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C. Ostermaier, G. Pozzovivo, B. Basnar, W. Schrenk, M. Schmid, L. Tóth, B. Pécz, J. Carlin, M. Gonschorek, N. Grandjean, G. Strasser, D. Pogany, J. Kuzmik:
"Metal-related gate sinking due to interfacial oxygen layer in Ir/InAlN high electron mobility transistors";
Applied Physics Letters, 96 (2010), 2635151 - 2635153.

We report on an annealing-induced "gate sinking" effect in a 2-nm-thin In0.17Al0.83N/AlN
barrier high electron mobility transistor with Ir gate. Investigations by transmission electron
microscopy linked the effect to an oxygen containing interlayer between the gate metal and the
InAlN layer and revealed diffusion of oxygen into iridium during annealing. Below 700 °C the
diffusion is inhomogeneous and seems to occur along grain boundaries, which is consistent with the
capacitance-voltage analysis. Annealing at 700 °C increased the gate capacitance over a factor 2,
shifted the threshold voltage from +0.3 to +1 V and increased the transconductance from 400 to
640 mS/mm.