THERMALLY STABLE PDIN OHMIC CONTACTS TO N-GAAS VIA EXCHANGE MECHANISM

Thermally stable, low-resistance ohmic contacts to GaAs (Si-doped, n=1 .6-1.8X10(18) cm(-3)) were formed using PdIn metallization sputter-dep osited from an alloy target. Average specific contact resistances (rho (c)) in the 10(-6) Ohm cm(2) range were reached upon annealing at 600 degrees C or higher. Contacts annealed under the optimum condition of 850 degrees C for 15 s exhibited an average rho(c) of 2.5X10(-6) Ohm c m(2). The 100 h of thermal aging at 400 or 500 degrees C increased the ir average rho(c) to 3.0X10(-6) and 1.0x1O(-5) Ohm cm(2), respectively . The ohmic behavior of the annealed contacts vl as ascribed to the ex change of In and Ga atoms between the metallization and the semiconduc tor and the concomitant formation of InxGa1-xAs, whose presence at the contact interface was confirmed using cross-sectional transmission el ectron microscopy. (C) 1997 American Institute of Physics.