Epitaxial stabilization of a monoclinic phase in Y(2)O(3) films on c-plane GaN

Abstract

Nanometer-thick Y(2)O(3) films were grown epitaxially on GaN (0 0 0 1) using molecular beam epitaxy (MBE). The structures of the oxide films were studied in situ by reflection high energy electron diffraction (RHEED) during the growth and ex situ by high resolution X-ray diffraction using synchrotron radiation. At atmospheric pressure. Y(2)O(3) exists in either cubic or hexagonal structure. For the first time, the high-pressure monoclinic phase of Y(2)O(3), stabilized by epitaxy, was prepared and preserved under atmospheric pressure. The electrical characterization carried out on the Y(2)O(3)/GaN metal-oxide-semiconductor (MOS) capacitors showed a leakage current density of similar to 3.3 x 10(-6) A/cm(2) at 1.5 MV/cm, which remained almost the same after 800 degrees C annealing. A dielectric constant of similar to 20 and a hysteresis of similar to 250 mV were deduced from the capacitance-voltage (C-V) curves for the epitaxial monoclinic Y(2)O(3). (C) 2010 Elsevier B.V. All rights reserved.