Electronic and optical properties of wurtzite GaN/AlGaN quantum-well with (10(1)over-bar0) crystal orientation

The electronic and the optical properties of (1010)-oriented wurtzite (WZ) GaN/AlGaN quantum well (QW) lasers are in investigated using the multiband effective-mass theory and the non-Markovian gain model with many-body effects. These results are compared with those of (0001)-oriented WZ GaN/AlGaN QW with strain-induced (PZ) and spontaneous (SP) polarization taken into account; The valence band structure of the (1010)-oriented GaN/AlGaN QW shows anisotropy (fourfold symetry) in the QW plane while the energy pattern of the (0001) orientation is completely isotropic. The flat-band (FB) model shows that the many-body optical gain of the (1010)-oriented QW is smaller than that of tire (0001)-oriented QW. This is because the Coulomb enhancement effect in the (0001)-oriented QW structure is more dominant due to its larger average hole effective mass compared to the (1010)-oriented QW structure. On the other hand, with the inclusion of internal fields, it is observed that the optical gain of the (0001)-oriented QW is significantly smaller than that of the (1010)-oriented QW in the range of investigated carrier densities and well widths. This is caused mainly by decrease in the optical-matrix element due to the spatial separation of the electron and hole wave functions in the (0001)-oriented QW. The optical gain gradually decreases with increasing well width fur both (0001)- and (1010)-oriented QWs. This can be explained by a decrease in the quasi-Fermi levels for carriers with increasing well width.