Characterization of silicon in the terahertz

Semiconductor materials are widely used in integrated circuit and are important material platform in the fabrication and development of different technologies. Their material properties, e.g. complex permittivity and permeability, must be accurately known when designing high frequency microwave and millimeter wave devices. The applications of terahertz (THz) waves is receiving considerable attention because of the many potential applications. In this paper we provide results of an initial study to characterize low resistance silicon. First a free-space measurement setup is used to measure the characteristics of four commercial silicon wafers. These differently doped silicon wafers have different resistivity, i.e. 10, 20, 30 & 40 Ω cm. The complex relative dielectric constant and the loss tangent of the four types of silicon are measured. Second, the absorption properties of the same samples are measured using a compact terahertz time domain spectrometer (THz-TDS). In both measurements the results show that the sample doped using Phosphorus has a higher loss (absorption) and lower permittivity in the THz range compared the three wafers doped with Boron. In the case of the three Boron doped samples the loss tangent was found to depend on the resistivity of the material.