Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices

We examine the phase and the period of the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices utilizing in-situ magnetic field calibration by Electron Spin Resonance of DiPhenyl-Picryl-Hydrazal. The results confirm a $f$-independent 1/4 cycle phase shift with respect to the $hf = jhbaromega_{c}$ condition for $j geq 1$, and they also suggest a small ($approx$ 2%) reduction in the effective mass ratio, $m^{*}/m$, with respect to the standard value for GaAs/AlGaAs devices.