Interband optical transitions in doping superlattices

The absorption coefficient associated with interband transitions in doping superlattices is studied theoretically. Our calculations are based on a multiband effective-mass theory which simultaneously determines the electron and hole subband states self-consistency. Valence band mixing effects are calculated using a Luttinger-Kohn Hamiltonian. The absorption coefficients of both hetero- and homo-doping superlattices are evaluated from the complex dielectric function. The calculated absorption coefficients show that there are remarkable differences between our model and the conventional, uncoupled parabolic band model. Our results show that the valence band mixing can essentially eliminate the strong step-like structure in the absorption spectrum predicted by the conventional model. This suggests that the lack of an experimental observation of the step-like structure in the absorption spectrum may be due to valence band mixing and need not be attributed to potential fluctuations, spatial variations in the design parameters, or inhomogeneous excitation.