GRAIN-BOUNDARY EFFECTS ON CARRIER TRANSPORT IN UNDOPED POLYCRYSTALLINE CHEMICAL-VAPOR-DEPOSITED DIAMOND

A quantitative measure of grain-boundary effects on the carrier transp ort 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 p arallel to the grain orientation. The applied electric field intensity was varied to adjust the mean-free carrier drift distance. The degrad ation in the carrier transport properties at an electric field intensi ty of 10 kV/cm by the grain-boundary appears to be approximately a fac tor of two in comparison to the intragrain carrier transport.