Investigating unsaturated output characteristics and potential applications of amorphous InGaZnO thin-film transistors with drain-connected field plate

In this study, a via-hole type thin-film transistor (TFT) device based on indium–gallium–zinc–oxide (IGZO) material with the drain-connected field plate (DCFP) structure is investigated. Compared to the traditional symmetric source/drain structure, the device with DCFP exhibits unsaturated output drain current properties during operation. Also, according to the electrical measurements and the simulation results, a high electrical field is generated on the etching stop layer (ESL) right underneath the extended field plate, resulting in the effect of drain-induced barrier lowering (DIBL) and the shifts of threshold voltage (Vt). On the other hand, the unsaturated output characteristics are applied as a variable resistor according to the given gate bias (Vg). Therefore, a high pass filter (HPF) circuit is demonstrated based on the TFT device with the DCFP structure, which suggests its potential application for variable resistors based on the gate bias in the future circuit designs.