Four different application oriented III-V compound semiconductors have been selected for investigation using Positron annihilation spectroscopy (PAS) techniques. First one is Fe-doped semi-insulating Indium Phosphide. Positron annihilation lifetime spectroscopy (PALS) and Doppler broadening annihilation radiation (DBAR) measurements have been done in 140 MeV O(6+) ion implanted Fe-doped semi-insulating InP sample to observe irradiation induced defects formation and recovery of those defects with annealing temperature. Second, third & last samples are undoped Indium Antimonide, undoped Indium Phosphide & n-type Gallium Arsenide. PALS & DBAR measurements have been carried out in 40 MeV alpha irradiated undoped InSb, undoped InP and n-type GaAs samples to observe irradiation induced defects formation and recovery of those defects with annealing temperature respectively.