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HL: Fachverband Halbleiterphysik

HL 19: Poster Session IV

HL 19.25: Poster

Donnerstag, 30. September 2021, 13:30–16:30, P

Contactless Measurement of the Sheet Resistance of two-dimensional Electron Gases — •Timo A. Kurschat, Arne Ludwig, 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. Thus a characterization is possible without destroying the wafer. This method can be used to create spatially resolved maps of whole wafers to evaluate quality and homogeneity prior to 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 capacitances, which are proportional to 1/ω C.

The electrodes have a diameter of 3 mm and 6 mm center-to-center distance. The measurement range starts at about 300 Ω/ and goes up to 50 kΩ/. The sheet resistance is determined by sweeping the frequency between 1 MHz and 400 MHz and then applying a fit.

Besides the measurements of samples with known sheet resistance, maps of complete wafers are shown. The lateral resolution of about 5 mm depends on the size of the electrodes and was estimated by etching a structure on a wafer.