MICROSCOPIC ANALYSIS OF SHOT-NOISE SUPPRESSION IN NONDEGENERATE BALLISTIC TRANSPORT

We present a numerical simulation of shot-noise suppression due to lon g-range Coulomb interaction in nondegenerate ballistic transport. Calc ulations make use of an ensemble Monte Carte simulator self-consistent ly coupled with a one-dimensional Poisson solver, and are applied to a ballistic semiconductor structure formed of a lightly doped active re gion surrounded by two contacts acting as reservoirs. The doping of th e injecting contacts and the applied voltage are taken as variable par ameters. At increasing voltages the transition from thermal to shot-no ise conditions is analysed. Space-charge is found to be responsible fo r an important suppression of shot noise even in the presence of linea r current-voltage characteristics. At increasing injection rates we ha ve found a strong tendency towards shot-noise suppression which scales with a dimensionless Debye length. The statistical properties of the electron flow along the structure are modified by Coulomb interaction, evidencing a sub-Poissonian behaviour. The frequency dependence of th e fluctuations is also analysed. The spectral density of current fluct uations exhibits structures related to the different characteristic ti mes involved in the carrier transport.