Wannier–Stark localization in a strained InGaAs/GaAs superlattice

We report the first room-temperature observation of Wannier–Stark localization in a strained InGaAs/GaAs superlattice. The localization effects are in close agreement to theory. At low electric fields, the room-temperature absorption data show a small Wannier exciton peak at the lower edge of the miniband, and a more prominent M1 exciton at higher energy. At higher fields, the miniband localizes to a single quantum well exciton with accompanying +1 and −1 transitions. At even higher fields the initial blue shift of the Wannier exciton changes to a Stark effect red shift with a Δα/α of about 3.