Excellent Au/Ge/Pd ohmic contacts to n-type GaAs using Mo/Ti as the diffusion barrier

Abstract

Au/Ge/Pd metallization system using Mo/Ti as the diffusion barrier between the Au overlayer and the Ge/Pd underlayer has been performed for the first time to achieve excellent ohmic contacts to n(+)-GaAs with the Si-doping concentration of about 2 x 10(18) cm(-3). The minimum specific contact resistivity as low as 1.2 x 10(-7) Ohm . cm(2) can be obtained after the rapid thermal annealing at 325 degrees C for 60 s, which is much lower than those of the conventional Au/Ge/Pd metallization systems. Furthermore, the available annealing temperature range for such low specific contact resistivities is also significantly extended from 325 degrees C to 400 degrees C. The improvement is attributed to the effective retardation of As-outdiffusion by the Mo/Ti barrier.