Record Responsivity-conductance Performance in Sub-bandgap-triggered Ga2O3 PCSS

Abstract: We present an investigation into the role of anode grid pitch and excitation spectrum on the performance of high-power optoelectronic switches utilizing Fe-doped $β$-Ga$2$O$3$. By systematically varying the anode grid pitch ($20-80\ μ\text{m}$) and the excitation spectrum ($235-500\ \text{nm}$), we identify a crucial sub-bandgap regime, centered at $272\ \text{nm}$, that effectively activates deep-level defect states. This activation is shown to enable highly efficient bulk carrier transport, a significant contrast to conventional above-bandgap excitation which is hampered by shallow surface absorption. The sub-bandgap illumination promotes strong photocurrent generation and substantially improved carrier collection efficiency. Under optimized conditions, specifically utilizing a $40\ μ\text{m}$ anode pitch, the fabricated device achieves a high peak photocurrent of $4.14\ \text{A}$ and a record-low on-resistance of $10.4\ Ω$. To quantify this simultaneous high-performance achievement, we introduce a responsivity-conductance figure of merit ($\text{FoM}{{RC}}$), which attains a record value of $4.7 \times 10^{-6}\ \text{S/W}$. These findings robustly demonstrate the superior suitability of Fe-doped $β$-Ga$_2$O$_3$ for next-generation high-power optoelectronic switching applications, enabling reliable ampere-level photocurrents coupled with minimized on-resistance through strategic device geometry optimization and sub-bandgap excitation.