Graphene RF transistors with buried bottom gate

To improve process induced mobility degradation of graphene, radio frequency (RF) transistors with buried bottom gates have been fabricated and characterized. In this process, graphene is transferred to the top of finished gates and source/drains as almost the very last step of the entire fabrication process. A unit graphene transistor shows the on-current of 130 μA/μm the I_on/I_off ratio of 5.31, and the maximum transconductance of 6.85μS/μm at V_D= 0.1 V. The graphene RF transistor with a channel length of 600 nm shows a maximum oscillation frequency (f_max) of 13 GHz and a cut-off frequency (f_T) of 2 GHz after de-embedding. The higher f_max than f_T is due to less source-drain resistance (R_DS) made by a fully-covered channel region by the buried gate. Because of the higher f_max the proposed device structure can be a promising candidate for graphene RF transistors and RF amplifiers.