RESPONSE OF A SEMICONDUCTOR TUNNELING STRUCTURE TO A TIME-DEPENDENT PERTURBATION

The one-dimensional electron resonant tunneling spectrum (I-V characteristics) is calculated for a GaAs/AlGaAs double barrier resonant tunneling structure in the presence of a small time-dependent electric field, assuming a coherent tunneling mechanism and local equilibrium in the electrodes. The small time-dependent signal is applied as a probe perturbation in addition to the usual dc voltage. When the perturbation frequency is 4.6 X 10(12) rad/s, the calculated current density at resonance is maximally decreased in response to the external ac perturbation. The current density returns to its dc value when the perturbation frequency is higher than omega(max) = 1.5 X 10(13) rad/s. It is interpreted that the response time for the tunneling electrons in this structure is of the order of tau = 1/omega(max) = 6.7 X 10(-14) s. The comparison of this calculation result with the experiment [tau = 6.5 X 10(-14) s, T. C. L. G. Sollner, E. R. Brown, W. D. Goodhue, and H. Q. Le, Physics of Quantum Electron Devices, edited by F. Capasso (Springer, Berlin, 1990), p. 147] suggests that the speed of the electron redistribution in the time-dependent wave functions is very fast in these tunneling structures.