We report the determination of free-electron concentration and mobility of free-standing GaN nanowires (NWs) by line shape analysis of the coupled longitudinal optical phonon-plasmon Raman modes (L+). The E2high phonon mode at 566.9cm1 with a sharp linewidth of 2.8cm1 indicates strain free NWs with high crystalline perfection. The lattice temperature of the NWs was varied between 313 and 472 K by varying the excitation laser beam power. For unintentionally doped samples at room temperature, an average electron concentration and mobility of strain free NWs were found to be 2×1017cm3 and 460cm2/Vs, respectively. We have shown that the electron concentration does not change significantly over a temperature range between 313 and 472 K. The electron mobility decreases at high temperatures, in agreement with literature data for compact layers. For Si-doped NWs, the L+ phonon peak is strongly upshifted indicating a higher free-carrier concentration of about 1×1018cm3. Asymmetric broadening observed at the lower frequency side of the L+ phonon peak might be ascribed to the enhancement in surface optical modes due to the high surface-to-volume ratio of NWs.

1.
E. D.
Minot
,
F.
Kelkensberg
,
M.
van Kouwen
,
J. A.
van Dam
,
L. P.
Kouwenhoven
,
V.
Zwiller
,
M. T.
Borgstrom
,
O.
Wunnicke
,
M. A.
Verheijen
, and
E. P. A. M.
Bakkers
,
Nano Lett.
7
,
367
(
2007
).
2.
Y.
Huang
,
X.
Duan
, and
C. M.
Lieber
,
Small
1
,
142
(
2005
).
3.
O.
Hayden
,
R. A.
Agarwal
, and
C. M.
Lieber
,
Nature Mater.
5
,
352
(
2006
).
4.
A. B.
Greytak
,
C. J.
Barrelet
,
Y.
Li
, and
C. M.
Lieber
,
Appl. Phys. Lett.
87
,
151103
(
2005
).
5.
J. C.
Johnson
,
H. -J.
Choi
,
K. P.
Knutsen
,
R. D.
Schaller
,
P.
Yang
, and
R. J.
Saykally
,
Nature Mater.
1
,
106
(
2002
).
6.
H.
Kind
,
H.
Yan
,
B.
Messer
,
M.
Law
, and
P.
Yang
,
Adv. Mater. (Weinheim, Ger.)
14
,
158
(
2002
).
7.
K.
Keem
,
H.
Kim
,
G. -T.
Kim
,
J. S.
Lee
,
B.
Min
,
K.
Cho
,
M. -Y.
Sung
, and
S.
Kim
,
Appl. Phys. Lett.
84
,
4376
(
2004
).
8.
F.
Patolsky
,
G.
Zheng
, and
C. M.
Lieber
,
Nanomedicine
1
,
51
(
2006
).
9.
F.
Patolsky
,
G. F.
Zheng
, and
C. M.
Lieber
,
Anal. Chem.
78
,
4260
(
2006
).
10.
Y.
Cui
,
Z.
Zhong
,
D.
Wang
,
W. U.
Wang
, and
C. M.
Lieber
,
Nano Lett.
3
,
149
(
2003
).
11.
Y.
Huang
,
X.
Duan
,
Y.
Cui
, and
C. M.
Lieber
,
Nano Lett.
2
,
101
(
2002
).
12.
R.
Meijers
,
T.
Richter
,
R.
Calarco
,
T.
Stoica
,
H. P.
Bochem
,
M.
Marso
, and
H.
Lüth
,
J. Cryst. Growth
289
,
381
(
2006
).
13.
T.
Kuykendall
,
P. J.
Pauzauskie
,
Y. F.
Zhang
,
J.
Goldberger
,
D.
Sirbuly
,
J.
Denlinger
, and
P. D.
Yang
,
Nature Mater.
3
,
524
(
2004
).
14.
E. A.
Stach
,
P. J.
Pauzauskie
,
T.
Kuykendall
,
J.
Goldberger
,
R. R.
He
, and
P. D.
Yang
,
Nano Lett.
3
,
867
(
2003
).
15.
X.
Duan
,
J.
Wang
, and
C. M.
Lieber
,
Appl. Phys. Lett.
76
,
1116
(
2000
).
16.
R.
Calarco
,
M.
Marso
,
T.
Richter
,
A. I.
Aykanat
,
R.
Meijers
,
A. v. d.
Hart
,
T.
Stoica
, and
H.
Luth
,
Nano Lett.
5
,
981
(
2005
).
17.
A.
Cavallini
,
L.
Polenta
,
M.
Rossi
,
T.
Richter
,
M.
Marso
,
R.
Meijers
,
R.
Calarco
, and
H.
Lüth
,
Nano Lett.
6
,
1548
(
2006
).
18.
D.
Wang
,
C. C.
Tin
,
J. R.
Williams
,
M.
Park
,
Y. S.
Park
,
C. M.
Park
,
T. W.
Kang
, and
W. C.
Yang
,
Appl. Phys. Lett.
87
,
242105
(
2005
).
19.
T.
Kozawa
,
T.
Kachi
,
H.
Kano
,
Y.
Taga
,
M.
Hashimoto
,
N.
Koide
, and
K.
Manabe
,
J. Appl. Phys.
75
,
1098
(
1994
).
20.
H.
Harima
,
J. Phys.: Condens. Matter
14
,
R967
(
2002
).
21.
M. V.
Klein
,
B. N.
Ganguly
, and
P. J.
Colwell
,
Phys. Rev. B
6
,
2380
(
1972
).
22.
C.
Wetzel
,
W.
Walukiewicz
,
E. E.
Haller
,
J.
Ager
,
I.
Grzegory
,
S.
Porowski
, and
T.
Suski
,
Phys. Rev. B
53
,
1322
(
1996
).
23.
H.
Siegle
,
G.
Kaczmarczyk
,
L.
Filippidis
,
A. P.
Litvinchuk
,
A.
Hoffmann
, and
C.
Thomsen
,
Phys. Rev. B
55
,
7000
(
1997
).
24.
H.
Harima
,
J. Phys.: Condens. Matter
14
,
R967
(
2002
).
25.
P.
Perlin
,
C.
Jauberthie-Carillon
,
J. P.
Itie
,
A. S.
Miguel
,
I.
Grzegory
, and
A.
Polian
,
Phys. Rev. B
45
,
83
(
1992
).
26.
V. Y.
Davydov
,
Y. E.
Kitaev
,
I. N.
Goncharuk
,
A. N.
Smirnov
,
J.
Graul
,
O.
Semchinova
,
D.
Uffmann
,
M. B.
Smirnov
,
A. P.
Mirgorodsky
, and
R. A.
Evarestov
,
Phys. Rev. B
58
,
12899
(
1998
).
27.
T.
Azuhata
,
T.
Sota
,
K.
Suzuki
, and
S.
Nakamura
,
J. Phys.: Condens. Matter
7
,
L129
(
1995
).
28.
P.
Perlin
,
J.
Camassel
,
W.
Knap
,
T.
Taliercio
,
J. C.
Chervin
,
T.
Suski
,
I.
Grzegory
, and
S.
Porowski
,
Appl. Phys. Lett.
67
,
2524
(
1995
).
29.
V. V.
Mamutin
,
V. A.
Vekshin
,
V. N.
Jmerik
,
V. V.
Ratnikov
,
V. Y.
Davydov
,
N. A.
Cherkashin
,
S. V.
Ivanov
,
G.
Pozina
,
J. P.
Bergman
, and
B.
Monemar
,
IPAP Conf. Ser.
1
,
413
(
2000
).
30.
H. W.
Lo
and
A.
Compaan
,
Phys. Rev. Lett.
44
,
1604
(
1980
).
31.
G.
Irmer
,
V. V.
Toporov
,
B. H.
Bairamov
, and
J.
Monecke
,
Phys. Status Solidi B
119
,
595
(
1983
).
32.
W.
Gotz
,
N. M.
Johnson
,
C.
Chen
,
H.
Liu
,
C.
Kuo
, and
W.
Imler
,
Appl. Phys. Lett.
68
,
3144
(
1996
).
33.
X. Q.
Shen
,
T.
Ide
,
S. H.
Cho
,
M.
Shimizu
,
S.
Hara
,
H.
Okumura
,
S.
Sonoda
, and
S.
Shimizu
,
Proceedings of the International Workshop on Nitride Semiconductors
X. Q.
Shen
,
T.
Ide
,
S. H.
Cho
,
M.
Shimizu
,
S.
Hara
,
H.
Okumura
,
S.
Sonoda
, and
S.
Shimizu
,[
IPAP Conf. Ser.
1
,
162
(
2000
)].
You do not currently have access to this content.