High performance top-gated multilayer WSe2 field effect transistors

• Published in: Nanotechnology 2017-10, Vol.28 (47), p.475202-475202
• Main Authors: Pudasaini, Pushpa Raj, Stanford, Michael G, Oyedele, Akinola, Wong, Anthony T, Hoffman, Anna N, Briggs, Dayrl P, Xiao, Kai, Mandrus, David G, Ward, Thomas Z, Rack, Philip D
• Format: Article
• Language: English
• Subjects: atomic layer deposition; field effect transistors; high k-dielectrics; interface engineering; NANOSCIENCE AND NANOTECHNOLOGY; transition metal dichalcogenide
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aa8081

In this paper, high performance top-gated WSe2 field effect transistor (FET) devices are demonstrated via a two-step remote plasma assisted ALD process. High-quality, low-leakage aluminum oxide (Al2O3) gate dielectric layers are deposited onto the WSe2 channel using a remote plasma assisted ALD process with an ultrathin (∼1 nm) titanium buffer layer. The first few nanometers (∼2 nm) of the Al2O3 dielectric film is deposited at relatively low temperature (i.e. 50 °C) and remainder of the film is deposited at 150 °C to ensure the conformal coating of Al2O3 on the WSe2 surface. Additionally, an ultra-thin titanium buffer layer is introduced at the WSe2 channel surface prior to ALD process to mitigate oxygen plasma induced doping effects. Excellent device characteristics with current on-off ratio in excess of 106 and a field effect mobility as high as 70.1 cm2 V-1 s-1 are achieved in a few-layer WSe2 FET device with a 30 nm Al2O3 top-gate dielectric. With further investigation and careful optimization, this method can play an important role for the realization of high performance top gated FETs for future optoelectronic device applications.