LOCAL MODULATION OF THE QUANTUM-WELL QUASI-CONTINUUM STATES USING CHARGED-CARRIER TRANSFER INDUCED BY INTERSUBBAND TRANSITIONS

By generating a local electric held across an asymmetrical coupled qua ntum-well structure and using resonant Raman spectroscopy as a probe, we were able to resolve two classes of continuum electronic states of energies close to the barrier height. The first class is related to a continuum resonant state that is located near the edge of the barrier and is extended across the barrier region but not across the coupled q uantum wells. The second class of continuum states is related to a qua sibound resonant state that is localized above the quantum wells. Ther efore, a local electric field across the coupled quantum wells modifie s the energy spectrum of the localized resonant state while keeping th e delocalized resonance unaffected. In our experiment the local electr ic field was generated by intersubband photoexcitation of carriers fro m one quantum well to the other. We observed a redshift of the quasibo und resonant state due to the intersubband photoexcitation.