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

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 2×10 18 cm -3 . The minimum specific contact resistivity as low as 1.2×10 -7 Ω·cm 2 can be obtained after the rapid thermal annealing at 325°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°C to 400°C. The improvement is attributed to the effective retardation of As-outdiffusion by the Mo/Ti barrier.