TEM studies of multilayer ohmic contacts to n-type AlGaN/GaN
Fay, Mike W. and Moldovan, Grigore and Harrison, Ian and Balmer, R.S. and Soley, D.E.J. and Hilton, K.P. and Hughes, B.T. and Uren, M.J. and Martin, T. and Brown, Paul D. (2003) TEM studies of multilayer ohmic contacts to n-type AlGaN/GaN. In: Microscopy of semiconducting materials 2003: proceedings of the Institute of Physics conference, Cambridge University, 31 March - 3 April. Institute of Physics conference series (180). IOP Publishing Ltd, Bristol, pp. 483-486. ISBN 9780750309790
Ti and Pd barrier layers between the Al/Ti diffusion couple and the Au capping layer of multilayer ohmic contacts to n-type AlGaN/GaN field effect transistors were found to be ineffective in preventing the diffusion of Au to the AlGaN following high temperature rapid thermal annealing. The formation of a band of TiN grains at the contact/AlGaN interface is responsible for the activation of the contact. The presence of interfacial Au and threading dislocations are implicated in the formation of additional Ti-nitride inclusions into the AlGaN, although these do not appear to disrupt the Ti-nitride layer at the original contact/nitride interface, nor significantly influence the contact resistance.
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