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Thin-film transistors (TFTs), which use zinc oxide (ZnO) as an active layer, were fabricated and investigated in detail. The transport properties of ZnO deposited by spray pyrolysis (SP) on a TFT structure are studied in a wide range of temperatures, electrical conditions (i.e., subthreshold, above-threshold linear, and saturation regions), and at different channel lengths. It is shown that ZnO deposited by SP is a nanocrystalline material; its field-effect mobility is temperature activated and increases with carrier concentration. On the basis of this analysis, we propose the multiple-trapping-and-release (MTR)-transport mechanism to describe the charge transport in ZnO. By means of numerical simulations, we prove that MTR is a suitable approach, and we calculate the density of states. We show that the tail states extend in a wide range of energy and that they strongly influence the transport properties. Finally, an analytical …
Publication date: 
16 Jun 2011

Fabrizio Torricelli, Juliaan R Meijboom, Edsger Smits, Ashutosh K Tripathi, Matteo Ferroni, Stefania Federici, Gerwin H Gelinck, Luigi Colalongo, Zsolt M Kovacs-Vajna, Dago de Leeuw, Eugenio Cantatore

Biblio References: 
Volume: 58 Issue: 8 Pages: 2610-2619
IEEE Transactions on Electron Devices