Growth and optical properties of polar-, nonpolar, and semi-polar wurtzite ScGaN films
Abstract
Wurtzite ScGaN offers a promising platform for anisotropic optoelectronic and piezoelectric functionalities, provided that its crystallographic orientation can be precisely controlled. Here, we demonstrate systematic orientation engineering of ScGaN thin films grown by reactive magnetron sputter epitaxy on c-, r-, and m-plane Al2O3 substrates, enabled by the strategic use of an ultra-thin GaN buffer layer. X-ray diffraction (XRD) and scanning transmission electron microscopy confirm the growth of polar, non-polar, and semi-polar ScGaN films on sapphire. A comparison of growth conditions reveals that the GaN buffer layer is essential for stabilizing these orientations and ensuring high epitaxial quality. Consequently, the c-plane ScGaN (0002), a-plane ScGaN (112¯0), and semi-polar-plane ScGaN (112¯2) were indexed through combined XRD and selected area electron diffraction. Spectroscopic ellipsometry combined with Mueller-matrix analysis reveals pronounced orientation-dependent optical anisotropy across all films. Cody-plot analysis further reveals that ScGaN has a wider bandgap (3.504 eV) than GaN (3.385 eV). This confirms polarization-resolved absorption onsets reflecting the wurtzite valence band anisotropy. The extracted optical-axis tilt angles quantitatively confirm polar, non-polar, and semi-polar configurations of ScGaN on sapphire substrates. Together, these results highlight buffer-assisted orientation control as an effective strategy to tailor the anisotropic properties of ScGaN.
Article Details
Journal Info
Applied Physics Letters
American Institute of Physics
Authors (17)
Yu-Hsuan Hsu
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Roger Magnusson
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Rohini Sanikop
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Shailesh Kalal
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Justinas Palisaitis
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Sagar Jathar
Inorganic Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University 2 , Box 538, SE-751 21 Uppsala,
Katrin Pingen
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Per Sandström
Department of Surgery in Linköping, Linköping University
Issa Nseir
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Arnaud le Febvrier
Inorganic Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University 2 , Box 538, SE-751 21 Uppsala,
Urban Forsberg
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Ray-Hua Horng
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Kenneth Järrendahl
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Per Eklund
Inorganic Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University 2 , Box 538, SE-751 21 Uppsala,
Vanya Darakchieva
Department of Physics, Chemistry and Biology (IFM)
Jens Birch
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,
Ching-Lien Hsiao
Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University 1 , SE-581 83 Linköping,