Low voltage thin film transistors based on solution-processed In2O3:W. A remarkably stable semiconductor under negative and positive bias stress

Paxinos, Kosta and Antoniou, Giorgos and Afouxenidis, Dimitrios and Mohamed, Ahmed and Dikko, Umar and Tsitsimpelis, Ioannis and Milne, William I. and Nathan, Arokia and Adamopoulos, George (2020) Low voltage thin film transistors based on solution-processed In2O3:W. A remarkably stable semiconductor under negative and positive bias stress. Applied Physics Letters, 116 (16): 163505. ISSN 0003-6951

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Abstract

We have investigated solution-processed tungsten-doped crystalline indium oxide (In2O3:W) as a function of the W content and their implementation in TFTs also employing spray coated Y2O3 gate dielectrics, and gold source and drain contacts. We showed that tungsten doping practically has no effect on the optical band gap whereas it shifts up the Urbach tail energy of In2O3:W films. The TFT performance employing In2O3:W channels also seems to decline at high tungsten concentration. Negative and positive bias stress under (dark) ambient conditions of TFTs employing In2O3:W(0.1 at%) showed remarkable improvement in their stability characteristics compared to the un-doped ones. This is evidenced by significantly smaller changes of the threshold voltage and subthreshold swing with insignificant change of the electron mobility that was practically unaffected under negative bias voltage. The negative bias stress results were interpreted in terms of the higher W-O bond dissociation energy compared to that of In-O, and the consequent oxygen vacancy suppression. However the positive bias stability results in a reduced accumulation of electrons in the back channel due to atmospheric oxygen absorption. The results presented in this report demonstrate the potential for stable, low operational voltage, high performance metal oxide-based TFTs employing gate dielectrics also grown from solutions, at low manufacturing cost.