Current‐voltage characteristics of Au contacts formed on films grown heteroepitaxially on both nominally (100) oriented and off‐axis (100) silicon substrates have been investigated. These contact diodes are rectifying, and very low reverse leakage currents are observed, particularly in off‐axis silicon substrates. The diode ideality factor is between 1.3 and 2.0 in all cases except in nominal (100) silicon substrates where it is greater than two. Logarithmic plots of the I‐V characteristics in the forward direction indicate space charge limited current conduction through the active volume of the diodes. The films grown on nominally (100) oriented substrates show the presence of two deep levels located approximately between 0.26 and 0.38 eV below the conduction bandedge. In some films on nominal (100) substrates, the I‐Vcharacteristics are also influenced by additional traps which are exponentially distributed in energy with a maximum occurring at the conduction bandedge. In contrast, the films deposited on off‐axis substrates have only one deep level located at approximately 0.49 eV for the 2° off (100) substrates and 0.57 eV for the 4° off (100) substrates. Previous microstructural analysis revealed that the nature and density of defects in the heteroepitaxial films on both nominal and off‐axis (100) silicon are similar except that the films on nominal (100) substrates have a high density of antiphase domain boundaries. Therefore, the presence of the shallower deep‐level states observed in the films grown on nominal (100) substrates is speculated to be due to the electrical activity of antiphase domain boundaries.