Epitaxial CoAl/AlAs/GaAs metal semiconductor heterostructures: Growth, structure, and electrical properties

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Abstract
Molecular beam epitaxial (MBE) growth, structural, and electrical properties of novel epitaxial metal/semiconductor heterostructures (MSHs), consisting of monocrystalline CoAl, an intermetallic compound, and AlAs/GaAs III‐V semiconductors have been studied. The CoAl with stoichiometric composition has a CsCl‐type crystal structure whose lattice constant is very close to half the lattice constant of GaAs and AlAs, hence, it is a good candidate as a constituent metal in epitaxial monocrystalline metal/semiconductor heterostructures. MBE growth of CoAl thin films on AlAs/GaAs, and also semiconductor overgrowth on ultrathin CoAl films, together with structural characterizations by in situ reflection 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 monocrystalline CoAl/AlAs/GaAs heterostructures with atomically abrupt interfaces have been successfully grown. Furthermore, the electrical properties of such novel heterostructures as Schottky barrier heights of CoAl/AlAs/GaAs MSHs and transport properties in ultrathin buried CoAl films are described.