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-plane 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 sapphire have [0 0 2] symmetric and [1 0 4] asymmetric full width at half maximum (FWHM) of about 60 and 132 arcsec, respectively. This compares with 408 and 600 arcsec, respectively, for GaN grown on sapphire having gone through conventional chemical cleaning.