Investigation of Photoconductive Semiconductor Switches for High-Voltage Applications

Two photoconductive semiconductor materials were studied for their application in high-voltage systems. Gallium arsenide (GaAs) and gallium nitride (GaN), both direct bandgap semiconductors, were evaluated across different topologies within the tens-of-kilovolts range. GaAs devices, fabricated from commercially available crystals, were tested using a lateral switching scheme. GaN devices, on the other hand, were predominantly tested in a vertical configuration, using crystals grown by a collaborator, with thicknesses reaching up to 4.3 mm; some lateral testing was also conducted. Typical lateral devices featured electrode gap spacings of 20–30 mm. GaAs experiments investigated the parallelization, jitter, and lifetime characteristics of GaAs devices under various voltages, achieving voltages as high as 80 kV and shot-to-shot jitter as low as 470 ps. GaN experiments showed high voltage holdoff, with up to 42 kV held across two 1.7 mm thick switches operated in series.