Giant optical anisotropy in M-plane GaN/AlGaN quantum wells due to crystal-field effect

The optical polarization of GaN/AlGaN wurtzite quantum wells in various orientations is studied using an arbitrarily-oriented [ h k i l ] 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 1 ¯ 0 ) -oriented layer plane) GaN/Al0.2Ga0.8N quantum well, due to the positive crystal-field split energy effect ( Δ CR > 0 ). The present theoretical results are consistent with the photoluminescence measurements presented in the literature [B. Rau, et al., Appl. Phys. Lett. 77 (2000) 3343].