Mobility enhancement in ZnO-based TFTs by H treatment

ZnO-based thin-film transistors (TFTs) have been fabricated by depositing ZnO (radio-frequency sputtering) on SiO₂/p-Si substrates at various temperatures ranging from room temperature to 300°C. When rapid thermal annealing in a forming gas ambient was used for H treatment on ZnO, the TFTs prepared at 200°C exhibited a high field-effect mobility of ∼1.93 cm²/V s but a low on/off current ratio of ∼10² while those fabricated at room temperature showed a low mobility (∼0.2 cm ²/V s) but a high on/off ratio ∼10⁶). The TFT fabricated at 300°C was the most highly conductive among all the TFTs studied but did not show current saturation. We conclude that H treatment on the ZnO channel at a high temperature leads to a high mobility but to a low on/off current ratio.