Effect of Nonlinear Elasticity on Interband and Intersubband Transition Energies in GaN/AlN Superlattices

We present a theoretical study of the effect of nonlinear elasticity on interband and intersubband transition energies in wurtzite GaN/AlN superlattices. The effect of nonlinear elasticity is considered by taking into account the changes of elastic constants caused by the intrinsic hydrostatic pressure, originating from lattice misfit between constituents of the superlattice. We show that the influence of the effect of the nonlinear elasticity on the interband and intersubband transition energies in the GaN/AlN superlattices depends crucially on the strain state of structures, in particular on the in-plane lattice constant of the buffer or the substrate. For the superlattices strained to AlGaN buffers with small aluminum concentrations, the effect of nonlinear elasticity increases significantly the interband transition energy and decreases the intersubband transition energy. For the superlattices strained to AlGaN buffers with large aluminum concentrations, the effect of nonlinear elasticity leads to a decrease in the interband transition energy and an increase in the intersubband transition energy.