Electronic structure theory of strained wurtzite ZnO

Abstract

We study the electronic structure of strained ZnO in the wurtzite structure (w-ZnO), in a four band model, where is the electronic wave vector and is the relativistic momentum operator. The four bands are: one conduction band and three valence bands in decreasing order of energy. The strain Hamiltonian is added to the Hamiltonian, following an approach developed earlier by one of the authors (GST) [J. Phys. Chem. Solids 112, 280 (2018)]. The Hamiltonian is diagonalised by considering the conduction band and one valence band at a time. The remote bands are then subjected to second order perturbation theory treatment. Effects of strain are considered by following the Bir-Pikus method, as described in Phys. Rev. B 54, 2491 (1996) for w-GaN. The double group basis functions in the presence of spin–orbit interaction are chosen, also from this work. We considered two sets of stiffness parameters; one set from a recent first-principles study [Phys. Rev. B 89, 195135 (2014)] and the other from experiments. We calculate point energy levels as functions of strain and the inter-band transition energies as functions of in-plane stress. Strain-dependence of spin–orbit parameters is also considered. Valence band dispersions are obtained for and compared with existing reports. Satisfactory agreement is noticed. Our calculations are extended to study the effective masses and g-factors for the conduction band and the three valence bands, as functions of strain and the wave-vector. Strain-dependence of the effective masses and the g-factors are novel features of our calculation.