共 33 条
Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
被引:12
作者:

Omanakuttan, Giriprasanth
论文数: 0 引用数: 0
h-index: 0
机构:
Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Martinez Sacristan, Oscar
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Valladolid, Dept Fis Mat Condensada, GdS Optronlab Grp, Edificio LUCIA,Paseo Belen 19, Valladolid 47011, Spain Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Marcinkevicius, Saulius
论文数: 0 引用数: 0
h-index: 0
机构:
Royal Inst Technol KTH, Dept Appl Phys, Unit Opt & Photon, Electrum 229, S-16440 Kista, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Uzdavinys, Tomas Kristijonas
论文数: 0 引用数: 0
h-index: 0
机构:
Royal Inst Technol KTH, Dept Appl Phys, Unit Opt & Photon, Electrum 229, S-16440 Kista, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Jimenez, Juan
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Valladolid, Dept Fis Mat Condensada, GdS Optronlab Grp, Edificio LUCIA,Paseo Belen 19, Valladolid 47011, Spain Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Ali, Hasan
论文数: 0 引用数: 0
h-index: 0
机构:
Uppsala Univ, Dept Engn Sci, Appl Mat Sci, Box 534, S-75121 Uppsala, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Leifer, Klaus
论文数: 0 引用数: 0
h-index: 0
机构:
Uppsala Univ, Dept Engn Sci, Appl Mat Sci, Box 534, S-75121 Uppsala, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Lourdudoss, Sebastian
论文数: 0 引用数: 0
h-index: 0
机构:
Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden

Sun, Yan-Ting
论文数: 0 引用数: 0
h-index: 0
机构:
Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden
机构:
[1] Royal Inst Technol KTH, Dept Appl Phys, Lab Semicond Mat, Electrum 229, S-16440 Kista, Sweden
[2] Univ Valladolid, Dept Fis Mat Condensada, GdS Optronlab Grp, Edificio LUCIA,Paseo Belen 19, Valladolid 47011, Spain
[3] Royal Inst Technol KTH, Dept Appl Phys, Unit Opt & Photon, Electrum 229, S-16440 Kista, Sweden
[4] Uppsala Univ, Dept Engn Sci, Appl Mat Sci, Box 534, S-75121 Uppsala, Sweden
基金:
瑞典研究理事会;
关键词:
VAPOR-PHASE EPITAXY;
GAAS SOLAR-CELLS;
SI;
SILICON;
LUMINESCENCE;
DEFECTS;
LASERS;
D O I:
10.1364/OME.9.001488
中图分类号:
T [工业技术];
学科分类号:
08 ;
摘要:
We fabricate and study direct InP/Si heterojunction by corrugated epitaxial lateral overgrowth (CELOG). The crystalline quality and depth-dependent charge carrier dynamics of InP/Si heterojunction are assessed by characterizing the cross-section of grown layer by low-temperature cathodoluminescence, time-resolved photoluminescence and transmission electron microscopy. Compared to the defective seed InP layer on Si, higher intensity band edge emission in cathodoluminescence spectra and enhanced carrier lifetime of InP are observed above the CELOG InP/Si interface despite large lattice mismatch, which are attributed to the reduced threading dislocation density realized by the CELOG method. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
引用
收藏
页码:1488 / 1500
页数:13
相关论文
共 33 条
[1]
MINORITY-CARRIER PROPERTIES OF GAAS ON SILICON
[J].
AHRENKIEL, RK
;
ALJASSIM, MM
;
DUNLAVY, DJ
;
JONES, KM
;
VERNON, SM
;
TOBIN, SP
;
HAVEN, VE
.
APPLIED PHYSICS LETTERS,
1988, 53 (03)
:222-224

AHRENKIEL, RK
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

ALJASSIM, MM
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

DUNLAVY, DJ
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

JONES, KM
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

VERNON, SM
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

TOBIN, SP
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730

HAVEN, VE
论文数: 0 引用数: 0
h-index: 0
机构:
SPIRE CORP,BEDFORD,MA 01730 SPIRE CORP,BEDFORD,MA 01730
[2]
MEASUREMENT OF MINORITY-CARRIER LIFETIME BY TIME-RESOLVED PHOTOLUMINESCENCE
[J].
AHRENKIEL, RK
.
SOLID-STATE ELECTRONICS,
1992, 35 (03)
:239-250

AHRENKIEL, RK
论文数: 0 引用数: 0
h-index: 0
机构: National Renewable Energy Laboratory, Golden, CO 80401
[3]
POSTGROWTH THERMAL ANNEALING OF GAAS ON SI(001) GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY
[J].
AYERS, JE
;
SCHOWALTER, LJ
;
GHANDHI, SK
.
JOURNAL OF CRYSTAL GROWTH,
1992, 125 (1-2)
:329-335

AYERS, JE
论文数: 0 引用数: 0
h-index: 0
机构:
RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180 RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180

SCHOWALTER, LJ
论文数: 0 引用数: 0
h-index: 0
机构:
RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180 RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180

GHANDHI, SK
论文数: 0 引用数: 0
h-index: 0
机构:
RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180 RENSSELAER POLYTECH INST,DEPT ELECT COMP & SYST ENGN,TROY,NY 12180
[4]
GALLIUM-ARSENIDE AND OTHER COMPOUND SEMICONDUCTORS ON SILICON
[J].
FANG, SF
;
ADOMI, K
;
IYER, S
;
MORKOC, H
;
ZABEL, H
;
CHOI, C
;
OTSUKA, N
.
JOURNAL OF APPLIED PHYSICS,
1990, 68 (07)
:R31-R58

FANG, SF
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

ADOMI, K
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

IYER, S
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

MORKOC, H
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

ZABEL, H
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

CHOI, C
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA

OTSUKA, N
论文数: 0 引用数: 0
h-index: 0
机构:
PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA PURDUE UNIV, SCH MAT ENGN, W LAFAYETTE, IN 47907 USA
[5]
EVIDENCE OF A GAS-PHASE TRANSPORT MECHANISM FOR SI INCORPORATION IN THE METALORGANIC CHEMICAL VAPOR-DEPOSITION OF GAAS
[J].
GEORGE, T
;
WEBER, ER
;
NOZAKI, S
;
MURRAY, JJ
;
WU, AT
;
UMENO, M
.
APPLIED PHYSICS LETTERS,
1989, 55 (20)
:2090-2092

GEORGE, T
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052

WEBER, ER
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052

NOZAKI, S
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052

MURRAY, JJ
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052

WU, AT
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052

UMENO, M
论文数: 0 引用数: 0
h-index: 0
机构: INTEL CORP,SANTA CLARA,CA 95052
[6]
Study of planar defect filtering in InP grown on Si by epitaxial lateral overgrowth
[J].
Junesand, Carl
;
Kataria, Himanshu
;
Metaferia, Wondwosen
;
Julian, Nick
;
Wang, Zhechao
;
Sun, Yan-Ting
;
Bowers, John
;
Pozina, Galia
;
Hultman, Lars
;
Lourdudoss, Sebastian
.
OPTICAL MATERIALS EXPRESS,
2013, 3 (11)
:1960-1973

Junesand, Carl
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Kataria, Himanshu
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Metaferia, Wondwosen
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Julian, Nick
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Wang, Zhechao
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden
Univ Ghent, Dept Informat Technol, B-9000 Ghent, Belgium KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Sun, Yan-Ting
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Bowers, John
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Pozina, Galia
论文数: 0 引用数: 0
h-index: 0
机构:
Linkoping Univ, Dept Phys, Thin Film Phys Div, S-58183 Linkoping, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Hultman, Lars
论文数: 0 引用数: 0
h-index: 0
机构:
Linkoping Univ, Dept Phys, Thin Film Phys Div, S-58183 Linkoping, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden

Lourdudoss, Sebastian
论文数: 0 引用数: 0
h-index: 0
机构:
KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden KTH Royal Inst Technol, Lab Semicond Mat, S-16440 Kista, Sweden
[7]
HEAT-TREATMENT OF SEMI-INSULATING INP-FE WITH PHOSPHOSILICATE GLASS ENCAPSULATION
[J].
KAMIJOH, T
;
TAKANO, H
;
SAKUTA, M
.
JOURNAL OF APPLIED PHYSICS,
1984, 55 (10)
:3756-3759

KAMIJOH, T
论文数: 0 引用数: 0
h-index: 0

TAKANO, H
论文数: 0 引用数: 0
h-index: 0

SAKUTA, M
论文数: 0 引用数: 0
h-index: 0
[8]
Two dimensional numerical simulations of carrier dynamics during time-resolved photoluminescence decays in two-photon microscopy measurements in semiconductors
[J].
Kanevce, Ana
;
Kuciauskas, Darius
;
Levi, Dean H.
;
Motz, Alyssa M. Allende
;
Johnston, Steven W.
.
JOURNAL OF APPLIED PHYSICS,
2015, 118 (04)

Kanevce, Ana
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Kuciauskas, Darius
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Levi, Dean H.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Motz, Alyssa M. Allende
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA
Colorado Sch Mines, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Johnston, Steven W.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA
[9]
Vertical-cavity surface-emitting lasers flip-chip bonded to gigabit-per-second CMOS circuits
[J].
Krishnamoorthy, AV
;
Chirovsky, LMF
;
Hobson, WS
;
Leibenguth, RE
;
Hui, SP
;
Zydzik, CJ
;
Goossen, KW
;
Wynn, JD
;
Tseng, BJ
;
Lopata, J
;
Walker, JA
;
Cunningham, JE
;
D'Asaro, LA
.
IEEE PHOTONICS TECHNOLOGY LETTERS,
1999, 11 (01)
:128-130

Krishnamoorthy, AV
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Chirovsky, LMF
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Hobson, WS
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Leibenguth, RE
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Hui, SP
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Zydzik, CJ
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Goossen, KW
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Wynn, JD
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Tseng, BJ
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Lopata, J
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Walker, JA
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

Cunningham, JE
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA

D'Asaro, LA
论文数: 0 引用数: 0
h-index: 0
机构:
AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA AT&T Bell Labs, Lucent Technol, Holmdel, NJ 07733 USA
[10]
Charge-carrier transport and recombination in heteroepitaxial CdTe
[J].
Kuciauskas, Darius
;
Farrell, Stuart
;
Dippo, Pat
;
Moseley, John
;
Moutinho, Helio
;
Li, Jian V.
;
Motz, A. M. Allende
;
Kanevce, Ana
;
Zaunbrecher, Katherine
;
Gessert, Timothy A.
;
Levi, Dean H.
;
Metzger, Wyatt K.
;
Colegrove, Eric
;
Sivananthan, S.
.
JOURNAL OF APPLIED PHYSICS,
2014, 116 (12)

Kuciauskas, Darius
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Farrell, Stuart
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Dippo, Pat
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Moseley, John
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Moutinho, Helio
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Li, Jian V.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Motz, A. M. Allende
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Kanevce, Ana
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Zaunbrecher, Katherine
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Gessert, Timothy A.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Levi, Dean H.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Metzger, Wyatt K.
论文数: 0 引用数: 0
h-index: 0
机构:
Natl Renewable Energy Lab, Golden, CO 80401 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Colegrove, Eric
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Illinois, Microphys Lab, Dept Phys, Chicago, IL 60612 USA Natl Renewable Energy Lab, Golden, CO 80401 USA

Sivananthan, S.
论文数: 0 引用数: 0
h-index: 0
机构:
Univ Illinois, Microphys Lab, Dept Phys, Chicago, IL 60612 USA Natl Renewable Energy Lab, Golden, CO 80401 USA