Positron study of vacancy defects in proton and neutron irradiated GaP, InP, and Si

In GaP, InP, and Si single crystals the annealing and fluence dependent concentration of defects produced by irradiation with fast neutrons and protons are studied by means of the positron annihilation technique (measurements of the positron lifetime and of the Doppler broadening lineshape of annihilation photons) and of internal friction measurements. In proton bombarded GaP a two stage annealing process is observed (stage I near 200° C and stage II near 600° C) and attributed to the annealing of point-like and extended defects, respectively. In neutron irradiated GaP all positron sensitive radiation defects disappear after annealing at 700° C. It is shown (i) that in all materials the positron lifetime and S-parameter increase with rising proton and neutron fluence and (ii) that elemental semiconductors exhibit stronger increases than compound semiconductors.