Molecular beam epitaxial growth of scandium nitride on hexagonal SiC, GaN, and AlN

RF plasma assisted MBE growth of scandium nitride (ScN) thin films on Ga-polar GaN (0001)/SiC, Al-polar AlN (0001)/Al2O3, and Si-face 6H-SiC (0001) hexagonal substrates is found to lead to a face centered cubic (rock salt) crystal structure with (111) out-of-plane orientation instead of hexagonal orientation. Cubic (111) twinned patterns in ScN are observed by in situ electron diffraction during epitaxy, and the twin domains in ScN are detected by electron backscattered diffraction and further corroborated by X-ray diffraction. The epitaxial ScN films display very smooth, subnanometer surface roughness at a growth temperature of 750 °C. Temperature-dependent Hall-effect measurements indicate a constant high n-type carrier concentration of ∼1 × 1020/cm3 and an electron mobility of ∼20 cm2/V s.