EPITAXIAL INSULATING FLUORIDE LAYERS ON SEMICONDUCTORS

The epitaxial growth of the rare earth fluorides HoF3 and GdF3 on Ge, Si, and GaAs has been investigated. At the same time the detailed nature of the interfaces formed has been probed by X-ray photoelectron spectroscopy. Epitaxial layers can readily be grown and it is shown that layers with the high temperature tysonite-like phase may be prepared in such a way as to be stable at room temperature. A critical thickness exists where the layer structure changes to a multidomain orthorhombic form; this is dependent on the degree of mismatch of the lattices of overlayer and substrate. Whereas the GdF3-Ge interface is unreactive, strong reactions are seen for HoF3-Si, GdF3-GaAs, and LaF3-Si. Reactions at the latter interface may be attenuated by an intermediate ordered layer of arsenic just one monolayer thick. © 1993 Academic Press, Inc.