We investigated the electrical properties and stability of short-channel half-Corbino amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs). In the linear region, the fabricated half-Corbino a-IGZO TFT with a channel length of 4.5 mu m achieves a geometrical factor (f(g)) of similar to 2.7, a threshold voltage (V-T) of similar to 2.4 V, a field-effect mobility (mu(eff)) of similar to 15 cm(2)/Vs, a subthreshold swing (SS) of similar to 320 mV/dec and an off-current (I-OFF) < 10 (13) A. In the saturation region, asymmetric electrical characteristics such as drain current were observed under different drain bias conditions. The electrical properties asymmetry of half-Corbino a-IGZO TFTs was explained by various geometrical factors owing to the short-channel effect. The reduced V-T and increased SS at V-DS = 15 V is explained by the drain-induced Schottky barrier lowering. In addition, the bias-temperature stress (BTS) was performed for half-Corbino a-IGZO TFTs with both amorphous silicon oxide (a-SiOx) single layer and a-SiOx/amorphous silicon nitride (a-SiNx) bilayer passivation (PV) structures. The device with bilayer PV shows a threshold voltage shift (Delta V-T) of + 2.07 and -0.5 V under positive (PBTS = + 15 V) and negative BTS (NBTS = -15 V) at 70 degrees C for 10 ks, respectively. The origins of Delta V-T during PBTS and NBTS for half-Corbino a-IGZO TFTs with single and bilayer PV structures were studied. To improve the device electrical stability, the bilayer PV structure should be used. (C) 2016 Elsevier Ltd. All rights reserved.