Graphene, a single atomic layer of sp2-hybridized carbon, has immense potential as a transparent conducting material in electronic applications owing to its superior properties, including optical transparency and high conductivity.
Particularly, the tunable work function of graphene enables the integration of graphene electrodes with various electronic devices. To achieve high performance in graphene-based devices, effective charge transport between the graphene electrode and the semiconducting material needs to be optimized; this is closely related to the modulation of the Schottky barrier (SB). In this study, we investigate the tunable charge transport properties as a function of graphene doping in n-channel thin-film transistors (TFTs) in terms of the electrical characteristics and low-frequency noise (LFN) behaviors. Alkali metal carbonates tuned the work function of graphene, resulting in a dramatic decrease in the SB and an improvement of the carrier injection in n-channel TFTs. The electrical performance of the TFTs was evaluated by extraction of the field-effect mobilities and ratio of contact resistance to total resistance. Furthermore, the level of contact noise created by the barrier height fluctuation and relative contribution of channel
noise and contact noise in the TFTs was investigated by LFN measurements to demonstrate the tunable charge transport. Our findings therefore provide new insights into the tunable charge transport mechanism in graphene-based devices and reveal the immense potential of graphene as electrodes in high performance flexible and transparent displays.