Cyclotron-resonance anomalies in an antidot array measured by microwave photoconductivity

A lateral antidot array with a lattice period of 400 nm fabricated with electron-beam lithography on GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterostructures was investigated by microwave photoconductivity. Commensurability effects and distinct deviations from the classical cyclotron resonance have been observed in agreement with model calculations based on nonlinear dynamics of the electrons.