Molecular-beam epitaxial growth of insulating AlN on surface-controlled 6H–SiC substrate by HCl gas etching

Insulating AlN layers were grown on surface-controlled 6H–SiC subtrates by molecular-beam epitaxy (MBE) using elemental Al and rf plasma-excited nitrogen (N*). HCl gas etching was introduced as an effective pretreatment method of substrate for MBE growth of AlN. 6H–SiC substrates pretreated by HCl gas etching had no surface polishing scratches and an atomically flat surface. In addition, evident (∛×∛)R30° surface reconstruction was observed even before thermal cleaning. AlN layers grown on this substrate had no defects related to surface polishing scratches and excellent insulating characteristics.