Positron annihilation in defective Ga2S3 and Ga2Se3 crystals doped with transition and rare-earth elements

The angular distributions of the annihilation gamma photons and the spectrum of the positron lifetimes were determined for defective Ga 2 S 3 and Ga 2 Se 4 compounds doped with transition and rare-earth elements. Such doping altered considerably the parameters of the angular distributions and the positron lifetimes. The experimental results were used to calculate the concentration of positron traps, which was (0.7-0.9)×10 18 cm -3