Interface structure characterization depending on the barrier film in TiAl-based metallizations to AlGaN/GaN heterostructures

The composition and structure of TiAl-based metallizations have been investigated depending on the Ti and Mo barriers. It is found out that the contact resistivity depends mainly on the Ti/Al ratio. The lowest contact resistivity of 4×10^-6 Q.cm² for a Ti barrier and 7×10^-6 Q.cm² for a Mo barrier is obtained at a Ti/Al ratio of 0.43 after annealing at 800°C. The XPS and TEM analyses reveal that Mo does not affect as an effective barrier for the Au in diffusion and Al out diffusion during annealing. The intensive diffusion processes lead to the formation of the semimetal TiN compound at the interface and intermetallic phases of Au, Al and Ti, which structure and composition depend on the barrier metal.