LAUSR

We investigated the optical and structural properties of ZnOS digital alloy grown on Si by atomic layer deposition. The refractive index and extinction coefficient were evaluated using spectroscopic ellipsometry. ZnOS alloy film shows a strong absorption tail extended to the below band gap regime, which is attributed to a high density of band tail states formed within the band gap owing to the amorphous crystallinity. The ZnOS alloy exhibits a large Urbach energy of 210–540 meV. After high-temperature annealing, the band tail states are reduced with a decrease in lattice disorder, which is confirmed by enhanced X-ray diffraction peaks.