Unveiling Additional Ambient Degradation Issues of Phosphorene FETs Under Laser Exposure and Positive Gate Bias

Abstract

Despite many extraordinary properties, phosphorene is not favorable for device applications due to its gradual degradation in ambient environmental conditions. The degradation process is mainly initiated by oxygen molecules attacking the lone pair of phosphorus atoms. However, the same is assisted by additional factors like water molecules, phosphorus vacancy, and negative gate bias. This work extended the journey further and revealed the role of positive gate bias and laser exposure on phosphorene degradation in the ambient environment. The work shows that in the case of phosphorene-based Field Effect Transistors (FETs), the material's degradation due to oxygen molecules can also be influenced by excess electrons due to positive gate bias in the channel. The first-principles molecular dynamics (MD) computations and Raman characterizations show that phosphorene degrades faster under positive gate bias (excess electron) than in pristine conditions (unbiased). The rapid degradation is mainly due to the enhanced oxidation by the excess electrons in the channel. The computational findings are experimentally verified using Raman characterization over phosphorene FETs. Additionally, the work also discusses the role of laser light on phosphorene degradation. The laser light does not play a direct role in pristine phosphorene degradation. However, the same assists the degradation process by etching the residual oxide formed over the phosphorene surface due to its ambient degradation. Our study reveals a unique reliability issue related to phosphorene FETs that gives a broader picture of the limitation of the material in the technology applications.