Growth and characterization of P-doped CVD diamond (1Â 1Â 1) thin films homoepitaxially grown using trimethylphosphine

We have homoepitaxially grown phosphorus-doped chemical-vapor-deposited (CVD) diamond (1 1 1) films using trimethylphosphine (TMP) as a more convenient dopant gas and have measured their electrical properties. On one hand, sheet Hall coefficients, RH, obtained at various temperatures, T, above room temperature (RT) by AC Hall method were all negative and had the maximum in the |RH|-1/T plots, suggesting that two types of electrons with substantially different mobilities existed in the P-doped specimens. On the other hand, a hopping conduction with an activation energy of 0.013 eV was observed below RT. A two-carrier model was proposed to consistently explain all of these data obtained. From a curve fitting procedure, we deduced the RT electron mobility of 100 cm2/V s in the conduction band, the activation energy of 0.59 eV from the donor to the conduction band and the compensation ratio of 1.6%. The smaller carrier mobility was estimated to be ≈1 cm2/V s. It is found that TMP yields a much higher doping efficiency for n-type diamond synthesis, as compared with PH3.