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Abstract Source/Drain extension doping is crucial for minimizing the series resistance of the ungated channel and reducing the contact resistance of field‐effect transistors (FETs) in complementary metal–oxide–semiconductor (CMOS) technology. 2D semiconductors, such as MoS2and WSe2, are promising channel materials for beyond‐silicon CMOS. A key challenge is to achieve extension doping for 2D monolayer FETs without damaging the atomically thin material. This work demonstrates extension doping with low‐resistance contacts for monolayer WSe2p‐FETs. Self‐limiting oxidation transforms a bilayer WSe2into a hetero‐bilayer of a high‐work‐function WOxSeyon a monolayer WSe2. Then, damage‐free nanolithography defines an undoped nano‐channel, preserving the high on‐current of WOxSey‐doped FETs while significantly improving their on/off ratio. The insertion of an amorphous WOxSeyinterlayer under the contacts achieves record‐low contact resistances for monolayer WSe2over a hole density range of 1012to 1013cm−2(1.2 ± 0.3 kΩ µm at 1013cm−2). The WOxSey‐doped extension exhibits a sheet resistance as low as 10 ± 1 kΩ □−1. Monolayer WSe2p‐FETs with sub‐50 nm channel lengths reach a maximum drain current of 154 µA µm−1with an on/off ratio of 107–108. These results define strategies for nanometer‐scale selective‐area doping in 2D FETs and other 2D architectures.
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Reversible photo-induced doping in WSe 2 field effect transistors
We report a reversible photo-induced doping effect in two-dimensional (2D) tungsten diselenide (WSe 2 ) field effect transistors on hexagonal boron nitride (h-BN) substrates under low-intensity visible light illumination (∼10 nW μm −2 ). Our experimental results have shown that this reversible doping process is mainly attributed to two types of defects in h-BN substrates. Moreover, the photo-doped WSe 2 transistors can be stable for more than one week in a dark environment and maintain the high on/off ratio (10 8 ) and carrier mobility, since there are no additional impurities involved during the photo-induced doping process to increase the columbic scattering in the conducting channel. These fundamental studies not only provide an accessible strategy to control the charge doping level and then to achieve a writing/erasing process in 2D transistors, but also shed light on the defect states and interfaces in 2D materials.
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- PAR ID:
- 10098076
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 11
- Issue:
- 15
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 7358 to 7363
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C8NR09929D
