10 kV $\beta$-Ga${}_2$O${}_3$ Sub-Bandgap Triggered Impurity Photoconductive Semiconductor Switches (i-PCSSs): Lessons for Optimal Design

Abstract

$\beta$-Ga${}_2$O${}_3$ photoconductive semiconductor switches (PCSSs) are attractive for high-voltage operation, but above-bandgap triggering requires deep-ultraviolet excitation. Here, we investigate a 650-um-thick, 0.01% Fe-doped $\beta$-Ga${}_2$O${}_3$ impurity PCSS with a 5-mm lateral gap under continuous-wave (CW) 808-nm sub-bandgap excitation at biases up to 10 kV ( 20 kV cm^-1). The device exhibited clear sub-bandgap photoconductive switching. As the optical power density increased from 0.64 to 3.18 W cm^-2, the ON-state current increased progressively while the ON-state resistance decreased, consistent with enhanced defect-assisted photocarrier generation. A higher applied bias further strengthened the switching response through enhanced field-assisted carrier transport. The ON/OFF ratio increases with optical power density but exhibits a nonmonotonic bias dependence, reaching approximately 15-16 near 5-7 kV. At 10 kV, increased OFF-state conduction and non-ideal transient behavior reduce the switching contrast. These results demonstrate near-infrared photoconductive switching but also highlight critical trade-offs in photoconductive thresholds for impurity states.

arXiv comment16 page; 5 Figures