Nikhil Tiwale¹, Ashwanth Subramanian², Zhongwei Dai¹, Sayantani Sikder², Jerzy T. Sadowski¹, Chang-Yong Nam^1,2*

1 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States

2 Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, New York 11794, United States

* Corresponding authors emails: cynam@bnl.gov

DOI10.24435/materialscloud:1t-g7 [version v1]

Publication date: Nov 13, 2020

How to cite this record

Nikhil Tiwale, Ashwanth Subramanian, Zhongwei Dai, Sayantani Sikder, Jerzy T. Sadowski, Chang-Yong Nam, Large mobility modulation in ultrathin amorphous titanium oxide transistors, Materials Cloud Archive 2020.146 (2020), doi: 10.24435/materialscloud:1t-g7.

Description

Recently, ultrathin metal-oxide thin film transistors (TFTs) have shown very high on-off ratio and ultra sharp subthreshold swing, making them promising candidates for applications beyond conventional large-area electronics. While the on-off operation in typical TFTs results primarily from the modulation of charge carrier density by gate voltage, the high on-off ratio in ultrathin oxide TFTs can be associated with a large carrier mobility modulation, whose origin remains unknown. We investigate 3.5 nm-thick titanium oxide based ultrathin TFTs exhibiting 6-decade on-off ratio, predominantly driven by gate induced mobility modulation. The power law behavior of the mobility features two regimes, with a very high exponent at low gate voltages, unprecedented for oxide TFTs. We find that this phenomenon is well explained by the presence of high-density tail states near the conduction band edge, which supports carrier transport via variable range hopping. The observed two-exponent regimes reflect the bi-exponential distribution of the density of band-tail states. This improved understanding would be significant in fabricating high-performance ultrathin oxide devices.

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Keywords

amorphous semiconductor titanium oxide field-effect transistor variable range hopping mobility modulation