Threshold voltage instabilities in perpetual switching of low-voltage thin-film transistors with solution-processed InO₃ channel layer

Thin-film transistors (TFTs) with solution-processed indium oxide (InO₃) as the channel layer and with aluminium oxide as the gate dielectric were fabricated. The fabricated InO₃ 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 InO₃ 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 InO₃ /AlO₃ interface, the results have implications for using the InO₃ TFTs in circuits in which they are biased or switched repeatedly.