Contact metallization and substrate doping and annealing temperature dependences of the contact resistivity

Author(s): M.Idrish Miah

We fabricated reliable contact structures on n-type GaAs using contact materialsAu, Ge and Pd with layer thicknesses 100 nm, 50 nm and 10 nm, respectively. The contact resistivities for the structures were measured using transmission line model. Contract structures were studied in dependences of the substrate doping density and annealing temperature. The contact resistivity was found to decrease with increasing annealing temperature up to ~180° C. However, a further increase of the annealing temperature, it increased. The contact resistivity was also found to decrease with increasing substrate doping density. The transfer characteristics and morphological study of the contact indicated an ohmic contact with low contact resistivity. The results, however, show that the inter-diffusion between contact materials is an important factor responsible for the low-resistivity transparent contacts and that using the proposed recipe transparent contacts could be achieved for a wide range of n-type substrate doping density.

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