ANNEALING UNDER VACUUM AND SE FLUX OF CAF2 MOLECULAR-BEAM EPITAXY SURFACES PRIOR TO PBSE CAF2/SI GROWTH/

In this paper, the molecular beam epitaxy (MBE) technique is applied t o IV-VI semiconducting materials such as PbSe. It is of interest to re alize heterostructures with infrared (IR) detection properties on a Si wafer in order to obtain a compact optoelectronic device. Because of the lattice mismatch between PbSe: and Si, a layer of CaF2 is used as a buffer layer with intermediary physicochemical parameters. The study presented in this paper is divided into two ways: optimization of the first interface CaF2/Si and the second interface. The annealing under vacuum of calcium fluoride film prepared by MBE is characterized by A uger electron spectroscopy, RHEED and atomic force microscopy. This tr eatment shows at low temperature (200 degrees C) a weak oxidization, f or temperatures above 600 degrees C a surface rearrangement due to dif fusion of CaF2 molecules and for temperatures above 900 degrees C CaF2 molecular desorption. With optimization of the second interface PbSe/ CaF2 annealing of the CaF2 surface under selenium flux enables CaF2 su rface stabilization over the 200-500 degrees C temperature range. This treatment avoids surface oxidization and leads to a significant Se in corporation from 400 degrees C necessary for good growth of the PbSe l ayer. (C) 1998 Elsevier Science B.V. All rights reserved.