Gate Spacer Investigation for Improving the Speed of High-Frequency Carbon Nanotube-Based Field-Effect Transistors.

Carbon nanotube (CNT)-based field-effect transistors have demonstrated great potential for high-frequency (HF) analog transceiver electronics. Despite significant advancements, one of the remaining challenges is the optimization of the device architecture for obtaining the highest possible speed and linearity. While most studies so far have concentrated on symmetrical top gated FET devices, we report on the impact of the device architecture on their HF performance. Based on a wafer-level nanotechnology platform and device simulations, transistors with a buried gate having different widths and positions in the FET channel have been fabricated. Analysis of several FETs with nonsymmetrical gate electrode location in the channel revealed a speed increase of up to 18% measured by the external transit frequency fT and maximum frequency of oscillation fmax. Although only randomly oriented CNTs with a density of 25 CNTs/μm and 280 nm long channels were used in this study, transit frequencies up to 14 GHz were obtained.