111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US007714345B2
`
`c12) United States Patent
`Negley
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7, 714,345 B2
`May 11,2010
`
`(54) LIGHT-EMITTING DEVICES HAVING
`COPLANAR ELECTRICAL CONTACTS
`ADJACENT TO A SUBSTRATE SURFACE
`OPPOSITE AN ACTIVE REGION AND
`METHODS OF FORMING THE SAME
`
`(75)
`
`Inventor: Gerald H. Negley, Carrboro, NC (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 235 days.
`
`(21) Appl. No.: 10/818,592
`
`(22) Filed:
`
`Apr. 6, 2004
`
`(65)
`
`Prior Publication Data
`
`US 2004/0217360Al
`
`Nov. 4, 2004
`
`Related U.S. Application Data
`
`5,631,190 A
`5,739,554 A
`
`5/1997 Negley ........................ 438/33
`4/1998 Edmond eta!. ............. 257/103
`
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`1 079 444 A2
`
`212001
`
`(Continued)
`
`OTHER PUBLICATIONS
`
`International Search Report and Written Opinion for PCT US2004/
`011357, Dec. 9, 2004.
`
`Primary Examiner-Allan R. Wilson
`(74) Attorney, Agent, or Firm-Myers Bigel Sibley &
`Sajovec
`
`(60) Provisional application No. 60/466,635, filed on Apr.
`30, 2003.
`
`(57)
`
`ABSTRACT
`
`(51)
`
`Int. Cl.
`HOJL 27115
`(2006.01)
`(52) U.S. Cl. ........... 257/99; 257/E33.062; 257/E33.066
`(58) Field of Classification Search . ... ... ... ... .. ... . 257/99,
`257/E33.062, E33.066
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4/1990 Edmond ...................... 257/77
`10/1990 Edmond ...................... 438/27
`6/1991 Edmond ..................... 257/103
`............. 438/22
`5/1993 Carter, Jr. et al.
`8/1994 Edmond eta!. ............... 257/76
`2/1995 Edmond eta!. ............... 257/77
`5/1995 Edmond eta!. ............... 257/76
`6/1996 Edmond eta!. ............... 257/77
`2/1997 Edmond eta!. ............... 438/45
`
`4,918,497 A
`4,966,862 A
`5,027,168 A
`5,210,051 A
`5,338,944 A
`5,393,993 A
`5,416,342 A
`5,523,589 A
`5,604,135 A
`
`A light-emitting device includes a substrate having first and
`second opposing surfaces. An active region is on the first
`surface and first and second electrical contacts are adjacent to
`the second surface and are conductively coupled to the active
`region. In other embodiments, a light-emitting device
`includes a substrate having first and second opposing sur(cid:173)
`faces. An active region is on the first surface and includes a
`first active layer having a first conductivity type on the first
`surface and a second active layer having a second conductiv(cid:173)
`ity type on the first active layer. A first electrical contact is
`adjacent to the second surface. A contact plug extends
`through the substrate and the active region and couples the
`first electrical contact to the second active layer. A second
`electrical contact is coupled to the substrate at the second
`surface .
`
`37 Claims, 5 Drawing Sheets
`
`235
`
`220
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`US 7,714,345 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`5,767,581 A
`5,912,477 A
`6,120,600 A
`6,177,688 B1
`6,187,606 B1
`6,201,262 B1
`6,303,485 B1
`6,455,343 B1 *
`6,630,366 B2 *
`6,657,236 B1 *
`6,812,502 B1 *
`
`6/1998 Nakamuraetal. .......... 257/749
`6/1999 Negley ........................ 257/95
`9/2000 Edmond eta!. ............... 117/89
`112001 Linthicum eta!. ............ 257/77
`212001 Edmond eta!. ............... 438/46
`3/2001 Edmond eta!. ............... 257/77
`10/2001 Sung eta!. .................. 438/604
`9/2002 Chen eta!. .................... 438/40
`10/2003 Taniguchi eta!. ............. 438/34
`12/2003 Thibeault eta!. .............. 257/98
`1112004 Chien eta!. ................... 257/99
`
`2002/0117681 A1
`2002/0121642 A1
`2002/0123164 A1
`2002/0135069 A1
`2003/0006418 A1
`2003/0222269 A1 *
`2004/0056260 A1
`
`8/2002 Weeks eta!. ................ 257/106
`9/2002 Doverspike et al ............ 257/97
`9/2002 Slater, Jr. eta!. .............. 438/39
`9/2002 Wood eta!. ................. 25717 58
`112003 Emerson et a!. ............... 257/79
`12/2003 Lin eta!. ...................... 257/99
`3/2004 Slater, Jr. et a!. .............. 257/79
`
`FOREIGN PATENT DOCUMENTS
`
`07030153
`JP
`* cited by examiner
`
`111995
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`U.S. Patent
`
`May 11, 2010
`
`Sheet 1 of 5
`
`US 7, 714,345 B2
`
`100
`
`/
`
`130
`
`t
`
`110b
`110a
`\
`
`J
`
`135
`120
`
`115
`
`1
`
`Substrate
`105
`
`FIG. 1
`(PRIOR ART)
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`U.S. Patent
`
`May 11,2010
`
`Sheet 2 of 5
`
`US 7, 714,345 B2
`
`220
`
`I/ 220
`
`I / 220
`
`235
`
`I 220
`
`Substrate
`205
`
`FIG. 2A
`
`225
`
`Substrate
`205
`
`FIG. 28
`
`230
`225
`
`Substrate
`205
`
`FIG. 2C
`
`230
`225
`
`Substrate
`205
`
`FIG. 20
`
`t
`
`210a
`210b
`\
`
`t
`210a
`210b
`\
`
`t
`210a
`210b
`\
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`U.S. Patent
`
`May 11, 2010
`
`Sheet 3 of 5
`
`US 7, 714,345 B2
`
`f
`210b
`210a
`\
`
`210b
`210a
`
`210b
`210a
`
`I! 220
`
`I! 235
`
`225
`230
`
`FIG. 2E
`
`220
`
`235
`
`220
`
`235
`
`FIG. 2F
`
`245
`
`225
`230
`
`FIG. 2G
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`U.S. Patent
`
`May 11,2010
`
`Sheet 4 of 5
`
`US 7, 714,345 B2
`
`240b
`
`220
`
`235
`
`220
`
`235
`
`220
`
`235
`
`FIG. 2H
`
`FIG. 21
`
`240b
`260
`
`FIG. 2J
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`U.S. Patent
`
`May 11, 2010
`
`Sheet 5 of 5
`
`US 7, 714,345 B2
`
`235
`
`230
`
`210a
`210b
`
`260
`240b
`FIG. 2K
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`US 7,714,345 B2
`
`1
`LIGHT-EMITTING DEVICES HAVING
`COPLANAR ELECTRICAL CONTACTS
`ADJACENT TO A SUBSTRATE SURFACE
`OPPOSITE AN ACTIVE REGION AND
`METHODS OF FORMING THE SAME
`
`RELATED APPLICATION
`
`This application claims the benefit of and priority to U.S.
`Provisional Patent Application No. 60/466,635, filed Apr. 30,
`2003, the disclosure of which is hereby incorporated herein
`by reference as if set forth in its entirety.
`
`2
`materials that form ohmic contacts to p-type gallium nitride
`and n-type gallium nitride may be used for ohmic contacts
`135 and 130, respectively.
`Examples of ohmic contacts ton-type gallium nitride lay(cid:173)
`ers and p-type gallium nitride layers are described, for
`example, in U.S. Pat. No. 5,767,581, the disclosure of which
`is hereby incorporated herein by reference.
`Unfortunately, LED devices that have coplanar electrical
`10 contacts on the active side (i.e., the diode region side) may use
`thicker diode regions than other vertical designed LEDs to
`reduce current crowding (i.e., forcing electrons to make sharp
`turns).
`
`BACKGROUND OF THE INVENTION
`
`15
`
`SUMMARY OF THE INVENTION
`
`The present invention relates generally to microelectronic
`devices and fabrication methods therefor, and, more particu(cid:173)
`larly, to light-emitting devices and fabrication methods there(cid:173)
`for.
`Light-emitting diodes (LEDs) are widely used in consumer
`and commercial applications. As is well known to those
`skilled in the art, a light-emitting diode generally includes a
`diode region on a microelectronic substrate. The microelec(cid:173)
`tronic substrate may comprise, for example, gallium arsenide,
`gallium phosphide, alloys thereof, silicon carbide, and/or sap(cid:173)
`phire. Continued developments in LEDs have resulted in
`highly efficient and mechanically robust light sources that can
`cover the visible spectrum and beyond. These attributes,
`coupled with the potentially long service life of solid state 30
`devices, may enable a variety of new display applications, and
`may place LEDs in a position to compete with well
`entrenched incandescent and fluorescent lamps.
`Referring now to FIG. 1, a conventional GaN-based LED 35
`100 comprises a substrate 105, such as sapphire (Al 20 3 ) or
`SiC, that has first and second opposing surfaces 11 Oa and lOb,
`respectively, and may be at least partially transparent to opti-
`cal radiation. A diode region, comprising ann-type layer 115
`and a p-type layer 120 is disposed on the second surface 11 Ob 40
`and is configured to emit optical radiation upon application of
`a voltage across the diode region, for example across ohmic
`contacts 130 and 135.
`The diode region including then-type layer 115 and/or the
`p-type layer 125 may comprise gallium nitride-based semi(cid:173)
`conductor layers, including alloys thereof, such as indium
`gallium nitride and/or aluminum indium gallium nitride. The
`fabrication of gallium nitride on SiC is known to those skilled
`in the art, and is described, for example, in U.S. Pat. No.
`6,177,688, the disclosure of which is hereby incorporated
`herein by reference. It will also be understood that a buffer
`layer or layers comprising aluminum nitride, for example,
`may be provided between then-type gallium nitride layer 115
`and the substrate 105, as described in U.S. Pat. Nos. 5,393,
`993, 5,523,589, 6,177,688, and application Ser. No. 09/154,
`363 entitled Vertical Geometry InGaN Light Emitting Diode,
`the disclosures of which are hereby incorporated herein by
`reference. Then-type gallium nitride layer 115 may comprise
`silicon-doped gallium nitride, while the p-type gallium
`nitride layer 120 may comprise magnesium-doped gallium 60
`nitride.
`In some LEDs, the ohmic contact 135 for the p-type gal(cid:173)
`lium nitride layer 120 comprises platinum, nickel and/or tita(cid:173)
`nium/gold. In other LEDs, a reflective ohmic contact com(cid:173)
`prising, for example, aluminum and/or silver, may be used. 65
`The ohmic contact 130 to then-type gallium nitride layer 115
`may comprise aluminum and/or titanium. Other suitable
`
`According to some embodiments of the present invention,
`a light-emitting device comprises a substrate having first and
`20 second Opposing surfaces. An active region is on the first
`surface and first and second electrical contacts are adjacent to
`the second surface and are conductively coupled to the active
`region. Advantageously, such configurations may allow elec-
`25 trical contacts to be coplanar on a non-active side of a sub(cid:173)
`strate, which may obviate the need to use relatively thick
`active regions to reduce current crowding when electrical
`contacts are made coplanar on a non-active side of the sub(cid:173)
`strate. As a result, more active devices may be formed on a
`single wafer.
`In other embodiments of the present invention, a light(cid:173)
`emitting device comprises a substrate having first and second
`opposing surfaces. An active region is on the first surface and
`comprises a first active layer having a first conductivity type
`on the first surface and a second active layer having a second
`conductivity type on the first active layer. A first electrical
`contact is adjacent to the second surface. A contact plug
`extends through the substrate and the active region and
`couples the first electrical contact to the second active layer. A
`second electrical contact is coupled to the substrate at the
`second surface.
`In still further embodiments, a dielectric spacer is disposed
`between the contact plug and the substrate and between the
`45 contact plug and the first active layer. The dielectric spacer
`may comprise a material, such as spin-on-glass, a polyimide,
`silicon-dioxide, and/or silicon-nitride.
`In still further embodiments, an ohmic contact layer is on
`50 the second active layer and the contact plug extends through
`the second active layer to contact the ohmic contact layer. The
`ohmic contact layer may comprise at least one of the follow(cid:173)
`ing materials: TiN, platinum, nickel/gold, nickel oxide/gold,
`nickel oxide/platinum, Ti, and titanium/gold. The ohmic con-
`55 tact layer may also have a thickness between about 10 A and
`about 100 A and may be at least partially transparent.
`In other embodiments, a buffer layer, which may comprise
`aluminum nitride, may be disposed between the active region
`and the substrate, such that the contact plug extends through
`the buffer layer.
`In further embodiments, the substrate comprises a conduc(cid:173)
`tive material, such as SiC, and the contact plug comprises a
`conductive material, such as gold, silver, gold alloys, and/or
`silver alloys. The first electrical contact may comprise plati(cid:173)
`num, nickel, and/or titanium/gold. The second electrical con(cid:173)
`tact may comprise aluminum and/or titanium.
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`BRIEF DESCRIPTION OF THE DRAWINGS
`
`5
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`40
`
`3
`Although described above primarily with respect to appa(cid:173)
`ratus aspects of the present invention, methods of forming
`light-emitting devices are also described herein.
`
`US 7,714,345 B2
`
`Other features of the present invention will be more readily
`understood from the following detailed description of spe(cid:173)
`cific embodiments thereof when read in conjunction with the
`accompanying drawings, in which:
`FIG. 1 is a cross-sectional diagram that illustrates a con(cid:173)
`ventional GaN-based light-emitting diode (LED); and
`FIGS. 2A-2K are cross sectional diagrams that illustrate
`light-emitting devices and methods of forming same in accor(cid:173)
`dance with various embodiments of the present invention.
`
`4
`regions may also be used in accordance with some embodi(cid:173)
`ments of the present invention.
`Examples of light-emitting devices that may be used in
`embodiments of the present invention include, but are not
`limited to, the devices described in the following U.S. Pat.
`Nos. 6,201,262, 6,187,606, 6,120,600, 5,912,477, 5,739,554,
`5,631,190, 5,604,135, 5,523,589, 5,416,342, 5,393,993,
`5,338,944, 5,210,051, 5,027,168, 5,027,168, 4,966,862 and/
`or4,918,497, the disclosures of which are incorporated herein
`by reference. Other suitable LEDs and/or lasers are described
`10 in U.S. patent application Ser. No. 10/140,796, entitled
`"GROUP III NITRIDE BASED LIGHT EMITTING DIODE
`STRUCTURES WITH A QUANTUM WELL AND SUPER(cid:173)
`LATTICE, GROUP III NITRIDE BASED QUANTUM
`WELL STRUCTURES AND GROUP III NITRIDE BASED
`15 SUPERLATTICE STRUCTURES", filed May 7, 2002, as
`well as U.S. patent application Ser. No. 10/057,821, filed Jan.
`25, 2002 entitled "LIGHT EMITTING DIODES INCLUD(cid:173)
`ING SUBSTRATE MODIFICATIONS FOR LIGHT
`EXTRACTION AND MANUFACTURING METHODS
`20 THEREFOR" the disclosures of which are incorporated
`While the invention is susceptible to various modifications
`herein as if set forth fully. Furthermore, phosphor coated
`LEDs, such as those described in U.S. patent application Ser.
`and alternative forms, specific embodiments thereof are
`shown by way of example in the drawings and will herein be
`No. 10/659,241 entitled "PHOSPHOR-COATED LIGHT
`EMITTING DIODES INCLUDING TAPERED SIDE-
`described in detail. It should be understood, however, that
`there is no intent to limit the invention to the particular forms
`WALLS, AND FABRICATION METHODS THEREFOR,"
`disclosed, but on the contrary, the invention is to cover all 25 filed Sep. 9, 2003, the disclosure of which is incorporated by
`modifications, equivalents, and alternatives falling within the
`reference herein as if set forth full, may also be suitable for
`spirit and scope of the invention as defined by the claims. Like
`use in embodiments of the present invention.
`numbers refer to like elements throughout the description of
`The LEDs and/or lasers may be configured to operate in a
`the figures. In the figures, the dimensions of layers and
`"flip-chip" configuration such that light emission occurs
`regions are exaggerated for clarity. Each embodiment 30 through the substrate. In such embodiments, the substrate
`described herein also includes its complementary conductiv-
`may be patterned so as to enhance light output of the devices
`ity type embodiment.
`as is described, for example, in U.S. patent application Ser.
`It will be understood that when an element such as a layer,
`No. 10/057,821, filed Jan. 25, 2002 entitled "LIGHT EMIT-
`region or substrate is referred to as being "on" another ele-
`TING DIODES INCLUDING SUBSTRATE MODIFICA-
`ment, it can be directly on the other element or intervening 35 TIONS FOR LIGHT EXTRACTION AND MANUFAC-
`elementsmay also be present. It will be understood that if part
`TURING METHODS THEREFOR" the disclosure of which
`of an element, such as a surface, is referred to as "inner," it is
`is incorporated herein by reference as if set forth fully herein.
`farther from the outside of the device than other parts of the
`Referring now to FIGS. 2A-2H, light-emitting devices and
`element. Furthermore, relative terms such as "beneath" or
`methods of forming same, in accordance with some embodi-
`"overlies" may be used herein to describe a relationship of
`ments of the present invention, will now be described. As
`one layer or region to another layer or region relative to a
`shown in FIG. 2A, a substrate 205, such as, for example, a SiC
`substrate or base layer as illustrated in the figures. It will be
`substrate, is provided. The substrate 205 has a first surface
`understood that these terms are intended to encompass dif-
`210a and a second surface 210b and may be at least partially
`ferent orientations of the device in addition to the orientation
`transparent to optical radiation. A buffer layer or layers 220
`depicted in the figures. Finally, the term "directly" means that
`comprising, for example, aluminum nitride may be formed on
`there are no intervening elements. As used herein, the term 45 the first surface 210a of the substrate 205 as described in the
`"and/or" includes any and all combinations of one or more of
`above-incorporated U.S. Pat. Nos. 5,393,993, 5,523,589,
`the associated listed items.
`6,177,688, and application Ser. No. 09/154,363 entitled Ver-
`It will be understood that, although the terms first, second,
`tical Geometry InGaN Light Emitting Diode.
`etc. may be used herein to describe various elements, com-
`Referring now to FIGS. 2B and 2C, an active region, such
`ponents, regions, layers and/or sections, these elements, com- 50 as, for example, a diode region comprising an n-type layer
`225 and a p-type layer 230 may be epitaxially grown on the
`ponents, regions, layers and/or sections should not be limited
`by these terms. These terms are only used to distinguish one
`buffer layer 220. The diode region, including then-type layer
`element, component, region, layer or section from another
`225 and/or the p-type layer 230 may comprise gallium
`region, layer or section. Thus, a first region, layer or section
`nitride-based semiconductor layers, including alloys thereof,
`discussed below could be termed a second region, layer or 55 such as indium gallium nitride, aluminum gallium nitride,
`section, and, similarly, a second without departing from the
`and/or aluminum indium gallium nitride. The fabrication of
`teachings of the present invention.
`gallium nitride layers is described, for example, in the above-
`Embodiments of the present invention will now be
`incorporated U.S. Pat. No. 6,177,688. Then-type gallium
`described, generally, with reference to GaN -based light-emit-
`nitride layer 225 may comprise silicon-doped gallium nitride,
`ting diodes (LEDs) on SiC-based substrates. The present
`while the p-type gallium nitride layer 230 may comprise
`invention, however, is not limited to such structures. Embodi- 60 magnesium-doped gallium nitride.
`ments of the invention may use other substrates including
`Referring now to FIG. 2D, an ohmic contact layer 235 may
`combinations, such as anAlGainP diode on a GaP substrate,
`be formed on the p-type gallium nitride layer 230. In accor-
`a GaN diode on a SiC substrate, an SiC diode on an SiC
`dance with various embodiments of the present invention, the
`substrate, and/or a nitride-based diode on a gallium nitride,
`ohmic contact layer 235 may comprise TIN, platinum, nickel/
`silicon carbide, aluminum nitride, zinc oxide and/or other 65 gold, nickel oxide/gold, nickel oxide/platinum, Ti, titanium/
`substrate. Moreover, the present invention is not limited to the
`gold and/or alloys thereof. The ohmic contact layer 235 may
`have a thickness between about 10 A and about 100 A and
`use of a diode region as an active region. Other types of active
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`US 7,714,345 B2
`
`6
`embodied as described in the above-referenced patents and/or
`applications. Moreover, additional layers, such as lattice
`strain layers, may also be incorporated in light-emitting
`devices in accordance with further embodiments of the
`present invention.
`In concluding the detailed description, it should be noted
`that many variations and modifications can be made to the
`preferred embodiments without substantially departing from
`the principles of the present invention. All such variations and
`modifications are intended to be included herein within the
`10 scope of the present invention, as set forth in the following
`claims.
`
`25
`
`5
`may be at least partially transparent to optical radiation in
`accordance with some embodiments of the present invention.
`Referring now to FIG. 2E, a via is formed through the
`substrate 205, the buffer layer 220, and the diode region 225,
`230. In some embodiments, the via may be formed by etching
`the substrate 205, the buffer layer 220, and the diode region
`225, 230 using the ohmic contact layer 235 as an etch stop
`layer. Various etching techniques may be used in accordance
`with different embodiments of the present invention, includ(cid:173)
`ing, but not limited to, wet etching, dry etching, and micro(cid:173)
`machining.
`Referring now to FIGS. 2F-2H, exemplary operations for
`forming a dielectric spacer on sides of the via will now be
`described. As shown in FIG. 2F, the via is at least partially
`filled with a dielectric material 240. By using, for example,
`sol-gel technology, spin-on-glass, a polyimide material, sili- 15
`con dioxide and/or silicon nitride the dielectric material 240
`may be formed in the via in the liquid state and later etched
`after curing to a solid. A mask 245 is formed on the second
`surface 210b of the substrate 205 and patterned so as to
`expose a portion of the dielectric material 240 as shown in 20
`FIG. 2G. Referring now to FIG. 2H, the dielectric material
`240 is etched through the mask 245 so as to leave a dielectric
`spacer 240a and 240b on sides of the via. Various etching
`techniques may be used in accordance with different embodi(cid:173)
`ments of the present invention, including, but not limited to,
`wet etching, dry etching, and micro-machining.
`Referring now to FIG. 2I, a contact plug 250 is formed in
`the via by, for example, plating the via with a conductive
`material, such as gold, silver, gold alloys, and/or silver alloys,
`in accordance with some embodiments of the present inven(cid:173)
`tion.
`Referring now to FIG. 21, a first electrical contact 255 is
`formed adjacent to the second surface 210b such that the
`contact plug 250 couples the first electrical contact 255 to the
`p-type gallium nitride layer 230 via the ohmic contact layer
`235. Advantageously, because the ohmic contact layer 235 35
`contacts the p-type gallium nitride layer 230 across a rela(cid:173)
`tively broad surface area, improved current spreading may be
`provided. The first electrical contact 255 for the p-type gal(cid:173)
`lium nitride layer 230 may comprise platinum, nickel, tita(cid:173)
`nium/gold and/or alloys thereof. In other embodiments, a
`reflective ohmic contact comprising, for example, alumilium
`and/or silver, may be used to implement the first electrical
`contact 255.
`As shown in FIG. 21, one or more second electrical
`contact(s) 260 are formed on the second surface 210b of the
`substrate 205. The second electrical contact(s) 260 for the
`n-type gallium nitride layer 225 may comprise aluminum,
`titanium and/or alloys thereof. Other suitable materials that
`form ohmic contact ton-type gallium nitride may be used for
`the second electrical contact(s) 260. Examples of ohmic con(cid:173)
`tacts to n-type gallium nitride layers and p-type gallium 50
`nitride layers are described, for example, in the above-incor(cid:173)
`porated U.S. Pat. No. 5,767,581. FIG. 2K shows the structure
`of FIG. 21 inverted with the diode region on top of the sub(cid:173)
`strate 205.
`Advantageously, light-emitting devices, according to some 55
`embodiments of the present invention, may allow electrical
`contacts to be coplanar on a non-active side of a substrate,
`which may obviate the need to use relatively thick diode
`regions to reduce current crowding when electrical contacts
`are made coplanar on the active side of the substrate. As a
`result, more active devices may be formed on a single wafer. 60
`Embodiments of the invention have been described above
`in which a diode is shown as an example of an active region.
`It should be understood, however, that an active region may
`include, but is not limited to, quantum wells, heterojunctions,
`homojunctions, multiple layers, combinations of the forego(cid:173)
`ing, or the like, in accordance with some embodiments of the
`present invention. For example, layers 225 and 230 may be
`
`30
`
`40
`
`That which is claimed:
`1. A light-emitting device, comprising:
`first and second opposing surfaces of a layer;
`an active region comprising a first active layer having a first
`conductivity type on the first surface and a second active
`layer having a second conductivity type on the first
`active layer;
`a first electrical contact adjacent to the second surface;
`a partially transparent current spreading layer on the sec(cid:173)
`ond active layer;
`a contact plug that is substantially non-adjacent an edge of
`the active region and extending through the active region
`to contact the current spreading layer so as to couple the
`first electrical contact to the second active layer; and
`a second electrical contact that is coupled to the second
`surface without extending through the second surface,
`wherein the current spreading layer forms an ohmic con(cid:173)
`tact with the second active layer, and
`wherein the ohmic contact comprises a reflective ohmic
`contact.
`2. The light-emitting device of claim 1, further comprising
`a dielectric spacer on sides of the contact plug that separate
`the contact plug from the first active layer and in contact
`with the current spreading layer,
`wherein the dielectric spacer comprises spin-on-glass and/
`or a polyimide.
`3. The light-emitting device of claim 1, wherein the ohmic
`contact layer comprises at least one of TiN, platinum, nickel/
`gold, nickel oxide/gold, nickel oxide/platinum, Ti, and tita(cid:173)
`nium/gold.
`4. The light-emitting device of claim 3, wherein the ohmic
`contact layer has a thickness between about 10 A and about
`45 100 A.
`5. The light-emitting device of claim 1, further comprising:
`a buffer layer adjacent the active region, the contact plug
`extending through the buffer layer.
`6. The light-emitting device of claim 5, wherein the buffer
`layer comprises aluminum nitride.
`7. The light-emitting device of claim 1, further comprising
`a substrate comprising the first and second opposing surfaces,
`wherein the substrate comprises SiC.
`8. The light-emitting device of claim 1, wherein the contact
`plug comprises gold, silver, a gold alloy, and/or a silver alloy.
`9. The light-emitting device of claim 1, wherein the first
`conductivity type is n-type, and wherein the second electrical
`contact comprises at least one of aluminum and titanium.
`10. The light-emitting device of claim 1, wherein the sec-
`ond conductivity type is p-type, and wherein the first electri(cid:173)
`cal contact comprises at least one of platinum, nickel, and
`titanium/gold.
`11. The light-emitting device of claim 1, wherein the first
`65 active layer comprises GaN.
`12. The light-emitting device of claim 1, wherein the sec(cid:173)
`ond active layer comprises GaN.
`
`EVERLIGHT ELECTRONICS CO., LTD.
`Exhibit 1013
`
`

`

`US 7,714,345 B2
`
`25
`
`30
`
`7
`13. A light-emitting device, comprising:
`first and second opposing surfaces of a layer;
`an active region on the first surface, the active region
`including a first active layer having a first conductivity
`type on the first surface and a second active layer having
`a second conductivity type on the first active layer;
`a partially transparent current spreading layer on the sec(cid:173)
`ond active layer of the active region, the current spread(cid:173)
`ing layer including a reflective ohmic contact that is
`substantially non-adjacent an edge of the active region; 10
`and
`first and second electrical contacts adjacent to the second
`surface that are conductively coupled to the active
`region, at least one of the first and second electrical
`contacts being disposed on the second surface without 15
`extending through the substrate.
`14. The light-emitting device of claim 13, further compris(cid:173)
`ing
`a contact plug extending through the active region to con(cid:173)
`tact the current spreading layer so as to couple the first 20
`electrical contact to the second active layer.
`15. The light-emitting device of claim 14, further compris(cid:173)
`ing:
`a dielectric spacer on sides of the contact plug that separate
`the contact plug from the first active layer.
`16. The light-emitting device of claim 15, wherein the
`dielectric spacer comprises spin-on-glass and/or a polyimide.
`17. The light-emitting device of claim 13, wherein the
`reflective ohmic contact layer comprises at least one of nickel
`oxide/gold and nickel oxide/platinum.
`18. The light-emitting device of claim 17, wherein the
`reflective ohmic contact layer has a thickness between about
`10 A and about 100 A.
`19. The light-emitting device of claim 14, further compris- 35
`ing:
`a buffer layer between the active region and the first sur(cid:173)
`face, the contact plug extending through the buffer layer.
`20. The light-emitting device of claim 19, wherein the
`buffer layer comprises aluminum nitride.
`21. The light-emitting device of claim 14, wherein the
`contact plug comprises gold, silver, a gold alloy, and/or a
`silver alloy.
`22. The light-emitting device of claim 13, wherein the first
`conductivity type is n-type, and wherein the second electrical 45
`contact comprises at least one of aluminum and titanium.
`23. The light-emitting device of claim 13, wherein the
`second conductivity type is p-type, and wherein the first elec(cid:173)
`trical contact comprises at least one of platinum, nickel, and
`titanium/gold.
`24. The light-emitting device of claim 13, wherein the first
`active layer comprises GaN.
`25. The light-emitting device of claim 13, wherein the
`second active layer comprises GaN.
`26. The light-emitting device of claim 13, further compris- 55
`ing a substrate comprising the first and second opposing
`surfaces, wherein the substrate comprises SiC.
`27. A method offorming a light-emitting device, compris(cid:173)
`ing:
`forming an active region on a first surface of first and
`second opposing surfaces of a layer;
`forming a partially transparent current spreading layer on
`the active region, the current spreading layer including a
`reflective ohmic contact with the active region, wherein
`
`8
`the reflective ohmic contact is substantially non-adja(cid:173)
`cent an edge of the active region;
`forming first and second electrical contacts adjacent to the
`second surface that are conductively coupled to the
`active region such that at least one of the first and second
`electrical contacts is disposed on the second surface
`without extending through the active region.
`28. The method of claim 27, wherein forming the active
`region comprises:
`forming a first active layer having a first conductivity type
`on the first surface and;
`forming a second active layer having a second conductivity
`type on the first active Layer; and
`wherein forming the current spreading layer comprises
`forming the current spreading layer on the second active
`layer.
`29. The method of claim 28, further comprising:
`forming a contact plug extending through the active region
`to contact the current spreading layer so as to couple the
`first electrical contact to the second active layer.
`30. The method of claim 29, further comprising:
`forming a dielectric spacer on sides of the contact plug that
`separate the contact plug from the first active layer.
`31. The method of claim 29, further comprising:
`forming a buffer layer between the active region and a
`substrate that includes the first and second opposing
`surfaces, the contact plug extending through the buffer
`layer.
`32. A light-emitting device, comprising:
`a flat planar surface defining a planar surface area and
`comprising first and second contact surfaces;
`an active region on the