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, R-H, obtained at various temperatures, T, above room temperature (RT) by AC Hall method were all negative and had the maximum in the vertical bar R(H)vertical bar-1 IT 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 cm(2)/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 approximate to 1 cm(2) /V s. It is found that TMP yields a much higher doping efficiency for n-type diamond synthesis, as compared with PH3. (c) 2004 Published by Elsevier B.V.