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Originally published in Science Express on 25 January 2007
Science 9 March 2007:
Vol. 315. no. 5817, pp. 1388 - 1391
DOI: 10.1126/science.1137430
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Reports

Quantum Hall Effect in Polar Oxide Heterostructures

A. Tsukazaki,1 A. Ohtomo,1,2* T. Kita,3,4 Y. Ohno,4 H. Ohno,3,4 M. Kawasaki1,5*

We observed Shubnikov–de Haas oscillation and the quantum Hall effect in a high-mobility two-dimensional electron gas in polar ZnO/MgxZn1–xO heterostructures grown by laser molecular beam epitaxy. The electron density could be controlled in a range of 0.7 x 1012 to 3.7 x 1012 per square centimeter by tuning the magnesium content in the barriers and the growth polarity. From the temperature dependence of the oscillation amplitude, the effective mass of the two-dimensional electrons was derived as 0.32 ± 0.03 times the free electron mass. Demonstration of the quantum Hall effect in an oxide heterostructure presents the possibility of combining quantum Hall physics with the versatile functionality of metal oxides in complex heterostructures.

1 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
2 PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
3 ERATO Semiconductor Spintronics Project, Japan Science and Technology Agency, Sendai 980-0023, Japan.
4 Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan.
5 CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.

* To whom correspondence should be addressed. E-mail: aohtomo{at}imr.tohoku.ac.jp (A.O.); kawasaki{at}imr.tohoku.ac.jp (M.K.)

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