DOPING-PROFILE EFFECTS ON THE TUNNELING TIMES OF ELECTRONS CONFINED IN DOUBLE-BARRIER HETEROSTRUCTURES

We study and compare the behavior of the left- and right-tunneling tim es of electrons quasiconfined in asymmetric double-barrier structures as a function of the bias for two different doping configurations in t he electrodes: uniform doping and gradual doping. The potential experi enced by the electrons is calculated self-consistently for each case b y simultaneously solving the Schrodinger and Poisson equations. Afterw ards, the stabilization method is employed to calculate the correspond ing tunneling times. The case of gradual doping is especially interest ing because an accumulation layer appears when the voltage is high eno ugh. To analyze the stabilization graphs in the range of voltages wher e the two-dimensional quasiconfined level in the emitter interacts wit h the quantum-well level we have introduced a three-level model. We pr esent a comparison of the tunneling times calculated for the two dopin g profiles with the ones obtained with a model potential. Finally, cha rge-accumulation effects are analyzed in the gradually doped case and critically discussed within the framework of available experimental da ta.