Effects of 6H-SiC surface reconstruction on lattice relaxation of AlN buffer layers in molecular-beam epitaxial growth of GaN

Abstract

Growth of GaN on on-axis 6H-SiC (0001) Si substrates with an AlN buffer layer was performed by molecular-beam epitaxy. The effects of SiC surface reconstruction on the lattice relaxation of AlN buffer layers and the crystalline quality of GaN layers were studied. High-temperature HCl-gas etching followed by HF chemical treatment resulted in an atomically flat SiC surface with a 1ϫ1 structure. The AlN layer grown on the surface showed slow lattice relaxation. GaN grown on the AlN buffer layer exhibited the narrowest ͑0002͒ x-ray rocking curve of 70 arcsec and 10 7 cm Ϫ2 screw-type dislocation density, which was two orders of magnitude smaller than that of GaN grown on as-received substrates.

Nucleation and growth mode of the molecular beam epitaxy of GaN on 4H–SiC exploiting real time spectroscopic ellipsometry

“…Nucleation layers consisting of uncoalesced islands resulting from the relatively poor wetting of GaN on SiC, and leading to 3D growth have also been reported [14]. This is generally overcome through the insertion of an AlN buffer layer [1][2][3]. The present data show that modification of the SiC/GaN interface by cleaning using 3 cycles of Ga flashoff and subsequent formation of a very thin nitrided layer, can modify the GaN nucleation and coalescence that evolves to a layer-by-layer growth established in approximately 120 Å .…”

“…III-N electronic devices operating at high power and high frequency require high resistivity and high thermal conductivity substrates. For this application, SiC is considered the most suitable choice because of its high thermal conductivity and relatively low lattice mismatch (3.4% with GaN and 0.9% with AlN) with III-Ns, which is expected to reduce interface defects resulting from the heteroepitaxial growth process, and yield improved structural quality of [1,2] since GaN buffer layers yield high conductivity at the substrate-epitaxial layer interface. The growth of AlN and GaN on SiC is different; for example AlN wets SiC more effectively at the initiation of epitaxy [3].…”

Aluminum monolayers on Si (111) for MBE-growth of GaN

“…Although about 1.3 ML Al deposition gave the best GaN epitaxial layer, the quality of GaN was still poor compared to the growth on sapphire or SiC [13]. We used TEM to examine the interface between Si and AlN with the extra Al monolayer.…”

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

“…This is probably because the polar SiC (0001) surface can lead to Al polarity, in which a high-quality epilayer can be obtained [2]; besides AlN is closely matched to SiC for both lattice constants and thermal expansion coefficients. The defect density of GaN is strongly influenced by the crystalline quality of AlN buffer layer [3]. Therefore, it is significant to improve the crystalline quality of AlN layer on a SiC substrate.…”