Growth of high quality GaN on (0001) 4H-SiC with an ultrathin AlN nucleation layer

Abstract

AlN nucleation layers (NLs) with different thicknesses were grown by a pulsed atomic-layer epitaxial method on (0001) 4H-SiC. The surface morphology evolutions of AlN NLs and the subsequent GaN buffer layers (BLs) were characterized. The GaN grown on 5 nm AlN NL showed a strong 3D growth mode and didn’t coalescence until 1.2 um. But GaN on 12 nm AlN coalesced at the thickness 300 nm, as well as the GaN BLs on 25 nm or 50 nm AlN NL. It denoted that AlN needed to reach certain thickness to completely screen the effect of the SiC substrates and provided a superior wetting template for GaN. The (0002) full width at half maximum (FWHM) and (10–12) FWHM of 1.5 um GaN on 12 nm AlN NL were 122 arcsec and 196 arcsec respectively. No pits were observed in the STEM images of GaN/AlN interfaces.