OBSERVATION OF CHARGE STORAGE AND INTERSUBBAND RELAXATION IN RESONANT TUNNELING VIA A HIGH-SENSITIVITY CAPACITIVE TECHNIQUE

In suitably designed resonant tunneling double barriers the capacitance-voltage curve exhibits well-defined features corresponding to the charging and discharging of the quantum well. From the bias dependence of the electron density in the well we find that in our think parabolic wells, electrons tunneling into the excited states relax to the lowest subband and sequentially tunnel out. Our experiments allow us to obtain the charge density accumulated in the well and the tunneling escape rate of electrons out of the well.