Boosting Carrier Mobility in Zinc Oxynitride Thin-Film Transistors via Tantalum Oxide Encapsulation.

Author(s) Kim, T.; Kim, M.Jae; Lee, J.; Jeong, J.Kyeong
Journal ACS Appl Mater Interfaces
Date Published 2019 Jun 13

Novel TaO encapsulation was presented to enhance the field-effect mobility (μ) of ZnON thin-film transistors (TFTs) consisting of a metallic Ta film deposited onto the ZnON surface followed by a modest annealing process. The resulting TaO /ZnON film stack exhibited a more uniform distribution of nanoscale ZnON crystallites with increased stoichiometric anion lattices compared to the control ZnON film. The control ZnON TFTs exhibited a reasonable μ, subthreshold gate swing (SS), and I ratio of 36.2 cm/V·s, 0.28 V/decade, and 2.9 × 10, respectively. A significantly enhanced μ value of 89.4 cm/V·s was achieved for ZnON TFTs with a TaO encapsulation layer, whereas the SS of 0.33 V/decade and I ratio of 8.6 × 10 were comparable to those of the control device. This improvement could be explained by scavenging and passivation effects of the TaO film on the ZnON channel layer. Density of states (DOS)-based modeling and simulation were performed to obtain greater insight with regard to increasing the performance of the ZnON TFTs with a TaO encapsulation layer. A smaller number of subgap states near the conduction band (CB) minimum and a higher net carrier density for the TaO -capped device increased the Fermi energy level toward the CB edge under thermal equilibrium conditions, leading to efficient band conduction and fast carrier transport under the on-state condition.

DOI 10.1021/acsami.9b03865
ISSN 1944-8252
Citation ACS Appl Mater Interfaces. 2019.

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