Improvement in the Positive Bias Temperature Stability of SnOx-Based Thin Film Transistors by Hf and Zn Doping.

We investigated the performance of tin oxide thin film transistors (TFTs) using DC magnetron sputtering. A remarkable improvement in the transfer characteristics was obtained for the Hf-doped tin oxide (HTO) TFT. We also developed amorphous hafnium-zinc-tin oxide (HZTO) thin film transistors and investigated the effects of hafnium doping on the electrical characteristics of the HTO TFTs. Doping with hafnium resulted in a reduced defect density in the tin oxide channel layer related to oxygen vacancies, which may result from increased field effect mobility. Zinc atoms have relatively higher oxidation potential compared to tin atoms, so more oxygen molecules can be absorbed and more electrons are trapped in the HZTO films. The HZTO TFTs exhibited good electrical characteristics with a field effect mobility of 10.98 cm2/Vs, and a high ION/IOFF ratio over 10(8).