Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition

The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition at a t...

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Bibliographic Details
Published in:Nanotechnology 2021-01, Vol.32 (1), p.015705-015705
Main Authors: Giannazzo, F, Dagher, R, Schilirò, E, Panasci, S E, Greco, G, Nicotra, G, Roccaforte, F, Agnello, S, Brault, J, Cordier, Y, Michon, A
Format: Article
Language:English
Subjects:
AlGaN
chemical vapour deposition
Condensed Matter
conductive atomic force microscopy
electron energy loss spectroscopy
graphene
Materials Science
Physics
transmission electron microscopy
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Summary:The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition at a temperature of 1350 °C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a ∼2 nm thick AlGaN surface region was confirmed by cross-sectional scanning transmission electron microscopy combined with electron energy loss spectroscopy, which also showed the presence of a bilayer of Gr with partial sp2/sp3 hybridization. Raman spectra indicated that the deposited Gr is nanocrystalline (with domain size ∼7 nm) and compressively strained. A Gr sheet resistance of ∼15.8 kΩ sq−1 was evaluated by four-point-probe measurements, consistently with the nanocrystalline nature of these films. Furthermore, nanoscale resolution current mapping by conductive atomic force microscopy indicated local variations of the Gr carrier density at a mesoscopic scale, which can be ascribed to changes in the charge transfer from the substrate due to local oxidation of AlGaN or to the presence of Gr wrinkles.
ISSN:0957-4484
1361-6528
DOI:10.1088/1361-6528/abb72b