Annealing under vacuum and Se flux of CaF 2 molecular beam epitaxy surfaces prior to PbSe/CaF 2/Si growth

Abstract

In this paper, the molecular beam epitaxy (MBE) technique is applied to IV–VI semiconducting materials such as PbSe. It is of interest to realize 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 CaF 2 is used as a buffer layer with intermediary physico-chemical parameters. The study presented in this paper is divided into two ways: optimization of the first interface CaF 2/Si and the second interface. The annealing under vacuum of calcium fluoride film prepared by MBE is characterized by Auger electron spectroscopy, RHEED and atomic force microscopy. This treatment shows at low temperature (200°C) a weak oxidization, for temperatures above 600°C a surface rearrangement due to diffusion of CaF 2 molecules and for temperatures above 900°C CaF 2 molecular desorption. With optimization of the second interface PbSe/CaF 2 annealing of the CaF 2 surface under selenium flux enables CaF 2 surface stabilization over the 200–500°C temperature range. This treatment avoids surface oxidization and leads to a significant Se incorporation from 400°C necessary for good growth of the PbSe layer.