Defect generation by radioactive decay of light elements in n-type silicon

Defects created by the decay of radioactive sodium, potassium and magnesium isotopes in n-type Si are studied by capacitance spectroscopy. In particular, we were interested in the creation of defects due to the large recoil energies involved in the radioactive decay. No evidence was found for an enhanced defect generation with concentrations exceeding those of the implanted mother isotopes. In our samples only defects are formed which contain mother or daughter isotopes and vacancies. The decay of 24Na isotopes results in two Mg-related defect levels. After implantation of radioactive 42K we observe one K-related acceptor at Ec-0.269eV. The decay to the stable isotope 42Ca generates the A-center in concentrations comparable to the K-related center. In the decay series of 28Mg via 28Al to 28Si a new level was detected which is thermally unstable at room temperature and converts to the A-center.