Growth of crack-free GaN films on Si(111) substrate and improvement of the crystalline quality using Si_xN_y inserting layer

High-quality crack-free GaN films have been grown on 2-inch diameter Si(111) substrate using AlN/GaN/AlN stack structure by metalorganic chemical vapor deposition. The dislocation density in GaN overlying layer remarkably reduced when introduce the Si_xN_y inserting layer. The high resolution X-ray diffraction (HRXRD) results of (002) symmetry and (102) asymmetry planes of GaN epilayers show that the dislocation density in GaN epilayer decreases with increasing Si_xN_y growth time. From transmission electron microscope (TEM) measurements, a GaN film with 300 up to 500 s of Si_xN_y deposition time shows that the misfit dislocations almost stop at the Si_xN_y inserting layer. The dislocation density of that sample was ∼ 5×10⁹ cm ^-2. Additionally, a strong band edge emission with FWHM 60 meV was obtained from the room temperature photoluminescence (PL) spectra.