To investigate the possibility of preparing a nonalloyed ohmic contact to n-type GaN, the effects of GaN surface treatments on the metal/GaN interface were studied using x-ray photoelectron spectroscopy. A specific contact resistance of 5.0×10−5 Ω cm2 for the Ti/Al nonalloyed ohmic contacts to (NH4)2Sx-treated n-type GaN can be obtained. The nonalloyed ohmic contact formation would be impeded by the native oxide and the hydroxyl induced from the surface treatment of chemical solutions.
