GaSe single crystals grown by Bridgman method have been doped by ion implantation technique. The samples were bombarded in the direction parallel to c-axis by Si ion beam of about 100 keV to doses of 1x10(16) ions/cm(2) at room temperature. The effects of Si implantation with annealing at 500 and 600 degreesC on the electrical properties have been studied by measuring the temperature dependent conductivity and photoconductivity under different illumination intensities in the temperature range of 100-320 K. It is observed that Si implantation increases the room temperature conductivity 10(-7) to 10(-3) (Ohm-cm)(-1) depending on the post annealing temperature. The analysis of temperature dependent conductivity shows that at high temperature region above 200 K, the transport mechanism is dominated by thermal excitation in the doped and undoped GaSe samples. At lower temperatures, the conduction of carriers is dominated by variable range hopping mechanism in the implanted samples. Annealing of the samples at and above 600 degreesC weakens the temperature dependence of the conductivity and photoconductivity. This indicates that annealing of the implanted samples activates Si-atoms and increases structural deformations and stacking faults. The same behavior was observed from photoconductivity measurements. Hence, photocurrent-illumination intensity dependence in the implanted samples obeys the power low I-pc proportional to Phi(n) with n between 1 and 2 which is an indication of continuous distribution of localized states in the band gap. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.