Ballistic transport in resonant tunnelling devices with wide quantum wells

Abstract
Resonant tunnelling is investigated in double-barrier devices based on n-GaAs/(AlGa)As. The central GaAs wells have widths of 60, 120 and 180 nm. The 60 nm wide well exhibits 18 clear quantum resonances in the conductance even at room temperature. At low temperatures, over 70 resonances are observed for the 120 nm well device. The amplitudes of the resonances are found to be modulated by a quantum interference effect involving the collector barrier. The electron traversal time across the well is typically 0.1 ps, corresponding to a mean velocity of about 9*105 m s-1.