Molecular beam epitaxial growth and characterization of CoAl on AlAs/GaAs

Abstract
We study molecular beam epitaxial growth and structural properties of intermetallic compound CoAl on AlAs/GaAs III-V semiconductors. CoAl has a CsCl structure whose lattice constant is nearly half the lattice constant of GaAs and AlAs, hence, it is a good candidate for the constituent material in epitaxial metal/semiconductor heterostructures. We investigate the dependence of crystallinity of Co1−xAlx epitaxial layers on Al composition x and on growth temperature Ts, by in situ reflection high-energy electron diffraction and ex situ x-ray measurements. It is found that the single-crystalline CoAl with high quality can be obtained at x=0.5 and Ts=350 °C. Under appropriate growth procedures and conditions, the epitaxial growth orientation is (001)[110]CoAl on (001)[110]AlAs/GaAs.