Selective Electron or Hole Conduction in Tungsten Diselenide (WSe2) Field-Effect Transistors by Sulfur-Assisted Metal-Induced Gap State Engineering

• Published in: IEEE transactions on electron devices Vol. 67; no. 1; pp. 383 - 388
• Main Authors: Ansh, Kumar, Jeevesh, Sheoran, Gaurav, Mishra, Ravikesh, Raghavan, Srinivasan, Shrivastava, Mayank
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Charge carrier processes; Chromium; CMOS; CMOS integrated circuits; Engineering; FET; Field effect transistors; Integrated circuits; metal-induced gap states (MIGSs); Nickel; Organic chemistry; Polarity; Selenides; Semiconductor devices; Silicon; Substrates; Sulfur; Surface treatment; Transistors; Transition metal compounds; Tungsten compounds; tungsten diselenide (WSe₂)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2019.2956781

For semiconductor industry to replace silicon CMOS integrated circuits by 2-D semiconductors or transition metal dichalcogenides (TMDs), TMD-based n-FETs as well as p-FETs having performance better than Si FETs are a must. While a lot of literature demonstrates n-channel characteristics, the major roadblocks in the realization of TMD-based CMOS integrated circuit are the lack of approach to realize p-channel transistors having performance comparable to n-channel transistors, all realized over the same TMD substrate. To address this, we propose a new technique by engineering WSe2/metal interface to realize WSe2-based high-performance p- and n-channel transistors and therefore unveil its potential toward CMOS-integrated technology. The technique involves a dry process, based on the chemistry between the sulfur atom and WSe2 surface, that induces unique metal-induced gap states in the source/drain (S/D) contact area, which causes improved hole (electron) injection when Cr (Ni) as S/D metal was used. This has enabled the controlled realization of high-performance WSe2 FETs with desired polarity (N, P, or ambipolar), which solely depends on the contact metal used and contact engineering (CE)/surface engineering. Fundamental investigations on the effect of the proposed CE on metal-WSe2 interface revealed interesting and counter-intuitive facts, which very well corroborate with experimental observations.