Laser and furnace annealed Au, Ag and Al ohmic contacts on n+ -GaAs

On n+ -GaAS substrates, gold-germanium eutectic films with a nickel overlayer, silver-germanium eutectic films with a nickel overlayer and aluminum-germanium films were evaporated. Samples from each of these three types of contacts were furnace and laser annealed with a pulsed excimer laser for optimum results. Gold-germanium and silver-germanium films gave ohmic contacts under both types of annealing. The laser annealed gold based contacts had a better surface morphology and somewhat smaller resistance than its furnace annealed counterpart. In case of silver based contacts, it was the furnace annealed contacts that had a lower resistance and better morphology. In case of aluminum based contacts, furnace annealing did not give an ohmic contact; with an anti-reflection coating, laser annealing gave ohmic contacts, which, however, were much more resistant and rough, compared to the gold and silver contacts