High gain, high voltage, photoconductive switches using Si and GaAs have been studied for at least the last two decades. A laser is used to generate charge carriers within the material to render the device conductive. In this mode, once triggered, the device will not transition back to an off state until the conduction current drops below a threshold. Semi-insulating silicon carbide has high breakdown strength (>250 kV/mm) and is relatively transparent to below bandgap light. This material appears to operate in a non-high gain mode and the on resistance of the bulk can be controlled directly with the laser intensity over many orders of magnitude. It is presently believed that the conduction mechanism may be due to (a) excitation of deep states or (b) multi-photon pumping of carriers from the valance band. We present the study of the physics processes and development of a device operating at >20-kV.