Field-driven blue shift of excitonic photoluminescence in Si-Ge quantum wells and superlattices

The electric field dependence of photoluminescence is studied in Si-based quantum structures. A higher energy shift of luminescence peaks for fields applied along the growth axis has been observed in GaAs/AlxGa1-xAs semiconductor superlattices and in superlattices involving SiGe materials. However, we have observed blue shifts not only in superlattices, but in quantum wells, especially at low fields. We attribute this observation to a large decrease of the exciton binding energy offset by the field-induced shifts of the band edge states. The variationally calculated values for the field-induced shifts are compared and discussed with the experimentally observed ones.