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HL: Fachverband Halbleiterphysik

HL 30: Poster I

HL 30.42: Poster

Dienstag, 17. März 2020, 13:30–15:45, P3

Contactless Measurement of the Sheet Resistance of two-dimensional Electron Gases — •Timo A. Kurschat, Arne Ludwig, and Andreas D. Wieck — Angewandte Festkoirperphysik, 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. Thus a characterization is possible without destroying the wafer. With this method quality and homogeneity can be evaluated before further processing.

The sheet resistance is measured by placing two electrodes (round metal plates) close to the sample. These electrodes form capacitances C with the conductive layer. With a high-frequency alternating voltage applied to one electrode, the transmitted power can be measured at the other one. The measured amplitude depends on the sample resistance and the impedance of the capacitance, which is proportional to 1/ω C.

The electrodes have a diameter of 3 mm and 6 mm center-to-center distance. For low surface resistances from 100 to over 1000 Ω/sq the amplitude was evaluated at a frequency of 10 GHz. At higher resistances up to some 10 kΩ/sq, a frequency sweep from 1 MHz to 400 MHz was performed, and the resistance was determined with a fit.

It is possible to create maps of complete wafers. The lateral resolution depends on the size of the electrodes, so we expect an effective footprint of around 5 mm diameter.