The influence of hydrogen and nitrogen III-carrier gas mixture on the GaN layers grown at a high temperature of 1100 o C by a novel six-wafer metal-organic chemical vapor deposition (MOCVD) were studied using optical microscopy, X-ray diffraction (XRD), and photoluminescence (PL). The different ratio of nitrogen and hydrogen of III-carrier gas strongly affect the growth mechanism of GaN layers. In the case of higher ratio of N 2 /(N 2 +H 2 ), the surface shows a hillock morphology. On the other hand, with decreasing the flow rate of N 2 to a smaller ratio of N 2 /(N 2 +H 2 ), the surface shows a mirror like morphology. In this case, the growth rate was also decreased. The measurement of X-ray diffraction (XRD) shows that the FWHM of XRD rocking curve of sample grown with smaller flow rate of N 2 becomes wider.