Effect of uncontrolled impurities on electrical properties of GaAs films grown by molecular-beam epitaxy

According to previous studies, the principal uncontrolled impurities in GaAs layers grown by molecular-beam epitaxy (MBE) are C, Mn, Si, and Ge. In this work, results of investigations of the nature of some impurities in GaAs films, grown in a single-chamber equipment for MBE without any locks, are presented and their effect on the electrical properties of tin (approximately 1.0 micrometers and thinner) GaAs layers is shown. By Hall and chemical spectral analysis methods in undoped GaAs films, prepared by MBE, the impurities Mn, Ni, Co, and Cu are detected, which affect the concentration and mobility of the free current carriers in GaAs films, undoped and doped with tin. By means of layerwise chemical etching, the dependence of the electrophysical properties of n-GaAs films on their thickness is investigated. The effect of a buffer layer on this dependence is demonstrated.