Enhanced electron transport in armchair graphene nanoribbon step barrier resonant tunnelling diodes through geometrical and field modifications

Abstract 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 ( I p ) and valley current ( I v ), 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 ( V g ) in the barrier regions, respectively. The smoother channel edges in the FM-DB structure ( V g1 = V g2 = 405 mV) reduce back scattering, enhance both I p and I v , but result in a lower PVR (14.81) than its GM-DB counterparts. However, pinning V g1 = 405 mV and V g2 = 605 mV generated FM-SDB, improved I p ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>~</mml:mo> </mml:math> 189 nA) and PVR ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>~</mml:mo> </mml:math> 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.