Stability enhancement of low temperature thin-film transistors with atomic-layer-deposited ZnO:Al channels

- The thin-film-transistors (TFTs) with atomic-layer-deposited Al-doped ZnO channels have been fabricated under the maximum process temperature of 200 °C.
- Different from the polycrystalline ZnO film, the Al-doped ZnO film can maintain an amorphous matrix by increasing Al concentration.
- The adoption of Al-doped ZnO channel improves significantly the stability of the device under illumination and gate bias stress.
- The Al-doped ZnO channel demonstrates stronger immunity to the surrounding ambient than the ZnO channel.

The electrical characteristics of TFTs with atomic-layer-deposited ZnO:Al (ZAO) channels have been studied in this work. By increasing Al doping concentration, the ZAO film changes from polycrystalline to amorphous, and its bandgap widens as well. With post-annealing at 200 °C, the superior electrical stabilities under illumination and gate bias stress were achieved in ZAO TFTs compared with ZnO TFTs. For the strong immunity to illumination in ZAO TFTs, it is attributed to the widening bandgap of channel material for the reduction of the carrier concentration. While for the improved electrical stability under positive bias stress, it is mainly due to the suppression of interactions between the amorphous channel and the surrounding ambient, which is verified by the observations in N2 ambient.

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