DEFECTS IN ELECTRON-IRRADIATED SI STUDIED BY POSITRON-LIFETIME SPECTROSCOPY

Differently doped and undoped silicon was irradiated with electrons to study the formation of nonequilibrium defects and their annealing beh avior. The annealing curves, measured by positron lifetime and also pa rtly by the shape parameters of the Doppler-broadened annihilation lin e, depend strongly on the doping concentration and the oxygen content. Ln addition, temperature-dependent positron-lifetime measurements sta rting at is K were performed after low-temperature and room-temperatur e irradiation with different doses and in different annealing states. Shallow positron traps were detected for all conductivity types of irr adiated Si. However, the concentration of shallow traps depends on the crystal-growth procedure. Electron-irradiated Czochralski-grown sampl es contain a higher number of shallow traps than electron-irradiated f loating-zone-grown material. Due to the different concentrations of ox ygen in these differently grown Si, we conclude that the oxygen atoms an a part of these traps. A possible candidate is the irradiation-indu ced A center. Correlated infrared-absorption investigations were carri ed out to support this interpretation. [S0163-1829(98)11239-0].