On the optical polarization properties of semipolar InGaN quantum wells

Polarized photoluminescence of strained quantum wells grown on c–plane, semipolar $(10\stackrel{-}{1}2)$, $(11\stackrel{-}{2}2)$, $(10\stackrel{-}{1}1)$, $(20\stackrel{-}{2}1)$ planes, and nonpolar GaN substrates was studied experimentally and in theory. The observed optical polarization switching between the substrate orientations $(10\stackrel{-}{1}2)$ and $(11\stackrel{-}{2}2)$ is in accordance with our general model of polarization switching, based on a $\overrightarrow{k}·\overrightarrow{p}$ model of arbitrary substrate orientation. Spectrally resolved measurements of the polarization degree stemming from $(10\stackrel{-}{1}2)$ samples show that the maximum of the polarization degree is red–shifted with respect to the maximum of the photoluminescence intensity. We ascribe this effect to an increased polarization of the transitions for higher indium content.