LEC grown GaP S doped single crystal samples were heated-treatment from room temperature to 1000℃ with interval of 50℃ and Ar was used as safeguarding gas.The defects in GaP samples were investigated with Positron Annililation Technology(PAT) and Scanning Electron Microscopy(SEM).The experimental results indicate

point defects and dislocations exist in GaP.The composition of defects changes with heat-treatment temperature.The results of PAT investigation express that positron annililation lifetime can decompose into two parts.As the heat treatment temperature were raised

its lifetime of capture component

τ

2

at first increases from 310 ps into 330 ps

then decreses into 280 ps.Intensity of capture component make corresponding change with temperature raised.It reflect that concentration of defects make relevant change with the temperature.