Anomalous low-frequency grain-boundary capacitance in silicon

The admittance of silicon bicrystals has been measured as a function of temperature, frequency, and dc voltage. In some cases the low-frequency capacitance is anomalously large. The ac response of a simple double depletion layer structure is calculated. The anomalous capacitive currents are due to an out-of-phase modulation of the barrier height caused by charge injected into grain-boundary traps.