Epitaxial Pb1−xSnxSe layers have been grown on Si substrates, and Schottky-barrier infrared sensors were fabricated in the layers using Pb blocking contacts. The observed current–voltage characteristics (saturation currents j0 and ideality factors n) as a function of temperature are quantitatively explained with a fluctuation model of the barrier heights [J. H. Werner, W. Güttler, J. Appl. Phys. 69, 1991 (1522)]. The amount of the mean barrier fluctuation σ, which is typically 10–30 meV, depends on the layer quality and fabrication procedure. Higher σ causes higher j0 with increasing saturation values at low temperatures. In addition, the fluctuations cause high n(>2) values at low temperatures. Layers with improved structural quality (higher mobilities and lower threading dislocation densities) lead to lower barrier fluctuations and, therefore, to increased sensitivities.