Frequency Response of Metal-Insulator-Metal Tunnel Junctions

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Abstract
Time-dependent tunneling currents in response to small input voltages applied to biased metal-insulator-metal tunnel junctions are calculated by means of the linear response theory based on the transfer Hamiltonian model for the direct electron-tunnelings. An exponentially decaying factor exp (-t/τ), where τ is a life time of a Bloch electron caused by scattering, is introduced into the formula for each elementary current due to a single tunneling-transition of an electron. Nevertheless, the terms including such a decaying factor completely cancel each other in the expressions for the main parts of the resultant tunneling-current responses. The time lags of the responses turn out to be much less than τ.