The defect properties of as-grown and annealed CuInSe2, CuIn0.5Ga0.5Se2, and CuGaSe2 single crystals grown by chemical vapor transport have been studied by photoluminescence, Hall effect, and resistivity measurements; The various observed defect levels are ascribed to intrinsic defect states taking into account stoichiometry, annealing conditions of the samples, and the formation enthalpy of these intrinsic defects, Furthermore, the obtained activation energies and the concentrations of these defects are compared for all three different compounds. The properties of the as-grown, p-type samples are dominated by copper and selenium vacancies (V-Cu, V-Se). The activation energies of these defects decrease slightly with the increase of In-content, which is in line with the change of the band-gap. In contrast, a vast difference is observed for the properties of a donor level induced by annealing in the presence of the corresponding group III element. This defect level is much shallower and more easily formed in In-containing compounds. It is tentatively ascribed to a V-Cu-IIICu defect pair. These differences in the defect physics can account for the lack of p-type conduction and the limited solar cell performance of Ga-rich materials.