$V_{\rm th}$ Shift in Single-Layer Graphene Field-Effect Transistors and Its Correlation With Raman Inspection

Raman measurement is carried out to understand V_th shift in single-layer graphene field-effect transistors (GFETs). The G (2D) peak shift in Raman spectra is correlated to the corresponding ΔV_th during stress and recovery phases. A blue (red) shift of G and 2D peaks is seen during stress (recovery) phase, indicating the corresponding trapping (detrapping) effects in the graphene device. It is interesting to note that, after forming gas annealing (H₂/Ar), the defects can be generated in graphene (evidenced by D peak of Raman spectra), leading to the increased ΔV_th for both negative bias temperature instability and positive bias temperature instability in single-layer GFETs.