OHMIC CONTACTS FOR GaAs AND GaAlAs

摘要

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<17> cm<-3> and about 10<19> cm<-3>. The ohmic contact has a nickel layer of between 40 ANGSTROM and 200 ANGSTROM deposited on the substrate, followed by a Ge deposition (4) of between 150 ANGSTROM and 400 ANGSTROM and finally an Au deposition (5, 6) of greater than 4000 ANGSTROM . The Au layer is preferably deposited in two separate layers of between 500 ANGSTROM and 1000 ANGSTROM , (5), and greater than 4000 ANGSTROM , (6). A preferred construction (1) is 50 ANGSTROM /200 ANGSTROM /800 ANGSTROM + 5000 ANGSTROM (Ni/Ge/Au + Au). The ohmic contact deposition must be followed by annealing, typically at temperatures between 300 DEG C and 500 DEG C for times of between 1 second and 200 seconds. The preferred annealing conditions are a temperature of 400 DEG C maintained for 15 seconds.