Ann-type semiconducting diamond thin film was obtained by microwave enhanced plasma chemical vapor deposition using phosphine(PH3)as a dopant source. A homoepitaxial diamond thin film with a thickness of about 300 nm was grown on the {111} surface of a type Ib diamond with a variety of dopant concentrations. Over a wide range of dopant concentrations (PH3/CH4:1000–20 000 ppm), then-type conduction was confirmed by Hall-effect measurements. The activation energy of carriers was 0.43 eV. The Hall mobility of about23 cm2/V shas been obtained at around 500 K for the 1000 ppm sample. No significant increase of hydrogen has been observed by secondary-ion-mass-spectroscopy analysis for the phosphorous doped layers. ©1997 American Institute of Physics.