Improvement in the bias stability of tin oxide thin-film transistors by hafnium doping

Thin-film transistors (TFTs) were fabricated with hafnium doped tin oxide (HTO) channels, and the effects of Hf content on the device performance of SnOx based TFTs was investigated. HTO TFTs exhibit improved electrical properties with increased field effect mobility and decreased subthreshold swing. We also investigated the influence of hafnium doping on bias stability in SnOx TFTs. HTO TFTs exhibited turn-on voltage (VON) shifts of + 7 V for positive stress bias, compared with + 18 V for SnOx TFTs. The improvement in the VON shift may be due to reduction in total trap density resulting from the suppression of defects related oxidation state of the Sn ion caused by the high binding energies of Hf ions.