DYNAMIC PROPERTIES OF DOUBLE-BARRIER RESONANT-TUNNELING STRUCTURES

In this paper we present an approach to the dynamic transport properties of a double-barrier resonant-tunneling system. Based on the nonequilibrium-Green's-function technique and the Feynman-path-integral theory, the essential ingredients of this microstructure will be properly treated in a self-consistent way: the quantum interference across the structure, the nonequilibrium distribution of tunneling electrons driven by the applied bias voltage, and the effect of reservoirs (electrodes). The transient behavior of the tunneling current, immediately after the switching on of a dc bias voltage, is characterized by the building-up process of tunneling electrons in the quantum well. The novel negative differential conductance demonstrates itself as a function of frequency of the small ac signal superimposed upon a dc bias. The imaginary part of admittance is shown to be related to the conductance via a Kronig-Kramers relation.