Optical polarization anisotropies in GaN films for different nonpolar orientations

摘要

We 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. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.