Optimization of the Fabrication Process for Phototransistors With IGZO/TiOx Bilayer Thin Films to Improve Electrical and Photoresponse Characteristics

Metal oxides are among the most popular research targets in electronic materials for their high charge carrier mobility, transparency, and versatility. Recently, semiconductors based on multilayers of oxide thin films have attracted interest for applications, such as resistive memories or phototransistors. Here, a phototransistor was fabricated based on a bilayer of indium gallium zinc oxide (IGZO) and nonstochiometric, oxygen-deficient titanium oxide (TiOx) thin films formed via sputtering. The device fabrication was optimized by varying the temperature of the thermal annealing step to enhance the electrical performance and photoresponse characteristics. The IGZO/TiOx bilayer-based devices exhibited maximal performance when annealed at 350 °C with good mobility, low subthreshold swing, a turn-on voltage around 0 V, and high photoresponse through a wide range of gate bias. The dynamic photoresponse was evaluated under discrete light pulses. The device characteristics were measured after storage in an exicator for more than five months, and reasonable stability in photoresponse was observed.