Aluminum nitride grown on lens shaped patterned sapphire by hydride vapor phase epitaxy

Thick c-plane aluminum nitride (AlN) films were grown directly onto lens shaped patterned c-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). The sapphire patterning consisted of convex hemispherical lenses in a hexagonal pattern. These films were fully coalesced, planar, colorless, specular and up to 20 mu m thick. Full widths at half maximum of X-ray rocking curves for the on-axis (0002) and off-axis (20 (2) over bar1) AlN reflections for fully coalesced films reached 914 and 1502 arcsec respectively. Plan view transmission electron microscopy was used to determine the threading dislocation density which was similar to 8 x 10(8) cm(-2). An interrupted growth series was also performed to evaluate the growth evolution of the AlN. Scanning electron microscopy was used to examine the initial growth and coalescence of the films. The AlN was determined to grow in hexagonal pillars initiated on the lenses, eventually coalescing together. These AlN films offer a promising substrate for AlGaN based UV optoelectronics thanks to both its transparency in the UV region and patterning effects. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim