Structural dependence of optical gain in dip-shaped InGaN/GaN quantum wells

The structural parameter dependence of the optical gain of dip-shaped InGaN/GaN quantum well (QW) structures was investigated using the multiband effective-mass theory. In the case of the QW structure with a relatively smaller In composition (0.05) in the shallow well, the optical gain is larger than that with a larger In composition (0.1) in the shallow well. This is mainly due to the fact that the former has a smaller internal field than the latter. In the case of the QW structure with a thin dip well width and a relatively smaller In composition (0.05) in the shallow well, the optical gain rapidly increases with increasing In composition in the dip well because the internal field effect is negligible and a quasi-Fermi level separation becomes larger. On the other hand, the increasing rate of the optical gain is greatly reduced with increasing well width due to the internal field effect.