Effect of annealing process parameters on the properties of AuGe ohmic contacts to GaAs

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The control of the electrical and the structural properties of ohmic contacts to GaAs is extremely important in the fabrication of GaAs devices. The annealing process parameters such as anneal ramp rate, anneal dwell temperature, dwell duration, and anneal atmosphere need to be precisely controlled to obtain low contact resistivities. The importance of the changes in the structural properties as a function of annealing process parameters, which in turn determine the contact resistance, is illustrated here. The extent of Ge in-diffusion to the metal-GaAs interface and the Ga out-diffusion from the substrate determined from Auger depth profiles seem to dictate even the small changes in the specific contact resistances. The lowest values of contact resistivity are obtained when the ratio of Ge in-diffusion to Ga out-diffusion approached one.

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Journal of Applied Physics