Metalorganic vapor phase epitaxial GaAs:Sb layers and Schottky barrier structures based on them have been investigated regarding defect evolution versus doping level. Three types of defects are considered such as surface morphology imperfections, structural defects in the epilayers, and interface defects at the Schottky barriers. A correlation between the defect behavior in the layers and the Schottky structures has been observed. It has been shown that an optimal Sb doping region exists where the defect density decreases compared with the undoped and highly Sb doped samples. The dominating defects in the Schottky barrier interface are dislocation-related states which can be effectively influenced by the isoelectronic doping.