Photocurrent self-oscillations in a spatially direct GaAs/AlGaAs superlattice

We report the observation of self-sustained photocurrent oscillations in a weakly coupled spatially direct intrinsic GaAs/Al0.3Ga0.7As superlattice. The oscillations are attributed to the dynamics of unstable electric field domains related to the Gamma-Gamma e1-e2 tunneling resonance. The observed oscillation period is much longer than the carrier recombination time and the interwell tunneling time. The nonlinear behavior shows a complex dependence on the optical power and the external bias. (C) 1999 American Institute of Physics. {[}S0003-6951(99)00640-3].