Domain boundary instability in weakly coupled GaAs/AlGaAs superlattices

Self-sustained oscillations of the current with a frequency ranging from 0.7 to 3.6 MHz have been detected in weakly coupled GaAs/AlGaAs superlattice at 4.2 K. A study of the static and dynamic characteristics of the structure showed that the spontaneous oscillations arise in the local region of the superlattice, restricted by a size of the domain boundary expansion. The oscillations arise in the negative differential conductivity regions due to the periodic coupling and decoupling of subbands in adjacent quantum wells, forming the expanded domain boundary. We suggest that the spatio-temporal oscillations of the domain boundary should be considered as oscillations of an ensemble of several strongly phase-coupled oscillators. Each oscillator is a couple of two adjacent quantum wells, which operates as a single resonant tunneling diode.