Influence of Waveguide Contact on Measured Complex Permittivity of Semiconductors

Abstract

Techniques employing rectangular waveguides to measure complex permittivity generally contain the tacit assumption that the material fills the waveguide uniformly. With semiconductors this assumption may be poorly satisfied near the waveguide walls due to (1) air gaps, (2) oxide layers, (3) potential barriers, and (4) distributed ``screening'' charges. The uniform‐filling assumption is removed in the present paper by treating the contact region with perturbation theory. The results are found to be simply represented by a lumped‐parameter equivalent circuit. Measurements performed on intrinsic germanium at 10.5 GHz agree well with the theory and indicate that unintentional air gaps and oxide layers dominate the measurements at high conductivities, even for ``tightly'' fitting samples.