Improvement of Electrical Characteristics and Stability in Low-Voltage Indium Oxide Thin-Film Transistors by Using Tungsten Doping

Recently, reducing the operating voltage of metal oxide transistors has become a priority because this enables their use in wearable electronics where low power consumption is a requirement. Here, we fabricate transistors that operate under low driving voltage after adding a solution-processed, tungsten-doped indium oxide (IWO) semiconductor deposited on top of a 20 nm aluminum oxide transparent high-k dielectric. To analyze the effect of the tungsten content on the characteristics of IWO thin film transistors (TFTs), devices based on films with 0.11, 0.22, and 0.34 mol% tungsten content were fabricated and compared to pristine indium oxide-based TFTs. Optimized tungsten (W) content at 0.11 mol% achieves a fivefold improvement in the charge carrier mobility, an ON/ OFF current ratio two orders of magnitude higher, and the subthreshold swing decreased to less than 0.1 V/dec. The bias stability of the device with optimal W concentration is also significantly better than undoped In2O3-based TFTs, probably because doping effectively suppresses the generation of oxygen vacancies in the IWO active channel layer and improves device stability. To test the feasibility of IWO devices in practical applications, a load-type inverter was fabricated using the optimally doped film.