Chemical bonding and electronic properties of Se-rich ZnSe–GaAs(001) interfaces

Abstract

We report synchrotron radiation, soft-x-ray photoemission spectroscopy studies of ZnSe–GaAs heterojunctions fabricated by molecular beam epitaxy in situ on GaAs(001)2×4 substrates. Measurements of the band offsets confirm that interfaces grown in Se-rich conditions exhibit relatively low valence band offsets (as low as 0.5 eV), while interfaces grown in Zn-rich conditions show relatively high valence band offsets (as high as 1.3 eV). In the Se-rich case, the improved surface sensitivity of the technique revealed previously unreported contributions to the As 3d and Ga 3d core lineshapes, with substantial (0.8–2 eV) chemical shifts. The shifts, as well as the coverage and escape-depth dependence of the results suggest enhanced atomic intermixing across Se-rich interfaces, with the formation of both Se–As and Se–Ga chemical bonds.