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Using practical high-density sputtering targets, we investigated the effect of Zn and W codoping on the thermal stability of the amorphous film and the electrical characteristics in thin film transistors. zinc oxide is a potentially conductive component while W oxide is an oxygen vacancy suppressor in oxide films. The oxygen vacancy from In-O and Zn-O was suppressed by the W additive because of the high oxygen bond dissociation energy. With controlled codoping of W and Zn, we demonstrated a high mobility with a maximum mobility of 40 cm2/V s with good stability under a negative bias stress in InWZnO thin film transistors. [ABSTRACT FROM AUTHOR]

The influence of a SiO2 passivation layer on the electrical properties and reliability of an In–W–Zn–O thin-film transistor (IWZO TFT) was investigated under various post-annealing temperatures (Ta). Although the TFT without passivation showed good transfer characteristics when the Ta is 150 °C, it has huge hysteresis and poor reliability. Furthermore, the TFTs without passivation changed from transistor to conductor when the Ta is 200 °C or higher. In contrast, the TFTs with passivation exhibited switching property even at Ta of 350 °C. Positive bias temperature stress reliability of the TFTs significantly improved by applying the Ta with passivation. Thus, a passivation layer is essential to increase the Ta, resulting in the improvement of electrical properties and reliability of the IWZO TFTs. [ABSTRACT FROM AUTHOR]