Simultaneous epitaxy and substrate out-diffusion at a metal-semiconductor interface: Fe/GaAs(001)-c(8 x 2)

Growth, structure and morphology of epitaxial Fe(0 0 1) films on GaAs(0 0 1)c(4 × 4)

We studied epitaxy, growth, structure and morphology of thin Fe(0 0 1) films on the As-rich GaAs(0 0 1)-c(4 × 4) surface, deposited by molecular beam epitaxy at growth temperatures between room temperature and 250° C. Electron and x-ray diffraction (XRD) techniques evidence epitaxial growth with Fe(0 0 1)[1 0 0] ∥ GaAs(0 0 1)[1 0 0]. The residual strain derived from the XRD results is consistent with recent stress measurements. Cross-sectional transmission electron microscopy reveals an abrupt interface for room-temperature films and the formation of a ∼10 nm thick crystalline Fe-Ga-As intermediate layer at 250° C. The dependence of the surface morphology on growth temperature and annealing evidences a kinetic roughening of the Fe surface at growth temperatures of 100-200° C due to the presence of step-edge barriers.

Stress and interdiffusion during molecular beam epitaxy of Fe on As-rich GaAs(001)

Interdiffusion during growth of Fe on As-rich GaAs(001) substrates has been investigated by real time stress measurements. Compared to Ga-rich GaAs(001), interdiffusion processes are decisively reduced. The optimum growth temperature (characterized by abrupt interfaces, pseudomorphic growth and negligible intermixing) is found to lie below 50 °C. At higher growth temperatures interdiffusion effects increase and eventually lead to the formation of a compact crystalline alloy layer of presumably Fe(2 + x)Ga(1 - x), as evidenced by transmission electron microscopy and x-ray diffraction.