Modulation doping effect in the optical gain of type-II GaAsSb/GaAs quantum-well structures

The effect of modulation doping on the optical gain characteristics of type-II GaAsSb/GaAs quantum-well (QW) lasers was investigated using a self-consistent method. The interband transition energy gradually increased with n-type modulation doping. However, in the case of p-type modulation doping, the rate of increase was found to be smaller than that of n-type modulation doping. The optical gain was found to be largely enhanced by an increasing n-type modulation doping density. This could be explained by the fact that the optical matrix element was greatly increased due to the band-bending effect. On the other hand, in the case of p-type modulation doping, the optical gain was slightly smaller than that for n-type modulation doping because the optical matrix element was reduced by the negative charge from the ionized acceptors near the well.