Effects of electrode geometry and sub-bandgap excitation in β -Ga2O3 photoconductive semiconductor switches

This work reports enhanced photoconductive switching performance in Fe-doped β-Ga2O3 PCSS by concurrently optimizing electrode geometry and the optical excitation wavelength. By systematically varying the anode grid pitch (20–80 μm) and excitation spectrum (235–500 nm), we identify a key sub-bandgap regime centered at 272 nm that activates deep-level defect states and enables efficient bulk carrier transport. In contrast to above-bandgap excitation, which is limited by shallow surface absorption, sub-bandgap illumination promotes strong photocurrent generation and improved carrier collection. Under optimized conditions with a 40 μm pitch, the device exhibits a high peak photocurrent of 4.14 A and a low on-resistance of 10.4 Ω. To quantify this simultaneous achievement, we define a responsivity–conductance figure of merit (FoMRC), which reaches a value of 4.7 × 10−6 S/W. These results underscore the strong potential of Fe-doped β-Ga2O3 for next-generation high-power optoelectronic switching, enabling robust ampere-level photocurrents together with low on-resistance through optimized device geometry and sub-bandgap excitation.