Deep-ultraviolet-light-driven reversible doping of WS2 field-effect transistors

Abstract

Improvement of the electrical and photoelectric characteristics is essential to achieve an advanced performance of field-effect transistors and optoelectronic devices. Here we have developed a doping technique to drastically improve electrical and photoelectric characteristics of single-layered, bi-layered and multi-layered WS₂ field-effect transistors (FET). After illuminating with deep ultraviolet (DUV) light in a nitrogen environment, WS₂ FET shows an enhanced charge carrier density, mobility and photocurrent response. The threshold voltage of WS₂ FET shifted toward the negative gate voltage, and the positions of E¹_2g and A_1g peaks in Raman spectra shifted toward lower wavenumbers, indicating the n-type doping effect of the WS₂ FET. The doping effect is reversible. The pristine characteristics of WS₂ FET can be restored by DUV light illumination in an oxygen environment. The DUV-driven doping technique in a gas environment provides a very stable, effective, easily applicable way to enhance the performance of WS₂ FET.