Influence of doping density and deposition technology on ohmic contacts to n-type gallium arsenide

A systematic series of measurements of specific contact resistance has been made for heat treated gold-germanium contacts to epitaxial n-type gallium arsenide. An inverse relationship is found between the specific contact resistance and the donor concentration of the original gallium arsenide for donor concentrations up to 4*1017 cm-3. Above this concentration the specific contact resistance becomes independent of doping. This result, together with measurements of the temperature dependence of specific contact resistance, confirms the 'two-barrier' models of the specific contact resistance, and specifically excludes the spreading resistance model. Further experiments show that the numerical values of specific contact resistance depend on whether the gold-germanium layer is deposited by sputtering or by thermal evaporation.

Source:IOPscience

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