Microstructural characterisation of TiAlTiAu and TiAlPdAu ohmic contacts to AlGaN/GaN
Fay, Mike W. and Harrison, Ian and Birbeck, J.C. and Hughes, B.T. and Uren, M.J. and Martin, T. and Brown, Paul D. (2001) Microstructural characterisation of TiAlTiAu and TiAlPdAu ohmic contacts to AlGaN/GaN. In: Electron microscopy and analysis 2001: proceedings of the Institute of Physics Electron Microscopy and Analysis Group Conference, University of Dundee, 5-7 September. Institute of Physics conference series (168). IOP Publishing Ltd, Bristol, pp. 497-500. ISBN 9780750308120
Ti/Al/Ti/Au and Ti/Al/Pd/Au contacts to AlGaN/GaN have been investigated to ascertain the effect of annealing temperature on the structural evolution of the contacts. Ti/Al/Ti/Au contacts become ohmic after rapid thermal annealing at 750°C or higher, corresponding to the formation of an interfacial TiN phase, with inclusions penetrating through the AlGaN layer observed after annealing at 950°C. The Pd layer is shown to be more efficient at inhibiting diffusion of Au to the interface than Ti. Ohmic behaviour was not seen with the Ti/Al/Pd/Au scheme. Either the presence of Au at the interface may improve ohmic behaviour, or the Ti:Al ratio is insufficient in this scheme.
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