Amorphous IZO-based transparent thin film transistors

Abstract

Active electronics implemented on cheap flexible polymer substrates offer the promise of novel display technologies, wearable electronics, large area memory, and a multitude of other, as-yet-unthought-of applications that require low cost and high volume manufacturing. Thin film transistors (TFT's) fabricated on temperature-sensitive plastic substrates at low temperatures are the key to this technology. TFT's that use metal (In, Zn, Sn, Ga) oxide channels offer both high mobility (relative to amorphous Si) and the advantage of optical transparency in the visible regime. We report on the fabrication and performance of amorphous oxide transparent thin film transistors that use dc-magnetron sputter techniques to deposit IZO (In 2O 3 — 10 wt.% ZnO) at low oxygen potential (0 vol.% O 2) for the source, drain, and gate-contact metallization and, at higher oxygen partial pressures (10 vol.% O 2), for the semi-conducting channel. The devices in this study were processed at room temperature except for a single 280 °C PECVD deposition step to deposit a 230 nm-thick SiO x gate dielectric. The devices are optically transparent and operate in depletion mode with a threshold voltage of − 5 V, mobility of 15 cm 2/V s, an on-off ratio of > 10 6 and, a sub-threshold slope of 1.2 V/decade. In addition, we report persistent photo-conductivity in the channel region of these devices when exposed to UV illumination.