Computer-Controlled Molecular Beam Epitaxy

Abstract

A versatile, computer-controlled MBE system has been developed for preparation of superfine multilayer structures consisting of GaAs, AlAs and their alloys. The capabilities of a high degree of precise control have been designed to achieve high-resolution structures which enable us to observe quantum-mechanical effects arising from the interaction of electron waves with tunneling barriers in high-quality monocrystalline semiconductors. In ultrahigh vacuum, a mass spectrometer, monitoring multiple beam intensities, provides input data for a process control computer which commands the entire operation. HEED and Auger analyzers examine the surface in situ during growth and a combination of Auger electron spectroscopy and ion sputter-etching makes it possible to profile the composition in the grown structures. We also report the recent experimental results of anomalous transport properties in our grown structures, such as double tunnel barriers and superlattices, which clearly manifest the predicted effects.