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An Initial Investigation of the Electrical and Microstructural Properties of Au/Ti and Au/Pd/Ti Ohmic Contact Structures for AlGaAs/GaAs HBTs

Published online by Cambridge University Press:  21 February 2011

Kuldip S. Sandhu
Affiliation:
Department of Materials, Imperial College, London University, London, SW7 2AZ, U.K.
Anne E. Staton-Bevan
Affiliation:
Department of Materials, Imperial College, London University, London, SW7 2AZ, U.K.
Bernard M. Henry
Affiliation:
Department of Materials, Imperial College, London University, London, SW7 2AZ, U.K.
Mark A. Crouch
Affiliation:
D.R.A., Electronics Division, St Andrews Road, Malvern, Worcs., WR14 3PS,U.K.
Sukhdev S. Gill
Affiliation:
D.R.A., Electronics Division, St Andrews Road, Malvern, Worcs., WR14 3PS,U.K.
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Abstract

The electrical and microstructural properties of Au/Ti and Au/Pd/Ti contacts to p+-GaAs (C-doped, 5×1018cm−3) were investigated. Current-voltage measurements as a function of temperature showed that the Ohmicity of the Au/Ti contact improved upon annealing. However, the annealed binary contact featured Au spiking into the GaAs making it unsuitable for HBT applications. The addition of a Pd diffusion barrier layer between the Au and Ti metallisation layers prevented spiking, but resulted in a decrease in the Ohmicity of the contact.

For all the contact systems it was found that thermionic-field emission dominates the current transport mechanism across the metal-semiconductor interface between the temperature range 198K and 348K. The Au/Pd/Ti contact structure shows HBT potential, however higher epilayer doping levels will be required to produce satisfactory specific contact resistivities.

Type
Research Article
Copyright
Copyright © Materials Research Society 1994

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References

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