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End-Bonded Metal Contacts on WSe2 Field-Effect Transistors
Chun-Hao Chu1, Ho-Chun Lin2,3, Chao-Hui Yeh1
1Department of Electrical Engineering , National Tsing Hua University , Hsinchu 30013 , Taiwan.
ACS Nano
|June 28, 2019
Summary
Engineered end-bonded contacts for transition metal dichalcogenide (TMD) field-effect transistors (FETs) significantly boost device performance. This novel approach overcomes limitations of traditional top-contact schemes, enabling higher on-current and mobility in TMD transistors.
Area of Science:
- Materials Science
- Nanotechnology
- Semiconductor Physics
Background:
- Contact engineering is critical for high-performance atomic thin transition metal dichalcogenide (TMD) field-effect transistors (FETs).
- Conventional top-contact schemes on TMDs suffer from significant contact barriers, hindering efficient charge injection.
- End-bonded contacts, forming covalent bonds at channel edges, offer a more efficient charge injection pathway but are underexplored.
Purpose of the Study:
- To demonstrate the seeded growth of end-bonded contacts for various TMDs using chemical vapor deposition (CVD).
- To investigate the performance enhancement of FETs utilizing end-bonded contacts compared to traditional top-contact configurations.
Main Methods:
- Utilized chemical vapor deposition (CVD) for seeded growth of end-bonded contacts on monolayer WSe2.
- Fabricated and characterized monolayer WSe2 FETs with both end-bonded and top-bonded contact schemes.
- Performed density functional theory (DFT) calculations to understand the electronic properties of end-bonded contacts.
Main Results:
- Monolayer WSe2 FETs with CVD-grown end contacts achieved superior performance: on-current density of 30 μA/μm, hole mobility of 90 cm2/V·s, and subthreshold swing of 94 mV/dec.
- Performance metrics were an order of magnitude better than those of top-contact FETs using the same channel material.
- Demonstrated a fundamental NOT logic gate using top-gated, end-bonded WSe2 and MoS2 FETs.
Conclusions:
- Seeded growth of end-bonded contacts via CVD is a viable method for fabricating high-performance TMD FETs.
- The end-bonded contact scheme significantly reduces contact barriers, leading to enhanced device characteristics.
- Stronger metal-TMD hybridization and substantial gap states in the end-contact configuration are responsible for the improved performance.
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