Growth and characterization of Ga2Se3/GaAs(100) epitaxial thin films

Single crystalline Ga2Se3 thin films were grown on GaAs(1 0 0) by molecular beam epitaxial (MBE) under Se-rich atmosphere. Reflection high-energy electron diffraction (RHEED) analysis suggests that the Ga2Se3 thin film is epitaxially grown on GaAs(1 0 0) with their [1 0 0] crystallographic directions aligned with each other. The electronic structure determined by the ultraviolet photoelectron spectroscopy (UPS) and electron energy loss spectroscopy (EELS) revealed the forbidden band gap of 2.7 eV. Transmission electron microscopy has shown that vacancies are distributed on one set of {1 1 1} crystal planes of alpha-Ga2Se3 structure by forming a root 3 x root 3 configuration, resulting in the three times larger modulation periodicity along one of the [1 1 0] crystal directions into vacancy ordered beta-Ga2Se3 structure. The crystal structure was consistent to a model proposed by Lubbers and Leute (J. Solid State Chem. 43 (1982) 339). There are two sets of planar defects, microtwin with {1 1 1} type twin planes and stacking faults. High population of planer defects observed in the thin film was regarded as a result of Ga vacancy ordering in the crystal structure of Ga2Se3. (C) 1999 Elsevier Science B.V. All rights reserved.