X-ray reflectivity from ZnSe/GaAs heterostructures

ZnSe/GaAs heterostructures have been studied using x-ray reflectivity. Two samples grown by molecular beam epitaxy (MBE) differed in initial growing conditions; the first was prepared by Se treatment of a GaAs substrate, and the second one was exposed to Zn before growth of the ZnSe film. The structure and morphology of the interface between the ZnSe film and GaAs substrate were investigated. The experimental x-ray reflectivity curves, measured at different wavelengths, were simulated using a distorted-wave Born approximation method. Fitting the experimental data indicated the presence of a Ga₂Se₃ transition layer between the ZnSe film and GaAs substrate for the Se-treated sample, confirming that Zn treatment during the MBE growing process improves the interface quality. Furthermore, the simulations indicated that the concentration of the Ga₂Se₃ was less than unity. From this, we propose that the transition layer is discontinuous, e.g., possesses an island-like morphology.