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arXiv 2006.10440physics.app-phcond-mat.mtrl-sci
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n型和p型MoS2场效应晶体管界面态密度的全能谱

Full energy spectra of interface state densities for n- and p-type MoS2 field-effect transistors

N. Fang, S. Toyoda, T. Taniguchi, K. Watanabe, K. Nagashio

摘要:

二维(2D)层状材料有望取代Si以克服最近的~5 nm长度的金属氧化物半导体场效应晶体管(MOSFET)的尺寸限制。然而,绝缘体/2D沟道界面严重降低了基于2D的MOSFET的性能,并且退化的起源在很大程度上仍未被探索。在这里,我们提出了完整的能量谱的界面态密度(Dit)的n-和p-MoS 2场效应管,基于全面和系统的研究,即,厚度范围从单层到块体,以及各种栅极堆叠结构,包括具有h-BN的2D异质结构以及典型的高k顶栅结构。对于n-MoS 2,中间带隙周围的Dit从高k顶栅MoS 2 FET的5* 10^12 cm-2 eV-1急剧降低到具有h-BN的异质结构FET的5* 10^11 cm-2 eV-1。另一方面,Dit仍然很高,约为10^13 cm-2 eV-1,即使对于p-MoS 2的异质结构FET也是如此。系统的研究阐明,通过衬底表面粗糙度和高k沉积工艺的外部诱导的应变是起源的界面退化的导带侧,而硫空位诱导的缺陷态主导的价带侧的界面退化。目前对界面性质的理解提供了进一步提高2D FET性能的关键。

英文摘要:

Two-dimensional (2D) layered materials are promising for replacing Si to overcome the scaling limit of recent ~5 nm-length metal-oxide-semiconductor field-effect transistors (MOSFETs). However, the insulator/2D channel interface severely degrades the performance of 2D-based MOSFETs, and the origin of the degradation remains largely unexplored. Here, we present the full energy spectra of the interface state densities (Dit) for both n- and p- MoS2 FETs, based on the comprehensive and systematic studies, i.e., thickness range from monolayer to bulk and various gate stack structures including 2D heterostructure with h-BN as well as typical high-k top-gate structure. For n-MoS2, Dit around the mid gap is drastically reduced to 5*10^11 cm-2eV-1 for the heterostructure FET with h-BN from 5*10^12 cm-2eV-1 for the high-k top-gate MoS2 FET. On the other hand, Dit remains high, ~10^13 cm-2eV-1, even for the heterostructure FET for p-MoS2. The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on the conduction band side, while sulfur-vacancy-induced defect-states dominate the interface degradation on the valance band side. The present understanding on the interface properties provides the key to further improving the performance of 2D FETs.

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