Short-pulse excitation of quantum Hall systems: delocalization times and inelastic scattering lengths of hot electrons

Abstract

We have investigated the time scale of the excitation of electrons from localized to delocalized states in two-dimensional electron gas systems of GaAs/AlGaAs heterostructures at the integer quantum Hall effect (IQHE) breakdown. The measurements were performed by applying short electrical pulses (0.3 ns⩽pulse width ⩽10 ns) near integer filling factors ( ν=2, 4, and 6) for different electron mobilities (10 T −1⩽ μ H⩽90 T −1). The IQHE breakdown occurs when exceeding a critical pulse width, which is a function of pulse amplitude, magnetic field, and electron mobility. Applying a simple model, we obtain an estimate for the critical drift lengths, which vary from about 1 to 25 μm. We interpret the critical times as drifting times for the delocalization, and the critical lengths as related to the inelastic scattering lengths l in of hot electrons causing the QHE breakdown.