Structure and electronic properties of ionic nano-layers MBE-grown on III-V semiconductors

Thin epitaxial NaCl and KBr layers of various thickness (from 3 to 100 monolayers) have been deposited on (100) surfaces of GaAs and InSb semiconductors by means of molecular beam epitaxy (MBE). Electronic and structural properties of the freshly prepared films were subsequently investigated in the attached UHV analytical chamber by means of low energy electron diffraction, low electron energy loss spectroscopy, Auger electron spectroscopy and an electron holography. Alkali halide growth mode was found to be a two-dimensional layer-by-layer type (Franck van der Merve growth mode). It was possible to demonstrate that the first. monolayer of alkali halide on the A(III)B(V) semiconductor is arranged by the strong bond formed between the halogen inn and the A(III) metallic element. In case of NaCl/GaAs(100) system a local atomic configuration was found for an early stage of epitaxy (three to five monolayers) by means of the electron holography. A detailed analysis of the reconstructed diffraction patterns revealed that an initial formation of the CI-Ga bond occurred in the system, and after deposition of five monolayers NaCl, the substrate was uniformly covered by a layer at least three monolayers thick. (C) 2000 Elsevier Science S.A. All rights reserved.