OSCILLATION OF THE SCATTERING TIME IN A 2D ELECTRON-SYSTEM WITH OVAL ANTIDOTS

Electron scattering by a single barrier is predicted to reveal singula rities as the magnetic field is changed, because the number of electro n collisions with the barrier dramatically increases as chaotic orbits around the barrier are changed into periodic orbits. To test this exp erimentally we have measured the magnetoresistance of AlGaAs/GaAs hete rostructures with a two-dimensional electron gas and a lateral lattice containing a macroscopic number of oval-shaped antidots fabricated us ing electron lithography. Reproducible fluctuations in the magnetoresi stance are observed at low field, which are due to the oscillations of the number of electron collisions with the antidots. The number of co llisions N before the electron escapes from the antidot has been calcu lated as a function of B in an electric field. The position of the max ima in N(B) obtained from calculations and experiment are in reasonabl e agreement.