Strain-assisted structural transformation and band gap tuning in BeO, MgTe, CdS and 2H-SiC: A hybrid density functional study

Abstract

Structural transformations and electronic structures of (0001) BeO, MgTe, CdS and 2H-SiC films under equibiaxial in-plane strains are studied using the HSE06 range-separated hybrid functionals. The main results are summarized as follows: I) The structural transition from the polar wurtzite to the nonpolar graphite-like phase is predicted for BeO, MgTe and CdS but not for 2H-SiC, which is more covalent in nature. II) Either a direct or an indirect band structure is displayed in wurtzite BeO and 2H-SiC based on the values of strain, while only a direct band gap is displayed in wurtzite MgTe and CdS. At large tensile strains, the band gaps of graphite-like BeO and CdS are always indirect, whereas the graphite-like MgTe undergoes a direct-to-indirect band gap transition. Furthermore, the decrease in band gap is observed for both types of strain, thereby enabling a number of important technological applications.