npj: 离子栅极过渡金属二卤化物晶体管—设计与优化

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离子栅极晶体管由于其强栅耦合，使得工作电压大大降低，使人们能够控制包括超导电性在内的电子相，在现代电子工业有着广阔的应用前景。过渡金属二羟基化合物（TMDs）为代表的材料体系可以适用于电子和自旋电子学应用，是下一代晶体管的良好候选器件。离子栅极有助于实现传统MOSFET难以实现的功能，为了提高离子栅极的功能，必须了解器件工作机理。在晶体管工作的理论研究中，漂移扩散（DD）方法被认为是计算器件内载流子的传输特性、能带分布和空间分布的有力工具。然而，目前还没有关于TMDs的离子门控晶体管的DD模拟的报道。

来自日本AIST的Akiko Ueda以及美国、德国的研究团队，开发了一个包括离子液体（IL）作为栅介质的二维层晶体管模型，建立了离子门控TMD晶体管的DD模型，并解释了离子门控WSe₂晶体管的特征输运行为。采用与泊松方程耦合的DD模型来计算带宽分布、载流子密度和电流。在Poisson方程中，采用包含电荷屏蔽效应的模型来计算IL的电位分布。在DD模型中，考虑了高载流子密度的广义爱因斯坦关系，采用了实际肖特基接触模型来考虑晶体管的肖特基和欧姆行为。2d材料离子门控晶体管的一个特点是，在栅极电压与带隙能量相当的情况下，具有双极性。模拟结果揭示了双极化传输和通道中p-n结形成的基本物理基础，表明DD模型与poisson方程耦合是研究离子门晶体管的一个有趣的工具。通过在DD模型中加入自旋、谷和自由度，可以检验离子门控晶体管的功能并设计其器件结构。

该文近期发表于npj Computational Materials 6: 24 (2020)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Ambipolar device simulation based on the drift-diffusion model in ion-gated transition metal dichalcogenide transistors

Akiko Ueda, Yijin Zhang, Nobuyuki Sano, Hiroshi Imamura and Yoshihiro Iwasa

Ionic gating is known as a powerful tool for investigation of electronic functionalities stemming from low voltage transistoroperation to gate-induced electronic phase control including superconductivity. Two-dimensional (2D) material is one of thearchetypal channel materials which exhibit a variety of gate-induced phenomena. Nevertheless, the device simulations on such iongated transistor devices have never been reported, despite its importance for the future design of device structures. In this paper, we developed a drift-diffusion (DD) model on a 2D material, WSe2 monolayer, attached with an ionic liquid, and succeeded insimulating the transport properties, potential profile, carrier density distributions in the transistor configuration. In particular, the simulation explains the ambipolar behavior with the gate voltage comparable to the band gap energy, as well as the formation ofp-n junctions in the channel reported in several experimental papers. Such peculiar behavior becomes possible by the dramaticchange of the potential profiles at the Schottky barrier by the ionic gating. The present result indicates that the DD model coupledto the Poisson equation is a fascinating platform to explain and predict further functionalities of ion-gated transistors throughincluding the spin, valley, and optical degrees of freedom.

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