Impact of SiC surface control on initial growth mode and crystalline quality of AlN grown by molecular-beam epitaxy

摘要

The surface pretreatment of SiC substrate for AlN heteroepitaxial growth was investigated to realize initial two-dimensional (2D) layer-by-layer growth. AlN layers were grown on atomically flat SiC (0001) substrates by plasma-assisted molecular-beam epitaxy (PA-MBE). To achieve initial 2D growth, the control of SiC surface chemistry was very important as well as that of surface flatness. Owing to Ga deposition on the SiC surface and subsequent flash-off, an oxygen-free (3~(1/2) x 3~(1/2)) R30° surface structure was achieved, and initial 2D growth with an evident RHEED intensity oscillation was demonstrated. The initial growth mode of AlN closely correlated with the crystalline quality of AlN layer.