ScGaN and ScAlN: emerging nitride materials

This review addresses the recent development and future prospects for Sc-based III-nitride alloys in energy-efficient device applications. Wurtzite-structure ScAlN and ScGaN alloys are wide band-gap semiconductors which can be stabilised at the low Sc contents relevant to devices, can be grown epitaxially, include the lattice-matched Sc0.18Al0.82N/GaN system, retain direct band gaps in the near-UV region up to 25% ScN and 50% ScN respectively, and should offer significantly higher exciton binding energies and piezoelectric coefficients compared to other III-nitrides. These properties greatly expand the options for band gap and polarisation engineering required for efficient optoelectronic devices, high-electron mobility transistors and energy-harvesting devices.