In this study, high quality bulk GaN crystals have been grown on sapphire substrates using the HVPE (hydride vapor phase epitaxy) technique. Ammonia, nitrogen, metallic gallium, hydrogen chloride were used as source materials. The effect of growth parameter such as HCl gas flow was investigated by PL (photoluminescence) and optical microscope. Surface quality of samples was clean. As a result of PL, GaN crystalline was improved in 10 sccm of HCl gas flow.