Modeling the Impact of Polymer Passivation on Graphene FET Stability

Graphene Field-Effect Transistors (GFETs) hold immense potential for sensing applications but suffer from severe performance instability in ambient environments due to unintentional p-doping by adsorbed oxygen and moisture. While Polyvinyl Alcohol (PVA) passivation is a promising solution to mitigate this degradation, the quantitative impact of the passivation layer thickness on device characteristics remains under-explored. This paper investigates the stabilizing role of PVA passivation using an analytical modified drift-diffusion model. By incorporating thickness-dependent specific capacitance and the chemical doping effects of hydroxyl groups, the model systematically evaluates how PVA thickness influences the Charge Neutrality Point (CNP) position and carrier transport. Simulation results reveal a critical trade-off: while the PVA layer acts as an n-type dopant to counteract ambient p-doping, excessive thickness functions as a bulk electron reservoir, over-compensating the channel into a unipolar n-type regime. Conversely, optimized thin-film passivation effectively restores the intrinsic ambipolar characteristic and realigns the CNP near zero bias. This study establishes a fast, predictive framework for designing stable, passivated GFETs to counteract environmental degradation without relying on complex numerical simulations or trial-and-error fabrication.