device of the present invention, the phosphor layer is composed of at least one oxide of Y, Ce, Al, Si, Ca, and Eu. Thereby, the wavelength conversion efficiency can be improved by using the surface plasmon even in the phosphor layer formed of these oxides formed by vapor deposition or sputtering. Therefore, the nitride semiconductor light emitting device 100 having the phosphor layer 60 with a high conversion rate and enabling white light emission at a low cost can be realized by using a conventional semiconductor process technology such as vapor deposition or sputtering.

  As described above, according to the present invention, it is possible to realize a nitride semiconductor light emitting device that has high phosphor wavelength conversion efficiency in the phosphor layer and enables white light emission excellent in color rendering.

  The metal layer constituting the nitride semiconductor light emitting device of the present invention may be composed of metal fine particles. In this case, the surface plasmon can be efficiently excited by the metal fine particles, and at the same time, the coverage of the nitride semiconductor surface can be reduced. Blue light can be effectively extracted outside the light emitting element as compared with the case where it is covered with a thin metal layer, and color rendering can be improved.

  In the nitride semiconductor light emitting device of the present invention, as described above, even if the dielectric layer, the metal layer, and the phosphor layer are sequentially stacked on the nitride semiconductor light emitting layer, the dielectric is formed on the nitride semiconductor light emitting layer. A layer, a phosphor layer, and a metal layer may be sequentially laminated. That is, the nitride semiconductor light emitting layer and the dielectric layer are laminated, and the metal layer and the phosphor layer may be laminated in either order on the dielectric layer. The same applies when the nitride semiconductor light emitting layer includes an undoped nitride semiconductor layer instead of the dielectric layer.

  As described above, the nitride semiconductor light emitting device and the manufacturing method thereof according to the present invention have been described based on the embodiment. However, the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to this embodiment, and the structure constructed | assembled combining the component in different embodiment is also contained in the scope of the present invention. .

  INDUSTRIAL APPLICABILITY The present invention can be used for a nitride semiconductor light emitting device and a method for manufacturing the same, and in particular, can be used for a nitride semiconductor light emitting device such as a high brightness nitride semiconductor light emitting diode for various displays or illumination and a method for manufacturing the same.

2, 302, 402, 502, 1005 Substrate 5a, 205a, 405a N-type nitride semiconductor layer 5b Light emitting portion 5c P-type nitride semiconductor layer 5d High-concentration n-type nitride semiconductor layer 6 Undoped nitride semiconductor layer 6a, 110a Nitride Metal semiconductor layer 10, 110, 210, 310, 410 Nitride semiconductor light emitting layer 15, 425, 525 First opening 20, 220, 520 N-type electrode 25 Second opening 30, 230, 530 P-type electrode 40a Dielectric layer 50, 150, 250, 460 Metal layer 50a, 150a Metal layer 60, 260, 450 Phosphor layer 60a Phosphor layer 70a, 70b Emitted light 100, 101, 200, 300, 400, 500 Nitride semiconductor light emitting device 140, 240, 340, 440 Dielectric layer 140a Dielectric layer 150a Metal layer 216, 516 Film 217,470 supporting substrate 305a n-type nitride semiconductor layer 325 openings 415 a transparent conductive layer 1000 LED wafer 1001 first electrode 1002 second electrode 1003 phosphor thin film 1004 epitaxial layer

Claims (13)

a nitride semiconductor light-emitting layer including an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light-emitting portion sandwiched between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer;
A dielectric layer formed on the nitride semiconductor light emitting layer;
A metal layer formed on the dielectric layer;
A nitride semiconductor light emitting device comprising: a phosphor layer that is formed between or on the metal layer and on the metal layer and emits fluorescence by absorbing light emitted from the nitride semiconductor light emitting layer. The nitride semiconductor light emitting element according to claim 1, wherein the dielectric layer, the metal layer, and the phosphor layer are sequentially formed on the nitride semiconductor light emitting layer. The nitride semiconductor light emitting element according to claim 1, wherein the dielectric layer, the phosphor layer, and the metal layer are sequentially formed on the nitride semiconductor light emitting layer. The nitride semiconductor light emitting element according to claim 1, wherein the dielectric layer is transparent to light emitted from the nitride semiconductor light emitting layer. The nitride semiconductor light emitting element according to claim 1, wherein the dielectric layer is made of an undoped nitride semiconductor. The said dielectric material layer, the said metal layer, and the said fluorescent substance layer are provided in the n-type nitride semiconductor layer side which comprises the said nitride semiconductor light emitting layer. Nitride semiconductor light emitting device. The thickness of the dielectric layer is equal to or less than a penetration depth of evanescent light generated when light emitted from the nitride semiconductor light emitting layer is totally reflected at an interface between the nitride semiconductor light emitting layer and the dielectric layer. Item 4. The nitride semiconductor light emitting device according to any one of Items 1 to 3. The nitride semiconductor light emitting element according to claim 1, wherein the metal layer is made of a metal containing Al or Ag. The said fluorescent substance layer is comprised from the oxide containing at least 1 of Y (yttrium), Ce (cerium), Al, Si, Ca, and Eu (eurobium). Nitride semiconductor light emitting device. The nitride semiconductor light emitting layer is
The nitride semiconductor light-emitting element according to claim 1, wherein the nitride semiconductor light-emitting element has an uneven shape on a side where the dielectric layer is formed. The nitride semiconductor light emitting device according to claim 1, wherein the metal layer has a thickness of 15 to 20 nm. The nitride semiconductor light emitting element according to claim 1, wherein the metal layer is composed of metal fine particles. A method for manufacturing a nitride semiconductor light emitting device, comprising:
A nitride semiconductor light emitting layer including an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light emitting portion sandwiched between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer is formed. Process,
Forming a dielectric layer on the nitride semiconductor light emitting layer;
Forming a metal layer on the dielectric layer;
Forming a phosphor layer that emits fluorescence by absorbing light emitted from the nitride semiconductor light emitting layer between or on the metal layer and the dielectric layer.

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