Effects of top-layer thickness on electrical performance and stability in VZTO/ZTO bi-layer thin-film transistors

We examined vanadium-incorporated zinc tin oxide (VZTO) thin film transistors (TFTs) with various V contents and found that VZTO films easily become semi-insulators, even at small V contents (≥1.7 at%). We also fabricated VZTO/ZTO bi-layer TFTs with various VZTO top-layer thicknesses and investigated their electrical performance and stability. Regardless of the VZTO top-layer thickness, the VZTO/ZTO TFTs exhibited the transfer characteristics of a typical TFT because VZTO top-layers had semiconducting properties, unlike single VZTO films. As compared to the reference ZTO TFT, the stability of all the bi-layer TFTs under bias and/or illumination stress was significantly improved. - Highlights: • Vanadium-doped zinc tin oxide (VZTO) TFTs with various V contents were examined. • VZTO films easily become semi-insulators, even at small V contents (≥1.7 at %). • VZTO/ZTO bi-layer TFTs with various VZTO top-layer thicknesses were investigated. • All VZTO top-layers have semiconducting properties, unlike single VZTO films. • All VZTO/ZTO bi-layer TFTs showed greatly improved stability.