>100> -semiinsulating InP was implanted with 600 keV Se-ions at temperatures between 300K and 425K with an ion dose of 1 ×1014 cm−2. After capping the samples with about 120 nm siliconoxynitride annealing was performed at 700°C up to 975°C using a graphite strip heater system. The annealed samples were analyzed with Rutherford backscattering, electron microscopy and conventional Hall measurements. The results show, that a strong correlation exists between defects remaining after annealing (for instance dislocations, loops, microtwins) and the measured electrical properties. An implantation temperature ≦ 395K and annealing at least at 800°C for 50 s is necessary to obtain high performance electrically active layers. The activation of selenium in InP can be well described using a simple thermodynamical model. The model yields an activation energy of EA = (1.0 ± 0. 1) eV which can be understood as the energy necessary to split-up selenium-vacancy-complexes and a diffusion energy of Ed = (2.0 ± 0.2) eV representing material transport of the semiconductor material.