Optical-Phonon Assisted Tunneling in an Asymmetric Double-Quantum-Well Structure

Electroreflectance (ER), time-integrated photoluminescence (PL) and time-resolved PL experiments were performed on an Al0.36Ga0.64As/GaAs asymmetric double-quantum well (ADQWs) structure with coupled narrow and wide quantum wells in order to investigate the optical-phonon assisted tunneling. At a certain external applied voltage, a distinct quenching of the time-integrated PL intensity for the narrow quantum well is observed. By calibrating the internal electric field through the ER measurements and calculating subband levels in the ADQWs structure, the quenching is attributed to the resonant optical-phonon assisted tunneling of electrons between the narrow and wide quantum wells. The decay time of electrons in the narrow quantum well was also found to become minima at the same applied voltage.