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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

  • Kuldip S. Sandhu (a1), Anne E. Staton-Bevan (a1), Bernard M. Henry (a1), Mark A. Crouch (a2) and Sukhdev S. Gill (a2)...

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.

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  • EISSN: 1946-4274
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