Investigation of a Hump Phenomenon in Back-Channel-Etched Amorphous In-Ga-Zn-O Thin-Film Transistors Under Negative Bias Stress

The hump phenomenon along with a negative shift of threshold voltage emerging in the transfer characteristics of amorphous InGaZnO thin-film transistors under negative bias stress was investigated. Higher measurement temperature and larger bias voltage can induce more and faster hole injection, thus leading to the increased parasitic ON-state current and more negative shift of the threshold voltage. Nevertheless, the parasitic current is independent of the channel width, illustrating that the parasitic channel originates from the hole trapping near the IGZO edges along the channel length. Integrated Systems Engineering Technology Computer-aided Design simulation confirms that the electric field near the IGZO edge is relatively dense, and the direction is more conducive for the holes in IGZO to inject into passivation (PV), to gate insulator (GI), or at PV/GI interface.