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A Tem Study of Optically Annealed Ohmic Contacts to GaAs Using a Zirconium Diboride Diffusion Barrier

Published online by Cambridge University Press:  26 February 2011

Mike Grimshaw  and
Anne Staton-Bevan
Mike Grimshaw
Affiliation:
Department of Materials, Imperial College of Science, Technology and Medicine, Prince Consort Road, London, S.J.7 2BP.
Anne Staton-Bevan
Affiliation:
Department of Materials, Imperial College of Science, Technology and Medicine, Prince Consort Road, London, S.J.7 2BP.
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Abstract

The morphology of a Ni(5nm), Au(45nm), Ge(20nm) ohmic contact with a ZrB2 (50nm) diffusion barrier, annealed to temperatures between 355°C and 485°C, was studied by TEM. The barrier was found to remain intact and unreacted after annealing. The contact annealed to 355°C reacted in the solid state to form αAu-Ga, Ge and orthorhombic NiGe phases. The morphology of contacts annealed above the melting point (∼ 380°C) consisted of two regions; type A contained αAu-Ca and NiGeAs, and type B contained αAu-Ga α′Au-Ga, NiGe and epitaxial Ge. αAu-Ga segregated to the contact pad edges at and above 403°C. The transition from rectifying to ohmic properties corresponded to annealing above the melting point of the contact. It was found that variations in contact resistance with temperature could be explained either by changes in the bulk or in the edge morphology.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 144: Symposium W – Advances in Materials, Processing and Devices in III-V Compound Semiconductors , 1988 , 589
Copyright
Copyright © Materials Research Society 1989

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References

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