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TEM studies of multilayer ohmic contacts to n-type AlGaN/GaN

By Mike W. Fay, Grigore Moldovan, Ian Harrison, R.S. Balmer, D.E.J. Soley, K.P. Hilton, B.T. Hughes, M.J. Uren, T. Martin and Paul D. Brown

Abstract

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

Publisher: IOP Publishing Ltd
OAI identifier: oai:eprints.nottingham.ac.uk:1463
Provided by: Nottingham ePrints

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