Effect of Pt barrier on thermal stability of Ti/Al/Pt/Au in ohmic contact with Si-implanted n-type GaN layers

We report the effect of the Pt barrier on the thermal stability of Ti/Al/Pt /Au in ohmic contact with Si-implanted n-type GaN layers. Ti/Al/Au (25/100/ 200 nm) and Ti/Al/Pt/Au (25/100/50/200 nm) multilayers were, respectively, deposited on as-implanted and recovered Si-implanted n-type GaN samples. Th e associated dependence of the specific contact resistance on the annealing time at various temperatures was compared. The long-term ohmic stability o f a Ti/Al/Pt/Au multilayer in contact with a Si-implanted n-type GaN layer was much better than that of the Ti/Al/Au multilayer. This superior stabili ty is attributed to the barrier function of the Pt interlayer. The Pt/Au bi layer can also passivate the propensity of oxidation for the conventional T i/Al bilayer in contact with n-type GaN layers at elevated temperatures.