Irradiated Silicon for Microwave and Millimeter Wave Applications

Complex permittivity measurements of irradiated high-resistivity float-zone silicon have been performed in this paper from microwave to millimeter wave frequencies employing three different resonance techniques. It has been proven that the irradiated silicon exhibits resistivity of the intrinsic silicon at temperatures larger than 295 K and the loss tangent due to phonon absorption reaches about 10-5 at room temperature. The total loss tangent of the room-temperature irradiated silicon is smaller than ca. 6x10-5 at frequencies larger than 5 GHz. The real part of the complex permittivity and the corresponding refractive index of silicon linearly increase with temperature for T > 200 K.