石墨炔/石墨烯异质结纳米共振隧穿晶体管第一原理研究

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

石墨烯和石墨炔的化学相容性表明它们能够以不同形式组合在一起,从而构建新型超高频纳米晶体管.通过石墨烯-石墨炔-石墨烯异质结纳米带构建双极器件模拟了两种新型纳米共振隧穿晶体管,根据基于密度泛函理论的第一原理和非平衡格林函数方法对该晶体管的电子结构和量子输运特性进行了理论计算.电子透射谱和电流-电压曲线的计算结果证明该晶体管的电流主要来源于共振隧穿跃迁并可由横向栅极电压控制,因此可用作超高频纳米晶体管.

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 negativedifferential- conductivity, which is the qualified attribute of ultra-high frequency nanotransistor. It follows from the I-Ub 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-Ub curve, which means the strong negative differential conductivity. Under a gate voltage of 4 V, when the biasvoltage 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.