Graphene field-effect transistors with high on/off current ratio and large transport band gap at room temperature

Graphene is considered to be a promising candidate for future nanoelectronics due to its exceptional electronic properties. Unfortunately, the graphene field-effect transistors (FETs) cannot be turned off effectively due to the absence of a band gap, leading to an on/off current ratio typically around 5 in top-gated graphene FETs. On the other hand, theoretical investigations and optical measurements suggest that a band gap up to a few hundred millielectronvolts can be created by the perpendicular E-field in bilayer graphenes. Although previous carrier transport measurements in bilayer graphene transistors did indicate a gate-induced insulating state at temperatures below 1 K, the electrical (or transport) band gap was estimated to be a few millielectronvolts, and the room temperature on/off current ratio in bilayer graphene FETs remains similar to those in single-layer graphene FETs. Here, for the first time, we report an on/off current ratio of around 100 and 2000 at room temperature and 20 K, respectively, in our dual-gate bilayer graphene FETs. We also measured an electrical band gap of >130 and 80 meV at average electric displacements of 2.2 and 1.3 V nm(-1), respectively. This demonstration reveals the great potential of bilayer graphene in applications such as digital electronics, pseudospintronics, terahertz technology, and infrared nanophotonics.