Correlations of a High-temperature AlN Buffer Layer and Al-Preseeding with the Structural and the Optical Properties of GaN on a Si(111) Substrate

GaN epilayers were grown on Si(111) substrates with high-temperature (HT) AlN huller layers by using metal-organic chemical vapor deposition (MOCVD). The correlations of the HT AlN buffer layer and Al-preseeding process with the structural and the optical properties of the GaN epilayer were investigated using optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and photoluminescence (PL) measurements. The results demonstrate that the structural and the optical properties of GaN on a Si(111) substrate strongly depended on such growth conditions as the AlN buffer layer thickness, the TMAl source flow rate and the Al-preseeding time. A nearly 2.5 mu m, crack-free GaN epilayer was obtained with a 120-nm-thick AlN buffer layer grown at a TMAl source flow rate of 18 mu mol/min and an Al-preseeding time of 5 sec. The near-band-edge emission peak with a full width at half maximum value of 44.93 meV at room temperature and a (002) X-ray rocking curve with a 385 arcsec linewidth attest to the high quality of GaN on the Si(111) substrate.