Ni-Ge-Au ohmic contacts for GaAs and GaAlAs

Abstract

A low resistance ohmic contact for n-type GaAs and GaAlAs is provided by Ni-Ge-Au structure (1). The contact is suitable for device substrates (2) which have carrier concentrations of between about 10.sup.17 cm.sup.-3 and about 10.sup.19 cm.sup.-3. The ohmic contact has a nickel layer of between 40 .ANG. and 200 .ANG. deposited on the substrate, followed by a Ge deposition (4) of between 150 .ANG. and 400 .ANG. and finally an Au deposition (5, 6) of greater than 4000 .ANG.. The Au layer is preferably deposited in two separate layers of between 500 .ANG. and 1000 .ANG., (5), and greater than 4000 .ANG., (6). A preferred construction (1) is 50 .ANG./200 .ANG./800 .ANG.+5000 .ANG. (Ni/Ge/Au+Au). The ohmic contact deposition must be followed by annealing, typically at temperatures between 300.degree. C. and 500.degree. C. for times of between 1 second and 200 seconds. The preferred annealing conditions are a temperature of 400.degree. C. maintained for 15 seconds.

Dependencies are inferred from the claim text.