Visible Light Illumination Effects on Instability of MoS2 Thin-Film Transistors for Optical Sensor Application

Abstract

With the advent of the trillion sensor era, molybdenum disulfide (MoS2) offers intriguing future optical device opportunities due to qualities such as its novel optoelectronic properties and preferable form factors. However, while a fundamental understanding of device reliability under illumination is significantly important, most of the previous research has focused on persistent photocurrent (PPC) effects. For this reason, understanding of a clear mechanism remains elusive. Herein the work reported, electrical-bias-dependent device instability and net optical illumination effects of MoS2 thin-film transistors (TFTs) are experimentally evaluated to decouple the origins of device instability coming from either net electrical bias stress or illumination stress. In addition, time-dependent monitoring of relaxation behaviors under illumination at different wavelength hints that excess carrier generation and remnant electrons after annihilation during illumination play a key role in determination of photo-initiated instability of a device. For practical suppression of device instability under ambient light, an operation scheme (using trapping time increase under positive bias) is adroitly utilized to provide reliable device performance. Systematic understanding of device instability of MoS2 TFTs, and of their suppression principles, is potentially beneficial for the design of next-generation devices on the basis of 2D materials.