The formation of a p–n junction in a polymer electrolyte top-gated bilayer graphene transistor

We show simultaneous p- and n-type carrier injection in a bilayer graphene channel by varying the longitudinal bias across the channel and the top-gate voltage. The top gate is applied electrochemically using solid polymer electrolyte and the gate capacitance is measured to be 1.5 µF cm−2, a value about 125 times higher than the conventional SiO2 back-gate capacitance. Unlike the single-layer graphene, the drain–source current does not saturate on varying the drain–source bias voltage. The energy gap opened between the valence and conduction bands using top- and back-gate geometry is estimated.