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Proceedings Paper

Formation of two-dimensional electron gas and enhancement of electron mobility by Zn polar ZnMgO/ZnO heterostructures
Author(s): H. Tampo; H. Shibata; K. Matsubara; A. Yamada; P. Fons; M. Yamagata; H. Kanie; S. Niki
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Paper Abstract

A two-dimensional electron gas (2DEG) was observed in Zn polar ZnMgO/ZnO (ZnMgO on ZnO) heterostructures grown by radical source molecular beam epitaxy. Reflection high energy electron diffraction patterns taken during the growth of the ZnMgO layer remained streaky; x-ray diffraction measurements showed no evidence of phase separation for up 44 % Mg composition. These results shows that the high quality ZnMgO layers up to 44 % Mg composition were obtained without phase separation. The electron mobility of the ZnMgO/ZnO heterostructures dramatically increased with increasing Mg composition and the electron mobility (&mgr;~250 cm2/Vs) at RT reached a value more than twice that of an undoped ZnO layer (&mgr;~100 cm2/Vs) due to the 2DEG formation. The carrier concentration in turn reached values as high as ~1x1013 cm-2 and remained nearly constant regardless of Mg composition. Strong confinement of electrons at the ZnMgO/ZnO interface was confirmed by C-V measurements with a concentration of over 4x1019 cm-3. Temperature-dependent Hall measurements of ZnMgO/ZnO heterostructures also exhibited properties associated with well defined heterostructures. The Hall mobility increased monotonically with decreasing temperature, reaching a value of 2750 cm2/Vs at 4 K. Zn polar "ZnMgO on ZnO" structures are easy to adapt to a top-gate device. These results open new possibilities for high electron mobility transistors (HEMTs) based upon ZnO based materials.

Paper Details

Date Published: 20 February 2007
PDF: 8 pages
Proc. SPIE 6474, Zinc Oxide Materials and Devices II, 64740J (20 February 2007); doi: 10.1117/12.714044
Show Author Affiliations
H. Tampo, National Institute of Advanced Industrial Science and Technology (Japan)
H. Shibata, National Institute of Advanced Industrial Science and Technology (Japan)
K. Matsubara, National Institute of Advanced Industrial Science and Technology (Japan)
A. Yamada, National Institute of Advanced Industrial Science and Technology (Japan)
P. Fons, National Institute of Advanced Industrial Science and Technology (Japan)
M. Yamagata, Tokyo Univ. of Science (Japan)
H. Kanie, Tokyo Univ. of Science (Japan)
S. Niki, National Institute of Advanced Industrial Science and Technology (Japan)


Published in SPIE Proceedings Vol. 6474:
Zinc Oxide Materials and Devices II
Ferechteh Hosseini Teherani; Cole W. Litton, Editor(s)

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