Metal-related gate sinking of interfacial oxygen layer in Ir/InAlN high electron mobility transistors

C. Ostermaier1, G. Pozzovivo1, B. Basnar1, W. Schrenk1, M. Schmid2, L. Tóth3, B. Pécz3, J.-F. Carlin4, M. Gonschorek4, E. Feltin4, N. Grandjean4, G. Strasser1, D. Pogany1, J. Kuzmik1,5

1 Institute of Solid State Electronics, Technische Universität Wien, 1040 Wien, Austria
2 Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
3 Research Institute for Technical Physics and Material Science, H-1525 Budapest, Hungary
4 Institute of Quantum Electronics and Photonics, EPFL Lausanne, CH-1015 Lausanne, Switzerland
5 Institute of Electrical Engineering, SAS, 84104 Bratislava, Slovakia

Appl. Phys. Lett. 96 (2010) 263515

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 V to +1 V and increased the transconductance from 400 mS/mm to 640 mS/mm.

Corresponding author: Clemens Ostermaier. Reprints also available from M. Schmid (schmid< encoded email address >).

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