Low dislocation density AlN on sapphire prepared by double sputtering and annealing

AlN on sapphire with dislocation density of 107 cm−2 was prepared by double sputtering and annealing processes. Full width at half maximum values of X-ray rocking curve for and diffractions of the AlN films were measured to be 10–20 arcsec and 65–82 arcsec, respectively. Dislocations were characterized by plan-view and cross-sectional transmission electron microscopy, and the total dislocation density was estimated as 4.3 × 107 cm−2. A polarity inversion layer was found between the two sputtered AlN layers, which increased the possibility of blocking dislocations stemming from the AlN/sapphire interface.