Contactless Observation of Microwave Induced Resistance Oscillations in ZnO/MgxZn1 –xO Heterojunction

In high-quality ZnO/Mg x Zn 1 – x O heterojunctions, microwave-induced magnetoresistance oscillations have been investigated using a contactless technique. The basic detection principle relies on the measurements of a signal transmission in the radio frequency range ( f ~ 50 MHz) between two T-shaped antennas, capacitively coupled to a two-dimensional electron system. When the sample is exposed to exciting microwave radiation with the frequency 60–140 GHz in low magnetic fields, at least three oscillations are well resolved in the high-frequency conductivity. The amplitude of the first oscillation is comparable in amplitude to Shubnikov–de Haas oscillations in strong magnetic fields. A significant advantage of this method is the absence of Ohmic contacts or metallization deposited on the sample surface, which provides additional information for understanding the origin of this phenomenon.