Enhanced Electron Transport in Armchair Graphene Nanoribbon Step Barrier Resonant Tunnelling Diodes Through Geometrical and Field Modifications

A novel step barrier resonant tunnelling diode (RTD) based on armchair graphene nanoribbon (AGNR) is proposed through geometric (GM) and field-modified (FM) effects. The transport properties are analysed by adopting the tight-binding model and the NEGF formalism. Among the proposed GM structures, i.e., single-barrier (SB), step-single-barrier (SSB), double-barrier (DB), and step-double-barrier (SDB), the SSB achieves the highest peak current (Ip) and valley current (Iv), resulting in a low peak-to-valley ratio (PVR). However, PVR improves significantly in the SDB structure with an optimized well length (29.82 Å). Its negative differential resistance is also exhibited for a shorter voltage range (0.08 V) compared to the DB structure (0.11 V), supporting its utility in ultra-fast switching applications. To further improve the PVR, FM-DB and SDB are introduced by applying symmetric and asymmetric gate voltages (Vg) in the barrier regions, respectively. The smoother channel edges in the FM-DB structure (Vg1 = Vg2 = 405 mV) reduce back scattering, enhance both Ip and Iv, but result in a lower PVR (14.81) than its GM-DB counterparts. However, pinning Vg1 = 405 mV and Vg2 = 605 mV generated FM-SDB, improved Ip (~189 nA) and PVR (~34.36), exceeding the earlier reported results. Our results provide insight into the potential of step barrier AGNR-RTDs for high-frequency 2D nanoelectronics devices.