Role of metal capping layer on highly enhanced electrical performance of In-free Si–Zn–Sn–O thin film transistor

•Better electrical properties by adopting simple structure using metal capping layer•High mobility over 100 cm2/V s•Prevention of adsorption/desorption reaction of ambient on the backchannel surface•Excellent stability of ΔVth ~ 0.6 V.

Metal capping (MC) layer for Si–Zn–Sn–O thin film of the back channel layer of thin film transistors is proposed to protect from ambient effect and to improve electrical properties. Field effect mobility is improved from 34.46 cm2/V s to 147.59 cm2/V s and excellent stability of Vth ~ 0.6 V is obtained. The floating MC-layer forms a strongly compact-shape current-path as a result of the effective control of the surface potential by the low-resistance of MC-layer. In addition, the proposed device structure effectively prevents the adsorption/desorption reaction of ambient oxygen and water molecules on the surface.