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 ${\mathrm{r}}_{\mathrm{s}}$ value when calculated from the valence-electron density. Positron lifetimes due to valence electrons are found to be proportional to ${\mathrm{r}}_{\mathrm{s}}^{3>\mathrm{}}$. Finer details, which result from the bonded character of the valence electrons, are 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.