Growth and characterizations of GaN on SiC substrates with buffer layers

High quality GaN epitaxial layers were grown on 6H–SiC substrates by using low-pressure metalorganic chemical vapor deposition method. Samples employing a three-period $GaN/Al0.08Ga0.92N$ $(100 Å/100 Å)$ as a buffer layer produce a good quality GaN epitaxial layer, with mobility and carrier concentration of $612 cm2/V⋅s$ and $1.3×1017 cm−3$ (at 300 K), respectively. The enhanced electron mobility in the $Al0.08Ga0.92N/GaN$ heterostructures is also observed. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility at 4.2 K for the $Al0.08Ga0.92N/GaN$ heterostructure are $5.8×1012 cm−2$ and $5300 cm2/V⋅s,$ respectively. Strong SdH (Shubnikov–de Haas) oscillations were observed to confirm the two-dimensional electron gas (2DEG) phenomenon at the AlGaN/GaN top heterointerface. In addition, an extra SdH oscillation also resulted from the high-quality 2DEG channel of the GaN/AlGaN bottom heterointerface.