The electron states are investigated for a resonant-tunneling diode in which the potential well of an accumulation layer prevents electrons from tunneling coherently from source to drain at resonance energies. They may be specified as extended states, incident from the drain (anode) side and reflected back to it, or as localized discrete ‘‘quasilevel’’ states, almost trapped in the overall barrier system and decaying to the continuum on the anode side. The relation between these two representations is investigated. Quasilevels that are at energies not near a barrier resonance energy in general have long escape (decay) times, while a quasilevel in a certain energy range around a barrier resonance energy (for the range of applied bias that places it there) has an escape time of the order of the Breit-Wigner response time of the resonant structure by itself. This energy range is proportional to the square root of, and in practice will be large compared with, the resonance energy width of the ‘‘stand alone’’ resonant structure. Resonant conduction may be expected to occur, for the corresponding bias range, by scattering transitions from the cathode source to the quasilevel followed by tunneling escape from the latter to the anode side.

• Received 5 August 1991

DOI:https://doi.org/10.1103/PhysRevB.45.9042