Stabilization of wurtzite Sc0.4Al0.6N in pseudomorphic epitaxial Sc Al1−N/In Al1−N superlattices

Abstract Pseudomorphic stabilization in wurtzite Sc x Al 1− x N/AlN and Sc x Al 1− x N/In y Al 1− y N superlattices ( x = 0.2, 0.3, and 0.4; y = 0.2–0.72), grown by reactive magnetron sputter epitaxy was investigated. X-ray diffraction and transmission electron microscopy show that in Sc x Al 1− x N/AlN superlattices the compressive biaxial stresses due to positive lattice mismatch in Sc 0.3 Al 0.7 N and Sc 0.4 Al 0.6 N lead to the loss of epitaxy, although the structure remains layered. For the negative lattice mismatched In-rich Sc x Al 1− x N/In y Al 1− y N superlattices, a tensile biaxial stress promotes the stabilization of wurtzite Sc x Al 1− x N even for the highest investigated concentration x = 0.4. Ab initio calculations with fixed in-plane lattice parameters show a reduction in mixing energy for wurtzite Sc x Al 1− x N under tensile stress when x ⩾ 0.375 and corroborate the experimental results.