n-CdS/p-InP heterojunctions have been fabricated by deposition of n-CdS thin films using a spray pyrolysis technique onto p-type InP[100]. Current density-voltage and capacitance-voltage measurements were performed to determine the electrical properties of the structures. The forward current involves tunneling and is explained by a multi-tunneling capture-emission model. The reverse current is limited by the carrier generation process. The capacitance-voltage behavior indicates an abrupt interface with a main-band discontinuity of 0.76 eV occurs in the valence band. Effect of InP doping density on photovoltaic parameters has also been investigated at different light intensities. The devices exhibit a maximum power conversion efficiency (up to 12%) using an optimum doping density of 1 x 10(15) cm(-3).