Ultraviolet photoconductivity of amorphous ZnAlSnO thin-film transistors

Abstract

Ultraviolet (UV) photoconductivity of solution-processed amorphous zinc-aluminum-tin oxide (a-ZATO) TFTs has been investigated in detail to clarify the device responses. The sensitivities of a-ZATO TFTs towards UV light are strongly dependent on the Al content. The UV exposure and recovery process are decided by the state changes of oxygen defects (V⁰_O and V_O²⁺). An appropriate Al addition can not only reduce the amounts of photogenerated carriers by increasing the band gap of ZATO films, but also markedly decrease the UV photoconductivity and recovery time, which benefits the TFT applications in the display fields. Based on UV behaviors of ZATO TFTs, a feasible and reasonable mechanism model has been proposed, which provides a fundamental insight to UV photoconductivity of ZATO TFTs and may also be applied to other AOS TFTs.