Thermally stable PdIn ohmic contacts to n-GaAs via exchange mechanism

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Thermally stable, low-resistance ohmic contacts to GaAs (Si-doped, n = 1.6-1.8×1018 cm-3) were formed using PdIn metallization sputter-deposited from an alloy target. Average specific contact resistances (ρc) in the 10-6 Ω cm2 range were reached upon annealing at 600 °C or higher. Contracts annealed under the optimum condition of 850 °C for 15 s exhibited an average ρc of 2.5X10-6 Ω cm2. The 100 h of thermal aging at 400 or 500 °C increased their average ρc to 3.0X10-6 and 1.0X10-5 Ω cm2, 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 InxGa1-xAs, whose presence at the contact interface was confirmed using cross-sectional transmission electron microscopy. © 1997 American Insntute of Physics.

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Journal of Applied Physics