(12) United States Patent
`Slater, Jr. et al.
`
`US006791119B2
`(io) Patent No.:
`US 6,791,119 B2
`(45) Date of Patent:
`Sep. 14,2004
`
`(54) LIGHT EMITTING DIODES INCLUDING
`MODIFICATIONS FOR LIGHT
`EXTRACTION
`
`(75)
`
`Inventors: David B. Slater, Jr., Raleigh, NC (US);
`Robert C. Glass, Chapel Hill, NC
`(US); Charles M. Swoboda,
`Morrisville, NC (US); Bernd Keller,
`Goleta, CA (US); James Ibbetson,
`Goleta, CA (US); Brian Thibeault,
`Santa Barbara, CA (US); Eric J. Tarsa,
`Goleta, CA (US)
`
`(73) Assignee: Cree, Inc., Durham, NC (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 10/057,821
`(22) Filed:
`Jan. 25, 2002
`Prior Publication Data
`(65)
`US 2002/0123164 Al Sep. 5, 2002
`
`Related U.S. Application Data
`(60) Provisional application No. 60/307,235, filed on Jul. 23,
`2001, and provisional application No. 60/265,707, filed on
`Feb. 1, 2001.
`(51) Int. CI.7
`(52) U.S. CI
`(58) Field of Search
`
`H01L 33/00
`257/99; 257/95; 257/98
`257/95, 98, 99
`
`(56)
`
`References Cited
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`Light-Emitting
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`Primary Examiner—Jerome Jackson
`(74) Attorney, Agent, or Firm—Myers Bigel Sibley &
`Sajovec
`(57)
`
`ABSTRACT
`
`Light emitting diodes include a substrate having first and
`second opposing faces and that is transparent to optical
`radiation in a predetermined wavelength range and that is
`patterned to define, in cross-section, a plurality of pedestals
`that extend into the substrate from the first face towards the
`second face. A diode region on the second face is configured
`to emit light in the predetermined wavelength range, into the
`substrate upon apphcation of voltage across the diode
`region. Amounting support on the diode region, opposite the
`substrate is configured to support the diode region, such that
`the light that is emitted from the diode region into the
`substrate, is emitted from the first face upon apphcation of
`voltage across the diode region. The first face of the sub­
`strate may include therein a plurality of grooves that define
`the plurality of triangular pedestals in the substrate. The
`grooves may include tapered sidewalk and/or a beveled
`floor. The first face of the substrate also may include therein
`an array of via holes. The via holes may include tapered
`sidewalls and/or a floor.
`104 Claims, 15 Drawing Sheets
`
`1750
`
`1738'
`bonding
`1736
`barrier
`1734-
`adhesion
`1700
`\ 1732\ Ohmic/reflector
`
`1730
`
`1724
`
`1310a
`
`1310
`
`1722
`
`1310b L
`
`1320
`
`Ohmic
`reflector
`barrier
`
`bonding
`
`1726
`
`1742
`
`1744^ "
`
`1746
`
`1748
`
`210
`
`1740
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`US 6,791,119 B2
`Page 2
`
`. 372/45
`. 307/86
`. 257/99
`. 257/77
`. 257/76
`. 257/77
`257/77
`. 437/22
`438/33
`. 117/84
`257/103
`
`257/749
`. 257/96
`. 216/24
`430/321
`257/95
`. 257/98
`257/89
`. 438/29
`257/98
`. 257/98
`257/98
`. 257/98
`323/312
`. 117/89
`. 257/99
`. 257/99
`257/103
`362/231
`325/225
`. 257/79
`. 257/77
`. 438/46
`. 257/94
`. 257/97
`. 257/98
`. 257/98
`. 257/94
`. 257/99
`. 257/79
`
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`61110476
`5/1986
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`06-232510
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`07-235729
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`12/1996
`08-321660
`3/1997
`9-82587
`09-223846
`8/1997
`10-163530
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`9/1998
`9/1998
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`6/1999
`11-150302 A
`11-191641
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`
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`
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`6/2001
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`OTHER PUBLICATIONS
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`cal Transitions Between Low-Lying Conduction Bands in
`n—Type Doped SiC Polytypes, Materials Science Forum,
`vols. 264-268, 1998, pp. 271-274.
`Craford, Overview of Device Issues in High-Brightness
`Light-Emitting Diodes, Chapter 2, High Brightness Light
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`Stringfellow et al. ed., Academic Press, 1997, pp. 47-63.
`Yoo et al., Bulk Crystal Growth of 61 ISiC on Polytype—
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`pp. 733-739.
`Biederman, The Optical Absorption Bands and Their Anisot-
`ropy in the Various Modifications of SiC, Solid State Com­
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`U.S. application Ser. No. 09/154,363, entitled Vertical
`Geometry InGaN LED.
`U.S. application Ser. No. 60,411,980, filed Sep. 19, 2002,
`Phosphor-Coated Light Emitting Diodes Including Tapered
`Sidewalls, and Fabrication Methods.
`U.S. application Ser. No. 10/003,331, filed Oct. 31, 2001,
`Low Temperature Formation of Backside Ohmic Contacts
`for Vertical Devices.
`U.S. application Ser. No. 60/294,445, filed May 30, 2001,
`Multi-Quantum Well Light Emitting Diode Structure.
`U.S. application Ser. No. 60/294,378, filed May 30, 2001,
`Light Emitting Diode Structure With Multi-Quantum Well
`and Superlattice Structure.
`U.S. application Ser. No. 60/294,308, filed May 30, 2001,
`Light Emitting Diode Structure With Superlattice Structure.
`U.S. application Ser. No. 09/787,189, filed Mar. 15, 2001,
`Low Temperature Formation of Backside Ohmic Contacts
`for Vertical Devices.
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`International Search Report, PCT/US02/02849, Dec. 2,
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`Mensz et al., In;l:GA1_;lJV/A/),GA1_yA/ Violet Light Emitting
`Diodes with Reflective p—Contacts for High Single Sided
`Light Extraction, Electronics Letters, vol. 33, No. 24, Nov.
`20, 1997, pp. 2066-2068.
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`for Flip—Chip Interconnection, Electronic Manufacturing
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`International, lS,h IEEE/CPMT, Dec. 4, 1995, pp. 113-116.
`Lee et al., Bonding of InP Laser Diodes byAu—Sn Solder and
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`ductor Science and Technology, vol. 9, No. 4, Apr. 1994, pp.
`379-386.
`* cited by examiner
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 1 of 15
`
`US 6,791,119 B2
`
`100
`
`\
`
`160
`
`FIG. 1
`
`p-GaN
`Active
`
`n-GaN
`
`150
`
`140
`^130 \ i7 0
`120
`
`SiC
`
`110b
`
`110
`
`110a
`
`FIG. 2
`200 \
`
`110a
`\
`
`110
`L
`
`282
`
`280
`
`170
`
`110b
`
`250
`
`120
`130
`240
`X
`140
`
`150
`
`220
`
`210
`
`^160
`
`230
`
`260
`
`270
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 2 of 15
`
`US 6,791,119 B2
`
`FIG. 3
`282
`
`390
`
`160'
`
`X
`
`110a /
`
`250
`
`110b
`Z
`
`280
`
`/
`
`230
`
`270
`
`300
`\
`
`170
`
`110
`\
`{ 120
`\
`130
`240
`X
`140
`
`150
`
`220
`
`210
`
`260
`
`FIG. 13
`
`1330 X
`
`1320a J
`
`1300
`
`\
`1310b
`
`1310a
`X
`
`1320
`
`1310
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 3 of 15
`
`US 6,791,119 B2
`
`FIG. 4
`
`7
`HOa
`110b 1
`
`400
`
`410
`
`130,
`140
`412
`414
`155
`220
`
`500
`
`FIG. 5
`110a
`
`110'
`
`130
`140
`410
`155
`220
`
`110
`
`120
`
`160
`
`155
`
`210
`
`110c
`
`120
`
`y l 6 0
`
`155
`/ 230
`
`210
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`K)
`W
`
`so
`
`d cn
`
`*"b
`O
`
`sr
`
`CZ3
`
`fD
`fD
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`
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`
`0
`ft
`
`cc
`d
`
`550
`
`500
`
`450
`
`400
`
`350
`
`Wavelength (nm)
`
`i » « »
`
`4H-LD
`4H-HD
`
`-hr- 6H
`
`FIG. 6
`
`0.0
`
`0.2
`
`0.4
`
`Absorption 0.6
`
`(a.u.)
`
`0.8
`
`1.0
`
`1.2
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 5 of 15
`
`US 6,791,119 B2
`
`FIG. 7A
`
`720
`
`\
`
`722
`
`710a
`/
`730
`
`7B
`A
`!
`
`730
`
`730
`
`7B'
`A
`
`730
`
`710a
`
`720
`
`FIG. 7B
`
`700
`
`730
`
`724
`
`722
`
`710b \
`
`710
`740
`
`730
`
`730
`
`722
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 6 of 15
`
`US 6,791,119 B2
`
`720
`
`FIG. 7C
`
`7103' \
`
`700'
`
`730
`
`724'
`
`.722'
`
`730'
`
`730
`
`722'
`
`710'
`740
`
`710b \
`
`FIG. 8C
`
`SlOa'
`
`800'
`
`820
`
`/
`
`824
`
`822
`
`810
`
`840
`
`810b
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 7 of 15
`
`US 6,791,119 B2
`
`FIG. 8A
`
`8B
`4
`i
`
`^
`
`)
`
`x
`
`824
`
`822
`
`824
`
`810a
`
`o
`
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`
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`
`o
`
`o
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`
`SB'
`4
`i
`
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`^
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`(
`
`ZJ
`
`810a
`
`820
`
`FIG. 8B
`
`824
`
`822
`
`810
`
`840
`
`810b
`
`800
`
`800
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 8 of 15
`
`US 6,791,119 B2
`
`FIG. 9
`
`7103'
`
`720
`
`900
`
`710
`
`740
`
`724'
`
`730
`
`730
`
`730
`
`722'
`
`722'
`
`710b i
`
`FIG. 10
`
`810a
`
`1010
`
`1001
`
`820 /
`
`824
`
`822
`
`810
`
`840
`
`810b
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 9 of 15
`
`US 6,791,119 B2
`
`FIG. 11
`
`710a
`\
`
`110i
`
`720
`
`730
`
`724
`
`730
`
`730
`
`722
`
`722
`
`710b \
`
`210
`
`710
`
`740
`412
`414
`155
`220
`
`FIG. 12
`
`810a
`
`1200
`
`820
`
`/
`
`824
`
`810b
`
`810
`
`840
`412
`414
`155
`220
`
`822
`
`210
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 10 of 15
`
`US 6,791,119 B2
`
`FIG. 14A
`
`720
`
`710a
`\
`
`140'
`
`730
`
`724 730
`722
`
`722
`
`730
`
`710b
`
`710
`
`740
`
`1420
`
`1410
`
`1430 1410
`
`FIG. 14B
`
`1400
`
`14A
`•
`
`'"x
`N
`
`V
`
`V
`
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`
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`
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`
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`
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`
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`
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`
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`
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`
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`
`V
`
`HA'
`4
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 11 of 15
`
`US 6,791,119 B2
`
`810a
`
`1500-
`
`820
`
`/
`
`824
`
`822
`
`I
`
`810
`
`840
`
`810b
`
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`
`1510
`
`FIG. 15A
`
`FIG. 15B
`
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`
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`
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`
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`
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`
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`
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`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 12 of 15
`
`US 6,791,119 B2
`
`FIG. 1 6
`
`1600
`\
`
`150
`
`170 <
`
`240
`130
`120
`
`1620
`
`110
`\
`
`160n
`140
`\1610x
`
`230
`
`210
`
`Ohmic
`P-GaN
`Active
`n-GaN
`
`SiC
`
`Ohmic
`reflector
`barrier
`bonding
`
`282
`
`390
`
`280 /
`
`220
`/
`
`270
`
`260
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 13 of 15
`
`US 6,791,119 B2
`
`1310a
`
`1730b
`
`1730a
`
`FIG. 17B
`
`FIG. 17A
`
`>1730
`
`1724
`
`1730b
`
`1750 y:
`
`bonding
`barrier
`adhesion
`Ohmic/reflector
`
`1310a
`
`1310
`
`1722
`
`1310b
`
`/
`
`1320
`
`Ohmic
`reflector
`barrier
`
`bonding
`
`1738
`1736
`1734
`
`1700
`
`\ 1732\
`
`1726
`
`1742
`
`1744
`
`1746
`
`1748
`
`210
`
`1740 C
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 14 of 15
`
`US 6,791,119 B2
`
`1800
`
`1822
`
`1824
`
`1826
`1828
`
`1830
`
`FIG. 1 8
`
`1840
`
`bonding
`
`barrier
`
`adhesion
`
`reflector
`Ohmic
`1320
`
`1310
`
`\ 1820
`
`1812^^
`
`1814^
`
`1816^^
`
`adhesion
`
`barrier
`bonding
`
`> 1810
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`U.S. Patent
`
`Sep. 14,2004
`
`Sheet 15 of 15
`
`US 6,791,119 B2
`
`FIG. 19
`
`LED Manufacturing
`
`V
`
`Fabricate diode region on
`silicon carbide substrate
`
`Form grooves and/or
`via holes
`
`i f
`Form semi-transparent
`electrode and/or reflector
`
`Dice
`
`Join
`
`Package
`
`X
`End
`
`1910
`
`1920
`
`1930
`
`1940
`
`1950
`
`1960
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`CROSS-REFERENCE TO PROVISIONAL
`APPLICATIONS
`
`5
`
`BACKGROUND OF THE INVENTION
`
`US 6,791,119 B2
`
`1
`LIGHT EMITTING DIODES INCLUDING
`MODIFICATIONS FOR LIGHT
`EXTRACTION
`
`FIELD OF THE INVENTION
`This invention relates to microelectronic devices and
`fabrication methods therefor, and more particularly to light
`emitting diodes (LEDs) and manufacturing methods there­
`for.
`
`2
`and high etch selectivity also may be used to allow the
`removal of at least some of the substrate if it is optically
`absorbent. Distributed Bragg reflectors also have been
`grown between an absorbing substrate and the diode region
`to decouple the emitting and absorbing regions.
`Other approaches for light extraction may involve
`mechanical shaping or texturing of the diode region and/or
`This application claims the benefit of Provisional Appli­
`the substrate. However, it may be desirable to provide other
`cation Serial No. 60/265,707, filed Feb. 1, 2001 entitled
`light extraction techniques that can allow further improve-
`Light Emitting Diode With Optically Transparent Silicon
`ments in extraction efficiency. Moreover, it may be desirable
`Carbide Substrate, and Provisional Application Serial No.
`to increase the area of an LED chip from about 0.1 mm2 to
`60/307,235, filed Jul. 23, 2001, entitled Light Emitting
`larger areas, to thereby provide larger LEDs. Unfortunately,
`Diodes Including Modifications for Light Extraction and
`the effectiveness of these shaping techniques may not be
`Manufacturing Methods Therefor, the disclosures of both of
`maintained as the chip dimensions are scaled up for higher
`which are hereby incorporated herein by reference in their l5 power/intensity and/or other applications,
`entirety as if set forth fully herein.
`Much development interest and commercial activity
`recently has focused on LEDs that are fabricated in or on
`STATEMENT OF FEDERAL SUPPORT
`silicon carbide, because these LEDs can emit radiation in the
`blue/green portions of the visible spectrum. See, for
`This invention was made possible with government sup­
`port under grant number 70NANB8H4022 from the 20 example, U.S. Pat. No. 5,416,342 to Edmond et al., entitled
`Blue Light-Emitting Diode With High External Quantum
`National Institute of Standards and Technology (Advanced
`Efficiency, assigned to the assignee of the present
`Technology Program). The United States government has
`application, the disclosure of which is hereby incorporated
`certain rights to this invention.
`herein by reference in its entirety as if set forth fully herein.
`25 There also has been much interest in LEDs that include
`gallium nitride-based diode regions on silicon carbide
`substrates, because these devices also may emit light with
`high efficiency. See, for example, U.S. Pat. No. 6,177,688 to
`Linthicum et al., entitled Pendeoepitaxial Gallium Nitride
`30 Semiconductor Layers On Silicon Carbide Substrates, the
`disclosure of which is hereby incorporated herein by refer­
`ence in its entirety as if set forth fully herein.
`in such silicon carbide LEDs or gallium nitride LEDs on
`Light emitting diodes are widely used in consumer and
`siiicon carbide, it may be difficult to use conventional
`commercial applications. As is well known to those having
`skill in the art, a light emitting diode generally includes a 35 techniques for light extraction. For example, it may be
`diode region on a microelectronic substrate. The microelec­
`difficult to use thick p-type window layers because of the
`tronic substrate may comprise, for example, gallium
`relatively low growth rate of gallium nitride. Also, although
`arsenide, gallium phosphide, alloys thereof, silicon carbide
`such LEDs may benefit from the use of Bragg reflectors
`and/or sapphire. Continued developments in LEDs have
`and/or substrate removal techniques, it may be difficult to
`resulted in highly efficient and mechanically robust light 40 fabricate a reflector between the substrate and the gallium
`sources that can cover the visible spectrum and beyond.
`nitride diode region and/or to etch away at least part of the
`These attributes, coupled with the potentially long service
`silicon carbide substrate.
`life of solid state devices, may enable a variety of new
`U.S. Pat. No. 4,966,862 to Edmond, entitled Method of
`Production of Light Emitting Diodes, assigned to the
`display applications, and may place LEDs in a position to
`compete with the well entrenched incandescent and fluores-
`45 assignee of the present application, the disclosure of which
`cent lamps.
`hereby incorporated herein by reference in its entirety as
`One measure of efficiency of LEDs is the cost per lumen.
`if set forth fully herein, describes a method for preparing a
`The cost per lumen for an LED may be a function of the
`plurality of light emitting diodes on a single substrate of a
`manufacturing cost per LED chip, the internal quantum
`semiconductor material. The method is used for structures
`efficiency of the LED material and the ability to couple or 50 where the substrate includes an epitaxial layer of the same
`extract the generated light out of the device. An overview of
`semiconductor material that in turn comprises layers of
`light extraction issues may be found in the textbook entitled
`p-type and n-type material that define a p-n junction ther­
`High Brightness Light Emitting Diodes to Stringfellow et al.,
`ebetween. The epitaxial layer and the substrate are etched in
`Academic Press, 1997, and particularly Chapter 2, entitled
`a predetermined pattern to define individual diode
`Overview of Device Issues in High-Brightness Light Emit- 55 precursors, and deeply enough to form mesas in the epitaxial
`ting Diodes, to Craford, at pp. 47-63.
`layer that delineate the p-n junctions in each diode precursor
`from one another. The substrate is then grooved from the
`Light extraction has been accomplished in many ways,
`side of the epitaxial layer and between the mesas to a
`depending, for example, on the materials that are used to
`predetermined depth to define side portions of diode pre-
`fabricate the diode region and the substrate. For example, in
`gallium arsenide and gallium phosphide material systems, a 60 cursors in the substrate while retaining enough of the
`thick, p-type, topside window layer may be used for light
`substrate beneath the grooves to maintain its mechanical
`extraction. The p-type window layer may be grown because
`stability. Ohmic contacts are added to the epitaxial layer and
`high epitaxial growth rates may be possible in the gallium
`to the substrate and a layer of insulating material is formed
`arsenide/gallium phosphide material systems using liquid
`on the diode precursor. The insulating layer covers the
`and/or vapor phase epitaxy. Moreover, current spreading 65 portions of the epitaxial layer that are not covered by the
`may be achieved due to the conductivity of the p-type
`ohmic contact, any portions of the one surface of the
`topside window layer. Chemical etching with high etch rates
`substrate adjacent the mesas, and the side portions of the
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`US 6,791,119 B2
`
`3
`4
`substrate. As a result, the junction and the side portions of
`In yet other embodiments of the invention, a reflector also
`is provided between the mounting support and the diode
`the substrate of each diode are insulated from electrical
`region or the substrate. The reflector may be configured to
`contact other than through the ohmic contacts. When the
`reflect light that is emitted from the diode region back
`diodes are separated they can be conventionally mounted
`with the junction side down in a conductive epoxy without 5
`through the diode region, through the substrate and from the
`pedestals, upon application of voltage across the diode
`concern that the epoxy will short circuit the resulting diode.
`region. In other embodiments, a transparent electrode also
`See the abstract of U.S. Pat. No. 4,966,862.
`may be provided between the diode region and the reflector.
`U.S. Pat. No. 5,210,051 to Carter, Jr., entitled High
`In still other embodiments, a solder preform and/or other
`Efficiency Light Emitting Diodes From Bipolar Gallium
`bonding region may be provided between the reflector and
`Nitride, assigned to the assignee of the present application,
`the mounting support and/or an optical element such as a
`the disclosure of which is hereby incorporated herein by
`window or lens may be provided adjacent the first face
`reference in its entirety as if set forth fully herein, describes
`opposite the diode region. In yet other embodiments, the
`a method of growing intrinsic, substantially undoped single
`diode region includes a peripheral portion and at least one
`17
`crystal gallium nitride with a donor concentration of 7x10
`central portion that is enclosed by the peripheral portion, and
`cm3 or less. The method comprises introducing a source of 15
`the light emitting diode further comprises at least one
`nitrogen into a reaction chamber containing a growth surface
`electrode on the diode region, that is confined to within the
`while introducing a source of gallium into the same reaction
`at least one central portion and does not extend onto the
`chamber and while directing nitrogen atoms and gallium
`peripheral portion. It will be understood that the central
`atoms to a growth surface upon which gallium nitride will
`portion need not be centered on the diode region.
`grow. The method further comprises concurrently maintain- 20
`In other embodiments of the invention, a contact structure
`ing the growth surface at a temperature high enough to
`for the substrate and/or the diode region of an LED includes
`provide sufficient surface mobility to the gallium and nitro­
`a transparent ohmic region, a reflector, a barrier region and
`gen atoms that strike the growth surface to reach and move
`a bonding region. The transparent ohmic region provides
`into proper lattice sites, thereby establishing good
`electrical contact and/or current spreading. The reflector
`crystallinity, to establish an effective sticking coefScient, 25
`reflects at least some incident radiation and also may provide
`and to thereby grow an epitaxial layer of gallium nitride on
`current spreading. The barrier region protects the reflector
`the growth surface, but low enough for the partial pressure
`and/or the ohmic region. The bonding region bonds the LED
`of nitrogen species in the reaction chamber to approach the
`package to a mounting support. In some embodiments, the
`equilibrium vapor pressure of those nitrogen species over
`functionality of the transparent ohmic region and the reflec­
`gallium nitride under the other ambient conditions of the 30
`tor can be combined in a single ohmic and reflector region.
`chamber to thereby minimize the loss of nitrogen from the
`Contact structures according to these embodiments of the
`gallium nitride and the nitrogen vacancies in the resulting
`invention also may be used with conventional silicon car­
`epitaxial layer. See the abstract of U.S. Pat. No. 5,210,051.
`bide LEDs, gallium nitride on silicon carbide LEDs and/or
`In view of the above discussion, improved light extraction
`35 other LEDs.
`techniques may be desirable for LEDs, especially LEDs that
`In still other embodiments of the present invention, the
`are fabricated from silicon carbide, that are fabricated from
`first face of the substrate may include therein at least one
`gallium nitride on silicon carbide and/or that have a rela­
`groove that defines a plurality of pedestals, such as trian­
`tively large area.
`gular pedestals, in the substrate. The grooves may include
`SUMMARY OF THE INVENTION
`40 tapered sidewalls and/or a beveled floor. The first and second
`faces of the substrate may have square perimeters, and/or the
`Light emitting diodes according to some embodiments of
`first face of the substrate may be textured. The light emitting
`the invention include a substrate having first and second
`diode may further include a plurality of emission regions
`opposing faces that is transparent to optical radiation in a
`and/or electrodes on the diode region, a respective one of
`predetermined wavelength range and that is patterned to
`define, in cross-section, a plurality of pedestals that extend 45 which is confined to within a respective one of the pedestals
`and does not extend beyond the respective one of the
`into the substrate from the first face towards the second face.
`pedestals.
`As used herein, the term "transparent" refers to an element,
`In yet other embodiments of the present invention, the
`such as a substrate, layer or region that allows some or all
`first face of the substrate includes therein an array of via
`optical radiation in a predetermined wavelength range to
`pass therethrough, i.e., not opaque. A diode region on the 50 holes. The via holes may include tapered sidewalls and/or a
`floor. The via holes preferably extend only part way through
`second face is configured to emit light in the predetermined
`the substrate, but in other embodiments they can extend all
`wavelength range, into the substrate upon application of
`the way through the substrate. The first and second substrate
`voltage across the diode region. In other embodiments, a
`faces may have square perimeters, and/or the first face may
`mounting support on the diode region, opposite the substrate
`is configured to support the diode region, such that the light 55 be textured. The light emitting diodes may further include at
`least one electrode on the diode region that does not overlap
`that is emitted from the diode region into the substrate, is
`the array of via holes.
`emitted from the first face upon application of voltage across
`the diode region. In some embodiments, the light emitting
`The pedestals and/or array of via holes also may be used
`diode on a transparent substrate with pedestals is flip-
`with light emitting diodes that include silicon carbide or
`mounted on a mounting support, with the diode region 60 non-silicon carbide substrates, to allow improved light
`adjacent to the mounting support and a substrate opposite
`extraction therefrom. Moreover, electrodes as described
`the mounting support, for light emission through the sub­
`above also may be used with light emitting diodes that
`strate. In other embodiments, the light emitting diode on a
`include a non-silicon carbide substrate. For example, when
`transparent substrate with pedestals is mounted on a mount­
`the first face of the substrate has smaller surface area than
`ing support, with the substrate adjacent to the mounting 65 the second face, and the diode region is on the second face,
`support and the diode region opposite the mounting support.
`an emission region may be provided on the diode region that
`is confined to within the smaller surface area of the first face.
`Thus, non-flip-chip mounting also may be provided.
`
`EVERLIGHT ELECTRONICS CO., LTD. ET AL.
`Exhibit 1012
`
`

`

`US 6,791,119 B2
`
`6
`textured. An electrode may be formed on the diode region
`that does not overlap the array of via holes.
`Sawing a plurality of intersecting grooves and/or reactive
`etching an array of via holes into the first face may be used
`for light emitting diodes that include a silicon carbide or
`non-silicon carbide substrate to allow improved light extrac­
`tion therefrom. Moreover, the formation of an emission
`region on the diode region that is confined to within the
`smaller surface area of the first face also may be used for
`1° other conventional light emitting diodes, to allow improved
`light extraction therefrom.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`5
`In other embodiments of the present invention, light
`emitting diodes include a compensated, colorless silicon
`carbide substrate having first and second opposing faces and
`a gallium nitride-based diode region on the second face that
`is configured to emit light into the substrate upon application 5
`of voltage across the diode region. Mounting supports,
`reflectors, contact structures, grooves, pedestals, texturing
`and/or confined emission areas/electrodes may be provided
`according to any of the embodiments that were described
`above.
`Accordingly, many of the above-described embodiments
`comprise embodiments of means for extracting from the
`substrate at least some of the light that is emitted into the
`substrate by the diode region. Examples of these means for
`extracting include compensating dopants in the silicon car- 15
`bide substrate to provide a colorless silicon carbide
`substrate, patterning the substrate to define, in cross-section,
`a plurality of pedestals that extend into the substrate from the
`first face toward the second face and/or many of the other
`embodiments that were described above, including mount­
`ing supports, reflectors, contact structures, grooves,
`pedestals, texturing and/or confined emission areas/
`electrodes.
`Light emitting diodes may be manufactured, according to
`some embodiments of the invention, by forming a diode 25
`region that is configured to emit light in a predetermined
`wavelength range on a second face of a substrate having first
`and second opposing faces, and that is transparent to the
`optical radiation in the predetermined wavelength range.
`The substrate is patterned before, during and/or after form- 3Q
`ing the diode region to define, in cross-section, a plurality of
`face
`pedestals that extend into the substrate from the first
`towards the second face. In other embodiments, the diode
`region is mounted onto a mounting substrate that is config­
`ured to support the diode region such that the light that is 35
`emitted from the diode region into the substrate is emitted
`from the first
`face upon application of voltage across the
`diode region. The mounting may be preceded by forming a
`reflector on the diode region such that the reflector is
`configured to reflect light that is emitted from the diode
`region back into the diode region through the substrate and
`from the first
`face, upon application of voltage across the
`diode region. Prior to forming the reflector, a transparent
`ohmic electrode also may be formed on the diode region
`opposite the substrate. A barrier region and/or an adhesion
`region also may be formed after forming the reflector. In
`other embodiments, a mounting support is placed adjacent
`the reflector with the barrier region and/or the adhesion
`region therebetween, and the LED is joined to the mounting
`support. In still other embodiments, an electrode is formed 50
`on the diode region that is confined to within the central
`The present invention now will be described more fully
`portion thereof and does not extend onto the peripheral
`hereinafter with reference to the accompanying drawings, in
`portion thereof.
`which preferred embodiments of the invention are shown.
`Other method embodiments include forming a plurality of
`This invention may, however, be embodied