Dynamics of electric-field domains and chaos in semiconductor superlattices

Abstract

A discrete drift model of sequential resonant tunneling in weakly-coupled doped or undoped GaAs AlAs superlattices (SL) under d.c. or d.c. + a.c. voltage bias and laser illumination is analyzed. In agreement with experiments our model shows an oscillatory I- V diagram for large enough values of the doping and/or laser illumination, multistability and hysteresis between stationary solutions and self-sustained time dependent oscillations of the current. Numerical and asymptotic analyses of the model show that these current oscillations are due to the formation, motion, annihilation and regeneration of negatively charged domain walls on the SL. For appropriate d.c. + a.c. voltage bias, chaotic current oscillations with loss of spatial coherence of the electric field will appear due to random nucleation of domains in the SL.