Background Photoconductive semiconductor switches are key optically triggered devices for high-frequency and high-power pulsed systems, in which kilovolt-level output, high voltage conversion efficiency, and sub-nanosecond response must be achieved simultaneously. Vanadium-doped semi-insulating 4H-SiC is particularly attractive for such switches because of its wide bandgap, high critical electric field, and suitability for fast high-voltage switching. However, the picosecond response of planar SiC photoconductive switches is strongly affected by the electrode geometry, optical excitation energy, and applied bias voltage.
Purpose Here we report a planar photoconductive semiconductor switch fabricated on a vanadium-doped semi-insulating 4H-SiC substrate with a partially asymmetric electrode configuration, and evaluate its picosecond photoelectric response under different gap-width, laser-energy, and bias-voltage conditions.
Methods Planar 4H-SiC photoconductive switch devices with different electrode gaps were fabricated and characterized. Their transient output voltage, voltage conversion efficiency, and rise time were measured under varied laser energies and bias voltages to assess the dependence of switching performance on device structure and operating conditions.
Results For the device with a 0.7 mm electrode gap, a maximum voltage conversion efficiency of approximately 81.6% was obtained at a bias voltage of 2 kV and a laser energy of 1.2 mJ, with a rise time of 229 ps. When the bias voltage was increased to 10 kV at the same laser energy, the device generated a maximum output voltage of 8.16 kV while maintaining a rise time of 241 ps.
Conclusions These results demonstrate that the vanadium-doped semi-insulating 4H-SiC planar photoconductive switch can provide efficient kilovolt-level pulse conversion with a picosecond-scale response. The proposed device structure offers a promising solid-state switching approach for compact, fast-response, high-power pulsed generation systems.
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