The interplay of process parameters and influence on the AlN films on sapphire fabricated by DC magnetron sputtering and annealing

This paper reports a high-quality aluminium nitride (AlN) film deposited on c-plane sapphire using a direct current reactive sputtering system. A comprehensive investigation on the effects of substrate temperature, sputtering power, Ar/N2 flow ratio, and process pressure on the morphology and crystalline quality of the AlN thin films was performed. Optimal process parameters including substrate temperature of 500 °C, process pressure of 0.5 Pa, gas flow ratio of Ar/N2 = 1/6, and sputtering power of 400 W was demonstrated. In addition, the crystallization quality was further improved after face-to-face annealing and homoepitaxial regrowth by metal–organic chemical vapor deposition. The full widths at half maximum values of the x-ray rocking curves of the (0002) and ( 101ˉ2 ) diffraction of AlN after the re-growth process reach as low as 49 and 360 arcsec, respectively, and the corresponding surface morphologies of the films were covered with atomic bi-layer steps. Finally, a ultraviolet-C light emitting diode with decent performance was demonstrated on top of the sputtered AlN thin film.