Gate-Tunable Photoresponse in SnSe₂ Field Effect Transistors

SnSe₂-based devices have emerged as promising candidates for photodetection applications due to their unique optoelectronic properties. As a member of the IVA-VIA group, SnSe₂ offers a combination of direct, indirect and forbidden transitions on its optical absorption edge, making it ideal for optoelectronic applications. In this study, SnSe₂ exhibits excellent conductivity, reaching a maximum current of 8.83 μ A at 100 mV, and a field-effect mobility ∼ 4 cm² V^-1 s^-1 at room temperature and pressure. Photoresponse analysis revealed a significant increase in drain current during illumination with a white laser, along with persistent photoconductivity. The photocurrent was found to be strongly dependent on the gate voltage, with more pronounced effects observed at negative gate. Analysis of the characteristic times during the excitation and relaxation phases identified two distinct mechanisms: faster indirect band-to-band transitions and slower photoexcitation from intrinsic and extrinsic trap states due to adsorbates or interfacial defects. Times of approximately 1 second, independent of gate voltage, were observed for faster transitions. These results highlight SnSe₂ 's potential for advanced optoelectronic applications, demonstrating its distinct photo-response behavior and sensitivity to gate voltage modulation.