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Interfacial Contact Effects in Top Gated Zinc Oxide Thin Film Transistors Grown by Atomic Layer Deposition.

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Title: Interfacial Contact Effects in Top Gated Zinc Oxide Thin Film Transistors Grown by Atomic Layer Deposition.
Authors: Ma, Alex M.1, Shen, Mei1, Afshar, Amir2, Tsui, Ying Y.1, Cadien, Kenneth C.2, Barlage, Douglas W.1
Source: IEEE Transactions on Electron Devices. Sep2016, Vol. 63 Issue 9, p3540-3546. 7p.
Subjects: Zinc oxide thin films, Atomic layer deposition, Electrodes, Logic circuits, Contact resistance (Materials science)
Abstract: Contact effects at the source/drain (S/D) electrodes in thin film transistors (TFTs) based on zinc oxide (ZnO) utilizing the top gate, bottom contact geometry are investigated using electrical and material studies. Low temperature atomic layer deposition (ALD) is employed to directly grow the ZnO active layer on Au, Ru, and TiW bottom electrodes. TFT performance varies significantly depending on the S/D metallization scheme. Au contacts are seen to uniquely promote the growth of a highly n-doped ZnO channel that degrades the TFT’s output impedance and controllability. On the other hand, TiW contacts suffer from poor carrier injection because of Schottky barrier formation. The best overall performance is demonstrated by Ru/ZnO TFTs based on their excellent switching capabilities alongside a moderately high mobility. From X-ray photoelectron spectroscopy measurements, the superior performance of Ru is the consequence of an oxidation-free interface that inhibits the adsorption of hydroxide surface dopants. Thus, the surface chemistry of the metal contact plays a large role on the ZnO growth and metal/ZnO interface energetics. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Contact effects at the source/drain (S/D) electrodes in thin film transistors (TFTs) based on zinc oxide (ZnO) utilizing the top gate, bottom contact geometry are investigated using electrical and material studies. Low temperature atomic layer deposition (ALD) is employed to directly grow the ZnO active layer on Au, Ru, and TiW bottom electrodes. TFT performance varies significantly depending on the S/D metallization scheme. Au contacts are seen to uniquely promote the growth of a highly n-doped ZnO channel that degrades the TFT’s output impedance and controllability. On the other hand, TiW contacts suffer from poor carrier injection because of Schottky barrier formation. The best overall performance is demonstrated by Ru/ZnO TFTs based on their excellent switching capabilities alongside a moderately high mobility. From X-ray photoelectron spectroscopy measurements, the superior performance of Ru is the consequence of an oxidation-free interface that inhibits the adsorption of hydroxide surface dopants. Thus, the surface chemistry of the metal contact plays a large role on the ZnO growth and metal/ZnO interface energetics. [ABSTRACT FROM AUTHOR]
ISSN:00189383
DOI:10.1109/TED.2016.2586418