Millimeter wave complex refractive index, complex dielectric permittivity and loss tangent of high purity and compensated silicon

Single-crystal high-resistivity (11000- Omega -cm) boron-doped silicon was found to exhibit the lowest absorption loss at room temperature (25 degrees C) in the entire millimeter-wave region. The millimeter-wave absorption coefficient values for the compensated silicon are at least one order of magnitude less than values obtained with undoped pure silicon. At 140 GHz, the loss tangent value of the compensated silicon is as low as 40 mu rad. The study of the dielectric properties of silicon as a function of resistivity reveals that the low-frequency free-carrier absorption present in all silicon (and other semiconductors) vanishes with increasing resistivity. The dispersive Fourier transform spectroscopic technique was utilized for the measurements.<>