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Growth of epitaxial ZnO thin films on lattice-matched buffer layer: Application of InGaO₃(ZnO)₆ single-crystalline thin film

Takeda, Y.  Nomura, K.  Ohta, H.  Yanagi, H.  Kamiya, T.  Hirano, M.  Hosono, H.  

Yujiro Takeda. Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-1, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan

Copyright (c) 2006 Elsevier B.V.

ABSTRACT

Effects of lattice-matched substrates on growth of ZnO epitaxial films were studied. ZnO thin films were grown on single-crystalline InGaO₃(ZnO)₆ (IGZO) layers, which have small lattice mismatches of ~0.8% and ~2.2% in a- and c-axes, respectively. Epitaxial ZnO films were grown with the epitaxial relationship between the ZnO film and the single-crystalline IGZO of [0001]_ZnO//[0001]_IGZO//[111]_YSZ and [112±?0]_ZnO//[112±?0]_IGZO//[11±?0]_YSZ. The use of the lattice-matched substrate and optimization of film microstructure and post-annealing condition led to atomically flat surfaces at maximum process temperatures as low as 700 ^oC. A large Hall electron mobility ~80 cm^2 (V s)^-^1 (N_e: ~2.8x10^1^8 cm^-^3) was obtained even if the film thickness was only 150 nm although comparable mobilities have been reported on films having much larger thicknesses (~1000 nm) fabricated at higher temperatures ~1000 ^oC.