Effect of nitrogen flow ratio on the structure and optical properties of AlN film

Abstract

Aluminum nitride (AlN) films with different optical properties were prepared by radio frequency (RF) reactive magnetron sputtering technique under different nitrogen (N2) flow ratios. The films' microstructure and optical properties were investigated by XRD, XPS, SEM, UV-VIS and PL. The results showed that all the prepared films had hexagonal wurtzite structure and the sample prepared at 35 % N2 flow ratio obtained higher crystal quality and larger grain size (39 nm). The selective orientation of the films changed from (100) to (002) with the N2 flow ratio, accompanied with a surface morphology changed from worm-like to mixed structure, and eventually to a very regular pebble shape with a compact arrangement. The average transmission of the films exceeded 83 % in the wavelength range of 300–800 nm. The major internal defect affecting the band gap of AlN films was nitrogen-vacancy (VN), and the growth orientation and internal defects of AlN films were controlled by the N2 flow ratio to achieve the regulation of the energy band gap in a small range (5.47–5.68 eV). This can meet the requirement of solar-blind ultraviolet (<280 nm) photoelectric detection.