Authors: T. Chu, Y. Zhao, Z. Chen
Affilation: Purdue University, United States
Pages: 21 - 24
Keywords: graphene, bandgap, P/N junction
Owing to its unique electronic, thermal, and mechanical properties, graphene has sparked enormous scientific interest since its discovery in 2004. However, the absence of a bandgap limits its applications in electronic and optoelectronic fields. Theoretical calculations and experimental measurements indicate that a direct band gap up to a few hundred meV can be created in bilayer graphene (BLG) by applying a vertical electrical field or chemical doping. The field induced on-site energy difference in the two graphene layers leads to a gap between the otherwise degenerate conduction and valence bands. In this paper, double-gated bilayer graphene transistors are fabricated and a record high on/off current ratio of ~120 is achieved at room temperature by opening a bandgap up to ~170meV. Compared to a previous report, the larger bandgap is achieved with half of the gate voltage. A unique method of using threshold current to extract the bandgap is introduced for BLG and compared with other extraction methods. In depth analysis of device performance is presented for both bilayer and single layer graphene devices. Last, a true semiconducting graphene P/N junction device with variable bandgaps is presented for the first time.