A Study of Anatase TiO2-Based Thin Film Phototransistors by Non-vacuum Thin Film Deposition Method

A nonvacuum thin-film deposition technology called ultrasonic spray pyrolysis deposition method is used to deposit fluorine-doped tin oxide, Al
₂
O
₃
, and TiO
₂
thin films, both of which are further applied on the anatase TiO
₂
-based thin-film phototransistors (PTs). The material characteristics of the anatase TiO
₂
such as selected area electron diffraction, X-ray photoelectron spectroscopy, photoluminescence spectrum, and deep-level transient spectroscopy are investigated. The anatase TiO
₂
-based thin-film PTs have a maximum output current of 4.56 mA/mm, subthreshold swing of 171 mV/dec, and threshold voltage of 0.7 V. The photoresponse characteristics of the anatase TiO
₂
-based thin-film PTs at different quiescent-points are measured and investigated. It is found that the present anatase TiO
₂
-based thin-film PTs can be operated in three different modes depending on the V
_DS
and V
_GS
biasing. In high-responsivity mode, the responsivity is 32.06 A/W; in high detectivity mode, the detectivity is 1.98 × 10
¹⁰
Jones; and in high ultraviolet (UV)-to-visible rejection ratio mode, the UV-to-visible rejection ratio is 1600.