Preparation of sapphire for high quality III-nitride growth

We developed a unique preparation technique to eliminate surface damage on the c-plane of sapphire and render it atomically flat. AFM images of c-plan e sapphire annealed at 1380 degreesC for 1 hour show terrace-like features with about 0.2 mum long terraces. The GaN layers grown by MBE on annealed s apphire have [0 0 2] symmetric and [1 0 4] asymmetric full width at half ma ximum (FWHM) of about 60 and 132 arcsec, respectively. This compares with 4 08 and 600 arcsec, respectively, for GaN grown on sapphire having gone thro ugh conventional chemical cleaning.