Abstract: Vacancy and interstitial defects in as-grown and annealed semi.insulating(SI)InP single crystal have been studied by using electrical measurement，positron lifetime spectroscopy and X-ray diffraction technique.As.grown Fe.doped SI.InP contains vacancy which gives rise to deep level compensation defects and deteriorates electrical property of the material.Vacaney is fully suppressed in SI material that is obtained by high temperature annealing undoped InP in iron phosphide ambient.A moderate concentration of interstitial exists in the annealed material.The influence of vacancy and interstitial on electrical property and thermal stability of SI-InP have been discussed based on the experimental results.

Key words: indium phosphide, semi·insulating, vacancy, interstitial