Electron microscopy analysis of microstructure of postannealed aluminum nitride template

The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200nm thickness on a sapphire (0001) substrate by metal-organic vapor phase epitaxy. The AlN template was annealed under (N-2 + CO) atmosphere at 1500-1650 degrees C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure. (C) 2016 The Japan Society of Applied Physics