Many-body optical gain of strained GaAsSb/GaAs quantum well lasers

The optical properties of type-II GaAsSb/GaAs quantum wells (QWs) are investigated using a self-consistent method. The results are also compared with those obtained from the flat-band model ignoring a screening effects. The subband energies for the self-consistent model are pushed downwards compared to those for the at-band model, and the shift of the subband energy due to the band-bending effect increases with increasing Sb composition. The self-consistent model shows an enhancement of the optical gain in addition to the large blueshift of a peak gain energy. The enhancement is mainly attributed to an increase in the optical matrix elements due to the bandbending effect. The relation between the carrier density and the band-gap renormalization is close to ΔEg proportional to n2D1/3 and is found to be independent of the Sb composition.