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Low temperature (down to 450 °C) annealed TiAl contacts on N‐type gallium nitride characterized by differential scanning calorimetry

2010; Wiley; Volume: 8; Issue: 2 Linguagem: Inglês

10.1002/pssc.201000597

1862-6351

Nicolas Thierry‐Jebali, Olivier Ménard, Rodica Chiriac, Emmanuel Collard, Christian Brylinski, F. Cayrel, Daniel Alquier,

Metal and Thin Film Mechanics

Abstract This work reports on Differential Scanning Calorimetry (DSC) measurements performed on Ti‐Al metallic layers stacks deposited on n + ‐GaN. The aim is to get better understanding of the mechanisms leading to ohmic contact formation during the annealing stage. Two exothermic peaks were found, one below 500 °C and the other one around 660 °C. They can be respectively attributed to Al 3 Ti and Al 2 Ti compounds formation. The locations of these peaks provide clear evidence of solid‐solid reactions. Lowest contact resistance is well correlated with the presence of Al 3 Ti compound, corresponding to Al(200nm)/Ti(50nm) stoichiometric ratio. Subsequently, Al(200 nm)Ti(50 nm) stacks on n + ‐GaN were annealed from 400 °C to 650 °C. Specific Contact Resistivity (SCR) values stay in the mid 10 ‐5 Ω.cm² range for annealing temperatures between 450 °C and 650 °C. Such low‐temperature annealed contacts on n+‐GaN may open new device processing routes, simpler and cheaper, in which Ohmic and Schottky contacts are annealed together. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)