First-principles study of graphyne/graphene heterostructure resonant tunneling nano-transistors

Abstract

Resonant tunneling transistors have received wide attention because of their ability to reduce the complexity of circuits, and promise to be an efficient candidate in ultra-high speed and ultra-high frequency applications. The chemical compatibility between graphene and graphdiyne implies that they can be combined into various configurations to fulfill ultra-high frequency nanotransistor. In the present paper, two novel resonant tunneling transistors based on graphene/graphdiyne/graphene double-heterojunction are theoretically developed to model two new kinds of bipolar devices with two representative graphdiyne nanoribbons. The electronic structures of two pristine graphdiyne nanoribbons are investigated by performing the first-principles calculations with all-electron relativistic numerical-orbit scheme as implemented in Dmol3 code. The electronic transport properties including quantum conductance (transmission spectrum) and electrical current varying with bias-voltage for each of the designed graphdiyne nanoribbon transistors are calculated in combination with non-equilibrium Green function formalism. The calculated electronic transmission and current-voltage characteristics of these transistors demonstrate that the current is dominantly determined by resonant tunneling transition and can be effectively controlled by gate electric field thereby representing the favorable negative-differential-conductivity, which is the qualified attribute of ultra-high frequency nanotransistor. It follows from the <i>I</i>-<i>U</i><sub>b</sub> variations explained by electronic transmission spectra that quantum resonance tunneling can occur in the proposed star-like graphdiyne (SGDY) and net-like graphdiyne (NGDY) nanoribbon transistors, with the resonance condition limited to a narrow bias-voltage range, leading to a characteristic resonant peak in <i>I</i>-<i>U</i><sub>b</sub> curve, which means the strong negative differential conductivity. Under a gate voltage of 4 V, when the bias-voltage rises up to 0.6 V (0.7 V), the Fermi level of source electrode aligns identically to the quantized level of SGDY (NGDY) nanoribbon channel, causing electron resonance tunneling as illustrated by the considerable transmission peak in bias window; once the source Fermi level deviates from the quantized level of SGDY (NGDY) channels at higher bias-voltage, the resonance tunneling transforms into ordinary electron tunneling, which results in the disappearing of the substantial transmission peak in bias window and the rapid declining of current. The designed SGDY and NGDY nanotransistors will achieve high-level negative differential conductivity with the peak-to-valley current ratio approaching to 4.5 and 6.0 respectively, which can be expected to be applied to quantum transmission nanoelectronic devices.