A high-voltage and high-frequency AlGaN/GaN photoconductive switch with a P-GaN-gate-controlled CAVET structure

• Dark-state leakage current limits the high-voltage application of con- ventional PCSS. • Reverse-biased pn junction depletion mechanism suppresses dark-state leakage current. • Novel structure enables high-frequency by regulating gate voltage-laser timing. • Concentration-regulated silicon enrichment layer used in modeling. Semi-insulating (SI) conventional photoconductive semiconductor switches (PCSSs) are characterized by favorable on-state performance. However, their ability to withstand high voltages is limited by the ohmic characteristic of the dark-state leakage current. PIN photodiodes exhibit high breakdown voltage but suffer from low photoelectric conversion efficiency and limited current-carrying capacity. Consequently, the growth of a cell array of current aperture vertical electron transistor (CAVET), exhibiting AlGaN/GaN high-electron-mobility transistor (HEMT) characteristics, on a SI GaN substrate is proposed. This design combines the advantages of both conventional PCSSs and PIN photodiodes, while effectively mitigating their inherent limitations. The device was designed based on the current level of normally-off p-GaN CAVET process, and the inevitable silicon doping enrichment problem on the SI GaN first epitaxial surface by HVPE growth method was fully considered in the design. Simulation results indicate that a withstand voltage of 60 kV can be achieved with a total device thickness of 502 μm. Moreover, the pulse width of the output photocurrent can be directly modulated, and its turn-off speed can be effectively accelerated through p-GaN gate control, thereby suggesting the potential for stable high-repetition-frequency operation.