U.S. patent application number 16/238736 was filed with the patent office on 2019-09-05 for transparent light emitting diodes.
This patent application is currently assigned to The Regents of the University of California. The applicant listed for this patent is The Regents of the University of California. Invention is credited to Hirokuni Asamizu, Steven P. DenBaars, Shuji Nakamura.
Application Number | 20190273194 16/238736 |
Document ID | / |
Family ID | 39512046 |
Filed Date | 2019-09-05 |
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United States Patent
Application |
20190273194 |
Kind Code |
A1 |
Nakamura; Shuji ; et
al. |
September 5, 2019 |
TRANSPARENT LIGHT EMITTING DIODES
Abstract
A transparent light emitting diode (LED) includes a plurality of
III-nitride layers, including an active region that emits light,
wherein all of the layers except for the active region are
transparent for an emission wavelength of the light, such that the
light is extracted effectively through all of the layers and in
multiple directions through the layers. Moreover, the surface of
one or more of the III-nitride layers may be roughened, textured,
patterned or shaped to enhance light extraction.
Inventors: |
Nakamura; Shuji; (Santa
Barbara, CA) ; DenBaars; Steven P.; (Goleta, CA)
; Asamizu; Hirokuni; (Goleta, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Regents of the University of California |
Oakland |
CA |
US |
|
|
Assignee: |
The Regents of the University of
California
Oakland
CA
|
Family ID: |
39512046 |
Appl. No.: |
16/238736 |
Filed: |
January 3, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14461151 |
Aug 15, 2014 |
10217916 |
|
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16238736 |
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13622884 |
Sep 19, 2012 |
8835959 |
|
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14461151 |
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11954154 |
Dec 11, 2007 |
8294166 |
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13622884 |
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60869447 |
Dec 11, 2006 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/48257
20130101; H01L 2224/48247 20130101; G02B 19/0028 20130101; H01L
33/62 20130101; H01L 33/54 20130101; H01L 2224/0554 20130101; H01L
2924/00014 20130101; H01L 2224/49107 20130101; H01L 33/387
20130101; H01L 33/22 20130101; H01L 2924/1815 20130101; H01L
2224/73265 20130101; H01L 33/60 20130101; H01L 2224/05573 20130101;
H01L 2933/0091 20130101; H01L 33/58 20130101; G02B 19/0061
20130101; H01L 2224/16245 20130101; H01L 2224/05568 20130101; H01L
2224/48091 20130101; H01L 2924/00014 20130101; H01L 2924/00014
20130101; H01L 2224/05599 20130101; H01L 2924/00014 20130101; H01L
2224/0555 20130101; H01L 2924/00014 20130101; H01L 2224/0556
20130101 |
International
Class: |
H01L 33/62 20060101
H01L033/62; G02B 19/00 20060101 G02B019/00; H01L 33/54 20060101
H01L033/54; H01L 33/58 20060101 H01L033/58; H01L 33/22 20060101
H01L033/22 |
Claims
1. A light emitting device, comprising: a lead frame having a
transparent plate; and a light emitting diode (LED) chip, placed on
or above the transparent plate in the lead frame, emitting light
through at least front and back sides of the LED chip; wherein the
transparent plate in the lead frame allows the light emitted from
the LED chip to be extracted out of the LED chip from the front or
back side of the LED chip.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation under 35 U.S.C. .sctn.
120 of:
[0002] U.S. Utility patent application Ser. No. 14/461,151, filed
on Aug. 15, 2014, by Shuji Nakamura, Steven P. DenBaars, and
Hirokuni Asamizu, entitled, "TRANSPARENT LIGHT EMITTING DIODES,"
attorney's docket number 30794.211-US-C2 (2007-282-4), which
application is a continuation under 35 U.S.C. .sctn. 120 of:
[0003] U.S. Utility patent application Ser. No. 13/622,884, filed
on Sep. 19, 2012, by Shuji Nakamura, Steven P. DenBaars, and
Hirokuni Asamizu, entitled, "TRANSPARENT LIGHT EMITTING DIODES,"
attorney's docket number 30794.211-US-C1 (2007-282-3), now U.S.
Pat. No. 8,835,959, issued Sep. 16, 2014, which application is a
continuation under 35 U.S.C. .sctn. 120 of:
[0004] U.S. Utility patent application Ser. No. 11/954,154, filed
on Dec. 11, 2007, by Shuji Nakamura, Steven P. DenBaars, and
Hirokuni Asamizu, entitled, "TRANSPARENT LIGHT EMITTING DIODES,"
attorney's docket number 30794.211-US-U1 (2007-282-2), now U.S.
Pat. No. 8,294,166, issued Oct. 23, 2012, which application claims
the benefit under 35 U.S.C. Section 119(e) of:
[0005] U.S. Provisional Patent Application Ser. No. 60/869,447,
filed on Dec. 11, 2006, by Shuji Nakamura, Steven P. DenBaars, and
Hirokuni Asamizu, entitled, "TRANSPARENT LEDS," attorney's docket
number 30794.211-US-P1 (2007-282-1);
[0006] all of which applications are incorporated by reference
herein.
[0007] This application is related to the following co-pending and
commonly-assigned applications:
[0008] 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," now U.S. Pat. No.
7,704,763, issued Apr. 27, 2010, attorney'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's docket number 30794.108-WO-01
(2004-063);
[0009] 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," now
U.S. Pat. No. 8,227,820, issued Jul. 24, 2012, attorney's docket
number 30794.112-US-01 (2004-208);
[0010] 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," now U.S. Pat. No.
7,344,958, issued Mar. 18, 2008, attorney'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's docket number 30794.116-US-P1
(2004-455-1);
[0011] U.S. Utility application Ser. No. 11/697,457, filed Apr. 6,
2007, by, Benjamin A. Haskell, Melvin B. McLaurin, Steven P.
DenBaars, James S. Speck, and Shuji Nakamura, entitled "GROWTH OF
PLANAR REDUCED DISLOCATION DENSITY M-PLANE GALLIUM NITRIDE BY
HYDRIDE VAPOR PHASE EPITAXY," now U.S. Pat. No. 7,956,360, issued
Jun. 7, 2011, attorneys' docket number 30794.119-US-C1
(2004-636-3), which application is a continuation of U.S. Utility
application Ser. No. 11/140,893, filed May 31, 2005, by, Benjamin
A. Haskell, Melvin B. McLaurin, Steven P. DenBaars, James S. Speck,
and Shuji Nakamura, entitled "GROWTH OF PLANAR REDUCED DISLOCATION
DENSITY M-PLANE GALLIUM NITRIDE BY HYDRIDE VAPOR PHASE EPITAXY,"
now U.S. Pat. No. 7,208,393, issued Apr. 24, 2007, attorneys'
docket number 30794.119-US-U1 (2004-636-2), which application
claims the benefit under 35 U.S.C. Section 119(e) of U.S.
Provisional Application Ser. No. 60/576,685, filed Jun. 3, 2004, by
Benjamin A. Haskell, Melvin B. McLaurin, Steven P. DenBaars, James
S. Speck, and Shuji Nakamura, entitled "GROWTH OF PLANAR REDUCED
DISLOCATION DENSITY M-PLANE GALLIUM NITRIDE BY HYDRIDE VAPOR PHASE
EPITAXY," attorneys' docket number 30794.119-US-P1
(2004-636-1);
[0012] 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," now U.S. Pat. No. 7,723,745,
issued May 25, 2010, attorneys' docket number 30794.121-US-01
(2005-144-1);
[0013] 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," now U.S. Pat. No. 7,755,096, issued Jul. 13, 2010,
attorneys' 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," now U.S. Pat. No. 7,291,864, issued Nov. 6,
2007, attorneys' docket number 30794.122-US-01 (2005-145-1);
[0014] 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," now U.S. Pat. No. 7,582,910,
issued Sep. 1, 2009, attorneys' docket number 30794.126-US-01
(2005-198-1);
[0015] U.S. Utility application Ser. No. 11/621,482, filed Jan. 9,
2007, by Troy J. Baker, Benjamin A. Haskell, Paul T. Fini, Steven
P. DenBaars, James S. Speck, and Shuji Nakamura, entitled
"TECHNIQUE FOR THE GROWTH OF PLANAR SEMI-POLAR GALLIUM NITRIDE,"
now U.S. Pat. No. 7,704,331, issued Apr. 27, 2010, attorneys'
docket number 30794.128-US-C1 (2005-471-3), which application is a
continuation of U.S. Utility application Ser. No. 11/372,914, filed
Mar. 10, 2006, by Troy J. Baker, Benjamin A. Haskell, Paul T. Fini,
Steven P. DenBaars, James S. Speck, and Shuji Nakamura, entitled
"TECHNIQUE FOR THE GROWTH OF PLANAR SEMI-POLAR GALLIUM NITRIDE,"
now U.S. Pat. No. 7,220,324, issued May 22, 2007, attorneys' docket
number 30794.128-US-U1 (2005-471-2), which application claims the
benefit under 35 U.S.C. Section 119(e) of U.S. Provisional
Application Ser. No. 60/660,283, filed Mar. 10, 2005, by Troy J.
Baker, Benjamin A. Haskell, Paul T. Fini, Steven P. DenBaars, James
S. Speck, and Shuji Nakamura, entitled "TECHNIQUE FOR THE GROWTH OF
PLANAR SEMI-POLAR GALLIUM NITRIDE," attorneys' docket number
30794.128-US-P1 (2005-471-1);
[0016] 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' 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' docket number 30794.131-US-P1 (2005-482-1);
[0017] 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," now U.S. Pat. No. 7,795,146, issued
Sep. 14, 2010, attorneys' 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' docket
number 30794.132-US-P1 (2005-509-1);
[0018] 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," now U.S. Pat. No. 7,719,020, issued May 18, 2010,
attorneys' 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' 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' 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' docket number 30794.134-US-P3
(2005-536-3);
[0019] U.S. Utility application Ser. No. 11/444,084, filed May 31,
2006, by Bilge M, Imer, James S. Speck, and Steven P. DenBaars,
entitled "DEFECT REDUCTION OF NON-POLAR GALLIUM NITRIDE WITH
SINGLE-STEP SIDEWALL LATERAL EPITAXIAL OVERGROWTH," now U.S. Pat.
No. 7,361,576, issued Apr. 22, 2008, attorneys' docket number
30794.135-US-U1 (2005-565-2), which claims the benefit under 35
U.S.C. 119(e) of U.S. Provisional Application Ser. No. 60/685,952,
filed on May 31, 2005, by Bilge M, Imer, James S. Speck, and Steven
P. DenBaars, entitled "DEFECT REDUCTION OF NON-POLAR GALLIUM
NITRIDE WITH SINGLE-STEP SIDEWALL LATERAL EPITAXIAL OVERGROWTH,"
attorneys' docket number 30794.135-US-P1 (2005-565-1);
[0020] U.S. Utility application Ser. No. 11/870,115, filed Oct. 10,
2007, by Bilge M, Imer, James S. Speck, Steven P. DenBaars and
Shuji Nakamura, entitled "GROWTH OF PLANAR NON-POLAR M-PLANE
III-NITRIDE USING METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD),"
now U.S. Pat. No. 8,097,481, issued Jan. 17, 2012, attorneys'
docket number 30794.136-US-C1 (2005-566-3), which application is a
continuation of U.S. Utility application Ser. No. 11/444,946, filed
May 31, 2006, by Bilge M, Imer, James S. Speck, and Steven P.
DenBaars, entitled "GROWTH OF PLANAR NON-POLAR {1-100} M-PLANE
GALLIUM NITRIDE WITH METALORGANIC CHEMICAL VAPOR DEPOSITION
(MOCVD)," now U.S. Pat. No. 7,338,828, issued Mar. 4, 2008,
attorneys' docket number 30794.136-US-U1 (2005-566-2), which claims
the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application
Ser. No. 60/685,908, filed on May 31, 2005, by Bilge M, Imer, James
S. Speck, and Steven P. DenBaars, entitled "GROWTH OF PLANAR
NON-POLAR {1-100} M-PLANE GALLIUM NITRIDE WITH METALORGANIC
CHEMICAL VAPOR DEPOSITION (MOCVD)," attorneys' docket number
30794.136-US-P1 (2005-566-1);
[0021] U.S. Utility application Ser. No. 11/444,946, filed Jun. 1,
2006, by Robert M. Farrell, Troy J. Baker, Arpan Chakraborty,
Benjamin A. Haskell, P. Morgan Pattison, Rajat Sharma, Umesh K.
Mishra, Steven P. DenBaars, James S. Speck, and Shuji Nakamura,
entitled "TECHNIQUE FOR THE GROWTH AND FABRICATION OF SEMIPOLAR
(Ga, Al, In, B)N THIN FILMS, HETEROSTRUCTURES, AND DEVICES," now
U.S. Pat. No. 7,846,757, issued Dec. 7, 2010, attorneys' docket
number 30794.140-US-U1 (2005-668-2), which claims the benefit under
35 U.S.C. 119(e) of U.S. Provisional Application Ser. No.
60/686,244, filed on Jun. 1, 2005, by Robert M. Farrell, Troy J.
Baker, Arpan Chakraborty, Benjamin A. Haskell, P. Morgan Pattison,
Rajat Sharma, Umesh K. Mishra, Steven P. DenBaars, James S. Speck,
and Shuji Nakamura, entitled "TECHNIQUE FOR THE GROWTH AND
FABRICATION OF SEMIPOLAR (Ga, Al, In, B)N THIN FILMS, HETERO
STRUCTURES, AND DEVICES," attorneys' docket number 30794.140-US-P1
(2005-668-1);
[0022] 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," now U.S. Pat. No. 7,768,023, issued Aug. 3,
2010, attorneys' docket number 30794.142-US-01 (2005-534-1);
[0023] 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," now U.S. Pat. No. 7,768,024,
issued Aug. 3, 2010, attorneys' 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' docket number 30794.143-US-P1
(2005-721-1);
[0024] U.S. Utility application Ser. No. 11/517,797, filed Sep. 8,
2006, by Michael Iza, Troy J. Baker, Benjamin A. Haskell, Steven P.
DenBaars, and Shuji Nakamura, entitled "METHOD FOR ENHANCING GROWTH
OF SEMIPOLAR (Al, In, Ga, B)N VIA METALORGANIC CHEMICAL VAPOR
DEPOSITION," now U.S. Pat. No. 7,575,947, issued Aug. 18, 2009,
attorneys' docket number 30794.144-US-U1 (2005-722-2), which claims
the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application
Ser. No. 60/715,491, filed on Sep. 9, 2005, by Michael Iza, Troy J.
Baker, Benjamin A. Haskell, Steven P. DenBaars, and Shuji Nakamura,
entitled "METHOD FOR ENHANCING GROWTH OF SEMIPOLAR (Al, In, Ga, B)N
VIA METALORGANIC CHEMICAL VAPOR DEPOSITION," attorneys' docket
number 30794.144-US-U1 (2005-722-1);
[0025] 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)," now U.S. Pat.
No. 7,994,527, issued Aug. 9, 2011, attorneys' 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' docket number 30794.161-US-P1 (2006-271-1);
[0026] 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)," now U.S.
Pat. No. 7,956,371, issued Jun. 7, 2011, attorneys' 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' 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' docket number 30794.164-US-P2 (2006-318-2);
[0027] 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," now U.S.
Pat. No. 7,858,996, issued Dec. 28, 2010, attorneys' 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' docket number 30794.173-US-P1
(2006-422-1);
[0028] U.S. Utility patent application Ser. No. 11/840,057, filed
on Aug. 16, 2007, by Michael Iza, Hitoshi Sato, Steven P. DenBaars,
and Shuji Nakamura, entitled "METHOD FOR DEPOSITION OF MAGNESIUM
DOPED (Al, In, Ga, B)N LAYERS," now U.S. Pat. No. 7,755,172, issued
Jul. 13, 2010, attorney's docket number 30794.187-US-U1
(2006-678-2), which claims the benefit under 35 U.S.C. 119(e) of
U.S. Provisional Patent Application Ser. No. 60/822,600, filed on
Aug. 16, 2006, by Michael Iza, Hitoshi Sato, Steven P. DenBaars,
and Shuji Nakamura, entitled "METHOD FOR DEPOSITION OF MAGNESIUM
DOPED (Al, In, Ga, B)N LAYERS," attorney's docket number
30794.187-US-P1 (2006-678-1);
[0029] U.S. Utility patent application Ser. No. 11/940,848, 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'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'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's docket number
30794.191-US-P2 (2007-047-2);
[0030] U.S. Utility patent application Ser. No. 11/940,853, 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 LIGHT EMITTING DIODES (LEDS) BY INDEX MATCHING
STRUCTURES," attorney'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's docket
number 30794.196-US-P1 (2007-114-1);
[0031] U.S. Utility patent application Ser. No. 11/940,866, filed
on Nov. 15, 2007, 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," now U.S. Pat. No. 7,977,694, issued
Jul. 12, 2011, attorney'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.
60/866,015, filed on Nov. 15, 2006, 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's docket number 30794.197-US-P1
(2007-113-1);
[0032] U.S. Utility patent application Ser. No. 11/940,876, 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'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's docket number 30794.201-US-P1
(2007-161-1);
[0033] U.S. Utility patent application Ser. No. 11/940,885, filed
on Nov. 15, 2007, by Natalie N. Fellows, Steven P. DenBaars and
Shuji Nakamura, entitled "TEXTURED PHOSPHOR CONVERSION LAYER LIGHT
EMITTING DIODE," attorney's docket number 30794.203-US-U1
(2007-270-2), now U.S. Pat. No. 8,860,051, issued Oct. 14, 2014,
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's docket number 30794.203-US-P1
(2007-270-1);
[0034] U.S. Utility patent application Ser. No. 11/940,872, filed
on Nov. 15, 2007, by Steven P. DenBaars, Shuji Nakamura and Hisashi
Masui, entitled "HIGH LIGHT EXTRACTION EFFICIENCY SPHERE LED,"
attorney's docket number 30794.204-US-U1 (2007-271-2), which
application claims the benefit under 35 U.S.C Section 119(e) of
U.S. Provisional Patent Application Ser. No. 60/866,025, filed on
Nov. 15, 2006, by Steven P. DenBaars, Shuji Nakamura and Hisashi
Masui, entitled "HIGH LIGHT EXTRACTION EFFICIENCY SPHERE LED,"
attorney's docket number 30794.204-US-P1 (2007-271-1);
[0035] U.S. Utility patent application Ser. No. 11/940,883, filed
on Nov. 15, 2007, by Shuji Nakamura and Steven P. DenBaars,
entitled "STANDING TRANSPARENT MIRRORLESS LIGHT EMITTING DIODE,"
now U.S. Pat. No. 7,687,813, issued Mar. 30, 2010, attorney'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's docket number 30794.205-US-P1 (2007-272-1);
[0036] U.S. Utility patent application Ser. No. 11/940,898, filed
on Nov. 15, 2007, by Steven P. DenBaars, Shuji Nakamura and James
S. Speck, entitled "TRANSPARENT MIRRORLESS LIGHT EMITTING DIODE,"
now U.S. Pat. No. 7,781,789, issued Aug. 24, 2010, attorney'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's docket number 30794.206-US-P1 (2007-273-1);
[0037] U.S. Utility patent application Ser. No. 11/954,163, filed
on Dec. 11, 2007, by Steven P. DenBaars and Shuji Nakamura,
entitled "LEAD FRAME FOR TRANSPARENT MIRRORLESS LIGHT EMITTING
DIODE," attorney's docket number 30794.210-US-U1 (2007-281-2),
which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional
Patent Application Ser. No. 60/869,454, filed on Dec. 11, 2006, by
Steven P. DenBaars and Shuji Nakamura, entitled "LEAD FRAME FOR
TM-LED," attorney's docket number 30794.210-US-P1 (2007-281-1);
[0038] U.S. Utility patent application Ser. No. 12/001,286, filed
on Dec. 11, 2007, by Mathew C. Schmidt, Kwang Choong Kim, Hitoshi
Sato, Steven P. DenBaars, James S. Speck, and Shuji Nakamura,
entitled "METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) GROWTH OF
HIGH PERFORMANCE NON-POLAR III-NITRIDE OPTICAL DEVICES," now U.S.
Pat. No. 7,842,527, issued Nov. 30, 2010, attorney's docket number
30794.212-US-U1 (2007-316-2), which claims the benefit under 35
U.S.C. 119(e) of U.S. Provisional Patent Application Ser. No.
60/869,535, filed on Dec. 11, 2006, by Mathew C. Schmidt, Kwang
Choong Kim, Hitoshi Sato, Steven P. DenBaars, James S. Speck, and
Shuji Nakamura, entitled "MOCVD GROWTH OF HIGH PERFORMANCE M-PLANE
GAN OPTICAL DEVICES," attorney's docket number 30794.212-US-P1
(2007-316-1);
[0039] U.S. Utility patent application Ser. No. 12/001,227, filed
on Dec. 11, 2007, by Steven P. DenBaars, Mathew C. Schmidt, Kwang
Choong Kim, James S. Speck, and Shuji Nakamura, entitled,
"NON-POLAR AND SEMI-POLAR EMITTING DEVICES," attorney's docket
number 30794.213-US-U1 (2007-317-2), now U.S. Pat. No. 9,130,119,
issued Sep. 8, 2015, which claims the benefit under 35 U.S.C.
119(e) of U.S. Provisional Patent Application Ser. No. 60/869,540,
filed on Dec. 11, 2006, by Steven P. DenBaars, Mathew C. Schmidt,
Kwang Choong Kim, James S. Speck, and Shuji Nakamura, entitled,
"NON-POLAR (M-PLANE) AND SEMI-POLAR EMITTING DEVICES," attorney's
docket number 30794.213-US-P1 (2007-317-1); and
[0040] U.S. Utility patent application Ser. No. 11/954,172, filed
on Dec. 11, 2007, by Kwang Choong Kim, Mathew C. Schmidt, Feng Wu,
Asako Hirai, Melvin B. McLaurin, Steven P. DenBaars, Shuji
Nakamura, and James S. Speck, entitled, "CRYSTAL GROWTH OF M-PLANE
AND SEMIPOLAR PLANES OF (AL, IN, GA, B)N ON VARIOUS SUBSTRATES,"
attorney's docket number 30794.214-US-U1 (2007-334-2), which claims
the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent
Application Ser. No. 60/869,701, filed on Dec. 12, 2006, by Kwang
Choong Kim, Mathew C. Schmidt, Feng Wu, Asako Hirai, Melvin B.
McLaurin, Steven P. DenBaars, Shuji Nakamura, and James S. Speck,
entitled, "CRYSTAL GROWTH OF M-PLANE AND SEMIPOLAR PLANES OF (AL,
IN, GA, B)N ON VARIOUS SUBSTRATES," attorney's docket number
30794.214-US-P1 (2007-334-1);
[0041] all of which applications are incorporated by reference
herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0042] The present invention is related to light extraction from
light emitting diodes (LEDs).
2. Description of the Related Art
[0043] (Note: This application references a number of different
publications as indicated throughout the specification. In
addition, a list of a number of different publications can be found
below in the section entitled "References." Each of these
publications is incorporated by reference herein.)
[0044] In order to increase the light output power from the front
side of a light emitting diode (LED), the emitted light is
reflected by a mirror placed on the backside of the substrate or is
reflected by a mirror coating on the lead frame, even if there are
no mirrors on the backside of the substrate, if the bonding
material is transparent on the emission wavelength. However, this
reflected light is re-absorbed by the emitting layer (active
layer), because the photon energy is almost same as the band-gap
energy of the light emitting species, such as AlInGaN multiple
quantum wells (MQWs). The efficiency or output power of the LEDs is
decreased due to this re-absorption of the light by the emitting
layer. See, for example, FIGS. 1, 2 and 3, which are described in
more detail below. See also Jpn. J. Appl. Phys., 34, L797-99 (1995)
and Jpn. J. Appl. Phys., 43, L180-82 (2004).
[0045] What is needed in the art are LED structures that more
effectively extract light. The present invention satisfies that
need.
SUMMARY OF THE INVENTION
[0046] The present invention describes a transparent light emitting
diode. Generally, the present invention describes a light emitting
device comprised of a plurality of III-nitride layers, including an
active region that emits light, wherein all of the layers except
for the active region are transparent for an emission wavelength of
the light, such that the light is extracted effectively through all
of the layers and in multiple directions through the layers.
Moreover, the surface of one or more of the III-nitride layers may
be roughened, textured, patterned or shaped to enhance light
extraction.
[0047] In one embodiment, the III-nitride layers reside on a
transparent substrate or sub-mount, wherein the III-nitride layers
are wafer bonded with the transparent substrate or sub-mount using
a transparent glue, a transparent epoxy, or other transparent
material, and light is extracted through the transparent substrate
or sub-mount. The transparent substrate or sub-mount are
electrically conductive, as is the transparent glue, transparent
epoxy, or other transparent material.
[0048] A lead frame supports the III-nitride layers (as well as the
transparent substrate or sub-mount), which reside on a transparent
plate in the lead frame. Thus, the light emitted from the
III-nitride layers is transmitted through the transparent plate in
the lead frame.
[0049] Moreover, the device may include one or more transparent
conducting layers that are positioned to electrically connect the
III-nitride layers, and one or more current spreading layers that
are deposited on the III-nitride layers, wherein the transparent
conducting layers are deposited on the current spreading layers.
Mirrors or mirrored surfaces are eliminated from the device to
minimize internal reflections in order to minimize re-absorption of
the light by the active region.
[0050] In another embodiment, the III-nitride layers are embedded
in or combined with a shaped optical element, and the light is
extracted from more than one surface of the III-nitride layers
before entering the shaped optical element and subsequently being
extracted. Specifically, at least a portion of the light entering
the shaped optical element lies within a critical angle and is
extracted. Moreover, one or more surfaces of the shaped optical
element may be roughened, textured, patterned or shaped to enhance
light extraction. Further, the shaped optical element may include a
phosphor layer, which may be roughened, textured, patterned or
shaped to enhance light extraction. The shaped optical element may
be an inverted cone shape, wherein the III-nitride layers are
positioned within the inverted cone shape such that the light is
reflected by sidewalls of the inverted cone shape.
[0051] In yet another embodiment, an insulating layer covering the
III-nitride layers is partially removed, and a conductive layer is
deposited within a hole or depression in the surface of the
insulating layer to make electrical contact with the III-nitride
layers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Referring now to the drawings in which like reference
numbers represent corresponding parts throughout:
[0053] FIGS. 1, 2 and 3 are cross-sectional schematic illustrations
of conventional LEDs.
[0054] FIGS. 4A and 4B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0055] FIGS. 5A and 5B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0056] FIG. 6 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0057] FIG. 7 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0058] FIGS. 8A and 8B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0059] FIG. 9 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0060] FIGS. 10A and 10B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0061] FIG. 11 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0062] FIGS. 12A and 12B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0063] FIG. 13 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0064] FIG. 14 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0065] FIGS. 15A and 15B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0066] FIG. 16 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0067] FIG. 17 is a schematic illustration of an improved LED
structure according to the preferred embodiment of the present
invention.
[0068] FIGS. 18A and 18B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0069] FIGS. 19A and 19B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0070] FIGS. 20A and 20B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0071] FIGS. 21A and 21B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
[0072] FIGS. 22A and 22B are schematic and plan view illustrations,
respectively, of an improved LED structure according to the
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0073] 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.
[0074] Overview
[0075] In the following description of the figures, the details of
the LED structures are not shown. Only the emitting layer (usually
AlInGaN MQW), p-type GaN layer, n-type GaN layer and sapphire
substrate are shown. Of course, there may be other layers in the
LED structure, such as a p-AlGaN electron blocking layer, InGaN/GaN
super lattices and others. In this invention, the most important
aspects are the surfaces of the LED structure, because the light
extraction efficiency is determined mainly by the surface layer or
condition of the epitaxial wafers. Consequently, only some aspects
(the surface layers) of the LED are shown in all of the
figures.
[0076] Conventional LED Structures
[0077] FIGS. 1, 2 and 3 are schematic illustrations of conventional
LEDs.
[0078] In conventional LEDs, in order to increase the light output
power from the front side of the LED, the emitting light is
reflected by the mirror on the backside of the sapphire substrate
or the mirror coating on the lead frame even if there is no mirrors
on the backside of the sapphire substrate and if the bonding
material is transparent on the emission wavelength. This reflected
light is 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 AlInGaN multi-quantum well (MQW). Then, the
efficiency or output power of the LEDs is decreased due to the
re-absorption by the emitting layer.
[0079] In FIG. 1, a conventional LED includes a sapphire substrate
100, emitting layer 102 (active layer), and semi-transparent or
transparent electrodes 104, such as ITO or ZnO. The LED is
die-bonded on a lead frame 106 with a clear epoxy molding 108
without any mirror on the back side of the sapphire substrate 100.
In this case, the coating material on the lead frame 106, or the
surface of the lead frame 106, becomes a mirror 110. If there is a
mirror 110 on the back side of the substrate 100, the LED chip is
die-bonded using an Ag paste. The active layer 102 emits light 112
towards the substrate 100 and emits light 114 towards the
electrodes 104. The emitting light 112 is reflected by the mirror
110 towards the electrode 104, becoming reflected light 116 which
is transmitted by the electrode 104 to escape the LED. The LED is
wire bonded 118 to the lead frame 106.
[0080] In FIG. 2, the conventional LED is similar to that shown in
FIG. 1, except that it is a flip-chip LED. The LED includes a
sapphire substrate 200 and emitting layer 202 (active layer), and a
highly reflective mirror 204. The LED is die-bonded 206 onto a lead
frame 208 and embedded in a clear epoxy molding 210. The active
layer 202 emits light 212 towards the substrate 200 and emits light
214 towards the highly reflective mirror 204. The emitting light
214 is reflected by the mirror 204 towards the substrate 200,
becoming reflected light 216 which is transmitted by the substrate
200 to escape the LED.
[0081] In FIG. 3, the conventional LED includes a conducting
sub-mount 300, high reflectivity mirror 302 (with Ag>94%
reflectivity (R)), a transparent ITO layer 304, a p-GaN layer 306,
an emitting or active layer 308, and an n-GaN layer 310. The LED is
shown without the epoxy molding, although similar molding may be
used. The emitting layer 308 emits LED emissions 312 towards the
mirror 302 and emits LED emissions 314 towards the n-GaN layer 310.
The emission 312 of the emitting layer 308 is reflected by the
mirror 302, where the reflective light emissions 316 are
re-absorbed by the emitting layer 308. The efficiency of the LED is
decreased due to this re-absorption. The n-GaN layer may be
roughened 317 to enhance extraction 318 of LED emissions 314.
[0082] Improved LED Structures
[0083] The present invention describes a transparent LED.
Generally, the present invention describes a light emitting device
comprised of a plurality of III-nitride layers, including an active
region that emits light, wherein all of the layers except for the
active region are transparent for an emission wavelength of the
light, such that the light is extracted effectively through all of
the layers and in multiple directions through the layers. The
surface of one or more of the III-nitride layers may be roughened,
textured, patterned or shaped to enhance light extraction.
[0084] FIG. 4A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an emitting
layer 400, an n-type GaN layer 402, a p-type GaN layer 404, a first
ITO layer 406, a second ITO layer 408, and a glass layer 410. The
n-type GaN layer 402 may have surface 412 that is roughened,
textured, patterned or shaped (e.g., a cone shaped surface), and
the glass layer 410 may have a surface 414 that is roughened,
textured, patterned or shaped (e.g., a cone shaped surface). The
LED is wire bonded 416 to a lead frame 418 via bonding pads 420,
422. FIG. 4B shows a top view of the lead frame 418.
[0085] In FIG. 4A, the LED structure is grown on a sapphire
substrate, which is removed using a laser de-bonding technique.
Thereafter, the first ITO layer 406 is deposited on the p-type GaN
layer 404. The LED structure is then attached to the glass layer
410, which is coated by the second ITO layer 408, using an epoxy as
a glue. The LED structure is then wire bonded 416 to the lead frame
418.
[0086] In FIG. 4A, there are no intentional mirrors at the front or
back sides of the LED. Instead, the lead frame 418 is designed to
effectively extract light 424 from both sides of the LED, because
the frame 418 does not obstruct the surfaces 412 and 414, i.e., the
back side 426 of the LED as well as the front side 428 of the LED.
FIG. 4B shows that the frame 418 supports the LED at the edges of
the glass layer 410, leaving the emitting surface of the glass
layer 410 and LED unobstructed.
[0087] An ohmic contact may be placed below the bonding pad 420 on
the n-GaN layer 402, but is not shown in the figure for
simplicity.
[0088] FIG. 5A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
multiple quantum well (MQW) layer as an emitting layer 500, an
n-type GaN layer 502, a p-type GaN layer 504, an ITO or ZnO layer
506, a transparent insulating layer 508, and transparent conductive
glue 510 for bonding the ITO or ZnO layer 506 to a transparent
conductive substrate 512. The transparent conductive substrate 512
may have a surface 514 that is roughened, textured, patterned or
shaped (e.g., a cone shaped surface), and the n-GaN layer 504 may
have a surface 516 that is roughened, textured, patterned or shaped
(e.g., a cone shaped surface). Preferably, the layers 500, 502, 504
and 506 have a combined thickness 518 of approximately 5 microns,
and the substrate 512 and glue 510 have a combined thickness 520 of
approximately 400 microns. Finally, ohmic electrode/bonding pads
522, 524 are placed on the LED.
[0089] The LED structure may be grown on a sapphire substrate,
which is removed using a laser de-bonding technique. The ITO layer
506 is then deposited on the p-type GaN layer 504. Before
deposition of the ITO layer 506, the insulating layer 508, which
may comprise SiO.sub.2 or SiN, is deposited as a current spreading
layer. Without the current spreading layer 508, the emission
intensity of the LED becomes small due to non-uniform current
flows. The transparent conductive substrate 512, which may be ZnO,
Ga.sub.2O.sub.3, or another material that is transparent at the
desired wavelengths, is wafer bonded or glued to the ITO layer 506
using the transparent conductive glue 510. Then, an n-GaN ohmic
electrode/bonding pad 522 and an p-GaN ohmic electrode/bonding pad
524 are formed on both sides of the LED structure. Finally, the
nitrogen-face (N-face) of the n-type GaN layer 502 is roughened,
textured, patterned or shaped 516 to enhance light extraction, for
example, using a wet etching, such as KOH or HCL, to form a
cone-shaped surface 516.
[0090] FIG. 5B is a plan view of the LED of FIG. 5A, and shows the
LED placed on a transparent plate 526, which resides on a lead
frame 528, both of which work to remove heat from the LED. The
p-side of the LED (i.e., the side with the substrate 512) is
attached to the transparent plate 526. Wire bonding is performed
between the bonding pad 524 of the n-type GaN layer 502 and the
lead frame 528.
[0091] There are no intentional mirrors at the front 530 or back
sides 532 of the LED. Instead, the lead frame 528 is designed to
effectively extract light from both sides of the LED, i.e., the
back side 532 of the LED as well as the front side 530 of the
LED.
[0092] Finally, an ohmic contact may be placed below the bonding
pad 524 of the n-GaN layer 502. However, this ohmic contact is not
shown in the figure for simplicity.
[0093] FIG. 6 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
MQW active layer 600, an n-GaN layer 602, a p-GaN layer 604, an
epoxy layer 606 (which is approximately 400 microns thick 608), a
bonding pad 610, an ohmic electrode/bonding pad 612, and an ITO or
ZnO layer 614. The combined thickness 616 of the n-GaN layer 602,
active layer 600 and p-GaN layer 604 is approximately 5
microns.
[0094] FIG. 7 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
MQW active layer 700, an n-GaN layer 702, a p-GaN layer 704, an
epoxy layer 706 (approximately 400 microns thick 708), a narrow
stripe Au connection 710, a bonding pad 712, an ohmic
electrode/bonding pad 714, and ITO or ZnO 716. The thickness 718 of
the n-GaN 702, active layer 700 and p-GaN layer 704 is
approximately 5 microns.
[0095] In both FIGS. 6 and 7, a thick epoxy layer 606, 706 is used,
rather than the glass layer 410 shown in FIG. 4. To make electrical
contact, the epoxy insulating layers 606, 706 are partially
removed, and the ITO layer 614, which is a transparent metal oxide,
or a narrow stripe of Au or other metal layer 710, are deposited on
the epoxy layers 606, 706, as well as within a hole or depression
618, 720 in the surface of the epoxy layers 606, 706, to make
electrical; contact with the p-GaN layer 604, 704.
[0096] In addition, both FIGS. 6 and 7 show that roughened,
textured, patterned or shaped surfaces 620, 722 are formed on the
nitrogen face (N-face) of the n-type GaN layers 602, 702. These
roughened, textured, patterned or shaped surfaces 620, 722 enhance
light extraction.
[0097] Note that, if a GaN substrate is used instead of a sapphire
substrate, laser de-bonding would not be required and, a result,
the sub-mounts 606, 706 would not be required. Moreover, if the LED
structure is created on a GaN substrate, the ITO layer 614 would be
deposited on the p-type GaN layer 604 and the backside of the GaN
substrate, which is an N-face GaN, could be etched using a wet
etching, such as KOH and HCL in order to form surfaces 620, 722
that are roughened, textured, patterned or shaped on the n-type GaN
layers 602, 702.
[0098] Note also that, if the surface of the ITO layer 614 is
roughened, textured, patterned or shaped, light extraction is
increased through the ITO layer 614. Even without the ITO layer 614
on the p-type GaN layer 604, the roughening, texturing, patterning
or shaping of the surface of the p-type GaN layer 604 is effective
to increase the light extraction through the p-type GaN layer
604.
[0099] Finally, an ohmic contact for the n-type GaN layer 612, and
the ITO or ZnO layer 614 may be used after the surface 620
roughening, texturing, patterning or shaping of the n-type GaN
layer 602. The ITO or ZnO layer 614 has a similar refractive index
as GaN and, as a result, the light reflection at the interface
between the ITO, ZnO and GaN is minimized.
[0100] FIG. 8A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an emitting
layer 800, an n-type GaN layer 802, a p-type GaN layer 804, a first
ITO layer 806, a second ITO layer 808, and a glass layer 810. The
n-type GaN layer 802 has a surface 812 that is roughened, textured,
patterned or shaped (e.g., a cone shape surface), and the glass
layer 810 has a surface 814 that is roughened, textured, patterned
or shaped (e.g., a cone shape surface). The LED is wire bonded 816
to a lead frame or sub-mount 818 using the bonding pads 820,
822.
[0101] The LED may be embedded with or contained in a molding or
shaped optical element 824, such as a sphere made of epoxy or
glass, forming, for example, a lens. The shaped optical element 824
may include a phosphor layer 826, which may be remote from the LED,
that is roughened, textured, patterned or shaped, for example, on
an outer surface of the shaped optical element 824. In this
embodiment, the emitting layer 800 emits light 828 towards the
surfaces 812 and 814, where the light can be extracted 830.
[0102] In this embodiment, because the shaped optical element 824
is a sphere, the LED structure can be considered a small spot light
source, because the direction of all of the light emitted from the
LED is substantially normal to the interface between air and the
sphere 824, and the light therefrom is effectively extracted to air
through the interface between air and the sphere 824.
[0103] In addition, if the phosphor layer 826 is placed on or near
the outer surface of the shaped optical element, the conversion
efficiency, for example, from blue light to white light, is
increased due to reduced re-absorption of the light 828 resulting
from reduced back scattering of the light 828 by the phosphor layer
826. Moreover, if the surface 834 of the phosphor layer 826 is
roughened, textured, patterned or shaped, light extraction is again
increased.
[0104] Finally, FIG. 8B is a top view of the device in FIG. 8A,
illustrating the lead frame 818.
[0105] FIG. 9 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
MQW emitting layer 900, an n-type GaN layer 902, a p-type GaN layer
904, an ITO layer 906 having a surface 908 that is roughened,
textured, patterned or shaped, a bonding pad 910, an ohmic
contact/bonding pad 912, a surface 914 of the n-type GaN layer 902
that is roughened, textured, patterned or shaped, and an epoxy
layer 916 that is deposited on the 908. The LED may be embedded
with or contained in a molding or shaped optical element 918, such
as a sphere made of epoxy or glass, forming, for example, a lens.
The shaped optical element 918 may include a phosphor layer 920,
which may be remote from the LED, that is roughened, textured,
patterned or shaped, for example, on an outer surface of the shaped
optical element 918.
[0106] In FIG. 9, the ITO or ZnO layer 906 is roughened, textured,
patterned or shaped to improve light extraction through the ITO or
ZnO layer 906. In addition, the epoxy 918 is sub-mounted.
Otherwise, the structure of FIG. 9 is the same as that shown in
FIGS. 6-8.
[0107] FIG. 10A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
MQW emitting layer 1000, an n-type GaN layer 1002, a p-type GaN
layer 1004, an ITO layer 1006, a bonding pad 1008, an ohmic
contact/bonding pad 1010, a surface 1012 of the ITO layer 1006 that
is roughened, textured, patterned or shaped, a surface 1014 of the
n-type GaN layer 1002 that is roughened, textured, patterned or
shaped, and an epoxy layer 1016 that is deposited on the surface
1012.
[0108] The LED may be embedded with or contained in a molding or
shaped optical element 1018, such as a sphere made of epoxy or
glass, forming, for example, a lens. The shaped optical element
1018 may include a phosphor layer 1020, which may be remote from
the LED, that is roughened, textured, patterned or shaped, for
example, on an outer surface of the shaped optical element
1018.
[0109] The LED may also include a current spreading layer 1022,
which may comprise SiN, SiO.sub.2, or some other insulating
material, for example, is deposited before the ITO or ZnO layer
1006 to flow the current uniformly through the p-type GaN layer
1004.
[0110] Finally, the LED is wire bonded 1024 to a lead frame 1026.
FIG. 10B shows a top view of the lead frame 1026.
[0111] FIG. 11 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an InGaN
MQW emitting layer 1100, an n-type GaN layer 1102, a p-type GaN
layer 1104, an ITO layer 1106, a bonding pad 1108, an ohmic
contact/bonding pad 1110, a surface 1112 of the ITO layer 1106 that
is roughened, textured, patterned or shaped, a surface 1114 of the
p-type GaN layer 1102 that is roughened, textured, patterned or
shaped, and an epoxy layer 1116 that is deposited on the surface
1112.
[0112] The LED may be embedded with or contained in a molding or
shaped optical element 1118, such as a sphere made of epoxy or
glass, forming, for example, a lens. The shaped optical element
1118 may include a phosphor layer 1120, which may be remote from
the LED, that is roughened, textured, patterned or shaped, for
example, on an outer surface of the shaped optical element
1118.
[0113] The LED may also include a current spreading layer 1122,
which may comprise SiN, SiO.sub.2, or some other insulating
material, for example, that is deposited before the ITO or ZnO
layer 1106 to flow the current uniformly through the p-type GaN
layer 1104.
[0114] Finally, the LED is wire bonded 1124 to a lead frame 1126.
FIG. 11B shows a top view of the lead frame 1126.
[0115] In the embodiment of FIG. 11, a mirror 1128 is placed
outside of the shaped optical element 1118, in order to obtain more
light from a front side 1130 of the device. The shape of the mirror
is designed to prevent reflected light from reaching the LED, in
order to reduce re-absorption of the light by the LED.
[0116] FIG. 12A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an emitting
layer 1200, an n-type GaN layer 1202, a p-type GaN layer 1204, an
ITO or ZnO layer 1206, and a substrate 1208, which may be a flat
sapphire substrate or a patterned sapphire substrate (PSS). The LED
is wire bonded 1210 to a lead frame 1212, and embedded in or
combined with moldings or shaped optical elements 1214, 1216, such
as inverted cone shapes made of epoxy or glass, forming, for
example, lenses. In this embodiment, the shaped optical elements
1214, 1216 are formed on opposite sides, e.g., the top/front and
bottom/back sides of the LED, wherein the emitting layer 1200 emits
light 1222 that is extracted from both the top/front and
bottom/back sides of the LED.
[0117] The LED is electrically connected to the lead frame 1218 via
bonding pads 1224, 1226. The bonding pad 1224 is deposited on the
ITO or ZnO layer 1206, and the ohmic contact/bonding pad 1226 is
deposited on the n-type GaN layer 1202 after the n-type GaN 1202
layer is exposed by a selective etch through the p-type GaN layer
1204.
[0118] As noted above, the LED may be combined with epoxy or glass
and molded as an inverted cone-shapes 1214, 1216 for both the front
1218 and back sides 1220, wherein the inverted cone molding shape
1214, 1216 provides enhanced light extraction. Specifically, most
of the light entering the inverted cone shapes 1214, 1216 lies
within a critical angle and is extracted. The light is reflected to
a top or emitting surface of the inverted cone shape 1214 by the
side walls of the inverted cone shape 1214 for emission through the
top surface of the inverted cone shape 1214, and similarly, the
light is reflected to a bottom or emitting surface of the inverted
cone shape 1216 by the side walls of the inverted cone shape 1216
for emission through the bottom surface of the inverted cone shape
1214.
[0119] Finally, note that a patterned sapphire substrate (PSS) 1208
improves the light extraction efficiency through the interface 1228
between the n-GaN layer 1202 and the substrate 1208. In addition,
the backside 1230 of the sapphire substrate 1208 may be roughened,
textured, patterned or shaped (e.g., a cone shaped surface) to
increase the light extraction efficiency.
[0120] FIG. 12B shows a top view of the lead frame 1212.
[0121] FIG. 13 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an emitting
layer 1300, an n-type GaN layer 1302, a p-type GaN layer 1304, an
ITO or ZnO layer 1306, and a substrate 1308, which may be a flat
sapphire substrate or a patterned sapphire substrate (PSS). The LED
is wire bonded 1310 to a lead frame 1312, and embedded in or
combined with moldings or shaped optical elements 1314, 1316, such
as inverted cone shapes made of epoxy or glass, forming, for
example, lenses. In this embodiment, the shaped optical elements
1314, 1316 are formed on opposite sides, e.g., the top/front and
bottom/back sides of the LED, wherein the emitting layer 1300 emits
light 1322 that is extracted from both the top/front and
bottom/back sides of the LED.
[0122] The LED is electrically connected to the lead frame 1318 via
bonding pads 1324, 1326. The bonding pad 1324 is deposited on the
ITO or ZnO layer 1306, and the ohmic contact/bonding pad 1326 is
deposited on the n-type GaN layer 1302 after the n-type GaN 1302
layer is exposed by a selective etch through the p-type GaN layer
1304.
[0123] As noted above, the LED may be combined with epoxy or glass
and molded as an inverted cone-shapes 1314, 1316 for both the front
1318 and back sides 1320, wherein the inverted cone molding shape
1314, 1316 provides enhanced light extraction. Specifically, most
of the light entering the inverted cone shapes 1314, 1316 lies
within a critical angle and is extracted. The light is reflected to
a top or emitting surface of the inverted cone shape 1314 by the
side walls of the inverted cone shape 1314 for emission through the
top surface of the inverted cone shape 1314, and similarly, the
light is reflected to a bottom or emitting surface of the inverted
cone shape 1316 by the side walls of the inverted cone shape 1316
for emission through the bottom surface of the inverted cone shape
1314. Moreover, the top/front surface 1328 of the shaped optical
elements 1314, and the bottom/back surface 1330 of the shaped
optical element 1316 may be roughened, textured, patterned, or
shaped to increase the light extraction through the elements 1314,
1316.
[0124] FIG. 14 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 1400 includes an
emitting layer 1402 and a substrate 1404 (as well as other layers),
and the substrate 1404 is a flat or patterned sapphire substrate.
The LED 1400 is wire bonded 1406 to a lead frame 1408, and embedded
in or combined with moldings or shaped optical elements 1410, 1412,
such as inverted cone shapes made of epoxy or glass, forming, for
example, lenses. In this embodiment, the shaped optical elements
1410, 1412 are formed on opposite sides, e.g., the top/front side
1414 and bottom/back side 1416 of the LED 1400, wherein the
emitting layer 1402 emits light 1418 that is extracted from both
the top/front side 1414 and bottom/back side 1416 of the LED
1400.
[0125] In FIG. 14, phosphor layers 1420 may be placed near the
top/front surface 1422 of the shaped optical element 1410 and the
bottom/back surface 1424 of the shaped optical element 1412.
Preferably, the phosphor layers 1420 should be positioned as far
away as possible from the LED 1400. In this case, the conversion
efficiency of the blue light to white light is increased, due to
reduced re-absorption of the emitted light by the LED 1400
resulting from reduced back-scattering of the light by the phosphor
layers 1420 to the LED 1400. Moreover, the surfaces 1426 of the
phosphor layers 1420 may be roughened, textured, patterned or
shaped to improve light extraction.
[0126] FIG. 15A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 1500 comprises an
emitting layer 1502, an n-type GaN layer 1504, a p-type GaN layer
1506, an ITO or ZnO layer 1508, and a substrate 1510, which may be
a flat sapphire substrate or a patterned sapphire substrate
(PSS).
[0127] The LED 1500 is wire bonded 1512 to a lead frame 1514,
wherein FIG. 15B is a schematic illustration showing the top view
of the lead frame 1514.
[0128] In this embodiment, the LED 1500 is embedded in or combined
with moldings or shaped optical elements 1516, 1518, such as
inverted cone shapes made of epoxy or glass, forming, for example,
lenses. The shaped optical elements 1516, 1518 are formed on
opposite sides, e.g., the top/front side 1520 and bottom/back side
1522 of the LED 1500, wherein the emitting layer 1502 emits light
1524 that is extracted from both the top/front side 1520 and
bottom/back side 1522 of the LED 1500.
[0129] A mirror 1526 may be placed inside the shaped optical
element 1518 to increase the light output to the front side 1528 of
the LED 1500. Moreover, the shape of the mirror 1526 is designed to
prevent reflections of the light 1530 emitted from the LED 1500
from being re-absorbed by the LED 1500, which would reduce the
output power or the efficiency of the LED. Instead, the mirror 1526
guides the reflected light 1530 away from the LED 1500.
[0130] In addition, the mirror 1526 is only partially attached (or
not attached at all) to the LED 1500 or the substrate 1510. This
differs from conventional LEDs, where mirrors are attached to the
entire surface of the LED, for example, as shown in FIGS. 1-3.
[0131] FIG. 16 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure comprises an emitting
layer 1600, an n-type GaN layer 1602, a p-type GaN layer 1604, an
ITO or ZnO layer 1606, and a substrate 1608, which may be a flat
sapphire substrate or a patterned sapphire substrate (PSS). The LED
is wire bonded 1610 to a lead frame 1612.
[0132] In this embodiment, the LED is embedded in or combined with
moldings or shaped optical elements 1614, 1616, such as inverted
cone shapes made of epoxy or glass, forming, for example, lenses.
The shaped optical elements 1614, 1616 are formed on opposite
sides, e.g., the top/front side 1618 and bottom/back side 1620 of
the LED, wherein the emitting layer 1602 emits light 1622 that is
extracted from both the top/front side 1618 and bottom/back side
1620 of the LED.
[0133] A mirror 1624 may be placed inside the shaped optical
element 1616 to increase the light output to the front side 1626 of
the LED. Moreover, the shape of the mirror 1624 is designed to
prevent reflections of the light 1628 emitted from the LED from
being re-absorbed by the LED, which would reduce the output power
or the efficiency of the LED. Instead, the mirror 1624 guides the
reflected light 1628 away from the LED.
[0134] In addition, the mirror 1624 is only partially attached (or
not attached at all) to the LED or the substrate 1608. This differs
from conventional LEDs, where mirrors are attached to the entire
surface of the LED, for example, as shown in FIGS. 1-3.
[0135] Finally, the top/front surface 1630 of the shaped optical
element 1614 is roughened, textured, patterned or shaped to improve
light extraction efficiency.
[0136] FIG. 17 is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 1700 includes an
emitting layer 1702 and a substrate 1704 (as well as other layers),
and the substrate 1704 is a flat or patterned sapphire substrate.
The LED 1700 is wire bonded 1706 to a lead frame 1708, and embedded
in or combined with moldings or shaped optical elements 1710, 1712,
such as inverted cone shapes made of epoxy or glass, forming, for
example, lenses. In this embodiment, the shaped optical elements
1710, 1712 are formed on opposite sides, e.g., the top/front side
1714 and bottom/back side 1716 of the LED 1700, wherein the
emitting layer 1702 emits light 1718 that is extracted from both
the top/front side 1714 and bottom/back side 1716 of the LED
1700.
[0137] In FIG. 17, a mirror 1720 may be placed inside the shaped
optical element 1712 to increase the light output directed to the
front side 1720 of the LED 1700. Moreover, a phosphor layer 1722
may be placed near the top surface 1724 of the shaped optical
element 1710. Preferably, the phosphor layer 1722 is positioned as
far away as possible from the LED 1700. In this case, the
conversion efficiency of the blue light to white light is
increased, due to reduced re-absorption of the light 1718 emitted
from the LED 1700 resulting from reduced back-scattering by the
phosphor layer 1722. In addition, the surface 1726 of the phosphor
layer 1722 may be roughened, textured, patterned or shaped to
improve light extraction through the phosphor layer 1722.
[0138] FIG. 18A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 1800 includes an
emitting layer 1802 and a substrate 1804 (as well as other layers).
The LED 1800 is wire bonded 1806 to a lead frame 1808, wherein FIG.
18B is an illustration showing the top view of the lead frame
1808.
[0139] In this embodiment, the LED 1800 is embedded in or combined
with a molding or shaped optical element 1810, such as an inverted
cone shape made of epoxy or glass, forming, for example, a lens.
Light 1812 emitted by the emitting layer 1802 is reflected by
mirrors 1814 positioned within the shaped optical element 1810,
towards the front side 1816 of the shaped optical element 1810,
away from the back side 1818 of the shaped optical element 1810,
wherein the reflected light 1820 is output from the shaped optical
element 1810.
[0140] FIG. 19A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 1900 includes an
emitting layer 1902 and a substrate 1904 (as well as other layers).
The LED 1900 is wire bonded 1906 to a lead frame 1908, wherein FIG.
19B is an illustration showing the top view of the lead frame
1908.
[0141] In this embodiment, the LED 1900 is embedded in or combined
with a molding or shaped optical element 1910, such as an inverted
cone shape made of epoxy or glass, forming, for example, a lens.
Light 1912 emitted by the emitting layer 1902 is reflected by the
sidewalls 1914 of the shaped optical element 1910, towards the
front side 1916 of the shaped optical element 1910, wherein the
reflected light 1918 is output from the shaped optical element
1910, and away from the back side 1920 of the shaped optical
element 1910.
[0142] Preferably, the LED 1900 is positioned within the shaped
optical element 1910 such that the light 1912 emitted by the LED is
reflected by mirrored surfaces 1922 of the sidewalls 1914, wherein
the mirrored surfaces 1922 are deposited or attached to the
sidewalls 1914. The angle 1924 of the sidewalls 1914 relative to
the base 1920 of the shaped optical element 1910 is a critical
angle that reflects the light 1912 emitted from the LED 1900 to the
front side 1916 of the shaped optical element 1910. For example,
the refractive index of epoxy is n.sub.2=1.5, the refractive index
of the air is n.sub.1=1, and, as a result, the critical angle of
the reflection is sin.sup.-1 (1/1.5). Therefore, the angle 1924 of
the sidewalls 1914 should be more than sin.sup.-1 (1/1.5). This
results in the reflected light 1912 from the LED 1900 being
effectively extracted from the top surface 1928 of the shaped
optical element in the direction labeled by 1926.
[0143] FIG. 20A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure includes an emitting
layer 2000 and a substrate 2002 (as well as other layers). The LED
is wire bonded 2004 to a lead frame 2006, wherein FIG. 20B is a top
view of the lead frame 2006.
[0144] In this embodiment, the LED is embedded in or combined with
a molding or shaped optical element 2008, such as an inverted cone
shape made of epoxy or glass, forming, for example, a lens. Light
2010 emitted by the emitting layer 2002 is reflected by the
sidewalls 2012 of the shaped optical element 2008, towards the
front side 2014 of the shaped optical element 2008, wherein the
reflected light 2016 is output from the shaped optical element
2008, and away from the back side 2018 of the shaped optical
element 2008.
[0145] Preferably, the LED is positioned within the shaped optical
element 2008 such that the light 2010 emitted by the LED is
reflected by the sidewalls 2012. Moreover, the front or top surface
2020 of the shaped optical element 2008 is roughened, textured,
patterned or shaped to increase light extraction.
[0146] The angle 2022 of the sidewalls 2012 relative to the base
2018 of the shaped optical element 2008 is a critical angle that
reflects the 2010 emitted from the LED to the front side 2014 of
the shaped optical element 2008. For example, the refractive index
of epoxy is n.sub.2=1.5, the refractive index of the air is
n.sub.1=1, and, as a result, the critical angle of the reflection
is sin.sup.-1 (1/1.5). Therefore, the angle 2022 of the sidewalls
2012 should be more than sin.sup.-1 (1/1.5). This results in the
reflected light 2010 from the LED being effectively extracted from
the front surface 2020 of the shaped optical element 2008.
[0147] FIG. 21A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 2100 includes an
emitting layer 2102 and a substrate 2104 (as well as other layers).
The LED 2100 is wire bonded 2106 to a lead frame 2108, wherein FIG.
21B shows a top view of the lead frame 2108.
[0148] In this embodiment, the LED 2100 is embedded in or combined
with a molding or shaped optical element 2110, such as an inverted
cone shape made of epoxy or glass, forming, for example, a lens.
Preferably, the LED 2100 is positioned within the shaped optical
element 2110 such that the light 2112 emitted by the LED is
reflected by the sidewalls 2114 of the shaped optical element 2110,
towards the front side 2116 of the shaped optical element 2110,
wherein the reflected light 2118 is output from the shaped optical
element 2110, and away from the back side 2120 of the shaped
optical element 2110.
[0149] A phosphor layer 2122 may be placed on or near the front or
top surface 2124 of the shaped optical element 2110. Preferably,
the phosphor layer 2122 is placed as far away as possible from the
LED 2100. In this example, the conversion efficiency of blue light
to white light is increased due to reduced re-absorption of the
light 2112 by the LED 2100 resulting from reduced back-scattering
by the phosphor layer 2122. In addition, the surface 2126 of the
phosphor layer 2122 may be roughened, textured, patterned or shaped
to increase light extraction.
[0150] FIG. 22A is a schematic illustrating a specific improved LED
structure according the preferred embodiment of the present
invention, wherein the improved LED structure 2200 includes an
emitting layer 2202 and a substrate 2204 (as well as other layers).
The LED 2200 is wire bonded 2206 to a lead frame 2208, wherein FIG.
22B shows a top view of the lead frame 2208.
[0151] The LED 2200 is embedded in or combined with moldings or
shaped optical elements 2210, 2212, such as inverted cone shapes
made of epoxy or glass, forming, for example, lenses. In this
embodiment, the shaped optical elements 2210, 2212 are formed on
opposite sides, e.g., the top/front side 2214 and bottom/back side
2216 of the LED 2200, wherein the emitting layer 2200 emits light
2218 that is extracted from both the top/front side 2214 and
bottom/back side 2216 of the LED 2200.
[0152] The lead frame 2208 includes a transparent plate 2220,
wherein the LED 2200 is bonded to the transparent plate 2220 using
a transparent/clear epoxy 2222 as a die-bonding material. The
transparent plate 2220 may be comprised of glass, quartz, sapphire,
diamond or other material transparent for the desired emission
wavelength, wherein the transparent glass plate 2220 effectively
extracts the light 2218 emitted from the LED 2200 to the shaped
optical element 2212.
Advantages and Improvements
[0153] One advantage of the present invention is that all of the
layers of the LED are transparent for the emission wavelength,
except for the emitting layer, such that the light is extracted
effectively through all of the layers.
[0154] Moreover, by avoiding the use of intentional mirrors with
the LED, re-absorption of light by the LED is minimized, light
extraction efficiency is increased, and light output power is
increased.
[0155] The combination of a transparent electrode with roughened,
textured, patterned or shaped surfaces, with the LED embedded
within a shaped optical element or lens, results in increased light
extraction.
REFERENCES
[0156] The following references are incorporated by reference
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(2004). [0161] 5. Jpn. J. Appl. Phys., 45, L1084-L1086 (2006).
[0162] 6. Jpn. J. Appl. Phys., 34, L797-99 (1995). [0163] 7. Jpn.
J. Appl. Phys., 43, L180-82 (2004). [0164] 8. Fujii T., Gao Y.,
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extraction efficiency of GaN-based light-emitting diodes via
surface roughening," Applied Physics Letters, vol. 84, no. 6, 9
Feb. 2004, pp. 855-7.
CONCLUSION
[0165] 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.
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