Corbino-capacitance technique for contactless measurements on conducting layers: application to persistent photoconductivity

The technique utilizes the capacitive coupling between a pair of Corbino electrodes and a conducting layer placed on top of and insulated from the electrodes. Measurements on heterostructures of GaAs/GaAlAs and GaAs/GaInP are reported. The audiofrequency impedance exhibits ShubnikovdeHaas oscillations. These oscillations are used to investigate persistent photoconductiity at 0. 635 tm and 1. 00 jim illumination. The role played by contacts is discussed.