Structural and piezoelectric properties of ultra-thin ScxAl1−xN films grown on GaN by molecular beam epitaxy
Abstract
ScxAl1−xN (x = 0.18–0.40) thin films of ∼28 nm thickness grown on metal polar GaN substrates by molecular beam epitaxy are found to exhibit smooth morphology with less than 0.5 nm roughness and predominantly single-phase wurtzite crystal structure throughout the composition range. Measurement of the piezoelectric d33 coefficient shows a 150% increase for lattice-matched Sc0.18Al0.82N relative to pure aluminum nitride, whereas higher Sc contents exhibit lower piezoelectric coefficients. The electromechanical response of the epitaxial films correlates with the crystal quality and the presence of zinc blende inclusions, as observed by high-resolution electron microscopy. It is further found that the polarity of the epitaxial ScxAl1−xN layers is locked to the underlying substrate. The measured electromechanical properties of epitaxial ScxAl1−xN, their relation to the atomic crystal structure and defects, and its crystal polarity provide useful guidance toward the applications of this material.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 14, 2020
- Source ID
- 10.1063/5.0013943
Entities
People
- Celesta S. Chang
- David A. Muller
- Debdeep Jena
- Huili Grace Xing
- John Wright
- Joseph Casamento
- Yu-tsun Shao
Organizations
- Air Force Office of Scientific Research
- Cornell University
- Defense Advanced Research Projects Agency
- National Science Foundation