Alleviating the Responsivity-Speed Dilemma of Photodetectors via Opposite Photogating Engineering with an Auxiliary Light Source beyond the Chip

The dilemma between responsivity and response speed (RS dilemma) limits the performance of photodetectors (PDs). Here, opposite photogating (OPG) engineering is proposed to alleviate this RS dilemma via an auxiliary light source beyond the chip. Based on a $\mathrm{W}\mathrm{S}\mathrm{e}_{2}/\mathrm{G}\mathrm{a}_{2}\mathrm{O}_{3}$ OPG JFET, $\mathrm{a}\gt 10^{3}$ times faster response speed for deep ultra-violet detection has been achieved with negligible sacrifice of responsivity (R). It further demonstrates a R of $2.28\times 10^{3}\mathrm{A}/\mathrm{W}$, specific detectivity of $3.64\times 10^{17}$ Jones, photo-to-dark current ratio of $8.99\times 10^{7}, \mathrm{R}_{\mathrm{D}}\mathrm{u}\mathrm{v}/\mathrm{R}_{\mathrm{v}\mathrm{i}\mathrm{s}\mathrm{i}\mathrm{b}}\mathrm{i}_{\mathrm{e}}$ rejection ratio $\gt 9.6\times 10^{5}$, and external quantum efficiency of $1.11\times 10^{6}$ %. The strong depletion effect on the channel induced by the auxiliary light facilitates the decay speed, while its weak compensation effect sacrifices negligible R. The OPG engineering provides potential inspiration for the design of highly sensitive PDs.