DFT Simulations of Zn_xMg_1–XO Solid Solutions for Solar-Blind UV Sensors: Evaluation of Electronic Structure and Phase Stability

In this research, density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of wurtzite and rocksalt Zn_xMg_1−xO pseudobinary compounds in their bulk phases. Calculated band gaps of Zn_xMg_1−xO solid solutions under study are further validated by means of spectroscopic ellipsometry and optical absorption. In agreement with an experiment, it is predicted that increase of Zn content in Zn_xMg_1−xO leads to narrowing of its band gap for both wurtzite and rocksalt phases. The calculated infra-red (IR) spectra show that the IR peaks are shifted towards larger frequencies along with decrease of Zn content. Presence of imaginary phonon frequencies in rocksalt Zn_xMg_1−xO of x > 0.625 allows us to suggest that it is necessary to use properly oriented substrates for epitaxial growth to overcome polycrystallinity inZn_xMg_1−xO thin films at concentration x = 0.4 – 0.6.