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

Abstract

Thin-film transistors (TFTs) with hafnium-doped zinc oxide (HZO) channels were fabricated and the effects of Hf content on the performance of ZnO-based TFT were investigated. HZO TFTs exhibit improved electrical characteristics, with increased ION/IOFF and decreased subthreshold swing. We also investigated the influence of hafnium doping on the bias stability of ZnO TFTs. HZO TFTs exhibited turn-on voltage (VON) shifts of ?1 V in negative stress bias, compared with ?8 V for intrinsic ZnO TFTs. The improvement in the VON shift may be due to a reduction in the total trap density resulting from the suppression of the defect-related oxidation state of the Zn ions caused by the high binding energy of Hf ions.