Current Boosting of Self‐Aligned Top‐Gate Amorphous InGaZnO Thin‐Film Transistors under Driving Conditions

Oxide semiconductor transistors control the brightness and color of organic light‐emitting diode (OLED) displays in large‐screen televisions to portable telecommunications devices. Oxide semiconductor thin‐film transistors under driving conditions are required to maintain a steady current through the OLED for constant illuminance. Interestingly, for driving conditions under strong saturation where both gate and drain bias are high, a boosting phenomenon of the drain current is discovered, even with compensation of the threshold voltage. In this paper, the current boosting effect of self‐aligned InGaZnO transistors under driving conditions is comprehensively investigated. Based on experimental extraction methods, two distinct regions within the device are identified: an electron‐capture‐dominant region including electron trapping in the gate insulator and O–O dimer bond‐breaking, and an electron‐emission‐dominant region caused by peroxide formation. A dual‐transistor‐in‐series model is proposed, where each region is modeled as a local transistor. The current boosting phenomena as a function of time are well‐reproduced for various channel length devices, which validate the accuracy of the model. Better understanding of the underlying mechanisms enables increased effectiveness of compensation schemes for transistors under long‐term current‐driving conditions. Self‐aligned InGaZnO transistors are fabricated to find a quantitative and holistic resolution to understanding the current boosting in driving conditions. Two distinct regions are governed by separate mechanisms: specifically, the carrier capture region (electron trapping, breaking of peroxy linkage), and the carrier emission region (oxygen dimer formation). A novel dual‐TFT‐in‐series analytical model accurately reproduces the experimentally observed current boosting phenomena.