Optical Gain of Type-II 1.55-μm GaAsSb/InGaNAs/GaAs Trilayer Quantum Wells

The optical gain characteristics of type-II GaAsSb/InGaNAs/GaAs trilayer quantum well (QW) structures with a wavelength of 1.55 μm were investigated by using the multiband effective-mass theory. The carrier density dependence of the transition wavelength is shown to decrease with decreasing InGaNAs layer width. The GaAsSb/InGaNAs/GaAs trilayer QW structure shows an optical gain that is much larger than that of the GaAsSb/GaAs single QW structure. This can be explained by the fact that the confinement of the electron in the conduction band is enhanced due to the deep potential well of the InGaNAs barrier. Also, the optical gain is observed to increase greatly with decreasing InGaNAs layer width because of the type-I-like emission from a trilayer QW with a thin InGaNAs layer.