Influence of Hydrogen Ions on the Performance of Thin-Film Transistors with Solution-Processed AlOx Gate Dielectrics

Over the past decade, there have been many reports on solution-processed oxide thin-film transistors (TFTs) with high mobility (even >100 cm(2) V(-1)s(-1)). However, the capacitance uncertainty of the solution-processed oxide gate dielectrics leads to serious overestimation of the mobility. Here, solution-processed AlOx dielectrics are investigated systematically, and the effect of mobile ions on the frequency-dependent capacitance of the solution-processed AlOx dielectrics is also studied. It was found that the capacitance of the AlOx depends on the frequency seriously when the annealing temperature is lower than 300 degrees C, and the water treatment causes more seriously frequency-dependent capacitance. The strong frequency-dependent capacitance of the AlOx annealed at 250 or 300 degrees C is attributed to relaxation polarization of the weakly bound ions in the incompletely decomposed AlOx films. The water treatment introduces a large number of protons (H+) that would migrate to the ITO/AlOx interface under a certain electric field and form an electric double layer (EDL) that has ultrahigh capacitance at low frequency.