Characteristics of ALD-ZnO Thin Film Transistor Using H2O and H2O2 as Oxygen Sources

Jun Yang, Amin Bahrami, Xingwei Ding, Sebastian Lehmann, Nadine Kruse, Shiyang He, Bowen Wang, Martin Hantusch, Kornelius Nielsch

ZnO thin films are deposited by atomic layer deposition (ALD) using diethylzinc as the Zn source and H2O and H2O2 as oxygen sources. The oxidant- and temperature-dependent electrical properties and growth characteristics are systematically investigated. Materials analysis results suggest that H2O2 provides an oxygen-rich environment so that the oxygen vacancies (VO) is suppressed, implying a lower carrier concentration and a higher resistivity. The lower growth rate makes it possible for the ZnO thin films to grow along the lower surface energy direction of <002>, leading to a lower Hall mobility. Furthermore, the ZnO semiconductor is integrated into thin film transistor (TFT) devices and the electrical properties are analyzed. The TFT with H2O2-ZnO grown at 150 °C shows good electrical properties, such as a high field-effect mobility of 10.7 cm2 V–1 s–1, a high ratio Ion/Ioff of 2 × 107, a sharp subthreshold swing of 0.25 V dec–1, and a low trapping state (Ntrap) of 2.77 × 1012 eV–1 cm–2, which provides a new pathway to optimize the performance of metal-oxide electronics.

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