Effects of modulation doping on the optical properties of a type-II 1.55-μm GaAsSb/InGaNAs/GaAs trilayer quantum-well structure

The effects of modulation doping on the optical properties of a GaAsSb/InGaNAs/GaAs trilayer quantum well (QW) structure are investigated by using a self-consistent method. As modulation doping increases, the potential well near the GaAsSb layer becomes sharper and deeper because the electric screening field is directed toward the center of the well and attracts the electrons toward the GaAsSb well. The interband transition wavelength gradually decreases with increasing modulation doping density, and the optical gain is shown to be enhanced due to the band-bending effect. The increase in the optical gain can be explained by the fact that the optical matrix element increases with increasing modulation-doping density.