High quality AlN and GaN on Si(111) by MBE with ammonia

摘要

We describe the growth of hexagonal AlN and GaN on Si(111) by gas source molecular beam epitaxy with ammonia. The initial high - temperature deposition of Al results in rapid transition to two-dimensional growth. High quality GaN can be grown on such AlN buffer layers. For GaN layers thicker than 1.5 mu m the full width at half maximum of the (0002) diffraction peak is less than 14 arcsec. We show that a short period superlattice of AlGaN / GaN grown on the AlN buffer can be used to block defects propagating through GaN, resulting in improved and luminescence properties. The room - temperature linewidth of the GaN free exciton peak is less than 40 meV, typical of the best samples grown on sapphire. Our growth procedure also results in complete elimination of cracking in thick (>2 mu m) GaN layers.