EPITAXIAL COAL ALAS/GAAS METAL-SEMICONDUCTOR HETEROSTRUCTURES - GROWTH, STRUCTURE, AND ELECTRICAL-PROPERTIES/

Molecular beam epitaxial (MBE) growth, structural, and electrical prop erties of novel epitaxial metal/semiconductor heterostructures (MSHs), consisting of monocrystalline CoAl, an intermetallic compound, and Al As/GaAs III-V semiconductors have been studied. The CoAl with stoichio metric composition has a CsCl-type crystal structure whose lattice con stant is very close to half the lattice constant of GaAs and AlAs, hen ce, it is a good candidate as a constituent metal in epitaxial monocry stalline metal/semiconductor heterostructures; MBE growth of CoAl thin films on AlAs/GaAs, and also semiconductor overgrowth on ultrathin Co Al films, together with structural characterizations by in situ reflec tion high energy electron diffractions, ex situ x-ray diffractions and cross sectional transmission electron microscopy have been explored. By optimizing the growth parameters and procedures, high quality monoc rystalline CoAl/AlAs/ GaAs heterostructures with atomically abrupt int erfaces have been successfully grown. Furthermore, the electrical prop erties of such novel heterostructures as Schottky barrier heights of C oAl/AlAs/GaAs MSHs and transport properties in ultrathin buried CoAl f ilms are described.