Positron line-shape parameters and lifetimes for semiconductors: Systematics and temperature effects

Positron Doppler broadening and lifetime experiments have been performed on C (diamond), SiC, Si, Ge, GaN, GaP, GaAs, GaSb, InP, InAs, and InSb. It was found that the Doppler-broadening parameter arising from valence 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). Finer details, which result from the bonded character of the valence electrons, an revealed by slight anisotropies of the S parameter. Temperature dependencies in the 100-600-K temperature range studied by means of Doppler broadening show a complex behavior which in part may be defect influenced.