Predicting interband transition energies for InAs/GaSb superlattices using the empirical pseudopotential method

Recent measurements surprisingly show that the lowest valence-to-conduction confined transitions in narrow (InAs)(8)/(GaSb)(n) and (InAs)(6)/(GaSb)(n) superlattices increase in energy as the barrier thickness n increases. We show that in addition to the mesoscopic geometric quantities (well and barrier sizes), an atomic-scale description of interdiffused interfaces is needed to correctly reproduce the observed spectroscopic trend. The interdiffused interface is modeled via diffusion equations. We compare our atomistic empirical pseudopotential calculation in which only the bulk binary data are fit to experiment, with contemporary methods in which agreement with experiment is forced using ideally abrupt interfaces.