The paper shows initial experimental results of research works taken by teams of the Institute of Electronic Materials Technology and Military University of Technology aimed at manufacturing in Poland photoconductive semiconductor switches (PCSSs) on semi-insulating (SI) gallium phosphide (GaP) wafers. These devices will allow pulsed switching of power circuits to high-voltage networks as well as triggering the high-energy of electromagnetic radiation. The properties and concentrations of deep-level defects, contributing to the charge compensation enabling the SI GaP crystals to be obtained, have been studied by the high-resolution photoinduced transient spectroscopy (HRPITS). The chips of switches with two planar electrodes separated by a gap of 2 mm were made and the connections enabling the dark current and photocurrent measurements as a function of the electric field strength to be carried out were assembled. The ways of increasing the switch amperage in the conductive state are discussed.