Excitation polarization anisotropy of the spontaneous emission from anM-plane GaN film: Competition between hole relaxation and exciton recombination

Abstract

We investigate a strongly anisotropically strained $M$-plane GaN film by photoluminescence spectroscopy. The spectra are dominated by the lowest-energy free-exciton transition, but the second lowest one is also detectable even at low temperatures. Rotating the linear polarization of the excitation results in a systematic change of the intensity ratio between these two transitions. We analyze this observation with the help of $6\ifmmode\times\else\texttimes\fi{}6$ $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ calculations and associated rate equation models. This analysis shows that the pronounced excitation polarization anisotropy for this $M$-plane GaN film originates from a competition between hole relaxation and exciton recombination.