On the giant optical anisotropy observed in M-plane GaN/AlGaN quantum wells by crystal-field effect

Optical polarizations of GaN/AlGaN wurtzite quantum wells in various orientations are studied using an arbitrarily-oriented [hkil] Hamiltonian potential matrix. The optical matrix elements in the wurtzite quantum wells are calculated using the k-p finite difference scheme. The results reveal the presence of giant in-plane optical anisotropy (polarized normal to [0001]) in the M-plane (i.e. the (10 1macr 0)-oriented layer plane) GaN/Al
_0.2
Ga
_0.8
N quantum well due to the positive crystal-field split energy effect (DeltaCR > 0). Presented theoretical results are consistent with the photoluminescence measurements presented in the literature