Magnetic field dependence of threshold for chaotic acoustoelectric oscillations in n-InSb at 77 K

We report on experimental evidences that identify more clearly the piezoelectric origin of chaotic acoustoelectric voltage oscillations observed in n-InSb in a transverse magnetic field at 77 K. Measurements of the threshold current for chaotic behaviour showed that oscillations are reduced in amplitude when large DC currents driving the chaos are injected in a direction perpendicular to the [111] piezoelectric orientation as expected. The threshold current density for both nonlinear and chaotic behaviour is seen to decrease with the magnitude of the transverse magnetic field. Furthermore, we observed that the chaotic threshold current density saturates at high field towards a value consistent with the zero field threshold for a nonlinear acoustoelectric instability. This behaviour can be surprisingly interpreted with a linear model of the acoustic wave gain used to explain sound amplification and domain formation in Insb along a piezoelectric direction.