Improved growth quality of epitaxial ZnTe thin films on Si (111) wafer with ZnSe buffer layer

Abstract

To achieve high-quality and low-cost ZnTe epitaxial films, a low-temperature (LT, 200 °C) ZnSe buffer layer with a thickness of 5 nm was grown on Si (111) wafers prior to the epitaxy of ZnTe layers by molecular beam epitaxy. Reflection high-energy electron diffraction patterns reveal that ZnTe epilayers grown at 335 °C with a thickness of 100 nm on the LT-ZnSe buffer layer present a completely two-dimensional growth mode. Film surfaces present smooth and flat morphology with the lowest surface roughness of ∼2.2 nm at a Te/Zn beam equivalent pressure ratio of 1.6. X-ray diffraction θ-2θ scanning indicates that the out-of-plane structure of ZnTe films is highly preferred with the (111) growth orientation of ZnSe/Si. X-ray diffraction φ scanning further confirms that the in-plane structure of ZnTe epilayer is also a single-crystal orientation growth. Thus, high-quality ZnTe (111) single-crystal epilayer with the lowest full-width at half-maximum of ∼200 arc sec and the smallest dislocation density of ∼1.12 × 108 cm−2 was grown on Si (111) wafers. In addition, the ZnSe buffer layer could alleviate the residual stress effectively for the heteroepitaxy of Si wafers. The most balanced residual stress for ZnTe/ZnSe/Si with σx of ∼96.5 MPa and σy of ∼94.2 MPa was obtained, which is essential for achieving high-performance and good mechanical properties of ZnTe-based devices.