Chirality-Dependent Cutoff Frequency and I–V Characteristics in Graphene Nanoribbon-Based FETs

Abstract

Graphene-based transistors are suitable candidates for overcoming the scaling problems of Si-based devices in radio frequency (RF) applications and nanoscale devices. The graphene nanoribbon (GNR) is a one-dimensional member of graphene-based materials which possesses the superior properties of graphene. The crucial demands in device technology, particularly the need for high-speed performance, have led to the selection of GNR field-effect transistor (FETs) as a solution for addressing and overcoming scaling issues. In the present work, the cutoff frequency, time delay, and I–V characteristics of GNR-based FETs are investigated as indispensable parameters for transistor speed, and their impact on the design and implementation of GNR-based FETs is explored. GNRs are employed in the channel region of metal–oxide–semiconductor FETs to numerically and analytically investigate the cutoff frequency and time delay, which are critical for high-speed switching performance. The Y-parameter in unity current gain magnitude (0 dB) within the quasi-static approximation is used in the model. Results show that increased delay time is associated with reduced channel conductance and corresponding decrease in cutoff frequency. Conversely, high-frequency operation is achieved at low drain–source voltage with small delay times and enhanced channel conductance. In addition, the small output conductance enables Early voltage reduction, leading to a significantly improved voltage gain as confirmed by the I–V characteristics. The proposed model demonstrates good agreement with conventional device behavior, validating its accuracy and applicability. Additionally, a comparison of the armchair GNR (AGNR) and zigzag GNR (ZGNR) channels shows that ZGNRs maintain stable current and cutoff frequency with minimal chirality and length effects, while AGNRs exhibit chirality-dependent reductions in current and increased cutoff frequency. This highlights ZGNRs’ stability and AGNRs’ sensitivity for future nanoscale device applications.