PHOTOEMISSION-STUDIES OF SEMICONDUCTOR INTERFACES - ELECTRONIC-STRUCTURE AND BARRIER HEIGHTS

Semiconductor interfaces are an interesting class of systems from a fundamental as well as applications-oriented point of view. Several recent examples will be given to demonstrate how photoelectron spectroscopy permits a detailed investigation of the electronic structure of semiconductor surfaces and interfaces, in particular of features which determine the transport properties, e.g. the valence band offset DELTA-E(v) in heterojunctions and the Schottky barrier height PHI(b) in metal-III-V-semiconductor junctions. For in situ studies, these properties can be examined at a microscopic level, i.e. as the interface is built from the lowest coverages onwards. The influence of chemical reactions at the interface, which in turn may have an influence on the electronic properties, is considered. Attention will also be paid to non-equilibrium processes such as the surface photovoltage, which may have a severe influence on the interpretation of Fermi level pinning data from photoemission. A combination of electronic structure information with recent advances in the determination of the geometric structure and morphology of overlayers on semiconductors provides new insights into this class of interfaces.