Extraction of intrinsic field-effect mobility of graphene considering effects of gate-bias-induced contact modulation

Carrier mobility is one of the most important parameters to evaluate the quality and uniformity of graphene. The mobility of graphene is typically extracted from the transconductance of a field-effect transistor fabricated with the graphene layer. However, the mobility value evaluated by this method is imprecise when the contact resistance is non-negligible, or the contact resistance is modulated by the gate bias, which is the case for typical graphene field-effect transistors. Here, we suggest a method for extracting the precise intrinsic field-effect mobility by considering the effective bias across the channel and its gate-induced modulation. We show that the contact resistances of typical graphene field-effect transistors are significantly modulated by gate bias and conventional methods can, therefore, cause a considerable error in the evaluation of the mobility. The proposed method in which the contact-induced error is removed gives a channel-length-independent intrinsic field-effect mobility. This method can be generally used to correctly evaluate the field-effect mobility of nano-scale or low-dimensional materials.