Quasi-Zero-Dimensional Source/Drain Contact for Fermi-Level Unpinning in a Tungsten Diselenide (WSe2) Transistor: Approaching Schottky-Mott Limit

Authors
Park, EuyjinKim, Seung-HwanMin, Seong-JiHan, Kyu-HyunKim, Jong-HyunKim, Seung-GeunAhn, Tae-HangYu, Hyun-Yong
Issue Date
2024-10
Publisher
American Chemical Society
Citation
ACS Nano, v.18, no.43, pp.29771 - 29778
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) known for their exceptional electrical and optical properties have emerged as promising channel materials for next-generation electronics. However, as strong Fermi-level pinning (FLP) between the metal and the 2D TMDC material at the source/drain (S/D) contact decides the Schottky barrier height (SBH), the transistor polarity is fixed to a certain type, which remains a challenge for the 2D TMDC field-effect transistors (FETs). Here, a S/D contact structure with a quasi-zero-dimensional (quasi-0D) contact interface, in which the dimensionality reduction effect alleviates FLP, was developed to gain controllability over the polarity of the 2D TMDC FET. As a result, conventional metal contacts on the WSe2 FET showed n-type characteristics due to strong FLP (pinning factor of 0.06) near the conduction band, and the proposed quasi-0D contact enabled by the Ag conductive filament on the WSe2 FET exhibited p-type characteristics with a SBH very close to the Schottky-Mott rule (pinning factor of 0.95). Furthermore, modeling of Schottky barriers of conventional contacts, one-dimensional (1D) contacts, and quasi-0D contacts revealed that the SBH of the quasi-0D contact is relatively less subject to interface dipoles that induce FLP, owing to more rapid decaying of dipole energy. The proposed contact in this study provided a method that progressed beyond the alleviation of FLP to achieve controllable polarity. Moreover, reducing the contact dimensionality to quasi-0D will enable high compatibility with the further scaled-down nanoscale device contact structure.
Keywords
Fermi-level pinning; Schottky barrier height modulation; two-dimensional transition metal dichalcogenides; conductivefilament; quasi-zero-dimensional
ISSN
1936-0851
URI
https://pubs.kist.re.kr/handle/201004/150889
DOI
10.1021/acsnano.4c09384
Appears in Collections:
KIST Article > 2024
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