Calculation of carrier density in separate confinement heterostructure layer

Recently, it has been discussed that the carrier overflow into the separate confinement heterostructure (SCH) layer has a significant impact on the performance of semiconductor lasers. To clearly determine the essential parameters related to carrier overflow, the numerical relationship between the carrier densities in the active and SCH layers was calculated, based on the assumption that the quasi-Fermi levels are invariant and the electron and hole densities are equal. The calculated result conformed to that obtained with a laser simulator which was based on the drift-diffusion model. These results suggest that the relationships in the product of the effective state densities of the conduction and valence bands, and the band gap between the active and SCH layers, are essential for the carrier overflow.