Effect of Titanium Cation Doping on the Performance of In2O3 Thin Film Transistors Grown via Atomic Layer Deposition

Indium oxide semiconductors, as one of the channel materials for thin film transistors (TFTs), have been extensively studied. However, the high carrier concentration and excess oxygen defects of intrinsic In2O3 can cause the devices to fail to work properly. We overcame this hurdle by incorporating the titanium cation (Ti4+) into In2O3 via atomic layer deposition (ALD). The InTiOx TFTs with an In:Ti atomic ratio of 15:1 demonstrated excellent electrical and optical properties, such as a lower threshold voltage (Vth) of 0.17 V, a lower subthreshold swing (SS) of 0.13 V/dec., a higher Ion/Ioff ratio of 107, and a transmittance greater than 90% in the visible region. With the doping ratio increasing from 20:1 to 10:1, the mobility decreased from 9.38 to 1.26 cm2/Vs. The threshold voltage shift (ΔVth) of InTiO (15:1) under 5 V positive bias stress (PBS) for 900 s is 0.93 V, which is less than other devices. The improvement in stability with increasing Ti4+ concentrations is attributed to the reduction of oxygen defects. Therefore, these InTiO (15:1) TFTs with excellent performance show great potential for future applications in transparent electronic devices.