Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: HL Posters III

HL 45.65: Poster

Thursday, April 4, 2019, 18:30–21:00, Poster E

Contactless Measurement of the Sheet Resistance of two-dimensional Electron Gases — •Timo A. Kurschat and Andreas D. Wieck — Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum

The aim of this work is to measure the sheet resistance of two-dimensional electron gases in GaAs without the need for built-in contacts. Such a method could be used to measure whole wafers in order to evaluate quality and homogeneity of the samples before further processing.

Therefore two electrodes (small metal plates) are placed close to the wafer so that they form capacitances C with the conducting layer. If an alternating voltage is applied, the transmitted signal can be measured, from which the sheet resistance can be calculated. The reactance of the capacitance is proportional to 1/ω C. To minimize the influence of the capacitance, either the frequency can be set high, or the capacitance can be determined from the phase or from the signal amplitude at multiple frequencies.

The lateral resolution depends on the size of the electrodes, which in turn determines the capacitance and frequency. In this work, circular electrodes with 3 mm diameter, 3 mm distance (6 mm distance center-to-center) and frequencies of some 100 MHz up to about 10 GHz are used. We expect an effective sensitivity footprint of about 5 mm diameter which is then the lateral resolution of this technique.