Enhancing DC and RF Performance of Zigzag–Armchair–Zigzag Graphene Nanoribbon Field-Effect Transistors With Graded and Stacked Dielectrics

Abstract

A dual-gate Zigzag–Armchair–Zigzag Graphene Nanoribbon FET (ZAZ-AGNRFET) is proposed employing metallic ZGNRs as source/drain electrodes and a semiconducting AGNR as the channel. This hybrid GNR ensures seamless material integration, minimizes lattice mismatch, and reduces contact resistance at the interfaces. Device performance is investigated using TCAD ATLAS and ATK-VNL considering three different dielectric arrangements. The results demonstrate substantial DC and RF performance enhancement through the combined benefits of GNR and dielectric engineering. Although high-κ dielectrics improve gate control but their use is often limited by increased short-channel effects. To overcome this, bi-dielectric structures employing lateral grading (LG) and vertical stacking (VS) are explored to improve electrostatic control, resulting in reduced leakage current and near-ideal subthreshold characteristics. The VS configuration achieves low I_OFF (∼ 10⁻⁹ A), high I_ON (7.05 × 10⁻³ A), and stable threshold voltage. The LG arrangement exhibits superior short-channel immunity with a low DIBL of 24 mV/V, near-ideal SS (∼ 60 mV/dec), and a high I_ON/I_OFF ratio of 3.59 × 10⁶. Furthermore, both bi-dielectric designs deliver high transconductance, low parasitic capacitance, terahertz-range cut-off frequency, high gain-bandwidth product and reduced transit time, demonstrating the effectiveness of using bi-dielectrics in optimising GNRFET for ultralow power applications.