Epitaxial GaN films on Si(111) with varied buffer layers

The buffer layers used in this study included an AlN/3C-SiC composite film stack and a single AlN layer. 3C-SiC in the composite film stack prepared by the 2-step process functioned better as a buffer layer than that prepared by direct epitaxial growth. The composite buffer prepared by this method was compared with the single AlN buffer. The GaN films grown on the composite buffer were significantly less susceptible to film cracking than those grown on a single AlN buffer. Photoluminescence evaluation showed that the GaN films deposited on the composite buffer were narrower in FWHM than those deposited on a single buffer. However, the GaN and AlGaN films grown on top of the single AlN buffer showed a smoother top surface and had higher electron mobility in the AlGaN/GaN heterojunction. Surface and film qualities of the GaN films grown on the composite buffer were improved by insertion of an AlGaN/GaN superlattice.