Effect of nitrogen flow ratio on the structural and optical properties of aluminum nitride thin films

Aluminum nitride (AlN) films have been deposited on glass substrates at various nitrogen flow ratios by rf reactive magnetron sputtering. The AlN film deposited at 10% of nitrogen flow ratio shows a strongly c-axis preferred orientation with a crystalline size of 100 nm, thickness of 1100 nm, and band gap energy of 4.38 eV. The optimum crystallographic structure occurs at a nitrogen flow ratio of 100%, where a considerable crystallinity enhancement of the AlN film is observed. The band gap energies Eg calculated by the Tauc model and parabolic bands are well described by a relationship, Eg=10−3X+4.39, where X is the nitrogen flow ratio. The results suggest that the nitrogen flow ratio plays a key role in growing the high-quality AlN films.