Epitaxial growth and optical band gap variation of ultrathin ZnTe films

Zinc telluride (ZnTe) has attracted interests for its semiconducting, optoelectronic, and electrical switching properties. However, the growth mechanism of ultrathin epitaxial films is not well established. Here we present a systematic study of the growth ultrathin ZnTe films on GaAs (0 0 1) by molecular-beam epitaxy. In situ reflection high-energy electron diffraction and synchrotron based high-resolution X-ray diffraction showed that both surface atomic ordering and single crystalline phase aligned to the substrate orientation with small variation of c-axis lattice in the ultrathin films. While the deviation of chemical compositions depended on the growth conditions, information on the variation of the band gap and in-gap states was obtained through spectroscopic ellipsometry analysis. Our study showed that single crystal ZnTe films can serve as a model system in the development of Ovonic threshold switching devices for cross-point device applications.