Bulk Microwave Conductivity of Semiconductors Determined from TEo01-Mode Reflectivity of Boule Surface

This paper describes an "electrodeless" technique for measuring microwave conductivity and dielectric constant of a bulk semiconductor boule without the necessity of fabricating samples. All that is required is that the boule be sufficiently large and that it have one planar surface. The planar surface is butted up to a flange terminating a circular waveguide. The complex TEo01 (circular E-field) mode-reflection coefficient at the surface is then measured with a reflection-coefficient bridge. Because of the particular properties of this mode, no contact impedance occurs as does in the case of the TE10¿ mode. Thus the measurements yield the true bulk properties of the material. To demonstrate the technique, 48- and 72-GHz measurements of the conductivity and permittivity of a number of semiconductor boules at room temperature are presented and are shown to agree favorably with results obtained by other means.