YxAl1−xN thin films

Reactive magnetron sputtering was used to deposit Y x Al 1− x N thin films, 0 ⩽ x ⩽ 0.22, onto Al 2 O 3 (0 0 0 1) and Si(1 0 0) substrates. X-ray diffraction and analytical electron microscopy show that the films are solid solutions. Lattice constants increase with Y concentration, in agreement with ab initio calculations. Spectroscopic ellipsometry measurements reveal a band gap decrease from 6.2 eV ( x = 0) down to 4.5 eV ( x = 0.22). Theoretical investigations within the special quasirandom structure approach show that the wurtzite structure has the lowest mixing enthalpy for 0 ⩽ x ⩽ 0.75.