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    • Keywords


      Wurtzite–Al$_{1-x}$Sc$_x$N; molecular beam epitaxy; phase separation.

    • Abstract


      Wurtzite–Al$_{1-x}$Sc$_x$N thin films deposited by solid-state alloying of AlN with ScN exhibit high piezoelectric coefficient and large band gap that makes it a promising material for a variety of applications in piezo-electronics, electronic, acoustoelectric devices, etc. Research on epitaxial Al$_{1-x}$Sc$_x$N growth in wurtzite crystal structure is still at an early stage and achieving high scandium (Sc) concentrations in epitaxial films without any phase separation or secondaryphase formation is still a critical challenge. Moreover, as most of the reports of wurtzite–Al$_{1-x}$Sc$_x$N growth thus far relies on low-vacuum growth techniques, such as magnetron sputtering that are prone to large impurities and contaminants detrimental for device applications, high-vacuum deposition techniques, such as molecular beam epitaxy method needs to be developed. In this paper, we report the epitaxial growth of wurtzite–Al$_{1-x}$Sc$_x$N on sapphire (Al$_2$O$_3$) substrates under different Sc fluxes using ultra-high vacuum plasma-assisted molecular beam epitaxy. To prevent ScN phase separation, a 30 nm AlN buffer layer is deposited in situ on GaN epilayers as well as Al$_2$O$_3$ substrates that result in phase-pure wurtzite–Al$_{1-x}$Sc$_x$N thin films without any phase separation or secondary phase formation. The structural and compositional analyses performed with high-resolution X-ray diffraction (HRXRD) and secondary ion mass spectroscopy(SIMS), reveal epitaxial wurtzite–Al$_{1-x}$Sc$_x$N growth with 0001 orientations on (0001) Al$_2$O$_3$ substrates and the presence of cubic ScN. Demonstration of phase-pure Al$_{1-x}$Sc$_x$N on AlN buffer layers will enable the development of devices with improved efficiencies.

    • Author Affiliations



      1. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru 560064, India
      2. International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru 560064, India
      3. School of Advanced Materials (SAMat), Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru 560064, India
      4. UGC-DAE Consortium for Scientific Research, University Campus, Indore 452001, India
    • Dates

  • Bulletin of Materials Science | News

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