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Chemical, Electrical, and Structural Properties of Au/Pd Contacts on Chemical Vapor Cleaned p-type GaN Surfaces

Published online by Cambridge University Press:  21 March 2011

P. J. Hartlieb ,
A. Roskowski ,
B. J. Rodriguez ,
R. J. Nemanich  and
R. F. Davis
P. J. Hartlieb
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907
A. Roskowski
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907
B. J. Rodriguez
Affiliation:
Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202
R. J. Nemanich
Affiliation:
Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202
R. F. Davis
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907
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Abstract

The chemical, electrical, and microstructural properties of Au/Pd contacts on p-type GaN(0001) surfaces previously cleaned either ex situ or ex situ and in situ have been investigated. The in situ process involved a high temperature, NH3-based chemical vapor clean (CVC); it produced ordered, stoichiometric, p-type GaN surfaces with no detectable C and an O constituent which was subsequently reduced from 15 at% on the ex situ treated surface to 2 ± 1 at% following the CVC process. The Pd contacting layer grew epitaxially in a layer-by-layer mode on the CVC surface and formed an abrupt, unreacted metal-semiconductor interface. The Au capping layer also grew epitaxially on the Pd. Au/Pd contacts on both HCl and CVC treated surfaces exhibited identical surface roughness values (RMS) in the as-deposited state and following a 500°C anneal. Contact structures on CVC treated surfaces demonstrated excellent high-temperature microstructural stability as evidenced by the absence of significant change in the surface roughness (RMS) with successive annealing at 600 and 700°C. Identical contact structures on ex situ cleaned surfaces exhibited poor high temperature microstructural stability, as indicated by a significant increase in the surface roughness (RMS) following successive anneals at 600 and 700°C. There was a significant degradation in the morphology of both surfaces following the 800°C anneal as evidenced by the formation of large voids in the contact metallization and the exposure of the underlying p-type GaN substrate. The lowest resistance contact structures with uniform metal coverage were obtained for Au/Pd contacts on a CVC treated surface annealed at 700°C.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 693 , 2001 , I11.40.1
Copyright
Copyright © Materials Research Society 2002

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