Difference in linear polarization of biaxially strained InxGa1−xN alloys on nonpolar a-plane and m-plane GaN

Abstract

InxGa1−xN structures epitaxially grown on a-plane or m-plane GaN exhibit in-plane optical polarization. Linear elasticity theory treats the two planes equivalently and is hence unable to explain the experimentally observed higher degree of linear polarization for m-plane than a-plane InxGa1−xN. Using density functional theory, we study the response of InxGa1−xN random alloys to finite biaxial strains on both nonpolar planes. The calculated m-plane InxGa1−xN valence band splitting is larger than that of the a plane, due to a greater degree of structural relaxation in a-plane InxGa1−xN. We provide a parametrization of the valence band splitting of InxGa1−xN strained to a-plane and m-plane GaN for In compositions between 0 and 0.5, which agrees with experimental measurements and qualitatively explains the experimentally observed difference between a-plane and m-plane polarization.