Effects of real-time monitored growth interrupt on crystalline quality of AlN epilayer grown on sapphire by molecular beam epitaxy

Crack-free aluminum nitride (AlN) epilayers were grown on sapphire using growth-interrupt technique by radio-frequency assisted molecular beam epitaxy. In-situ reflectance spectroscopy was introduced for real-time monitoring of the growth of AlN epilayers. X-ray diffraction and atomic force microscopy measurements reveal that the threading dislocation density decreases considerably by using the growth-interrupt technique. Raman spectroscopy is used to characterize the residual stress of AlN epilayers. The optical transmittance and absorption spectra of AlN epilayers show a high transmittance and a sharp absorption edge.