Silicon induced stability and mobility of indium zinc oxide based bilayer thin film transistors

Indium zinc oxide (IZO), silicon containing IZO, and IZO/IZO:Si bilayer thin films have been prepared by dual radio frequency magnetron sputtering on glass and SiO₂/Si substrates for studying their chemical compositions and electrical characteristics in order to ascertain reliability for thin film transistor (TFT) applications. An attempt is therefore made here to fabricate single IZO and IZO/IZO:Si bilayer TFTs to study the effect of film thickness, silicon incorporation, and bilayer active channel on device performance and negative bias illumination stress (NBIS) stability. TFTs with increasing single active IZO layer thickness exhibit decrease in carrier mobility but steady improvement in NBIS; the best values being μ_FE ∼ 27.0, 22.0 cm²/Vs and ΔV_th ∼ -13.00, -6.75 V for a channel thickness of 7 and 27 nm, respectively. While silicon incorporation is shown to reduce the mobility somewhat, it raises the stability markedly (ΔV_th ∼ -1.20 V). Further, IZO (7 nm)/IZO:Si (27 nm) bilayer based TFTs display useful characteristics (field effect mobility, μ_FE = 15.3 cm²/Vs and NBIS value, ΔV_th =-0.75 V) for their application in transparent electronics.