Microwave volt–impedance spectroscopy of semiconductors

We have tested experimentally the proposed method of microwave volt-impedance spectroscopy of semiconductors. The method allows to determine the local values of the semiconductor electrophysical parameters. The studies were performed on a homogeneous single-crystal GaAs wafer with a concentric antenna system formed on its surface. The resolution is determined by the diameter of the antenna central disk, which was amounted $a$ = 12, 27, 57 $\mu$m. A constant bias voltage of 0 $\le U \le$ 5 V was applied between the contact pads of the antennas. The complex impedance spectrum $Z (f, U)$ of each antenna was measured using a Cascade Microtech probe station in the frequency range $f$ = 0.1 – 10 GHz. The electrophysical characteristics of the semiconductor were determined from $Z(f, U)$ spectra by the inverse problem solving. We have established the $n$-type for our semiconductor and determined the electrical potential difference on the metal-semiconductor interface. We have found as well the electron concentration, mobility and conductivity. Measurements of the same parameters by Hall four-probe method (giving the surface averaging) showed good mutual agreement of the results for the homogeneous sample under study.