Controllable bistabilities and bifurcations in a photoexcited GaAs AlAs superlattice

Self-sustained photocurrent oscillations and bifurcation process have been demonstrated on an undoped photoexcited GaAs/AlAs superlattice. The effects of carrier density, varied by changing the laser intensity, on the transition between static and oscillating domains are investigated. Within a certain range of intermediate intensities, the time-average photocurrent vs voltage plot exhibits a controllable bistability region near the edge of the first photocurrent plateau and the oscillations disappear via a subcritical Hopf bifurcation (HB) with increasing DC bias. Below this range, the oscillations disappear via a supercritical HB, while above it, a homoclinic connection is observed.