Very-low Resistance Contact to 2D Electron Gas by Annealing Induced Penetration Without Spikes Using TaAl/Au on Non-recessed i-AlGaN/GaN

A novel ohmic contact formation mechanism is revealed for the annealed Ta0.83 Al0.17/Au stacks on non-recessed i-AlGaN/GaN. It is demonstrated that the contact metal alloy mainly composed by Au penetrates the AlGaN layer without apparent Ta-related solid phase reactions, establishing a spike-free contact to the 2D electron gas. A low contact resistivity of $0.14\Omega ~\cdot $ mm (4.24E- $7~\Omega \cdot $ cm2) is then obtained after 900 °C/60s annealing.