We have generated shift and injection currents in unstrained, undoped (110)-grown GaAsAl0.3Ga0.7As quantum wells with a single optical pulse and detected them via free-space terahertz experiments. By properly choosing the polarization state of the excitation pulse, it is possible to generate both currents alone along certain crystal directions or to simultaneously generate them along the same crystal direction. A comparison of injection and shift currents allows us to estimate the strength of the injection current. At an excitation energy of 1.53eV the injection current tensor element is i2×107A(V2s). This corresponds to an injection of electrons with an average velocity of 10kms. Moreover, a comparison of the intensity dependence of shift and injection currents under identical experimental conditions demonstrates a stronger saturation of the shift current.

1.
A.
Haché
,
Y.
Kostoulas
,
R.
Atanasov
,
J. L. P.
Hughes
,
J. E.
Sipe
, and
H. M.
van Driel
,
Phys. Rev. Lett.
78
,
306
(
1997
).
2.
S. D.
Ganichev
,
E. L.
Ivchenko
,
S. N.
Danilov
,
J.
Eroms
,
W.
Wegscheider
,
D.
Weiss
, and
W.
Prettl
,
Phys. Rev. Lett.
86
,
4358
(
2001
).
3.
M. J.
Stevens
,
A. L.
Smirl
,
R. D. R.
Bhat
,
A.
Najmaie
,
J. E.
Sipe
, and
H. M.
van Driel
,
Phys. Rev. Lett.
90
,
136603
(
2003
).
4.
J.
Hübner
,
W. W.
Rühle
,
M.
Klude
,
D.
Hommel
,
R. D. R.
Bhat
,
J. E.
Sipe
, and
H. M.
van Driel
,
Phys. Rev. Lett.
90
,
216601
(
2003
).
5.
H.
Zhao
,
X.
Pan
,
A. L.
Smirl
,
R. D. R.
Bhat
,
A.
Najmaie
,
J. E.
Sipe
, and
H. M.
van Driel
,
Phys. Rev. B
72
,
201302
(
2005
).
6.
D.
Côté
,
N.
Laman
, and
H. M.
van Driel
,
Appl. Phys. Lett.
80
,
905
(
2002
).
7.
X.-C.
Zhang
,
Y.
Jin
,
K.
Yang
, and
L. J.
Schowalter
,
Phys. Rev. Lett.
69
,
2303
(
1992
).
8.
A.
Haché
,
J. E.
Sipe
, and
H. M.
van Driel
,
IEEE J. Quantum Electron.
34
,
1144
(
1998
).
9.
J. E.
Sipe
and
A. I.
Shkrebtii
,
Phys. Rev. B
61
,
5337
(
2000
).
10.
S. D.
Ganichev
and
W.
Prettl
,
J. Phys.: Condens. Matter
15
,
R935
(
2003
).
11.
M.
Bieler
,
N.
Laman
,
H. M.
van Driel
, and
A. L.
Smirl
,
Appl. Phys. Lett.
86
,
061102
(
2005
).
12.
N.
Laman
,
M.
Bieler
, and
H. M.
van Driel
,
J. Appl. Phys.
98
,
103507
(
2005
).
13.
V. V.
Bel’kov
 et al,
Solid State Commun.
128
,
283
(
2003
).
14.
S. L.
Chuang
,
S.
Schmitt-Rink
,
B. I.
Greene
,
P. N.
Saeta
, and
A. F. J.
Levi
,
Phys. Rev. Lett.
68
,
102
(
1992
).
15.
X. C.
Zhang
,
Y.
Jin
, and
X. F.
Ma
,
Appl. Phys. Lett.
61
,
2764
(
1992
).
16.
S. D.
Ganichev
,
U.
Rössler
,
W.
Prettl
,
E. L.
Ivchenko
,
V. V.
Bel’kov
,
R.
Neumann
,
K.
Brunner
, and
G.
Abstreiter
,
Phys. Rev. B
66
,
075328
(
2002
).
17.
B. I.
Sturman
and
V. M.
Fridkin
,
The Photovoltaic and Photorefractive Effects in Noncentrosymmetric Materials
(
Gordon and Breach
,
Philadelphia
,
1992
).
18.
R. W.
Boyd
,
Nonlinear Optics
(
Academic
,
New York
,
1992
).
19.
J.
Shah
,
Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures
, 2nd ed. (
Springer
,
Berlin
,
1999
).
20.

The samples used in Ref. 11 were not perfectly (110) oriented. Their normal vector was tilted by 6° towards the (111) axis. Moreover, the QW regions were embedded in a pin structure. It is very likely that also the detailed structural parameters of the QW system, e.g., the properties of the well∕barrier interfaces, influence the size of the injection current tensor element.

21.

The ratio of the terahertz peak-to-peak signals directly corresponds to the ratio of the current amplitudes since the shapes of the terahertz traces of shift and injection currents are identical.

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