Optically active defects in diamond find a wide range of applications from lasers to single photon emitters essential for quantum communications. Ion implantation followed by thermal annealing is a mature technique used to create such defects. Implanted at a fixed energy, ions form a thin layer of optically active defects. Low temperature photoluminescence spectra of Xe-related defects in pure CVD diamond show peculiar behavior: the narrow zero-phonon line at 811.7 nm changes its shape significantly with the increase of implantation dose from 1.1 × 1011 to 5 × 1012 ion cm−2. This work investigates the possible causes of this effect: planar geometry of the defects distribution and/or the complex defect structure.