Photoluminescence and optical reflectance investigation of semipolar and nonpolar GaN

摘要

Optical properties of semipolar and nonpolar unstrained GaN are studied employing photoluminescence, optical reflectance and the k.p perturbation theory in this article. We find that donor bound and free A excitons show a strong polarization for photoluminescence in {11 (2) over bar2} and {10 (1) over bar0} GaN, while that of B excitons has only a little dependence on crystal orientations. Optical reflectance measurements are also performed to investigate resonance energies and transition probabilities of free excitons. The oscillator strength of A and C excitons has a strong dependency on the angle between c-axis and growth direction, while that of B is nearly unchanged in every unstrained GaN plane. The experimental results can be well explained by our k.p calculations. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.