Valley splitting and selection rules for inter-doublets optical transitions in strained [001]-Si/SiGe heterostructures

By an sp3d5s* tight-binding model we investigate temperature and electric field effects on the optical intersubband transitions between valley split conduction states confined in strained Si/SiGe [0 0 1]-quantum wells. By the same model we analyze the symmetry of the confined states and deduce selection rules for the involved optical transitions. The selection rules here provided predict specific signatures in the intersubband absorption spectra which can be tuned by proper control of thermal population of the states and by changes in the intervally coupling induced by perpendicular electric fields.