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 elec tron diffraction (RHEED) analysis suggests that the Ga2Se3 thin film is epi taxially grown on GaAs(1 0 0) with their [1 0 0] crystallographic direction s aligned with each other. The electronic structure determined by the ultra violet photoelectron spectroscopy (UPS) and electron energy loss spectrosco py (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} c rystal planes of alpha-Ga2Se3 structure by forming a root 3 x root 3 config uration, resulting in the three times larger modulation periodicity along o ne of the [1 1 0] crystal directions into vacancy ordered beta-Ga2Se3 struc ture. The crystal structure was consistent to a model proposed by Lubbers a nd 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 r esult of Ga vacancy ordering in the crystal structure of Ga2Se3. (C) 1999 E lsevier Science B.V. All rights reserved.