Quantum Confined Stark Effect In Asymmetric Double Quantum Wells

The effects of an external electric field on the luminescence and absorbtion properties of asymmetric coupled quantum wells (ACQW) structures consisting of two quantum wells of different width and depth are investigated. Experimental results are presented for two GaAs/AlGaAs coupled well systems, demonstrating the large shift and the sharp turnoff of the wavefunction overlap. We have observed the transition from type I (spatially direct) to type II (spatially indirect) in GaAs/AlGaAs ACQW. 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. 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.