A detailed study of the structural and optoelectronic properties of boron- and phosphorus-implanted a-SiC:H thin films is presented. The films have been deposited by ultra high vacuum plasma-enhanced chemical vapour deposition and have energy gap values of about 2 eV. The effects of varying carbon content, boron-and phosphorus-implanted dose and annealing temperatures are reported. It is found that ion implantation strongly modifies the structure, producing an increase of monohydride bonds. After annealing the defect density is mainly affected by dopant type and concentration rather than by residual radiation damage. We also show that no enhanced gap shrinkage is produced by boron with respect to phosphorus doping if the film composition is the same. A comparison with gas phase doping is also reported.