Grain boundary effects on carrier transport in undoped polycrystalline chemical-vapor-deposited diamond

A quantitative measure of grain-boundary effects on the carrier transport properties in polycrystalline chemical-vapor-deposited diamond has been obtained using a 10-ns hard x-ray excitation source. Two device geometries were used to gain insight into the extent of grain-boundary effects: one having the applied electric field normal and the other parallel to the grain orientation. The applied electric field intensity was varied to adjust the mean-free carrier drift distance. The degradation in the carrier transport properties at an electric field intensity of 10 kV/cm by the grain-boundary appears to be approximately a factor of two in comparison to the intragrain carrier transport.