Low On-Resistance and Ultrafast Rise Time Based on Vertical Diamond Photoconductive Switch with NPN Structure

Diamond photoconductive switch devices are expected to be candidates for microwave generation systems based on their attractive characteristics. Herein, a nitrogen-doped diamond single-crystal layer is grown on a boron-doped diamond substrate by microwave plasma chemical vapor deposition, which forms the NPN structure, extraordinarily reducing the on-resistance of the photoconductive switch. Compared with the traditional diamond photoconductive switch with a nitrogen-doped diamond substrate as well as a nitrogen-doped epilayer, the on-resistance of the NPN structure photoconductive switch is reduced by an order of magnitude. Especially, the rise time is only 62 ps when low laser energy is used to activate the NPN structure diamond photoconductive switch. At a 3.5 kV applied voltage and irradiation with a 4 mJ saturated energy laser, the output voltage waveform is observed with a voltage conversion efficiency of roughly 72.6% and a rise time of less than 150 ps as well as the minimum on-state resistance of approximately 18.9 Ω.