Dynamical description of the buildup process in resonant tunneling: Evidence of exponential and nonexponential contributions

The buildup process of the probability density inside the quantum well of a double-barrier resonant structure is studied by considering the analytic solution of the time dependent Schrodinger equation with the initial condition of a cutoff plane wave. For one level systems at resonance condition we show that the buildup of the probability density obeys a simple charging up law, /Psi(tau)/phi/ = 1 -e(-tau/tau 0), where phi is the stationary wave function and the transient time constant tau(0) is exactly two lifetimes. We illustrate that the above formula holds both for symmetrical and asymmetrical potential profiles with typical parameters, and even for incidence at different resonance energies. Theoretical evidence of a crossover to nonexponential buildup is also discussed. [S0163-1829(99)51728-1].