High temperature characteristics of amorphous TiWSix nonalloyed ohmic contacts to GaAs

Abstract

This article reports on amorphous (α) nonalloyed TiWSix ohmic contacts on n-GaAs using an intervening graded-band-gap layer of InxGa1−xAs grown by the low pressure organometallic chemical vapor deposition method. The metal silicide contacts consisted of extremely thin alternating layers of TiW and Si sequentially deposited by rf magnetron sputtering to a total thickness of 500 Å. The as-deposited contacts exhibited ohmic behavior without requiring post-deposition heat treatment, and yielded specific contact resistivity values as low as 9×10−7 Ω cm2. These contacts were shown to be stable and retained excellent surface morphology after 600 °C thermal annealing. Rutherford backscattering and Auger electron spectroscopy investigations revealed no apparent interdiffusion at the metal/semiconductor interface under the above annealing conditions.