Threshold Voltage Instabilities in Perpetual Switching of Low-Voltage Thin-Film Transistors with Solution-Processed In2O3 Channel Layer

Abstract

Thin-film transistors (TFTs) with solution-processed indium oxide (In 2 O 3 ) as the channel layer and with aluminium oxide as the gate dielectric were fabricated. The fabricated In 2 O 3 TFTs are tested for reliability in low-voltage operation. Measurement results show that the threshold voltage (V th ) increases from 0.6 V to 1.4 V under positive bias stress (PBS) and decreases from 0.55 V to 0.22 V under negative bias stress (NBS). Upon relaxation for long enough time, V th restores close to the pristine values. When switching the In 2 O 3 TFTs repeatedly by applying a pulsed voltage of ± 3V to the gate, the V th shift ($\\lt p\gt Delta {V}_{th}$) depends on the pulse width. While $\Delta {V}_{th}$ generally decreases with the pulse width under pulsed NBS, V th instability is considerably worse under pulsed PBS, particularly when the pulse width is between 5 $\mu$ s and 50 ms. Apart from revealing the differences in the trapping and de-trapping of electrons and holes at the In 2 O 3 /Al 2 O 3 interface, the results have implications for using the In 2 O 3 TFTs in circuits in which they are biased or switched repeatedly.