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

Abstract

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.

Esaki Diode Behavior in Highly Uniform MoS2/Silicon Carbide Heterojunctions

“…[10,11] Beside silicon, other semiconductors (including group III Nitrides and silicon carbide) have been considered as platform for graphene and 2D materials integration. [8,9,[12][13][14] In this context, silicon carbide represents a very interesting case. Owing to its outstanding physical properties (wide bandgap, high-critical electric field, and thermal conductivity) [15] and high technological maturity, the 4H-SiC polytype is nowadays the material of choice for high-power devices, which are crucial in strategic fields (energy conversion systems, electric vehicles, and trains, ..) for modern economy and society.…”

Influence of Graphene Stability on III-Nitride Remote Epitaxy for Exfoliation

“…Maybe direct CVD growth of graphene on the AlN/sapphire template 29,30 is a better choice to achieve a better graphene layer.…”

“…Besides, the monolayer graphene transferred onto the AlN surface presents a certain density of defects, as shown in Figure . Maybe direct CVD growth of graphene on the AlN/sapphire template , is a better choice to achieve a better graphene layer.…”

Integrating 2D layered materials with 3D bulk materials as van der Waals heterostructures for photodetections: Current status and perspectives

“…Therefore, CVD has overall control over material properties contrast to other growth methods and has been proven to be a versatile tool for fundamental studies of 2DLMs. In recent decades, various types of 2D/3D heterostructures have been realized by this method, for example, MoS 2 /GaN, 32,33 MoS 2 /Al 2 O 3, 34 graphene/Ge, 35 and graphene/AlGaN 36 . However, a wide grain‐size distribution, random nucleation sites, and irregular grain orientations usually occur during the CVD synthesis and lead to the formation of grain boundaries and defects which would bring negative effects on the electrical property of 2DLMs 30,37 .…”