Tuning graphene nanoribbon field effect transistors via controlling doping level

By performing first-principles transport simulations, we demonstrate that n-type transfer curves can be obtained in armchair-edged graphene nanoribbon field effect transistors by the potassium atom and cobaltocene molecule doping, or substituting the carbon by nitrogen atom. The Dirac point shifts downward from 0 to -12 V when the n-type impurity concentration increases from 0 to 1.37%, while the transfer curves basically maintain symmetric feature with respect to the Dirac point. In general, the on/off current ratios are decreased and subthreshold swings are increased with the increasing doping level. Therefore, the performance of armchair-edged graphene nanoribbon field effect transistors can be controlled via tuning the impurity doping level.