Optical polarization anisotropies in GaN films for different nonpolar orientations

Abstract

AbstractWe have used polarized photoreflectance spectroscopy to study the electronic‐band‐structure modification of GaN films grown along different nonpolar orientations due to biaxial, anisotropic in‐plane strain. For nonpolar oriented films, the c‐axis of GaN lies in the film plane. In four different GaN films with a nonpolar orientation (M ‐ and A ‐plane), we observe a large in‐plane optical polarization anisotropy, which is much larger for the M ‐plane films due to the much larger strain in at least one of the in‐plane directions. The experimental results for the transition energies and oscillator strengths are compared with theoretical results obtained using the k·p perturbation approach. The large optical polarization anisotropy in M ‐plane GaN films can be used for polarization filtering and polarization‐sensitive photodetectors. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)