Buffer layers promote lateral growth of films due to a decrease in the interfacial free energy between the film and substrate, and large 2-dimensional nucleation and a smooth surface of the buffer layer are desired. Optimum conditions for GaN-buffer growth on the vicinal surface of 6H-SiC(0001) were determined by means of atomic force microscopy (AFM). GaN depositions were carried out in a horizontal MOCVD system using trimethylgallium and NH3. AFM analysis of the GaN nucleation layers led to optimum growth conditions for the GaN-buffer layer and this was confirmed by cross-sectional transmission electron microscopy, Hall measurement and photoluminescence spectra. The optimum growth condition for a GaN-buffer layer on SiC(0001) was determined to be 1 minute of growth at 550 degrees C.