Solution processed, high mobility thin film transistors employing Yttrium-doped Indium Zinc Oxide semiconducting channels

Afouxenidis, Dimitrios and Vourlias, G. and Milne, W.I. and Adamopoulos, George (2017) Solution processed, high mobility thin film transistors employing Yttrium-doped Indium Zinc Oxide semiconducting channels. In: EMRS 2017, 2017-05-22 - 2017-05-26, FRANCE.

Abstract

Metal oxide semiconductors have recently been of high interest due to their excellent electrical performance combined with optical transparency and mechanical flexibility. Thin-film transistors implementing a number of metal oxides semiconducting channels have been demonstrated already. They have excellent performance that is superior to that of amorphous silicon (a-Si:H). Amongst them, Indium Zinc Oxide-based materials constitute the most promising next-generation TFT materials of choice, due to their high mobility caused by direct overlap of the isotropic s orbitals of its Indium atoms. One remaining issue, however, is the formation of oxygen vacancies that destabilize the material’s electronic properties. To address this issue, Ga doping has been used in an effort to suppress the oxygen vacancies. This work reports on the physical properties of an alternative metal oxide material-Indium Zinc Oxide thin films doped with yttrium (IZO:Y). The IZO:Y films were processed from solutions at 400 oC in air by spray pyrolysis of b-diketonates and chlorides and characterised by UV-Vis absorption spectroscopy, FTIR, AFM, x-ray diffraction, spectroscopic ellipsometry and field effect measurements. Analyses revealed very smooth polycrystalline films with wide band gaps in the order of 3.5 eV. TFTs employing Al2O3 gate dielectrics and IZO:Y semiconducting channels exhibit excellent operating characteristics for the optimal Y doping content of 0.4 mole i.e. a high electron mobility in excess of 20 cm2/Vs and current modulation ratio in the order of 10^6.