A simple contactless method for evaluating the low-temperature parameters of a two-dimensional electron gas

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Abstract
A sample of two-dimensional electron-gas material is stuck, face upward, onto two flat, Corbino-configuration metal electrodes, thereby providing capacitive coupling (a few pF) to the gas through the high-dielectric-constant substrate material. At high magnetic fields and low temperatures, the minima in σxx produce a high resistance in series with the two coupling capacitors, and this resistance can be measured with an audio-frequency (10 kHz) capacitance bridge. The resistance peaks in high-mobility samples are very sharply defined, and their periodicity in 1/B gives directly the electron concentration. At low fields, prior to the appearance of the peaks, the resistance is proportional to μB2/n, thus relative mobilities may be determined.