Design and Evaluation of a Compact Silicon Carbide Photoconductive Semiconductor Switch

A high-power vertical photoconductive switch was fabricated from a high-purity semi-insulating 4H-SiC wafer. The device was fabricated from an as-grown wafer with resistivity > 10(9) Omega . cm and had a dark resistance of greater than 6 x 10(9) Omega. The switch was operated at 15 kV/cm and achieved a peak photocurrent of 14 A into a 25-Omega load. Optimization of the excitation wavelength and switch geometry using an optical parametric oscillator was studied in order to decrease the laser requirements for optical triggering. This has led to a decrease in ON-state resistance of almost two orders of magnitude for similar excitation energy levels at visible wavelengths. This work forms the basis for developing very compact high-voltage photoconductive switches.