Improving Reliability of High-Performance Ultraviolet Sensor in a-InGaZnO Thin Film Transistors

High-performance ultraviolet (UV) sensors using amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) can detect ION/IOFF ratio up to 106 and match the a-IGZO panel process. However, it has a reliability issue under long-term detection. When the top gate length of the dual gate TFT is small, it is twice as reliable as a TFT where the top gate fully covers the device. The electrical properties of the device correspond to the a-IGZO energy band, such that the top gate length was positively related to the underlying energy band diagram. The integrated systems engineering technology computer aided design (ISE-TCAD) electric field simulations show that the etch stop layer (ESL) electric field is weak in the small top gate device. This means that it is difficult for the holes to either be trapped in the ESL or to generate ionized oxygen vacancies.