Zinc tin oxide (ZTO) is a transparent semiconductor based on earth-abundant elements. In this work, ZTO films prepared by spin coating via a solution route have been applied as the active semiconductor layer in a thin film transistor (TFT) with SiO₂ dielectrics and Si gate. With thickness less than 10 nm, the ZTO film exhibits a good field-effect mobility of ~10 cm²/Vs, small subthreshold slope of ~0.5 V/decade and high on/off current ratio of ~10⁷.

Under light illumination of 405 nm wavelength (below ZTO bandgap), the photoresponse of ZTO TFT is related to the ionization of neutral oxygen vacancies to positively-charged oxygen vacancies, which simultaneously produce photogenerated electron carriers. With power density upto 1 mW/cm², the light sensitivity is in the order of 10⁵~10⁶ for the I_D-off region. The light responsibility of ZTO TFT reaches around 740 A/W. Additionally, the characteristics of 405nm light-gated ZTO TFT under different gate biases are investigated. The ionized oxygen vacancies generated by light illumination provide a positive electric field. As a result, it is possible to control the transistor with the incident optical power density instead of gate voltage. The drain current versus power density (I_D-P) curve showed on/off switching behavior. Besides, the I_D-V_D curves of light-gated ZTO TFTs are similar to electricity-gated ones where I_D increases linearly with increasing V_D first and gets saturated after a certain V_D value.