Investigation of defects in GaP using positron annihilation

The defects and their thermal treating behaviour in LEC GaP:S are investigated by PAT. The positron lifetime is measured at room temperature on samples after isochronal annealing from 200 to 600 0C. Two components τ1 and τ2 of the positron lifetime in GaP:S are obtained. τ1 is the positron lifetime of the free state in the perfect zone of the crystal. τ2 is the positron lifetime of the trapped state in the defect zone of the crystal. Results show that the positron average lifetime τ is 228 ps and τ1 = 209 ps, τ2 = 388 ps in the non-thermal treated sample. During the thermal treating process, τ1 is unchanged but τ2 is changed in two stages. The results are analyzed by a defect reaction model. (author)