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Title: Effect of indium low doping in ZnO based TFTs on electrical parameters and bias stress stability

Some applications of thin film transistors (TFTs) need the bottom-gate architecture and unpassivated channel backside. We propose a simple routine to fabricate indium doped ZnO-based TFT with satisfactory characteristics and acceptable stability against a bias stress in ambient room air. To this end, a channel layer of 15 nm in thickness was deposited on cold substrate by DC reactive magnetron co-sputtering of metal Zn-In target. It is demonstrated that the increase of In concentration in ZnO matrix up to 5% leads to negative threshold voltage (V{sub T}) shift and an increase of field effect mobility (μ) and a decrease of subthreshold swing (SS). When dopant concentration reaches the upper level of 5% the best TFT parameters are achieved such as V{sub T} = 3.6 V, μ = 15.2 cm{sup 2}/V s, SS = 0.5 V/dec. The TFTs operate in enhancement mode exhibiting high turn on/turn off current ratio more than 10{sup 6}. It is shown that the oxidative post-fabrication annealing at 250{sup o}C in pure oxygen and next ageing in dry air for several hours provide highly stable operational characteristics under negative and positive bias stresses despite open channel backside. A possible cause of this effect is discussed.
Authors:
; ;  [1]
  1. Physico-Technical Department, Petrozavodsk State University, Petrozavodsk 185910 (Russian Federation)
Publication Date:
OSTI Identifier:
22492181
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 5; Journal Issue: 11; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABUNDANCE; AGING; ANNEALING; CONCENTRATION RATIO; DOPED MATERIALS; ELECTRIC POTENTIAL; INDIUM; LAYERS; MATRIX MATERIALS; MOBILITY; OXIDATION; OXYGEN; SPUTTERING; SUBSTRATES; THIN FILMS; TRANSISTORS; ZINC OXIDES