SEQUENTIAL TUNNELING VERSUS RESONANT-TUNNELING IN A DOUBLE-BARRIER DIODE

The proposed sequential tunneling model predicts that the negative dif ferential resistance in a double-barrier diode (DBD) can exist indepen dent of a resonant Fabry-Perot effect. The proof is based on the exist ence of quasi-two-dimensional states for electrons in the quantum well . However, we find that existence of the quasi-two-dimensional states depends on a Fabry-Perot resonance. Therefore, if coherence of electro ns in the quantum well is completely lost, then the quasi-two-dimensio nal states will also disappear. We find that the damped Fabry-Perot mo del can provide a unified formula for electron transport in the DBD fr om pure coherent tunneling to pure incoherent tunneling. In the latter case, the negative differential resistance disappears.