Temperature effects on the positron annihilation characteristics in III-VI layered semiconductors

Positron lifetime and Doppler broadening measurements have been performed on the layered semiconductors GaS, GaSe and GaTe in the temperature range 8-320 K. The temperature dependences of the annihilation parameters in GaS and GaSe are analysed in terms of the thermal expansion coefficient of the lattice and a volume coefficient of the annihilation parameter. The results reveal a noticeable volume effect on the positron annihilation characteristics in the bulk of GaS and GaSe; no evidence for positron trapping at grown-in defects was found in these samples.