POSITRON LINE-SHAPE PARAMETERS AND LIFETIMES FOR SEMICONDUCTORS - SYSTEMATICS AND TEMPERATURE EFFECTS

Positron Doppler broadening and lifetime experiments have been perform ed on C (diamond), SiC, Si, Ge, GaN, GaP, GaAs, GaSb, InP, InAs, and I nSb. It was found that the Doppler-broadening parameter arising from v alence electrons depends linearly on the free-electron gas r(s) value when calculated from the valence-electron density. Positron lifetimes due to valence electrons are found to be proportional to r(s)(3). Fine r details, which result from the bonded character of the valence elect rons, an revealed by slight anisotropies of the S parameter. Temperatu re dependencies in the 100-600-K temperature range studied by means of Doppler broadening show a complex behavior which in part may be defec t influenced.