Local Environment of Sc and Y Dopant Ions in Aluminum Nitride Thin Films

Abstract

The local environments of Sc and Y in predominantly ⟨002⟩ textured, Al 1−x Do x N (Do = Sc, x = 0.25, 0.30 or Y, x = 0.25) sputtered thin films with wurtzite symmetry were investigated using X-ray absorption (XAS) and photoelectron (XPS) spectroscopies. We present evidence from the X-ray absorption fine structure (XAFS) spectra that, when x = 0.25, both Sc 3+ and Y 3+ ions are able to substitute for Al 3+ , thereby acquiring four tetrahedrally coordinated nitrogen ligands, i.e., coordination number (CN) of 4. On this basis, the crystal radius of the dopant species in the wurtzite lattice, not available heretofore, could be calculated. By modeling the scandium local environment, extended XAFS (EXAFS) analysis suggests that when x increases from 0.25 to 0.30, CN for a fraction of the Sc ions increases from 4 to 6, signaling octahedral coordination. This change occurs at a dopant concentration significantly lower than the reported maximum concentration of Sc (42 mol % Sc) in wurtzite (Al, Sc)N. XPS spectra provide support for our observation that the local environment of Sc in (Al, Sc)N may include more than one type of coordination.

Iterative Bragg peak removal on X-ray absorption spectra with automatic intensity correction

“…Comparison of the IBR-AIC data with the manually deglitched data of 30° from literature (Cohen et al, 2024). The XAS in (a) energy space, (b) k 2 -weighted EXAFS spectra, and (c) Fourier transform magnitude of the k 2 -weighted EXAFS spectra.).…”