Molecular beam epitaxial growth of ZnSe on GaAs substrates: Influence of precursors on interface quality

The initial growth of thin ZnSe layers, grown on GaAs(0 0 1) using molecular beam epitaxy (MBE), has been studied using real-time reflection high-energy electron diffraction (RHEED), as well as X-ray double-crystal rocking curves (DCRC), reflectivity difference spectroscopy (RDS) and transmission electron microscopy (TEM). A noticeable difference in interface quality and growth was observed depending upon the initial precursor. Exposure to Se flux before growth led initially to three-dimensional growth, whereas exposure to Zn flux or no precursor led immediately to two-dimensional growth. X-ray DCRC and RDS confirmed that the overall sample quality was better with two-dimensional growth, and TEM observations were consistent with previous studies which have shown that initial three-dimensional growth is related to the formation of Ga₂Se₃ at the interface, leading to high densities of stacking faults and edge dislocations.