Theoretical investigations on anisotropic optical properties in semipolar and nonpolar InGaN quantum wells

The anisotropic band structures and spontaneous emission of the non c plane InGaN/GaN quantum wells (QWs) were computed based on the k·p perturbation theory. Spontaneous emission due to the A valence band is strongly polarized perpendicular to the c axis, while that from the B band has 90°-rotated polarization, for the crystal angle θ larger than 50°. However, it was found that excited carriers can distribute into both the A and B bands, so that the effective polarization P_eff defined by the integrated luminescence intensity is much reduced even for nonpolar InGaN/GaN QWs. Thus, P_eff was systematically studied for arbitrary planes. We found that the energy separation between the A and B bands becomes significant and carrier population of the B valence band is suppressed as the In content increases, when P_eff approaches unity.