Au–W(Ti)/n-GaAs diodes were constructed for the purpose of examining the thermal stability of the metal–GaAs interface and the integrity of the W(Ti) diffusion barrier. The evaluation procedure consisted of using measurements of the Schottky barrier height and other electrical parameters as a function of annealing temperatures. Barrier heights, Vb(Io), determined by measurement of the zero voltage current intercept, Io, were found to increase with annealing temperatures up to 600°C. Values determined by the measurement of forward current activation energies were in agreement with Vb(Io) up to 500°C. Above 500°C, however, this method was not applicable, due to the onset of excess forward current at low voltages. This current was accompanied by evidence of gold interdiffusion, compensation, and high electric field strength in the depletion layer. Direct identification of the excess current source, however, was not accomplished.