Highly Stable ZnON Thin-Film Transistors With High Field-Effect Mobility Exceeding 50 $\mathrm{cm}^{2}$ /Vs

High-performance thin-film transistors (TFTs) based on ZnON channels were fabricated using a dc reactive sputtering method. To improve the photoinduced bias stability, a postannealing process was carried out at a low ambient pressure (
$\sim 100$
mTorr, air ambient) at 250 °C for various annealing times (1–5 h). The transfer characteristics of the postannealed ZnON TFTs exhibited an improved subthreshold swing ranging from 0.60 to 0.42 V/decade. Other transport properties remained similar including a high mobility (
$\mu _{\rm sat}$
) of >50
$\mathrm{cm}^{2}$
/Vs, a threshold voltage (
$V_{\rm th}$
) of −2.5 V, and an ON-OFF drain current ratio of
$> 10^{8}$
. In addition, photoinduced bias reliability under a gate bias stress (
$V_{G} = -20$
V) was significantly improved from −10.88 V (1 h) to −2.28 V (5 h). These results can be explained by the enhancement of bonding properties between Zn metal and two different anions (O, N) as stable N–Zn–O states.