Magnetic-field effects on undriven chaos in a weakly coupled GaAs/AlAs superlattice

We have investigated the effect of a perpendicular magnetic field on the sp ontaneous current oscillations in a weakly coupled GaAs/AlAs superlattice. At zero magnetic field, voltage regions of periodic as well as chaotic osci llations are observed. With increasing magnetic field B, the voltage region s for chaotic oscillations become larger and those for periodic oscillation s smaller. At B=9 T, the whole voltage range consists of chaotic oscillatio ns. At the same time, the time-averaged current-voltage characteristic hard ly changes. The experimental observations demonstrate that the quantization by the perpendicular magnetic field results in an equalization of the sequ ential resonant tunneling process over the whole superlattice, suppressing scattering effects due to disorder. (C) 2000 American Institute of Physics. [S0003-6951(00)03120-X].