Full Energy Spectra of Interface State Densities for n ‐ and p ‐type MoS 2 Field‐Effect Transistors

• Published in: Advanced functional materials Vol. 29; no. 49
• Main Authors: Fang, Nan, Toyoda, Satoshi, Taniguchi, Takashi, Watanabe, Kenji, Nagashio, Kosuke
• Format: Journal Article
• Language: English
• Published: 01.12.2019
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201904465

Abstract 2D materials are promising to overcome the scaling limit of Si field‐effect transistors (FETs). However, the insulator/2D channel interface severely degrades the performance of 2D FETs, and the origin of the degradation remains largely unexplored. Here, the full energy spectra of the interface state densities ( D it ) are presented for both n ‐ and p ‐ MoS 2 FETs, based on the comprehensive and systematic studies, i.e., full rage of channel thickness and various gate stack structures with h ‐BN as well as high‐ k oxides. For n ‐MoS 2 , D it around the mid‐gap is drastically reduced to 5 × 10 11 cm −2 eV −1 for the heterostructure FET with h ‐BN from 5 × 10 12 cm −2 eV −1 for the high‐ k top‐gate. On the other hand, D it remains high, ≈ 10 13 cm −2 eV −1 , even for the heterostructure FET for p ‐MoS 2 . 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 conduction band side, while sulfur‐vacancy‐induced defect states dominate the interface degradation on valance band side. The present understanding of the interface properties provides the key to further improving the performance of 2D FETs.