Deep level transient spectroscopy measurements have been performed to investigate deep levels in epitaxially grown n-type Si layers introduced by high-energy He2+ irradiation and subsequent annealing at various temperatures. Three deep levels (D-1: 0.46-0.49 eV; D-2: 0.52 eV; D-3: 0.64 eV) are found to be generated near the mid-gap level after post-annealing at temperatures of 300-450degreesC. The generation behavior of these deep levels is in reasonable agreement with the annihilation of divacancies. Therefore these energy levels are associated with high-order vacancy clusters which are formed by combination of some vacancies during the anneal-out of divacancies, and are probably attributed to various dangling-bonds like electronic states presenting on the internal surfaces of the clusters.