Variable energy positron beam spectroscopy is employed to study defects and arsenic precipitates in GaAs epilayers grown at low temperatures by Molecular Beam Epitaxy (MBE). We have measured the S‐parameter as a function of positron implantation energy. We have obtained results for the depth profiles of the Ga monovacancy defects in unannealed LT‐GaAs and Ga monovacancies and arsenic clusters related defects in annealed LT‐GaAs.