Growth evolution of Si_xN_y on the GaN underlayer and its effects on GaN-on-Si (111) heteroepitaxial quality

The GaN epilayers were grown on Si(111) substrates via combining the techniques of AlN buffer, the graded AlGaN structure and the Si _xN_y interlayer by metalorganic chemical vapor deposition. The Si_xN_y interlayers with various growth times of 0-60 s were introduced into the growth of GaN epilayers. To thoroughly realize the growth evolution of Si_xN_y, measurements of atomic force microscopy, field emission scanning electron microscopy and nano-Auger electron spectroscopy were performed. From the measurement by transmission electron microscopy, it can be proven that nanocrystalline Si_xN_y is preferentially located at the dislocation cores and pits during the growth process. For the fabrication of GaN/graded AlGaN/AlN/Si, the full width at half maximum of the X-ray diffraction rocking curve at the GaN(102) plane was reduced effectively from 965 to 771 arcsec by inserting Si_xN_y into the GaN epilayer, which resulted from the bending and annihilation of dislocations.