High-quality Ir/n-Si Schottky diodes have been prepared. The diodes exhibit ideal behavior at room temperature according to thermionic emission theory with linear log (I)-V characteristics over eight current decades. Ideality factors less than 1.02 were obtained. Schottky barrier heights determined by forward I-V and C-V characterization are close to 0.9 eV. Current-voltage characteristics show deviations from the simple thermionic emission law at low temperature. This anomalous behavior is explained in terms of spatial inhomogeneities in the barrier height that result from the presence of a polycrystalline interlayer at the metal-semiconductor interface. The flat-band Schottky barrier height (0.98 eV) at 0 K and the temperature coefficient of the barrier (-3.8 x 10(-4) V K-1) agree with those reported for the IrSi phase implying that some reaction between Ir and Si has taken place.