Control of phase purity in high scandium fraction heteroepitaxial ScAlN grown by molecular beam epitaxy
Matthew T. Hardy, Eric N. Jin, Neeraj Nepal, D. S. Katzer, Brian P. Downey, Vikrant J. Gokhale, David F. Storm, David J. Meyer
Abstract
ScAlN is a promising material for applications spanning wide-bandwidth filters, high-electron-mobility transistors, and ferroelectric memory. We investigate conditions influencing wurtzite phase purity for heteroepitaxial ScAlN, and present methods to rapidly identify phase purity degradation. Even for N-rich samples, phase purity is sensitive to the III/V ratio near the N-rich to metal-rich transition. Epitaxial ScxAl1−xN samples can be grown at 700 °C with x = 0.06–0.22, although the phase purity degrades for x = 0.32. By reducing the substrate temperature to 390 °C, we demonstrate 200 nm Sc0.32Al0.68N heteroepitaxial films with a record low rocking curve full-width at half-maximum of 1840 arcsec.