Electron-hole liquids and band-gap renormalization in short-period semiconductor superlattices

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Abstract
In short-period superlattices, excited electrons and holes are subject to a one-dimensional perturbation with spatial dimension comparable to the bulk excitonic radius and strength comparable to the bulk excitonic binding energy. We study the stability of the electron-hole liquid and band-gap renormalization as a function of the perturbing potentials (band offsets) using the density-functional approach. We find that there is no universal band-gap renormalization in superlattices, that type-II staggered superlattices are the best candidates for observing the electron-hole liquid, and that a luminescence line in these systems should show a blue shift at intermediate electron-hole densities due to a positive differential band-gap renormalization.