Nonlinear growth in the amplitude of radiation-induced magnetoresistance oscillations

We report the observation of inverse magnetic field periodic, radiation-induced magnetoresistance oscillations in GaAs/AlGaAs heterostructures prepared in W. Wegscheider's group, compare their characteristics with similar oscillations in V. Umansky's material, and describe the lineshape variation vs the radiation power, P, in the two systems. We find that the radiation-induced oscillatory resistance, Delta R(xx), in both materials, can be described by Delta R(xx)=-A exp(-lambda/B)sin(2 pi F/B), where A is the amplitude, lambda is the damping parameter, and F is the oscillation frequency. Both lambda and F turn out to be insensitive to P. On the other hand, A grows nonlinearly with P.