Type I–type II anticrossing and enhanced Stark effect in asymmetric coupled quantum wells

Abstract

We have observed the transition from type I (spatially direct) to type II (spatially indirect) in GaAs/AlGaAs asymmetric coupled quantum well structures at 10 K. The transition is manifested as a strong electric field induced quenching of the photoluminescence which correlates well with the results of a single particle calculation of the electron-hole overlap. By properly designing the coupled well structure, photoluminescence quenching (90%–10%) is observed for a change in bias field of only 5 kV/cm. Observations of the absorption spectrum clearly demonstrate that the type I–type II transition occurs by an electronic level anticrossing. Owing to the large level repulsion, a Stark shift of 5 meV is observed when the bias field is switched by only 18 kV/cm.