Al composition dependence of the optical properties in wurtzite GaN/AlGaN quantum wells with arbitrary crystal orientation

The optical properties of wurtzite (WZ) GaN/AlGaN quantum-wells (QWs) with an arbitrary crystal orientation are investigated as a function of the Al composition by using the multiband effective-mass theory. The induced potential energy, qF(z)(w)L(w), largely increases with increasing Al composition and rapidly decreases with increasing crystal orientation. The transition energy shows a strong dependence on the Al composition near theta = 0degrees and increases with increasing crystal orientation, except, for the QW structure with low A1 composition (Al=0.1). In the case of the QW structure with low Al composition (Al=0.1), the transition energy is nearly independent of the crystal angle. The, many-body optical gain increases with increasing crystal angle and reaches a maximum near theta = 50degrees or 60degrees, except for the QW structure with low Al composition (Al=0.1). The rapid increase of the optical gain near theta = 0degrees is mainly attributed to the fact that the internal field decreases with increasing crystal orientation. For a crystal orientation near theta = 90degrees; the. QW structure with high Al composition has a larger optical-gain than that with low Al composition.