Pt and Pd Silicides and Pd Germanide as Contact Metallizations for GaAs

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Abstract
Refractory metal silicides have been shown to form stable Schottky barriers on GaAs up to an annealing temperature of ∼850°C. In this study, the metallurgical and electrical stability of near noble metal (Pd and Pt) silicide contacts to GaAs have been investigated. It is observed that Pd and Pt silicides are metallurgically more stable than Pd and Pt alone on GaAs. A correlation between the stability of silicide contacts and the heat of formation of the silicides normalized to per metal atom is found, thus allowing the prediction of contact stability of other silicides on GaAs. We have also investigated the feasibility of using solid-phase epitaxy (SPE) to grow a highly doped Ge epitaxial layer on GaAs to form a non-alloyed ohmic contact. This approach of forming a Ge/GaAs heterojunction alleviates the high vacuum requirement of MBE techniques. Our preliminary results indicate that relatively low contact resistivities can be obtained by SPE using the Ge-Sb-Pd system.

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