Performance comparison of Pt/Au and Ni/Au Schottky contacts on Al_xGa_1-x N/GaN heterostructures at high temperatures

In contrast with Au/Ni/Al_0.25Ga_0.75N/GaN Schottky contacts, this paper systematically investigates the effect of thermal annealing of Au/Pt/Al_0.25Ga_0.75N/GaN structures on electrical properties of the two-dimensional electron gas in Al_0.25Ga_0.75N/GaN heterostructures by means of temperature-dependent Hall and temperature-dependent current–voltage measurements. The two-dimensional electron gas density of the samples with Pt cap layer increases after annealing in N₂ ambience at 600 ^\circC while the annealing treatment has little effect on the two-dimensional electron gas mobility in comparison with the samples with Ni cap layer. The experimental results indicate that the Au/Pt/Al_0.25Ga_0.75N/GaN Schottky contacts reduce the reverse leakage current density at high annealing temperatures of 400–600 ^\circC. As a conclusion, the better thermal stability of the Au/Pt/Al_0.25Ga_0.75N/GaN Schottky contacts than the Au/Ni/Al_0.25Ga_0.75N/GaN Schottky contacts at high temperatures can be attributed to the inertness of the interface between Pt and Al_xGa_1-xN.