We report on the growth of phosphorus doped nc-Si:H thin films by plasma enhanced chemical vapor deposition and employ micro-Raman scattering and conductivity measurements to investigate the doping dependence of the structural properties. The grain size obtained from Raman spectra hardly changes with the doping concentration except for the highly doped sample, which is consistent with the results from X-ray diffraction measurements. The yielded strain values are found to relax with the increase of doping concentration. In addition, the comparison study of grain size distribution in both the doped and intrinsic nc-Si:H thin films reveals more ordered structures in the doped samples. The observed structural properties by optical measurements have been further confirmed by the electrical conductivity measurements. (C) 2003 Elsevier B.V. All rights reserved.