Amorphous TiO2-Based Thin-Film Phototransistor

This letter presents amorphous TiO2-based thin-film phototransistors whose structures are designed for front-side and back-side illumination. The channel and gate dielectric layers are deposited by ultrasonic spray pyrolysis deposition, which is a non-vacuum, cost-effective, thin-film deposition technique similar to chemical vapor deposition. The material structure, chemical composition, and optical characteristics of the amorphous TiO2 thin film are analyzed. The phototransistor shows the typical current-voltage (I-V) characteristics of field-effect transistors. It demonstrates a UV-to-visible rejection ratio of approximately 70-80, a high responsivity of 13.64 A/W, and a high detectivity of 1.64 x 10(12) Jones. The phototransistor can be operated in the high-photo-responsivity and highdetectivity modes by biasing at different quiescent points.