A study was made of the volt-ampere characteristics of Pd-GaAs Schottky barriers in relation to the defectiveness of the gallium arsenide. The defect content of the material was checked metallographically and by the method of x-ray topography. Single crystals of GaAs doped with Ge, Ge + Sb, and Ge + In were studied. Here, the electron concentration was (1 4) · 1015 cm-3, and mean dislocation density ranged from 4·104 to 2·102 cm-2. The defectiveness of the material was altered by the introduction of different concentrations of isovalent impurities. It was shown that for diodes produced by the same technology, the manifestation of low-temperature VAC anomalies and the current mechanism are determined by structural features of the semiconductor (by dislocations and microdefects).