Substrate effects in high gain, low operating voltage SnSe2 photoconductor

TL;DR

This study investigates substrate effects on SnSe2 photoconductors, revealing how substrate interactions influence responsivity and transient response, and demonstrating a methodology to understand intrinsic device behavior at ultra-low voltages.

Contribution

It introduces a comparative analysis of supported and suspended SnSe2 photoconductors, highlighting substrate-induced trap effects and providing a generic approach for studying layered material devices.

Findings

Supported device achieves high responsivity at ultra-low voltages.

Suspended device shows reduced responsivity but faster transient response.

Substrate interface significantly impacts gain and response characteristics.

Abstract

High gain photoconductive devices find wide spread applications in low intensity light detection. Ultra-thin layered materials have recently attracted a lot of attention from researchers in this regard. However, in general, a large operating voltage is required to obtain large responsivity in these devices. In addition, the characteristics are often confounded by substrate induced trap effects. Here we report multi-layer SnSe2 based photoconductive devices using two different structures: (1) SiO2 substrate supported interdigitated electrode (IDE), and (2) suspended channel. The IDE device exhibits a responsivity of ~ 10^3 A/W and 8.66x10^4 A/W at operating voltages of 1 mV and 100 mV, respectively - a superior low voltage performance over existing literature on planar 2D structures. However, the responsivity reduces by more than two orders of magnitude, while the transient response improves for the suspended device - providing insights into the critical role played by the channel-substrate interface in the gain mechanism. The results, on one hand, are promising for highly sensitive photoconductive applications consuming ultra-low power, and on the other hand, show a generic methodology that could be applied to other layered material based photoconductive devices as well for extracting the intrinsic behavior.