The electrical properties and stability of ultra-high definition (UHD) amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) arrays with short channel (width/length = 12/3 mu m) were examined. A-IGZO TFT arrays have a mobility of similar to 6 cm(2)/V s, subthreshold swing (S.S.) of 0.34 V/decade, threshold voltage of 3.32 V, and drain current (I-d) on/off ratio of < 10(9) with I-off below 10 (13) A. Overall these devices showed slightly different electrical characteristics as compared to the long channel devices; non-saturation of output curve at high drain-to-source voltage (V-ds), negative shift of threshold voltage with increasing V-ds, and the mobility reduction at high gate voltage (V-gs) were observed. The second derivative method adopting Tikhonov's regularization theory is suggested for the robust threshold voltage extraction. The temperature dependency of gamma-value was established after taking into consideration the impact of source/drain contact resistances. The AC bias-temperature stress was used to simulate the actual operation of active matrix liquid crystal displays (AM-LCDs). The threshold voltage shift had a dependency on the magnitude of drain bias stress, frequency, and duty cycle due to the impact ionization accelerated at high temperature. This study demonstrates that the short channel effects, source/drain contact resistances and impact ionization have to be taken into account during optimization of UHD AM-LCDs. (C) 2015 Elsevier Ltd. All rights reserved.