A study on strain affecting electronic structures and optical properties of wurtzite Mg0.25 Zn0.75O by first-principles

We have made a first principles study to investigate density ofstates, band structure, the dielectric function and absorptionspectra of wurtzite Mg_0.25Zn_0.75O. The calculation iscarried out in a-axis and c-axis strain changing in the rangefrom 0.3 to --0.2 in intervals of 0.1. The results calculated fromdensity of states show that the bottom of conduction band is alwaysdominated by Zn 4s and the top of valence band is always dominatedby O 2p in a-axis and c-axis strain. Zn 4s will shift to higherenergy range when a-axis strain changes in the range from 0.3 to0, and then shift to lower energy range when a-axis strain changesin the range from 0 to --0.2. But Zn 4s will always shift to higherenergy range when c-axis strain changes in the range from 0.3 to--0.2. The variations of band gap calculated from band structure andabsorption spectra are also investigated, which are consistent withthe results obtained from density of states. In addition, weanalyse and discuss the imaginary part of the dielectric functionε₂.