Giant microwave photoresistance of two-dimensional electron gas

We measure microwave frequency (4–40 GHz) photoresistance at low magnetic field B, in high mobility two-dimensional electron gas samples, excited by signals applied to a transmission line fabricated on the sample surface. Oscillatory photoresistance vs B is observed. For excitation at the cyclotron resonance frequency, we find a giant relative photoresistance ΔR/R of up to 250%. The photoresistance is apparently proportional to the square root of applied power, and disappears as the temperature is increased.