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Investigation of Cu-Ge/Gaas Metal-Semiconductor Interfaces for Low Resistance Ohmic Contacts

Published online by Cambridge University Press:  03 September 2012

Serge Oktyabrsky ,
M.A. Borek ,
M.O. Aboelfotoh  and
J. Narayan
Serge Oktyabrsky
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
M.A. Borek
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
M.O. Aboelfotoh
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
J. Narayan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
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Abstract

Chemistry and interfacial reactions of the Cu-Ge alloyed ohmic contacts to n-GaAs with extremely low specific contact resistivity (6.5×10-7 Ω·cm2 for n~1017 cm-3) have been investigated by transmission electron microscopy, EDX and SIMS. Unique properties of the contact layers are related to the formation (at Ge concentration above 15 at.%) of a polycrystalline layer of ordered orthorhombic ε1-Cu3Ge phase. Formation of the ε1-phase is believed to be responsible for high thermal stability, interface sharpness and uniform chemical composition. The results suggest that the formation of the ζ- and ε1,-Cu3Ge phases creates a highly Ge-doped n+-GaAs interfacial layer which provides the low contact resistivity. Layers with Ge deficiency to form ζ-phase show nonuniform intermediate layer of hexagonal β-Cu3As phase which grows epitaxially on Ga{111} planes of GaAs. In this case, released Ga diffuses out and dissolves in the alloyed layer stabilizing the ζ-phase which is formed in the structures with average Ge concentration of as low as 5 at.%. These layers also exhibit ohmic behavior.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 448: Symposium M – Control of Semiconductor Surfaces and Interfaces , 1996 , 383
Copyright
Copyright © Materials Research Society 1997

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