Enhanced As-Sb intermixing of GaSb monolayer superlattices in low-temperature grown GaAs

As-Sb compositional intermixing was studied by transmission electron microscopy (TEM) in GaAs films grown by molecular-beam epitaxy at low temperature (LT) and delta doped with antimony. The TEM technique was calibrated by imaging the as-grown films with delta layers containing various amounts of Sb. The calibration allowed us to deduce the effective As-Sb interdiffusion coefficient from apparent thickness of the Sb delta layers in the films subjected to isochronal anneals at 400-600 degreesC. The As-Sb intermixing in LT GaAs was found to be much enhanced when compared to conventional material. Its temperature dependence yields a diffusion coefficient of DAs-Sb=2x10(-14) exp(-0.62 +/-0.15 eV/kt) cm(2) s(-1). Since the kick-out mechanism operating under equilibrium conditions is valid for As-Sb interdiffusion in GaAs, the enhanced intermixing was attributed to an oversaturation of arsenic self-interstitials in the LT GaAs films. The effective activation energy for As-Sb interdiffusion in LT GaAs seems to be reasonably close to the migration enthalpy of As interstitials, whereas their concentration was roughly estimated as 10(18) cm(-3). (C) 2001 American Institute of Physics.