SUBSTRATE NITRIDATION EFFECTS ON GAN GROWN ON GAAS SUBSTRATES BY MOLECULAR-BEAM EPITAXY USING RF-RADICAL NITROGEN-SOURCE

The initial substrate nitridation effects on the crystal structure of GaN epitaxial layers grown on GaAs substrates by gas source molecular beam epitaxy using RF-radical N-2 as a nitrogen source were investigated. The crystal structure of GaN grown on (100) GaAs substrates was critically influenced by substrate nitridation time, that is, zincblende GaN was grown on the substrate without nitridation, and wurtzite GaN was grown on the nitrided substrate (longer than 120 s). The substrate misorientation effects on surface morphology and X-ray full width at half-maximum of zincblende GaN layers were also studied. A featureless smooth surface was obtained for a layer grown under the high V/III beam flux ratio condition.