Abstract: Al and Ti/Al/Pt/Au Ohmic contacts were studied on GaN epitaxial layers grown by lamp-heating low pressure metalorganic chemical vapor deposition on Si（111） substrrates. Al and GaN contacts achieved the minimum contact resistivity of 7.5×10^-3 Ω cm² after annealing in N₂ for 3 min at 600℃, and the further annealing degraded the contacts. Ti/Al/Pt/Au and GaN contacts achieved the minimum contact resistivity of 8.4×10^-5 Ω cm² after annealing in N₂ for 20 second at 650℃, and these contacts showed a better thermal stability than Al/GaN contacts.