Optical band gap energy values in wurtzite InxGa1-xN

Abstract

The narrow bandgap in InN has been known as a notorious example of local density approximation or generalized gradient approximation (LDA or GGA) calculations to give a metallic state. Various density functional methods are applied to optimize the atomic structures of the systems. These numerical results are used as the input values for the subsequent GW calculations, which can be applied to estimate the band gap value without phenomenological parameters. It is found that LDA with GW₀ or the hybrid functional with self-consistent GW₀ approximation provides sufficient theoretical results for both of the investigated compounds of GaN and InN. Although they are still time-consuming, due to less computational cost the former method is selected as a trial to compute the electronic structure in the entire range in ternary In_xGa_1-xN alloys without any arbitrary parameters. The present theoretical studies in ternary In_xGa_1-xN alloy were carried out by LDA with GW₀. As a result, a good agreement between theoretical and experimental results is obtained, and it is also shown that zone bending could be well-approximated using a quadratic function with a constant, independent of x, parameter equal to 1.85 eV, which is close to the recent experimental results.