Ohmic contacts to p-type InGaSb have been investigated. The factors that influence the contact resistance, thermal stability, and shallowness of the contacts are examined. The most desirable contact studied in this work employs three layers. A very thin layer of palladium is deposited on the p-InGaSb first and is found to lower the resistance at the metal/semiconductor interface. The next layer is W, which is predicted to be in thermodynamic equilibrium with InGaSb and which serves as a diffusion barrier to protect the semiconductor from the reaction with the final capping layer. The final capping layer is a 100 or 150 nm Au layer. The Au lowers the metal sheet resistance, which we have found both experimentally and through modeling to influence the contact resistance measurements, and the Au layer provides a contact surface that does not oxidize. The contact resistance of the as-deposited Pd/W/Au (5/50/145 nm) contact is 0.08 Ohm min (corresponding to a specific contact resistance of < 3 X 10(-7) Ohm cm(2)), while the more thermally stable Pd/W/Au (5/145/100 nm) contact exhibits a contact resistance of 0.08 Ohm mm only after annealing at 250 degreesC for 3 h, in both cases on a p-In0.25Ga0.75Sb layer with a semiconductor sheet resistance of approximately 300 Ohm/square. The thermal stability of the Pd/W/Au contacts was also examined. The Pd/W/Au (5/145/100 nm) contacts remained shallow and exhibited no measurable electrical degradation when aged at 250 degreesC in N-2 for 100 h, while they survived at 250 degreesC for 14 days in sealed, evacuated, quartz tubes. (C) 2003 American Vacuum Society.