Higher harmonics in the current oscillations in weakly coupled GaAs/AlGaAs superlattices

It is shown that the self-sustained oscillations observed in weakly coupled GaAs/AlGaAs superlattices result from the superposition of sinusoidal oscillations of several coupled oscillators. Each oscillator is a single-barrier resonant tunneling diode. The coupled oscillators form an expanded boundary of an electric-field domain under conditions of negative differential conductance.