Abstract:
This invention is related to LED Light Extraction for optoelectronic applications. More particularly the invention relates to (Al, Ga, In)N combined with optimized optics for highly efficient (Al, Ga, In)N based light emitting diodes applications, and its fabrication method. A further extension is the general combination of a shaped high refractive index light extraction material combined with a sphere shaped molding.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to the following co-pending and commonly-assigned applications: 
         [0002]    U.S. Utility application Ser. No. 10/581,940, filed on Jun. 7, 2006, by Tetsuo Fujii, Yan Gao, Evelyn. L. Hu, and Shuji Nakamura, entitled “HIGHLY EFFICIENT GALLIUM NITRIDE BASED LIGHT EMITTING DIODES VIA SURFACE ROUGHENING,” attorney&#39;s docket number 30794.108-US-WO (2004-063), which application claims the benefit under 35 U.S.C Section 365(c) of PCT Application Serial No. US2003/03921, filed on 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,” attorney&#39;s docket number 30794.108-WO-01 (2004-063); 
         [0003]    U.S. Utility application Ser. No. 11/054,271, filed on Feb. 9, 2005, by Rajat Sharma, P. Morgan Pattison, John F. Kaeding, and Shuji Nakamura, entitled “SEMICONDUCTOR LIGHT EMITTING DEVICE,” attorney&#39;s docket number 30794.112-US-01 (2004-208); 
         [0004]    U.S. Utility application Ser. No. 11/175,761, filed on Jul. 6, 2005, by Akihiko Murai, Lee McCarthy, Umesh K. Mishra and Steven P. DenBaars, entitled “METHOD FOR WAFER BONDING (Al, In, Ga)N and Zn(S, Se) FOR OPTOELECTRONICS APPLICATIONS,” attorney&#39;s docket number 30794.116-US-U1 (2004-455), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/585,673, filed Jul. 6, 2004, by Akihiko Murai, Lee McCarthy, Umesh K. Mishra and Steven P. DenBaars, entitled “METHOD FOR WAFER BONDING (Al, In, Ga)N and Zn(S, Se) FOR OPTOELECTRONICS APPLICATIONS,” attorney&#39;s docket number 30794.116-US-P1 (2004-455-1); 
         [0005]    U.S. Utility application Ser. No. 11/067,957, filed Feb. 28, 2005, by Claude C. A. Weisbuch, Aurelien J. F. David, James S. Speck and Steven P. DenBaars, entitled “HORIZONTAL EMITTING, VERITCAL EMITTING, BEAM SHAPED, DISTRIBUTED FEEDBACK (DFB) LASERS BY GROWTH OVER A PATTERNED SUBSTRATE,” attorneys&#39; docket number 30794.121-US-01 (2005-144-1); 
         [0006]    U.S. Utility application Ser. No. 11/923,414, filed Oct. 24, 2007, by Claude C. A. Weisbuch, Aurelien J. F. David, James S. Speck and Steven P. DenBaars, entitled “SINGLE OR MULTI-COLOR HIGH EFFICIENCY LIGHT EMITTING DIODE (LED) BY GROWTH OVER A PATTERNED SUBSTRATE,” attorneys&#39; docket number 30794.122-US-C1 (2005-145-2), which application is a continuation of U.S. Pat. No. 7,291,864, issued Nov. 6, 2007, to Claude C. A. Weisbuch, Aurelien J. F. David, James S. Speck and Steven P. DenBaars, entitled “SINGLE OR MULTI-COLOR HIGH EFFICIENCY LIGHT EMITTING DIODE (LED) BY GROWTH OVER A PATTERNED SUBSTRATE,” attorneys&#39; docket number 30794.122-US-01 (2005-145-1); 
         [0007]    U.S. Utility application Ser. No. 11/067,956, filed Feb. 28, 2005, by Aurelien J. F. David, Claude C. A Weisbuch and Steven P. DenBaars, entitled “HIGH EFFICIENCY LIGHT EMITTING DIODE (LED) WITH OPTIMIZED PHOTONIC CRYSTAL EXTRACTOR,” attorneys&#39; docket number 30794.126-US-01 (2005-198-1); U.S. Utility application Ser. No. 11/403,624, filed Apr. 13, 2006, by James S. Speck, Troy J. Baker and Benjamin A. Haskell, entitled “WAFER SEPARATION TECHNIQUE FOR THE FABRICATION OF FREE-STANDING (AL, IN, GA)N WAFERS,” attorneys&#39; docket number 30794.131-US-U1 (2005-482-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/670,810, filed Apr. 13, 2005, by James S. Speck, Troy J. Baker and Benjamin A. Haskell, entitled “WAFER SEPARATION TECHNIQUE FOR THE FABRICATION OF FREE-STANDING (AL, IN, GA)N WAFERS,” attorneys&#39; docket number 30794.131-US-P1 (2005-482-1); 
         [0008]    U.S. Utility application Ser. No. 11/403,288, filed Apr. 13, 2006, by James S. Speck, Benjamin A. Haskell, P. Morgan Pattison and Troy J. Baker, entitled “ETCHING TECHNIQUE FOR THE FABRICATION OF THIN (AL, IN, GA)N LAYERS,” attorneys&#39; docket number 30794.132-US-U1 (2005-509-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/670,790, filed Apr. 13, 2005, by James S. Speck, Benjamin A. Haskell, P. Morgan Pattison and Troy J. Baker, entitled “ETCHING TECHNIQUE FOR THE FABRICATION OF THIN (AL, IN, GA)N LAYERS,” attorneys&#39; docket number 30794.132-US-P1 (2005-509-1); 
         [0009]    U.S. Utility application Ser. No. 11/454,691, filed on Jun. 16, 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 BONDING STRUCTURE FOR OPTOELECTRONIC APPLICATIONS AND ITS FABRICATION METHOD,” attorneys&#39; docket number 30794.134-US-U1 (2005-536-4), which application claims the benefit under 35 U.S.C Section 119(e) of 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,” attorneys&#39; docket number 30794.134-US-P1 (2005-536-1), U.S. Provisional Application Ser. No. 60/732,319, filed on Nov. 1, 2005, 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,” attorneys&#39; docket number 30794.134-US-P2 (2005-536-2), and 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,” attorneys&#39; docket number 30794.134-US-P3 (2005-536-3); 
         [0010]    U.S. Utility application Ser. No. 11/251,365 filed Oct. 14, 2005, by Frederic S. Diana, Aurelien J. F. David, Pierre M. Petroff, and Claude C. A. Weisbuch, entitled “PHOTONIC STRUCTURES FOR EFFICIENT LIGHT EXTRACTION AND CONVERSION IN MULTI-COLOR LIGHT EMITTING DEVICES,” attorneys&#39; docket number 30794.142-US-01 (2005-534-1); 
         [0011]    U.S. Utility application Ser. No. 11/633,148, filed Dec. 4, 2006, Claude C. A. Weisbuch and Shuji Nakamura, entitled “IMPROVED HORIZONTAL EMITTING, VERTICAL EMITTING, BEAM SHAPED, DISTRIBUTED FEEDBACK (DFB) LASERS FABRICATED BY GROWTH OVER A PATTERNED SUBSTRATE WITH MULTIPLE OVERGROWTH,” attorneys&#39; docket number 30794.143-US-U1 (2005-721-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/741,935, filed Dec. 2, 2005, Claude C. A. Weisbuch and Shuji Nakamura, entitled “IMPROVED HORIZONTAL EMITTING, VERTICAL EMITTING, BEAM SHAPED, DFB LASERS FABRICATED BY GROWTH OVER PATTERNED SUBSTRATE WITH MULTIPLE OVERGROWTH,” attorneys&#39; docket number 30794.143-US-P1 (2005-721-1); 
         [0012]    U.S. Utility application Ser. No. 11/593,268, filed on Nov. 6, 2006, by Steven P. DenBaars, Shuji Nakamura, Hisashi Masui, Natalie N. Fellows, and Akihiko Murai, entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED),” attorneys&#39; docket number 30794.161-US-U1 (2006-271-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/734,040, filed on Nov. 4, 2005, by Steven P. DenBaars, Shuji Nakamura, Hisashi Masui, Natalie N. Fellows, and Akihiko Murai, entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED),” attorneys&#39; docket number 30794.161-US-P1 (2006-271-1); 
         [0013]    U.S. Utility application Ser. No. 11/608,439, filed on Dec. 8, 2006, by Steven P. DenBaars, Shuji Nakamura and James S. Speck, entitled “HIGH EFFICIENCY LIGHT EMITTING DIODE (LED),” attorneys&#39; docket number 30794.164-US-U1 (2006-318-3), which application claims the benefit under 35 U.S.C Section 119(e) of 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),” attorneys&#39; docket number 30794.164-US-P1 (2006-318-1), 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),” attorneys&#39; docket number 30794.164-US-P2 (2006-318-2); 
         [0014]    U.S. Utility application Ser. No. 11/676,999, filed on Feb. 20, 2007, by Hong Zhong, John F. Kaeding, Rajat Sharma, James S. Speck, Steven P. DenBaars and Shuji Nakamura, entitled “METHOD FOR GROWTH OF SEMIPOLAR (Al,In,Ga,B)N OPTOELECTRONIC DEVICES,” attorneys&#39; docket number 30794.173-US-U1 (2006-422-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Application Ser. No. 60/774,467, filed on Feb. 17, 2006, by Hong Zhong, John F. Kaeding, Rajat Sharma, James S. Speck, Steven P. DenBaars and Shuji Nakamura, entitled “METHOD FOR GROWTH OF SEMIPOLAR (Al,In,Ga,B)N OPTOELECTRONIC DEVICES,” attorneys&#39; docket number 30794.173-US-P1 (2006-422-1); U.S. Utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Aurelien J. F. David, Claude C. A. Weisbuch and Steven P. DenBaars entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) THROUGH MULTIPLE EXTRACTORS,” attorney&#39;s docket number 30794. 191-US-U1 (2007-047-3), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,014, filed on Nov. 15, 2006, by Aurelien J. F. David, Claude C. A. Weisbuch and Steven P. DenBaars entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) THROUGH MULTIPLE EXTRACTORS,” attorney&#39;s docket number 30794. 191-US-P1 (2007-047-1), and U.S. Provisional Patent Application Ser. No. 60/883,977, filed on Jan. 8, 2007, by Aurelien J. F. David, Claude C. A. Weisbuch and Steven P. DenBaars entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) THROUGH MULTIPLE EXTRACTORS,” attorney&#39;s docket number 30794. 191-US-P2 (2007-047-2); 
         [0015]    U.S. utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Claude C. A. Weisbuch, James S. Speck and Steven P. DenBaars entitled “HIGH EFFICIENCY WHITE, SINGLE OR MULTI-COLOUR LED BY INDEX MATCHING STRUCTURES,” attorney&#39;s docket number 30794. 196-US-U1 (2007-114-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,026, filed on Nov. 15, 2006, by Claude C. A. Weisbuch, James S. Speck and Steven P. DenBaars entitled “HIGH EFFICIENCY WHITE, SINGLE OR MULTI-COLOUR LED BY INDEX MATCHING STRUCTURES,” attorney&#39;s docket number 30794. 196-US-P1 (2007-114-1); 
         [0016]    U.S. Utility patent application Ser. No. ______, filed on same date herewith, by Aurelien J. F. David, Claude C. A. Weisbuch, Steven P. DenBaars and Stacia Keller, entitled “HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) WITH EMITTERS WITHIN STRUCTURED MATERIALS,” attorney&#39;s docket number 30794.197-US-U1 (2007-113-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional patent application Ser. No. ______, filed on same date herewith, by Aurelien J. F. David, Claude C. A. Weisbuch, Steven P. DenBaars and Stacia Keller, entitled “HIGH LIGHT EXTRACTION EFFICIENCY LED WITH EMITTERS WITHIN STRUCTURED MATERIALS,” attorney&#39;s docket number 30794.197-US-P1 (2007-113-1); 
         [0017]    U.S. Utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Evelyn L. Hu, Shuji Nakamura, Yong Seok Choi, Rajat Sharma and Chiou-Fu Wang, entitled “ION BEAM TREATMENT FOR THE STRUCTURAL INTEGRITY OF AIR-GAP III-NITRIDE DEVICES PRODUCED BY PHOTOELECTROCHEMICAL (PEC) ETCHING,” attorney&#39;s docket number 30794.201-US-U1 (2007-161-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,027, filed on Nov. 15, 2006, by Evelyn L. Hu, Shuji Nakamura, Yong Seok Choi, Rajat Sharma and Chiou-Fu Wang, entitled “ION BEAM TREATMENT FOR THE STRUCTURAL INTEGRITY OF AIR-GAP III-NITRIDE DEVICES PRODUCED BY PHOTOELECTROCHEMICAL (PEC) ETCHING,” attorney&#39;s docket number 30794.201-US-P1 (2007-161-1); 
         [0018]    U.S. Utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Natalie N. Fellows, Steven P. DenBaars and Shuji Nakamura, entitled “TEXTURED PHOSPHOR CONVERSION LAYER LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.203-US-U1 (2007-270-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,024, filed on Nov. 15, 2006, by Natalie N. Fellows, Steven P. DenBaars and Shuji Nakamura, entitled “TEXTURED PHOSPHOR CONVERSION LAYER LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.203-US-P1 (2007-270-1); 
         [0019]    U.S. Utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Shuji Nakamura and Steven P. DenBaars, entitled “STANDING TRANSPARENT MIRROR-LESS (STML) LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.205-US-U1 (2007-272-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,017, filed on Nov. 15, 2006, by Shuji Nakamura and Steven P. DenBaars, entitled “STANDING TRANSPARENT MIRROR-LESS (STML) LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.205-US-P1 (2007-272-1); and 
         [0020]    U.S. Utility patent application Ser. No. ______, filed on Nov. 15, 2007, by Steven P. DenBaars, Shuji Nakamura and James S. Speck, entitled “TRANSPARENT MIRROR-LESS (TML) LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.206-US-U1 (2007-273-2), which application claims the benefit under 35 U.S.C Section 119(e) of U.S. Provisional Patent Application Ser. No. 60/866,023, filed on Nov. 15, 2006, by Steven P. DenBaars, Shuji Nakamura and James S. Speck, entitled “TRANSPARENT MIRROR-LESS (TML) LIGHT EMITTING DIODE,” attorney&#39;s docket number 30794.206-US-P1 (2007-273-1); all of which applications are incorporated by reference herein. 
         [0021]    This application claims the benefit under 35 U.S.C. Section 119(e) of co-pending and commonly-assigned U.S. provisional patent application Ser. No. 60/866,025, filed Nov. 15, 2006, entitled “HIGH LIGHT EXTRACTION EFFICIENCY SPHERE LED,” by Steven P. DenBaars et al., which application is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0022]    1. Field of the Invention 
         [0023]    This invention is related to LED Light Extraction and white LEDs with high luminous efficacy for optoelectronic applications. More particularly the invention relates to (Al, Ga, In)N LEDs and light extraction structure combined with a spherical package to extract light emitted in all directions. The overall effect is to achieve a device with superior luminous efficacy and a high output power. 
         [0024]    2. Description of the Related Art 
         [0025]    (Note: This application references a number of different publications as indicated throughout the specification. A list of these different publications can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.) 
         [0026]    In conventional Light Emitting Diodes (LEDs), in order to increase the light output power for the front side of the LED, the emitting light is reflected by a mirror on the backside of the sapphire substrate, or a mirror coating is placed on the lead frame when the bonding material is transparent at the emission wavelength. This reflected light is often re-absorbed by the emitting layer (active layer) because the photon energy is almost same as the band-gap energy of the quantum well of a AlInGaN multi-quantum well (MQW). Thus, the efficiency or output power of the LEDs is decreased due to the re-absorption of LED light by the emitting layer. See  FIGS. 2-3 . From the top side of p-type layer, the semi-transparent thin metal or ITO or ZnO transparent electrode was used to improve the light extraction efficiency. (J. J. Appl. Phys. 34, L797-99 (1995)), (J. J. Appl. Phys. 43, L180-82 (2004)). 
         [0027]    The present invention minimizes the internal reflection of LED light inside the LED package and minimizes the re-absorption of the LED light by the emitting layer (or the active layer) of the LED. The present invention furthermore combines the high light extraction efficiency LED chip with shaped (textured) phosphor layers to increase the total luminous efficacy of the device. As a result, this combined structure extracts more light out of the LED. 
       SUMMARY OF THE INVENTION 
       [0028]    The present invention describes a high efficient LED by minimizing the internal reflection inside of the molding with a sphere-shaped molded package, which is typically made from plastic. Assuming that the LED is a point light source and the size of the sphere molding is large, the direction of the all of the LED light beams to perpendicular to the surface of the sphere molding as shown in  FIG. 1 . Thus, all of the light can be extracted from the spherical LED package. 
         [0029]    Also, the present invention describes an (Al, Ga, In)N and light emitting diode (LED) in which the multi directions of light can be extracted from the surfaces of the chip before entering the sphere shaped plastic optical element and subsequently extracted to air. In particular the (Al, Ga, In)N and transparent contact layers (ITO or ZnO) is combined with a sphere shaped lens in which most light entering lens lies within the critical angle and is therefore extracted. The present includes invention minimizing the internal reflection of LED light by mirrors without any intentional mirrors attached to LED chip in order to minimize the re-absorption of the LED light by the emitting layer (or the active layer) of the LED. In order to minimize the internal reflection of the LED light, transparent electrodes such as ITO or ZnO, or the surface roughening of AlInGaN by patterning or anisotropically etching, are used to extract more light from the LED. The present invention furthermore combines the high light extraction efficiency LED chip with shaped (textured) phosphor layers to increase the total luminous efficacy of the device. As a result, this combined structure extracts more light out of the LED. 
         [0030]    A LED in accordance with the present invention comprises a LED chip, the LED chip emitting light at least a first emission wavelength; and a package, surrounding the LED chip, wherein the package has a substantially spherical shape. 
         [0031]    Such an LED further optionally comprises the LED chip being located substantially at the center of the package, the package being made from a material that is transparent at the emission wavelength of the LED chip, a transparent conductor layer being placed on a p-type AlGaInN layer of the LED, the transparent conductor layer being made from a material selected from a group comprising Indium Tin Oxide (ITO) and Zinc Oxide (ZnO), the surface of the transparent conductor layer being roughened, a current spreading layer being deposited before the transparent conductor layer, the current spreading layer being made from a material selected from a group comprising SiO2, SiN, and other insulating materials, at least one surface of the LED chip being roughened, the LED chip emitting light from more than one side of the LED chip, the LED chip being fabricated on a sapphire substrate, wherein a back side of the sapphire substrate is roughened, a phosphor layer, coupled to the package, wherein the phosphor layer is located remotely from the LED chip, the LED chip being attached to a lead frame, the lead frame allowing for emission of light from opposite directions of the LED chip, the LED chip being made from a material selected from a group comprising a (Al, Ga, In)N material system, a (Al, Ga, In)As material system, a (Al, Ga, In)P material system, a (Al, Ga, In)AsPNSb material system, a ZnGeN2 material system, and a ZnSnGeN2 material system, and a mirror, optically coupled to the LED chip, wherein light emitted from one side of the LED chip is reflected to substantially align with light emitted from another side of the LED chip. 
         [0032]    Another LED in accordance with the present invention comprises a group-III nitride based emission source, comprising an active layer and a textured surface layer, for emission of light in a first direction, and a second surface layer, opposite that of the textured surface layer, for emission of light in a second direction substantially opposite that of the first direction, and an encapsulation material, surrounding the group-III nitride based emission source, wherein the encapsulation material is substantially spherically shaped, a diameter of the encapsulation material being substantially larger than a width of the group-III nitride based emission source. 
         [0033]    Such an LED further optionally comprises the second surface layer being textured, a phosphor layer, coupled to the encapsulation material, wherein light emitted from the LED excites the phosphor, a transparent conductive layer, coupled to the active layer, wherein the active layer emits light through the transparent conductive layer, the transparent conductive layer being made from a material selected from a group comprising Indium Tin Oxide and Zinc Oxide. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
           [0035]      FIG. 1  illustrates a spherical LED in accordance with the present invention; 
           [0036]      FIG. 2  illustrates a conventional LED package; 
           [0037]      FIG. 3  illustrates a conventional LED package with a flip-chip LED; 
           [0038]      FIG. 4  illustrates use of a conventional LED chip with the present invention; 
           [0039]      FIGS. 5A and 5B  illustrate an embodiment of the LED of the present invention; 
           [0040]      FIG. 6  illustrates additional details of an embodiment of the present invention; 
           [0041]      FIG. 7  illustrates details of another embodiment of the present invention; 
           [0042]      FIGS. 8-15  illustrates embodiments of a spherical LED in accordance with the present invention; and 
           [0043]      FIG. 16  illustrates the relative efficiency of various light sources, including the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    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 
       [0045]    The present invention describes a high efficiency LED which minimizes the internal reflection inside of the molding via a sphere-shape molding. If the LED is considered a point light source and the size of the sphere molding is large compared to the LED chip, the direction of the LED light beams is approximately perpendicular to the surface of the spherical molding. Then, all of the light that is emitted from the LED is extracted from the sphere-shape molding into air. In conventional LEDs, the shape of molding is not spherical, as shown in  FIGS. 2-4 , so some of the LED light is reflected by the interface between the molding of the epoxy and the air due to a difference of the refractive index. This reflection reduces the efficiency or the output power of the LED due to a poor light extraction efficiency from the poor molding shape. 
         [0046]    The present invention also describes an (Al, Ga, In)N light emitting diode (LED) in which the multiple directions of light can be extracted from the surfaces of the chip before entering the sphere shaped plastic optical element and subsequently extracted to air. In particular the (Al, Ga, In)N and transparent contact layers (ITO or ZnO) are combined with a spherically-shaped lens in which most light entering lens lies within the critical angle and is therefore extracted. 
         [0047]    The present invention includes a high efficiency LED which minimizing the re-absorption of LED emission without any intentional mirrors attached to the LED chip. The conventional LEDs use a highly reflective mirror in order to increase the front emission by reflecting the LED light forward direction. See  FIGS. 2-4 . However, this reflected emission is typically partly re-absorbed by the emission layer or active layer of the LED, which reduces the efficiency or the output power of the LED. The present invention reduces reflection from the plastic encapsulating surface, reduces reflection from the ITO or ZnO surfaces, reduces reflection from the GaN by patterning or anisotropically etched surface (microcones), and minimizes light re-absorption by the emitting layer (active layer) without any intentional mirrors attached to the LED chip, which enables uniform light emission from the active layer to both sides of front and back sides. The present invention furthermore combines the high light extraction efficiency LED chip with shaped (textured) phosphor layers to increase the total luminous efficacy of the device. As a result, this combined structure extracts more light out of the LED. 
       Technical Description 
       [0048]    In  FIGS. 1-16 , the details of LED structure is not always shown. Only the emitting layer (usually AlInGaN MQW), p-type GaN, n-GaN, and the substrate are shown. In a typical LED structure, there are other layers such as a p-AlGaN electron blocking layer, InGaN/GaN super lattices, and others. Here, the most important parts are surface of the LED chip because the light extraction efficiency is determined mainly by the surface layer or condition of the epitaxial wafers, so, only these operational parts of the LED chip are shown in the figures. 
         [0049]      FIG. 1  illustrates a spherical LED in accordance with the present invention. 
         [0050]    LED  100 , having chip  102  and molding  104 , is shown. When the LED chip  102  is located at or near a center of a spherically-shaped molding  104 , all of the LED light  106  generated by chip  102  is extracted from the molding  104  because the direction of the light  106  becomes substantially perpendicular to the surface  108  of the molding  104 . In this case, the LED chip  102  should be like a spot light source. The molding  104  is typically a lens, made of plastic or epoxy, but can be made of glass or other transparent materials as desired. Further, the diameter of molding  104  is typically much larger than the width of chip  102 , as shown in the drawing D&gt;&gt;W. The LED chip  102  can be point-like, or be of some size, so long as D&gt;&gt;W as shown in  FIG. 1 . Further, the LED light  106  can be of any color, e.g., blue, yellow, red, white, orange, etc., depending on the doping of the active layer of the LED chip  102 . 
         [0051]      FIG. 2  illustrates a conventional LED package, and  FIG. 3  illustrates a conventional LED package with a flip-chip LED. 
         [0052]    In conventional LED packaging  200  shown in  FIG. 2 , the shape of the epoxy molding  202  is generally dome-shaped, not spherically-shaped. Thus, some of the LED light  204  generated by chip  206  is not extracted from the epoxy molding  202  of the dome, due to reflections inside of the epoxy molding  202 . In such a dome-shaped molded package  200 , the incident angle of the light  204  is often at an angle that is larger than a critical angle at the interface between the epoxy and the air, and thus is reflected back into the molding  202 , and possibly reabsorbed by the active layer of the LED  206 . 
         [0053]    Also, in conventional LEDs  200 , in order to increase the light  204  output power for the front side of the LED  206 , the emitting light is reflected by a mirror  208  on the backside of the sapphire substrate  210 . Other techniques for reflection of the light to the front side include a mirror coating on the lead frame when the bonding material is transparent at the emission wavelength. This reflected light is also re-absorbed by the emitting layer  206  (active layer) because the photon energy is almost same as the band-gap energy of the quantum well of AlInGaN multi-quantum well (MQW). Thus, the efficiency or output power of the LEDs  200  is decreased due to the re-absorption by the emitting layer. 
         [0054]    In  FIG. 2 , the LED chip  212  is die-bonded on the lead frame  214  with a clear epoxy without any mirror on the back side of the sapphire substrate  210 . In this case, the coating  208  material on the lead frame  214  becomes a mirror. If there is a mirror on the back side of the substrate, the LED chip is typically die-bonded by Ag paste. 
         [0055]      FIG. 3  illustrates a typical flip-chip packaging schema. 
         [0056]    LED package  300  is shown, similar to LED package  200 . In LED package  300 , however, chip  212  is flip-chip mounted to lead frames  214  using electrically conductive bumps  302 , which are typically indium but can be any electrically conductive material that is compatible with LED  212 . Now, light  304  reflects from mirrored surface  208  and becomes light  306 , which can then exit package  300  if the angle of the reflected light  300  is less than the critical angle at the interface between package  300  and the air or other material that is in contact with the outside of package  300 . 
         [0057]      FIG. 4  illustrates use of a conventional LED chip with the present invention. 
         [0058]    In  FIG. 4  the epoxy molding  104  in accordance with the present invention is not shown. The spherically-shaped molding  104  is typically attached as shown in  FIG. 1  using a conventional LED chip  102  to increase the light extraction efficiency. The diameter of the sphere molding should be much larger than size of the LED chip  102  to ensure that the light emitted by the LED chip will strike the interface between the epoxy molding and the air at a perpendicular or normal angle, which allows the light to leave the plastic and enter the air. Any light that strikes the interface between lens and air at less than the critical angle will escape into the air, but to make that angle uniform across the entire LED device, a sphere is chosen. However, any shape where the surface profile between lens and air is less than the critical angle will allow the light to escape, and is in accordance with the present invention. 
         [0059]    LED chip  400  with substrate  402 , active layer  404 , and surface layer  406  is shown. Additional layers  408 ,  410 , and  412  are also shown, to show the entire structure of chip  400 . Surface layer  406  of the present invention is not a planar surface. Surface layer  406  has a top surface  414  that is textured, patterned, or otherwise roughened to allow for light  416  that is incident on surface  414  to escape into the surrounding medium. The surrounding medium in most cases is molding  100 , but could be other materials without departing from the scope of the present invention. Since the critical angle of molding  100  allows for any perpendicular or substantially perpendicular light to escape from package  100 , the direction of light  416  is not so critical as it is in the packages  200  and  300  shown in  FIGS. 2 and 3  respectively. 
         [0060]    Further, light  418  can be reflected from substrate  402 , or layers  410 - 412 , such that light  418  becomes light  420 , which also has an opportunity to escape from chip  400 . 
         [0061]      FIGS. 5A and 5B  illustrate an embodiment of the LED of the present invention. 
         [0062]    LED  500  with emitted light  502  and active layer  504  are shown. Lead frame  506  and electrode  508  are shown as supporting glass plate  510 . 
         [0063]    In  FIG. 5 , the LED structure  500  is shown as being grown on a sapphire substrate. Then, Indium Tin Oxide (ITO) layer  512  is deposited on p-type GaN layer  514 . Then, an ITO layer  516  is coated onto glass plate  510 , and is attached to the deposited ITO layer  512  using epoxy as a glue. The other side  518  of glass plate  510  is roughened, patterned, or otherwise given a non-planar profile by a sand blast or other roughening technique, such as etching. Then, the sapphire substrate is removed using the laser de-bonding technique. Then, the Nitrogen-face (N face) GaN  520  is etched with wet etching such as KOH or HCL. Then, a cone-shaped surface  522  is formed on Nitrogen-face GaN  520 . Then, LED chip  500  is put on a lead frame  506  which works for removing any heat that is generated by the LED chip  500 . The wire bonding  524  and  526  is done between bonding pads of the LED chip  528  and  530  and a lead frame  506  and electrode  508  to allow an electric current to flow through the lead frame  506 . There are no intentional mirrors at the front and back sides of LED chip  500 . The lead frame  506  is designed to extract the light from the back side of the LED chip effectively as shown in the figure, because lead frame  506  acts as a support around the edges of LED chip  500 , rather than supporting the entire underside of chip  500 . As such, the LED light  532  is effectively extracted to both sides as emitted light  502 . The ohmic contact below the bonding pad of n-GaN is not shown for simplicity. Then, the LED chip  500  is molded with a sphere shape molding  100  of plastic, epoxy, or glass, which acts as a lens to assist the emitted light  532  to escape from the LED and enter the air. 
         [0064]      FIG. 6  illustrates additional details of an embodiment of the present invention, and  FIG. 7  illustrates details of another embodiment of the present invention. 
         [0065]    In  FIGS. 6 and 7 , instead of the glass layer  510  as shown in  FIG. 5 , a thick epoxy  600  is used. To make the electric contact, the epoxy  600  is partially removed, and ITO or a narrow stripe Au layer  602  is deposited on the epoxy  600  and the hole  604 . The operation of the LED is similar to the LED described with respect to  FIG. 5 , except layer  514  is now roughened on the opposite side of active layer  504  to allow for additional light to be emitted from the reverse side of active layer  502 . 
         [0066]    In  FIGS. 5-7 , if a GaN substrate is used instead of a sapphire substrate, the laser de-bonding step is not required, and, as such, the glass and thick epoxy sub-mount are also not required. After the LED structure growth on GaN substrate, ITO is deposited on p-type GaN and the backside of GaN substrate (typically Nitrogen-face GaN) is etched with a wet etching such as KOH and HCL. Then a cone-shaped surface is formed on the Nitrogen face GaN. The remainder of the fabrication and operational steps are similar to the LED described with respect to  FIG. 5 . 
         [0067]    Also, when the surface of ITO layers, e.g., layers  512 ,  516 , etc., are roughened, the light extraction through the ITO layers  512 ,  516  is increased. Even without the ITO layer  512  that is deposited on the p-type GaN layer  514 , the roughening of the surface of p-type GaN  514  as surface  700  is effective to increase the light extraction through the p-type GaN  514 . To create an ohmic contact for n-type GaN layer  520 , ITO or ZnO are typically used after the surface roughening of Nitrogen-face GaN layer  520 . Since ITO and ZnO have a similar refractive index as GaN, the light reflection at the interface between ITO (ZnO) and GaN is minimized. 
         [0068]      FIGS. 8-15  illustrates embodiments of a spherical LED in accordance with the present invention. 
         [0069]    In  FIG. 8A , the LED chip of  FIG. 5  is molded with epoxy or glass  800  as a sphere shape. In this case, the light  532  is extracted to air through the sphere molding  800  effectively, because the LED chip  500  is a small spot light source compared to the diameter of the spherical lens  800 . In addition, a phosphor layer  802  is placed or deposited near the outside surface of the lens molding  800 . In this case, the conversion efficiency of the blue light to white light is increased due to a small re-absorption of the LED light  532  due to a small back scattering of the LED light  532  by the phosphor layer  802 . Also, when the surface of the molding  800  or the phosphor layer  802  is roughened, the light extraction is increased from the molding  800  and/or the phosphor  802  to the air.  FIG. 8B  illustrates that chip  500  is mounted on frame  506  such that light  532  is also emitted from led  500  via surface  518  on the back side of chip  500 . 
         [0070]    In  FIG. 9 , in the LED chip of  FIGS. 6-7 , the ITO or ZnO is roughened as surface  700  to improve the light extraction through the ITO or ZnO. Then, the epoxy  900  is sub-mounted. 
         [0071]    In  FIG. 10 , before the ITO or ZnO deposition, a current spreading layer (SiO2, SiN, transparent insulating material)  1000  is deposited to allow a uniform current to flow through the p-type GaN layer  512 , and contact  1002  is provided to contact frame  506 . 
         [0072]    In  FIG. 11 , a mirror  1100  is put outside of the sphere molding  800  in order to direct more light to a specific side of the LED package  500 . The shape of the mirror  1100  is typically designed such that any reflected light is directed away from the LED chip  500  to avoid or minimize reabsorption of light by the active layer  502  of the LED chip  500 . 
         [0073]    In  FIG. 12 , the LED structure  1200  is shown as grown on a flat sapphire substrate or a patterned sapphire substrate (PSS)  1202  to improve the light extraction efficiency through the interface between the GaN and the sapphire substrate  1202 . Also, the backside of the sapphire substrate  1202  is roughened to increase the light extraction from the sapphire substrate  1202  to the air or epoxy or glass. Typically, the preferred shape of the roughened surface has a cone-shaped surface, but other surfaces may be used in accordance with the present invention. Then ITO or ZnO layer  1204  is deposited on p-type GaN  1206 . Then, bonding pads on ITO or ZnO and an ohmic contact/bonding pad on n-type GaN  1208  are formed after the n-type GaN  1208  is selectively etched. Then, the LED chip  1200  is molded with a lens  1210  of approximately spherical shape. 
         [0074]    In  FIG. 13 , the surface  1300  of the epoxy molding  1210  is roughened to increase the light extraction through the epoxy molding  1210 . Similar roughening techniques can be applied to glass or other transparent materials used for molding  1210  without departing from the scope of the present invention. 
         [0075]    In  FIG. 14 , a phosphor layer  1400  is deposited or placed near the top surface of the lens epoxy molding  1210 . This allows for the phosphor layer  1400  to be placed a relatively far distance from the LED chip  500 , which allows for an increase in the conversion efficiency of the blue light to white light due to a small re-absorption of the LED light  532  via a small back scattering by the phosphor  1400  to the LED chip  500 . The surface  1402  of the phosphor layer  1400  can be roughened to improve the light extraction through the phosphor layer  1400 . 
         [0076]    In  FIG. 15 , a lead frame  506  is used, and the LED chip is put on a transparent plate  1500  such as glass, quartz, sapphire, diamond or other transparent materials, using a transparent epoxy  1502  as a die-bonding material. The transparent glass plate  1500  is used to extract the LED light to the epoxy molding  1210  more effectively. 
         [0077]      FIG. 16  illustrates the relative efficiency of various light sources, including the present invention. 
         [0078]    In  FIG. 16 , table  1600  compares the spherical LED of the present invention to other LED packages and LED types, and it can be seen that the highest output power and efficiency is achieved by the spherical LED  500  of the present invention compared to other LED types with a different molding shape. Although LED  500  is shown in  FIG. 16 , similar packaging would be shown for any of the spherical LEDs of the present invention described in  FIGS. 5-15 . 
       Advantages and Improvements 
       [0079]    The present invention describes a high efficient LED by minimizing the internal reflection inside of the molding with a sphere-shape molding. By packaging the epoxy and LED such that LED approximates a point light source, the direction of all of the LED light beams end up as being perpendicular to the surface of the spherical lens molding. 
         [0080]    Also, by combining the LED structure without any intentional mirrors attached to LED chip (the mirror coated on lead frame is also included as the intentional mirrors), the re-absorption of LED light is minimized and the light extraction efficiency is increased dramatically. Thus, the light output power of the LEDs is also increased dramatically. 
         [0081]    The combination of a transparent oxide electrode with a surface roughened nitride LED and shaped lens results in further increases in light extraction. 
       REFERENCES 
       [0082]    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. Jpn. J. Appl. Physics, 45, No. 41, L1084-L1086 (2006).   6. Fujii T, Gao Y, Sharma R, Hu E L, DenBaars S P, Nakamura S. Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening.  Applied Physics Letters , vol. 84, no. 6, 9 Feb. 2004, pp. 855-7. Publisher: AIP, USA   
 
       CONCLUSION 
       [0089]    The present invention describes light emitting diodes. A LED in accordance with the present invention comprises a LED chip, the LED chip emitting light at least a first emission wavelength; and a package, surrounding the LED chip, wherein the package has a substantially spherical shape. 
         [0090]    Such an LED further optionally comprises the LED chip being located substantially at the center of the package, the package being made from a material that is transparent at the emission wavelength of the LED chip, a transparent conductor layer being placed on a p-type AlGaInN layer of the LED, the transparent conductor layer being made from a material selected from a group comprising Indium Tin Oxide (ITO) and Zinc Oxide (ZnO), the surface of the transparent conductor layer being roughened, a current spreading layer being deposited before the transparent conductor layer, the current spreading layer being made from a material selected from a group comprising SiO2, SiN, and other insulating materials, at least one surface of the LED chip being roughened, the LED chip emitting light from more than one side of the LED chip, the LED chip being fabricated on a sapphire substrate, wherein a back side of the sapphire substrate is roughened, a phosphor layer, coupled to the package, wherein the phosphor layer is located remotely from the LED chip, the LED chip being attached to a lead frame, the lead frame allowing for emission of light from opposite directions of the LED chip, the LED chip being made from a material selected from a group comprising a (Al, Ga, In)N material system, a (Al, Ga, In)As material system, a (Al, Ga, In)P material system, a (Al, Ga, In)AsPNSb material system, a ZnGeN2 material system, and a ZnSnGeN2 material system, and a mirror, optically coupled to the LED chip, wherein light emitted from one side of the LED chip is reflected to substantially align with light emitted from another side of the LED chip. 
         [0091]    Another LED in accordance with the present invention comprises a group-III nitride based emission source, comprising an active layer and a textured surface layer, for emission of light in a first direction, and a second surface layer, opposite that of the textured surface layer, for emission of light in a second direction substantially opposite that of the first direction, and an encapsulation material, surrounding the group-III nitride based emission source, wherein the encapsulation material is substantially spherically shaped, a diameter of the encapsulation material being substantially larger than a width of the group-III nitride based emission source. 
         [0092]    Such an LED further optionally comprises the second surface layer being textured, a phosphor layer, coupled to the encapsulation material, wherein light emitted from the LED excites the phosphor, a transparent conductive layer, coupled to the active layer, wherein the active layer emits light through the transparent conductive layer, the transparent conductive layer being made from a material selected from a group comprising Indium Tin Oxide and Zinc Oxide. 
         [0093]    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 and the full range and scope of equivalents to the claims.