Using sputter-deposited PtIn2 films as metallizations, it is demonstrated that the recently identified exchange mechanism may be utilized to form ohmic contacts to n-GaAs. Specific contact resistances as low as 3.0×10−6 Ω cm2 are obtained upon annealing in the temperature range of 800–850 °C. Contacts processed under optimum conditions show little degradation in electrical properties after 100 h of thermal aging at 400 or 500 °C. Auger depth profiles of as-deposited and annealed samples are consistent with the hypothesis of an exchange of In and Ga atoms at the contact interface.

Thermally stable, low-resistance ohmic contacts to 18 cm Ϫ3͒ were formed using PdIn metallization sputter-deposited from an alloy target. Average specific contact resistances ͑ c ͒ in the 10 Ϫ6 ⍀ cm 2 range were reached upon annealing at 600°C or higher. Contacts annealed under the optimum condition of 850°C for 15 s exhibited an average c of 2.5ϫ10 Ϫ6 ⍀ cm 2 . The 100 h of thermal aging at 400 or 500°C increased their average c to 3.0ϫ10 Ϫ6 and 1.0ϫ10 Ϫ5 ⍀ cm 2 , respectively. The ohmic behavior of the annealed contacts was ascribed to the exchange of In and Ga atoms between the metallization and the semiconductor and the concomitant formation of In x Ga 1Ϫx As, whose presence at the contact interface was confirmed using cross-sectional transmission electron microscopy.