Impact of $4H$– and $6H–SiC(0001)$ nitridation on Ga wetting layer development and GaN growth by molecular beam epitaxy

GaN epitaxial layers have been grown by plasma-assisted molecular beam epitaxy on Si-face $4H$– and $6H–SiC(0001)Si$ substrates. The impact of the SiC surface preparation and oxide removal achieved via a Ga flash-off process followed by nitridation on the structure and properties of GaN epitaxial layers is articulated. A correlation among the SiC surface nitridation conditions, the Ga wetting layer development, the nucleation layer, and GaN crystalline properties is revealed.