Dielectric Anomalies in Silicon Single Crystals

Abstract

Dielectric constant κ′ and dielectric loss κ″ of Si single crystals with resistivities 12.5, 1000, and 16 000 Ω·cm were measured in the frequency range 103 to 109 cps at temperatures from 4.2°K to 300°K. The dielectric constant at 300°K decreases with frequency and reaches a constant value of 12 above 107 cps. The dielectric loss decreases linearly with frequency in the whole frequency range. The variation of dielectric constant and loss with temperature shows a sharp conductivity-dependent jump at 25°K. Below 25°K the dielectric constant and loss reach constant values. The value of the dielectric constant below 25°K corresponds to the square of refractive index. Between 30° and 80°K the dielectric constant reaches a frequency-independent plateau. The height of the plateau depends on the conductivity of the sample. Above 80°K the dielectric constant is frequency-dependent and increases exponentially with temperature. The irregular variation of dielectric properties is correlated to the formation and trapping of charge carriers.