First-principles study of structural, electronic, optical, mechanical, piezoelectric, and ferroelectric properties in AlScN

Abstract

Scandium-doped wurtzite AlN (AlScN) has emerged as a highly promising wide-bandgap semiconductor. However, complete understanding in the atomistic origins of its simultaneously enhanced electronic, optical, elastic, piezoelectric, and ferroelectric properties remain elusive. Here, using systematic first-principles calculations, we elucidate how Sc doping governs the hierarchical structure-property relationships in AlN. Sc substitution induces anisotropic lattice expansion, softens the phonon spectrum, and promotes strong Sc-d/Al-p/N-p orbital hybridization, leading to band gap reduction and Fermi-surface reconstruction. The resulting narrower band gap, red-shifted absorption edge, and enhanced dielectric polarizability are quantitatively linked to orbital-resolved transition probabilities. Mechanically, continuous Sc incorporation induces shear softening that reduces hardness while retaining intrinsic