In this study, the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Au/n-GaAs Schottky diodes have been measured over a wide temperature range, 80–480 K. The diodes were rectifying throughout the range and showed good thermal stability. Room temperature values for the ideality factor, I–V barrier height and C–V barrier height were found to be n =1.10, ϕIVϕIV=0.85 eV and ϕCVϕCV=0.96 eV, respectively. ϕIVϕIV increases and n decreases with an increase in temperature. We investigated the effect of elevated temperatures on the barrier height and ideality factor by measuring the diodes at a high temperature (annealing mode) then immediately afterwards measuring at room temperature (post annealing mode). The measurements indicate I–V characteristics that degrade permanently above 300 K. Permanent changes to the C–V characteristics were observed only above 400 K. We also noted a discrepancy in the C–V barrier height and carrier concentration between 340 and 400 K, which we attribute to the influence of the EL2 defect (positioned 0.83 eV below the conduction band minima) on the free carrier density. Consequently, we were able to fit the ϕCVϕCV versus temperature curve into two regions with temperature coefficients −6.9×10−4 eV/K and −2.2×10−4 eV/K above and below 400 K.