Abstract:
An (Al, Ga, In)N light emitting diode (LED), wherein light extraction from chip and/or phosphor conversion layer is optimized. By novel shaping of LED and package optics, a high efficiency light emitting diode is achieved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following co-pending and commonly-assigned applications: 
     U.S. Provisional Application Ser. No. 60/691,710, filed on Jun. 17, 2005, by Akihiko Murai, Christina Ye Chen, Lee S. McCarthy, Steven P. DenBaars, Shuji Nakamura, and Umesh K. Mishra, entitled “(Al, Ga, In)N AND ZnO DIRECT WAFER BONDING STRUCTURE FOR OPTOELECTRONIC APPLICATIONS AND ITS FABRICATION METHOD,”; 
     U.S. Provisional Application Ser. No. 60/732,319, filed on Nov. 1, 2005, by Akihiko Murai, Christina Ye Chen, Daniel B. Thompson, Lee McCarthy, Steven P. DenBaars, Shuji Nakamura, and Umesh K. Mishra, entitled “(Al, Ga, In)N AND ZnO DIRECT WAFER BONDED STRUCTURE FOR OPTOELECTRONIC APPLICATIONS, AND ITS FABRICATION METHOD,”; 
     U.S. Provisional Application Ser. No. 60/764,881, filed on Feb. 3, 2006, by Akihiko Murai, Christina Ye Chen, Daniel B. Thompson, Lee S. McCarthy, Steven P. DenBaars, Shuji Nakamura, and Umesh K. Mishra, entitled “(Al, Ga, In)N AND ZnO DIRECT WAFER BONDED STRUCTURE FOR OPTOELECTRONIC APPLICATIONS AND ITS FABRICATION METHOD,”; 
     U.S. Provisional Application Ser. No. 60/734,040, filed on Nov. 11, 2005, by Steven P. DenBaars, Shuji Nakamura, Hisashi Masui, Natalie N. Fellows, and Akihiko Murai, entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED),”; and 
     all of which applications are incorporated by reference herein. 
     This application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned U.S. patent applications: 
     U.S. Provisional Application Ser. No. 60/748,480, filed on Dec. 8, 2005, by Steven P. DenBaars, Shuji Nakamura and James S. Speck, entitled “HIGH EFFICIENCY LIGHT EMITTING DIODE (LED),”; and 
     U.S. Provisional Application Ser. No. 60/764,975, filed on Feb. 3, 2006, by Steven P. DenBaars, Shuji Nakamura and James S. Speck, entitled “HIGH EFFICIENCY LIGHT EMITTING DIODE (LED),”; 
     both of which applications are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is related to light emitting diode (LED) light extraction for optoelectronic applications. 
     2. Description of the Related Art 
     Wafer bonding technology using different combinations of materials, such as InP/GaAs, AlGaInP/GaP, GaAs/GaN, ZnSSe/GaN, has been studied for applications of optoelectronic integration, light emitting diodes (LEDs), vertical cavity surface emitting lasers (VCSELs), and electronic devices (Appl. Phys. Lett. 56, 737-39 (1990); Appl. Phys. Lett. 64, 2839-41 (1994); Appl. Phys. Lett. 81, 3152-54 (2002); and J. J. Appl. Phys. 43, L1275-77 (2004)). 
     In a nitride LED system, there are several reports of fabricating transparent electrodes on a p-type GaN layer. The general method is to use thin metals of Ni and Au (J. J. Appl. Phys. 34, L797-99 (1995)). Because of the light absorption in the metal, transmittance is only around 60%. Also, surface feature shaping for improving light extraction efficiency is difficult because of the hardness of GaN material and the instability of p-type GaN conductivity. 
     Another approach is to use ZnO layer growth on p-type GaN (J. J. Appl. Phys. 43, L180-82 (2004)). However, this method requires ZnO crystal growth equipment, which uses ultra-high vacuum conditions. Moreover, it is difficult to grow thick layers, e.g., 500 μm thick layers, that are suitable for feature shaping for the purpose of light extraction. 
     SUMMARY OF THE INVENTION 
     The present invention describes an (Al, Ga, In)N and ZnO direct wafer bonded light emitting diode (LED) combined with a shaped plastic optical element and a phosphor down-conversion layer. 
     In summary, the present invention comprises optical devices, usually Light Emitting Diodes (LEDs), that emit multiple wavelengths of light, typically comprising white light. Such devices are usually higher efficiency than comparable devices. 
     An optical device in accordance with the present invention comprises a III-nitride light emitting region comprised of at least an active region, at least one first shaped optical element wafer bonded to at least one side of the III-nitride light emitting region, at least one second shaped optical element encapsulating both the III-nitride light emitting region and the at least one first shaped optical element for extracting light emitted by the LED and the first shaped optical elements, and a phosphor, optically coupled to the at least one second shaped optical element, wherein light in at least a first wavelength region emitted by the III-nitride light emitting region passes through the at least one second shaped optical elements and excites the phosphor to emit light in at least a second wavelength region. 
     Such an optical device further optionally includes at least one of the at least one first shaped optical elements comprising a n-type ZnO optical element, at least one of the at least one first shaped optical elements being shaped to increase light extraction from the III-nitride light emitting region, at least one first shaped optical element including angles adjusted for light extraction efficiency from the III-nitride light emitting region, at least one of the at least one first shaped optical elements being cone-shaped and the at least one second shaped optical element comprising a lens. 
     The optical device can further optionally include the at least one second shaped optical element being shaped for light extraction the at least one second shaped optical element including angles that are adjusted for light extraction efficiency, a layer forming an interface between the III-nitride light emitting region and the at least one first shaped optical elements having a roughened surface, an additional phosphor layer coupled to the phosphor layer, a third shaped optical element encapsulating the optical device, the at least one first shaped optical elements and the at least one second shaped optical elements for extracting light emitted by the LED, the first shaped optical elements, and the second shaped optical elements, the third shaped optical element comprising a reflector cup, and the phosphor layer being shaped for light extraction efficiency. 
     The optical device can also include the III-nitride light emitting layer comprises at least one of the group consisting of: (Al, Ga, In)N materials, (Al, Ga, In)As materials, (Al, Ga, In)P materials, compound semiconductor material from (Al, Ga, In)AsPNSb materials, and compound semiconductor material from ZnGeN 2  or ZnSnGeN 2  materials, a reflective coating coupled to the at least one first optical element, a reflector positioned between the phosphor layer and the III-nitride light emitting region which passes at least the first wavelength region and reflects at least a portion of light in the second wavelength region, and the reflector being a distributed Bragg reflector. 
     Another embodiment of the present invention is a Light Emitting Diode assembly. Such an assembly in accordance with the present invention comprises a substrate, a light emitting device, comprising an n-type Group III nitride layer coupled to the substrate, an active layer, coupled to the n-type Group III nitride layer, wherein the active layer emits light in at least a first wavelength region, and a p-type Group III nitride layer, coupled to the active layer, at least one oxide layer, coupled to the light emitting device, the at least one oxide layer being shaped into a form that increases the efficiency of the light emitting device by reducing light absorption in the light emitting device, an optical element, coupled to the at least one oxide layer, and a phosphor, optically coupled to the at least one oxide layer, wherein light in at least the first wavelength region emitted by the light emitting device passes through the phosphor and excites the phosphor to emit light in at least a second wavelength region. 
     Another embodiment of the present invention is a Light Emitting Diode (LED) emitting multiple wavelength regions of light, which comprises an active Group III nitride layer, wherein the active Group III nitride layer emits light in at least a first wavelength region, at least one oxide layer, coupled to the light emitting device, wherein the at least one oxide layer is substantially transparent in the first wavelength region, the at least one oxide layer being shaped into a form that increases the efficiency of the LED by reducing light absorption in the LED, and a phosphor, optically coupled to the at least one oxide layer such that light in at least the first wavelength region strikes the phosphor and excites the phosphor to emit light in at least a second wavelength region, such that light in at least the first wavelength region and the second wavelength region are emitted by the LED. 
     Such an embodiment further optionally includes a lens, coupled between the oxide layer and the phosphor, wherein the lens increases the efficiency of the LED by reducing light absorption in the LED. 
     Other features and advantages are inherent in the system disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  shows a schematic representation of a high light extraction efficiency light emitting diode according to the preferred embodiment of the present invention. 
         FIG. 2  is a variation of  FIG. 1  showing the cone-shaped LED with a remotely-located phosphor down-conversion layer in a high index layer. 
         FIG. 3  is a variation of  FIG. 2  showing the shaped white light conversion layer with a distributed Bragg reflector (DBR) on the backside of the phosphor layer. 
         FIG. 4  illustrates the cone-shaped optical element of the present invention. 
         FIG. 5  is a variation of  FIG. 1  with a different shaped lens and no phosphor layer. 
         FIG. 6  is a variation of  FIG. 1  with a different shaped lens and no phosphor layer. 
         FIG. 7  is a variation of  FIG. 5  with a phosphor layer on the two top sides of the lens. 
         FIG. 8  is a variation of  FIG. 6  with a phosphor layer on the two top sides of the lens. 
         FIG. 9  shows a schematic representation of a high light extraction efficiency LED according to the preferred embodiment of the present invention. 
         FIG. 10  is a variation of  FIG. 9 , wherein the phosphor plate placed on top of the reflector cup includes a roughened side and a smoothed side to assist in light extraction. 
         FIG. 11  shows a schematic representation of a multi-cone LED according to the preferred embodiment of the present invention. 
         FIG. 12  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. 
         FIG. 13  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. 
         FIG. 14  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. 
         FIG. 15  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. 
         FIG. 16  shows a schematic representation of a high light extraction efficiency LED according to the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Overview 
     The purpose of the present invention is to provide a means of increasing the light extraction efficiency from a light emitting diode (LED) by combining shaped high refractive index elements with an (Al, Ga, In)N LED and shaped optical elements. By increasing light transmittance and light extraction, subsequent device performance is increased. 
     In one embodiment of the present invention, a high refractive index ZnO layer is wafer bonded to a GaN LED. A cone is etched in the high refractive index ZnO layer and contacts are fabricated on the GaN LED. The ZnO/GaN hybrid LED is then placed within various configured lenses and covered by a phosphor layer for high efficiency light extraction. 
     Technical Description 
       FIG. 1  shows a schematic representation of a high light extraction efficiency LED  100  according to the preferred embodiment of the present invention. Generally, the LED  100  is an (Al, Ga, In)N and ZnO direct wafer-bonded LED structure. In this example, one or more III-nitride LEDs  102  on a sapphire substrate, wherein the III-nitride LED  102  comprises an n-type III-nitride layer  106 , an active layer  108 , and a p-type III-nitride layer  110 . One or more n-type electrodes  112  or contacts may reside on the III-nitride LED  102 . 
     One or more, or at least one, n-type ZnO cones  114  having a typical index of refraction of n 0 =2.1 reside on top of the LED  102 , with a p-type electrode  116  or contact on top of the n-type ZnO cone  114 . Both the LED  102  and the n-ZnO cones  114  are encapsulated within or under one or more tapered or conical plastic lenses  118  having an index of refraction of n encap =1.5. However, additional cones  114 , made of different materials and/or different shapes, such as pyramidal, conical, hexagonal, hemispherical, or other shapes, can be used on the same LED  102  without departing from the scope of the present invention. 
     Consequently, this figure illustrates the concept of the present invention of providing for high efficiency light extraction by combining an (Al, Ga, In)N based LED  102 , one or more first “shaped” optical elements (e.g., the n-ZnO cone  114 ) of higher refractive index that are adjacent to, on the surface of, or surrounding the (Al, Ga, In)N LED  102 , and one or more second “shaped” optical elements (e.g., the lens  118 ) of lower refractive index that encapsulate both the (Al, Ga, In)N LED  102  and the first shaped optical elements  114 . 
     The top (opposite the side in contact with the LED  102 ) of the n-ZnO cone  114  is shaped to obtain the highest light extraction efficiency. Moreover, the n-ZnO cone  114  may have a highly reflective coating to guide light, through reflections, toward the top of the cone  114 , which is uncoated. In addition, the top of the n-ZnO cone  114  is in direct contact with the conical plastic lens  118  to obtain the highest light extraction efficiency. 
     The critical angles Θc of the n-ZnO cone  114  and conical plastic lens  118  may be adjusted as desired. If the critical angle Θc is approximately 60°, most light emitted by the LED  102  makes it out of the cone  114  on the first pass, since the majority of the light is within the escape cone. 
     In addition, a remote phosphor layer  120  may be placed on top of the plastic lens. In this embodiment, the phosphor layer  120  is a down-conversion layer, however, the phosphor layer  120  can be an up-conversion layer, or can be both an up-conversion layer and a down-conversion layer. The phosphor layer  120  may be shaped in a manner similar to the first and second shaped optical elements to enhance light extraction efficiency. 
     In addition, a mirror or reflector layer may be placed on the backside of the substrate  104 , in order to reflect light and enhance extraction efficiency. 
     As light  122  escapes from cone  114 , light  122  strikes phosphor layer  120 . Typically, the wavelength of light  122  is in the blue or ultraviolet region, and escapes from LED  100  as blue or ultraviolet light. However, as light  124  strikes phosphor  120 , the blue/ultraviolet light  124  is down-converted to yellow light  126 . As such, both blue light  122  and yellow light  126  emit from LED  100 , which thus produces white light. 
     LED  102  can produce other colors of light other than blue/ultraviolet light. By properly doping the LED  102 , green, red, and blue light can be produced, or other colors, and by designing LED assembly  100  with the proper emissions from LED  102  and the desired additional colors of light present by exciting phosphor layer  120 , LED  100  can produce white light by other combinations besides blue and yellow light. 
     Angle  128 , which defines the shape of cone  114 , and angle  130 , which defines the edge and top surface of lens  118 , can be adjusted to increase light emission. Angle  128  is adjusted to increase the light emission from LED  102 ; angle  130  increase the light emission from the lens  118 . Although these angles  128  and  130  are typically the same numerical value, e.g., approximately 60 degrees, angles  128  and  130  may vary from this typical value and vary from each other depending on the material being used for LED  102 , the material being used for cone  114 , the material being used for lens  118 , as well as the wavelength of light that is being emitted from LED  102  and striking the top surface of lens  118 . All of these angles are within the scope of the present invention, and the approximately 60 degree angle shown in the figures is merely for purposes of illustration and not meant to limit the present invention. Even with the changes in angles  128  and  130 , there is typically some light  132  that is reflected from the top surface of lens  118  and reflected back into lens  118 . 
       FIG. 2  is a variation of  FIG. 1  that combines the cone-shaped LED  200  with a remotely-located phosphor down-conversion layer  202  in a high index layer  204 . In this embodiment, the phosphor down-conversion layer  202  is shaped for maximum light extraction efficiency, wherein the lower surface  206  of the high index layer (facing the LED) is smooth and the phosphor down-conversion layer is shaped on outer surface  208  to obtain the highest light extraction efficiency for the down-converted light  126  and pump (LED) light  122 . Specifically, in this embodiment, the phosphor layer  202  is a white light conversion layer shaped as a plurality of cones or pyramids for the highest possible light extraction efficiency. 
       FIG. 3  is a variation of  FIG. 2  that combines the shaped white light conversion layer  204  with a distributed Bragg reflector (DBR)  300  on the backside of the phosphor layer  202 , in order to reflect yellow, red, or green light, but to allow blue-ultraviolet (UV) pumped light  122  to pass. Specifically, the DBR  300  can be tuned to reflect light in the red through green spectrum, while passing light in the blue through UV spectrum. Additionally, the shaped surface  208  of phosphor  202  can refract some wavelengths of light  302 , while reflecting other wavelengths  304 , which can assist DBR  300 , or perform some of the reflections of light that would make DBR  300  easier to manufacture. Designs for the phosphor layer  202  and DBR  300  can complement each other to increase efficiency of the overall device. 
       FIG. 4  illustrates that, for an approximately 60 degree angle  128  cone  114 , most of the light  124  makes it out on the first pass, since the majority of the light is within the escape cone. Examples, of the materials that may be used, with their different indices of refraction and critical angles, is provided below: 
     Air/plastic=1/1.5, Θc=42°, 
     Plastic/ZnO=1.5/2.1, Θc=46°, 
     ZnO/GaN=2.1/2.3, Θc=66°, and 
     Air/ZNO=1/2.1, Θc=28°. 
     Other materials and angles can be used without departing from the scope of the present invention. 
       FIG. 5  is a variation of  FIG. 1  with a differently shaped lens and no phosphor layer. 
     As shown in  FIG. 5 , rather than have light  132  reflect back into lens  118 , thus reducing the brightness and/or efficiency of device  100 , lens  118  can take on a shape that maximizes the light emission from device  100 . Angles B  500  and C  502  are selected to maximize the light emission of light  504 - 508  from device  100 . Angles B  500  and C  502  can change based on the materials used for cone  114 , lens  118 , and angle  128 , as well as the frequency of light emitted by LED  102 . 
       FIG. 6  is a variation of  FIG. 1  with a differently shaped lens and no phosphor layer. 
     Other surface profiles for lens  118  can also be used, where angles D  600  and E  602  will allow light  124  to emit from the top surface of lens  118 , while other light  604  will reflect and emit from the side of lens  118 . As seen in  FIGS. 5 and 6 , many possible geometries for lens  118  are possible within the scope of the present invention. 
       FIG. 7  is a variation of  FIG. 5  with a phosphor layer on the two top sides of the lens. 
     With the addition of phosphor layer  120  to the upper surfaces of lens  118 , light  124  now has the opportunity to escape directly, as well as having light  700  excite phosphor  120  in multiple places during reflections within lens  118 . Some of light  700  will also escape from lens  118 , but the multiple reflections of light  700  from phosphor  120  will provide additional down-conversion or up-conversion of light  700  to other wavelengths. 
       FIG. 8  is a variation of  FIG. 6  with a phosphor layer on the two top sides of the lens. As with  FIG. 7 , light  800  now also has multiple opportunities to excite phosphor layer  120  within lens  118 . This will provide wavelength balancing or wavelength preferences as needed to provide white light, or, if desired, the LED  102  can be tuned to emit certain wavelengths based on the characteristics of phosphor  120  and the shape of lens  118 . For example, and not by way of limitation, the shape of lens  118  and characteristics of phosphor  120  can be tuned to provide a certain “color” of white light, e.g., “warm” light, by designing assembly  100  to produce a certain number of reflections and emissions to emulate the warm light. 
       FIG. 9  shows a schematic representation of a high light extraction efficiency LED according to the preferred embodiment of the present invention. 
     In this embodiment, which includes both the LED  102  with an n-type ZnO cone  114 , a reflective coating  900  is applied to the side of the n-ZnO cone, a spherical plastic lens is positioned on top of the n-ZnO cone, and the lens and top of the n-ZnO cone are encapsulated within a reflector cup, which is a third “shaped” optical element. The highly reflective coating  900  on the n-ZnO cone  114  guides light, through reflections, toward the top of the cone  114 , which is uncoated, wherein the top of the n-ZnO cone  114  is surrounded by the reflector cup  902 . 
     In addition, a phosphor plate  120  is placed on top of the reflector cup  900 . The phosphor plate  120  is a remotely located phosphor down-conversion layer comprised of phosphor embedded in a high index layer. The lower surface  904  of the high index layer (facing the LED) is smooth and the top surface  906  of the high index layer is rough, so as to obtain the highest light extraction efficiency from the down-conversion layer  120 . 
       FIG. 10  is a variation of  FIG. 9 , wherein the phosphor plate placed on top of the reflector cup includes a roughened side and a smoothed side to assist in light extraction. Also in this embodiment, a transparent conducting oxide (TCO) layer  1000 , which can be made from Indium Tin Oxide (ITO), Zinc Oxide (ZnO), and/or other materials that are transparent or mostly transparent in the wavelength region of interest is positioned between the LED  102  and the n-type ZnO cone  114 , wherein the n-type ZnO cone  114  is made from an insulating high index material, such as Titanium Dioxide (TiO 2 ). 
       FIG. 11  shows a schematic representation of a multi-cone LED according to the preferred embodiment of the present invention. Specifically, a top cone  1100 , which acts as a third shaped optical element, resides on top of the phosphor layer  120 . 
       FIG. 12  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. Specifically, a plurality of phosphor layers, e.g. layers  120  and  1200 , are shown, wherein a second phosphor layer  1200  encapsulates a first phosphor layer  120 . 
       FIG. 13  shows a schematic representation of a multi-shape LED according to the preferred embodiment of the present invention. Specifically, a plurality of phosphor layers, layer  120  and layer  1200  are shown, wherein a second phosphor layer  1200  encapsulates a first phosphor layer  120  and the first phosphor layer  120  comprises a plurality of cones. 
       FIG. 14  shows a schematic representation of an LED according to the preferred embodiment of the present invention. Specifically, a plurality of first “shaped” optical elements (e.g., the n-ZnO cones  114 ) of higher refractive index are adjacent to, on the surface of, or surrounding one or more (Al, Ga, In)N LEDs  106 , wherein one or more second “shaped” optical elements (e.g., the lens  118 ) of lower refractive index encapsulate the (Al, Ga, In)N LEDs  106  and the first shaped optical elements  114 . 
       FIG. 15  is a schematic representation of an LED according to the preferred embodiment of the present invention. Specifically, a plurality of first “shaped” optical elements (e.g., the n-ZnO cones  114 ) of higher refractive index are adjacent to, on the surface of, or surrounding one or more (Al, Ga, In)N LEDs  106 , wherein one or more second “shaped” optical elements (e.g., the lens  118 ) of lower refractive index encapsulate the (Al, Ga, In)N LEDs  106  and the first shaped optical elements  114 . This embodiment, however, includes first and second n-ZnO cone-shaped elements  114  on both sides of the LED  100 . The LEDs  102 , and first and second n-ZnO cone-shaped elements  114  are all encapsulated by the lens  118 . 
       FIG. 16  is a schematic representation of an LED according to the preferred embodiment of the present invention. Specifically, in this embodiment, the p-Gan layer  110  that forms the interface between the LED and the n-ZnO cone  114  may be roughened or shaped to enhance light extraction. This surface roughening may use techniques described in the following related applications: PCT International Application Number PCT/US03/39211, filed Dec. 9, 2003, by Tetsuo Fujii, Yan Gao, Evelyn L. Hu, and Shuji Nakamura, entitled HIGHLY EFFICIENT GALLIUM NITRIDE BASED LIGHT EMITTING DIODES VIA SURFACE ROUGHENING; and U.S. patent application Ser. No. 10/938,704, filed Sep. 10, 2004, by Carole Schwach, Claude C. A. Weisbuch, Steven P. DenBaars, Henri Benisty, and Shuji Nakamura, entitled WHITE, SINGLE OR MULTI-COLOR LIGHT EMITTING DIODES BY RECYCLING GUIDED MODES, which applications are hereby incorporated by reference herein. 
     Advantages and Improvements 
     The advantages of the present invention derive from bonding and shaping (Al, Ga, In)N and ZnO LEDs in combination with shaped optical elements designed to extract the light emitting from the LEDs. This combination is novel and has advantages over existing device designs, especially for LED applications. 
     The III-nitride LED may be comprised of (Al, Ga, In)N materials, (Al, Ga, In)As materials, (Al, Ga, In)P materials, compound semiconductor material from (Al, Ga, In)AsPNSb materials, or compound semiconductor material from ZnGeN 2  or ZnSnGeN 2  materials. 
     With regard to the (Al, Ga, In)N materials, the LED may be comprised of c-face {0001} (polar) (Al, Ga, In)N, a-face {11-20}, m-face {1-100} (nonpolar) (Al, Ga, In)N, or (semipolar) (Al, Ga, In)N, wherein semipolar refers to a wide variety of planes that possess two nonzero h, i, or k Miller indices, and a nonzero l Miller index, {hikl}. 
     In addition, the LED may be grown on a sapphire, silicon carbide, silicon, germanium, gallium arsenide, gallium phosphide, indium phosphide, or spinel wafers, or on gallium nitride, including a free-standing gallium nitride removed from other substrates. 
     The high refractive index materials may be comprised of many different materials, including ZnO, TiO 2 , GaN, SiC, SiON, SiN, SiO 2 , high refractive index metal oxides, high refractive index polymers, or high refractive index plastic material. The low refractive index materials may also be comprised of many different types of materials, including plastics. These materials may be roughened, smoothed or shaped using any number of different methods. 
     The phosphor may be Cerium(III)-doped YAG (YAG:Ce 3+ , or Y 3 Al 5 O 12 :Ce 3+ ), including Ce 3+ :YAG tuned by substituting the cerium with other rare earth elements such as terbium and gadolinium, or adjusted by substituting some or all of the aluminum in the YAG with gallium. 
     Although specific angles of A, B, C, D and Θc are described herein, those skilled in the art will recognize that these angles of A, B, C, D and Θc may be otherwise adjusted to obtain the highest light extraction efficiency. 
     As noted above, in one embodiment, the LED is comprised of (Al, Ga, In)N layers and the high refractive index light extraction materials are comprised of ZnO layers that are wafer bonded to the (Al, Ga, In)N layers. The ZnO reduces light reflections occurring repeatedly inside the LED, and thus extracts more light out of the LED. The highly transparent characteristic of ZnO reduces light absorption inside an LED. The electrically conductive characteristic of ZnO enables uniform light emitting from the active region in an LED. The resulting external quantum efficiency of this new hybrid GaN/ZnO/shaped lens design should be higher than that of existing GaN-based LED devices. 
     Moreover, the combination of a transparent ZnO electrode with a nitride LED grown on electrically conductive substrates, such as SiC or GaN, can reduce the number of process steps required for the fabrication of LEDs, because an electrode can be easily formed on the electrically conductive material. However, in other embodiments, the ZnO may be not necessarily wafer bonded, but can be deposited by a wide variety of means. 
     Finally, with regard to the number of cones, lens or other shaped optical elements, smaller numbers are better, because each cone could absorb the emission from the next cone. When there is only one cone, there are no effects (no absorption) from a next cone (because there is no next cone). 
     Nonetheless, those skilled in the art will recognize that there may be any number of LEDs, first shaped optical elements and second shaped optical elements arranged in any number of configurations. Further, the LEDs, first shaped optical elements and second shaped optical elements may comprise any number of geometries or shapes and are not restricted to cones, pyramids, etc. 
     REFERENCES 
     The following references are incorporated by reference herein:
     1. Appl. Phys. Lett. 56, 737-39 (1990).   2. Appl. Phys. Lett. 64, 2839-41 (1994).   3. Appl. Phys. Lett. 81, 3152-54 (2002).   4. Jpn. J. Appl. Phys. 43, L1275-77 (2004).   5. Appl. Phys. Lett. 84, 855 (2004).   

     CONCLUSION 
     In summary, the present invention comprises optical devices, usually Light Emitting Diodes (LEDs), that emit multiple wavelengths of light, typically comprising white light. Such devices are usually higher efficiency than comparable devices. 
     An optical device in accordance with the present invention comprises a III-nitride light emitting region comprised of at least an active region, at least one first shaped optical element wafer bonded to at least one side of the III-nitride light emitting region, at least one second shaped optical element encapsulating both the III-nitride light emitting region and the at least one first shaped optical element for extracting light emitted by the LED and the first shaped optical elements, and a phosphor, optically coupled to the at least one second shaped optical element, wherein light in at least a first wavelength region emitted by the III-nitride light emitting region passes through the at least one second shaped optical elements and excites the phosphor to emit light in at least a second wavelength region. 
     Such an optical device further optionally includes at least one of the at least one first shaped optical elements comprising a n-type ZnO optical element, at least one of the at least one first shaped optical elements being shaped to increase light extraction from the III-nitride light emitting region, at least one first shaped optical element including angles adjusted for light extraction efficiency from the III-nitride light emitting region, at least one of the at least one first shaped optical elements being cone-shaped and the at least one second shaped optical element comprising a lens. 
     The optical device can further optionally include the at least one second shaped optical element being shaped for light extraction. the at least one second shaped optical element including angles that are adjusted for light extraction efficiency, a layer forming an interface between the III-nitride light emitting region and the at least one first shaped optical elements having a roughened surface, an additional phosphor layer coupled to the phosphor layer, a third shaped optical element encapsulating the optical device, the at least one first shaped optical elements and the at least one second shaped optical elements for extracting light emitted by the LED, the first shaped optical elements, and the second shaped optical elements, the third shaped optical element comprising a reflector cup, and the phosphor layer being shaped for light extraction efficiency. 
     The optical device can also include the III-nitride light emitting layer comprises at least one of the group consisting of: (Al, Ga, In)N materials, (Al, Ga, In)As materials, (Al, Ga, In)P materials, compound semiconductor material from (Al, Ga, In)AsPNSb materials, and compound semiconductor material from ZnGeN 2  or ZnSnGeN 2  materials, a reflective coating coupled to the at least one first optical element, a reflector positioned between the phosphor layer and the III-nitride light emitting region which passes at least the first wavelength region and reflects at least a portion of light in the second wavelength region, and the reflector being a distributed Bragg reflector. 
     Another embodiment of the present invention is a Light Emitting Diode assembly. Such an assembly in accordance with the present invention comprises a substrate, a light emitting device, comprising an n-type Group III nitride layer coupled to the substrate, an active layer, coupled to the n-type Group III nitride layer, wherein the active layer emits light in at least a first wavelength region, and a p-type Group III nitride layer, coupled to the active layer, at least one oxide layer, coupled to the light emitting device, the at least one oxide layer being shaped into a form that increases the efficiency of the light emitting device by reducing light absorption in the light emitting device, an optical element, coupled to the at least one oxide layer, and a phosphor, optically coupled to the at least one oxide layer, wherein light in at least the first wavelength region emitted by the light emitting device passes through the phosphor and excites the phosphor to emit light in at least a second wavelength region. 
     Another embodiment of the present invention is a Light Emitting Diode (LED) emitting multiple wavelength regions of light, which comprises an active Group III nitride layer, wherein the active Group III nitride layer emits light in at least a first wavelength region, at least one oxide layer, coupled to the light emitting device, wherein the at least one oxide layer is substantially transparent in the first wavelength region, the at least one oxide layer being shaped into a form that increases the efficiency of the LED by reducing light absorption in the LED, and a phosphor, optically coupled to the at least one oxide layer such that light in at least the first wavelength region strikes the phosphor and excites the phosphor to emit light in at least a second wavelength region, such that light in at least the first wavelength region and the second wavelength region are emitted by the LED. 
     Such an embodiment further optionally includes a lens, coupled between the oxide layer and the phosphor, wherein the lens increases the efficiency of the LED by reducing light absorption in the LED. 
     This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.