Large optical polarization anisotropy due to anisotropic in-plane strain in m-plane GaInN quantum well structures grown on m-plane 6H-SiC

Abstract

We investigated the optical polarization anisotropy of m-plane GaInN/GaN quantum well structures on m-plane SiC and bulk GaN substrates. On bulk GaN, the degree of polarization increases with increasing indium content according to the larger strain-induced separation of the topmost valence bands. On m-plane SiC, however, we observe constantly large polarization ratios of around 90% and more. From an x-ray strain state analysis and calculations of the valence band energies, we find that an anisotropic strain of the GaN buffer layer leads to a very strong separation of the topmost valence bands resulting in a large degree of polarization.