The influence of doping on the (opto)electronic properties of a-Si:H films is investigated by transient photoconductivity and photo-induced absorption measurements. The decay rate of the majority charge carrier decreases with doping due to fast minority carrier trapping already active at low doping levels. The transition from electron to hole conduction is observed at 3 ppm B2H6, At high doping levels the recombination rate becomes faster by recombination via doping-induced defects. (C) 2001 Elsevier Science B.V. All rights reserved.