Stark effect and Stark-ladder effect in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells

Photoluminescence (PL) measurements at 10 K were performed in order to investigate the influence of electric fields on the exciton states in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells (ACMQW) grown by molecular-beam epitaxy. The coupling of the electronic energy levels in the wells led to an enhancement of the quantum-confined Stark effect. The PL intensity decreased as the electric field increased. Calculated values of the intersubband transition energies were in good agreement with the experimental values for the ACMQW, and these values showed a similar behavior as those for the step quantum well. When the external applied field was very strong, Stark-ladder transitions were observed, and the measured dependence of the field-induced energy shifts of the Stark-ladder transitions for the ACMQW agreed with theory. These results indicate that the Stark effect and the Stark-ladder transitions in a unique ACMQW based on the AlxGa1−xAs/GaAs structure were observed simultaneously.