Origins of threshold voltage shifts in room-temperature deposited and annealed a-In–Ga–Zn–O thin-film transistors

Nomura, Kenji; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo
July 2009
Applied Physics Letters;7/6/2009, Vol. 95 Issue 1, p013502
Academic Journal
Threshold voltage (Vth) stability was examined under constant current stress for a-In–Ga–Zn–O thin film transistors (TFTs) deposited at room temperature and annealed at 400 °C in dry or wet O2 atmospheres. All the TFTs exhibited positive Vth shifts (ΔVth) and the ΔVth value was reduced by the thermal annealing to <2 V for 50 h. TFT simulations revealed that the ΔVth for the annealed TFTs is explained by increase in deep charged defects. Large ΔVth over 10 V and deterioration in subthreshold voltage swing were observed in the unannealed TFTs, which are attributed to the increase in shallow trap states.


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