Ohmic contacts to n+-GaAs with refractory metal sidewall diffusion barrier

This paper presents a comparative analysis of the parameters of non-alloyed Pd/Ge/Ta/Cu and alloyed Ge/Au/Ni/Ta/Au ohmic contacts to n⁺-GaAs, both with planar as well planar and sidewall diffusion barriers based on Ta films formed by magnetron sputtering. It has been found that use of sidewall diffusion barriers reduces the value of specific contact resistance of ohmic contacts of both types and improves the thermal stability of the edge morphology of the contact pad in the case of alloyed Ge/Au/Ni/Ta/Au ohmic contacts. The effects observed for the samples with effective diffusion barrier are explained by limiting diffusion, as well as limiting the interaction of Au or Cu atoms with underlying metallization layers and with gallium arsenide, taking place along the sidewall surfaces of the ohmic contact.