Lifetime of Resonant State in a Resonant Tunneling System

Time evolution of an electron wave packet is investigated to estimate the limit to operation speed of resonant tunneling devices. The wave packet localizes in a quantum well for a finite lifetime. The lifetime is related to the energy width of the resonant level due to the uncertainty principle, and is inversely proportional to the tunneling probability of the funnet barrier. When barriers of the quantum well are asymmetric, the lifetime is determined by the barrier that has the higher tunneling probability.