Elastic energy absorption measurements were performed on semiconducting, semi-insulating and Fe-doped samples. A thermally activated relaxation process was found only in the semi-insulating state, and was identified with the hopping of H atoms that were trapped at In vacancies. It was proposed that the presence of In vacancies, in samples which were prepared by using the liquid encapsulated Czochralski method, was due to a lowering of their energy by saturation of the P dangling bonds with H atoms which were dissolved from a capping liquid that contained H2O. The conversion of Fe-free samples to the semi-insulating state, during high-temperature treatment, was expected to be due to H loss; with transformation of H-saturated In vacancies, VIn-H4 donors, into neutral and acceptor VIn-Hn complexes, where n was equal to 4 or less. Such complexes were expected to produce the observed anelastic relaxation, and could also act as deep acceptors that neutralized unwanted donor impurities.

Mechanisms of the Semi-Insulating Conversion of InP by Anelastic Spectroscopy. R.Cantelli, F.Cordero, O.Palumbo, G.Cannelli, F.Trequattrini, G.M.Guadalupi, B.Molinas: Physical Review B, 2000, 62[3], 1828-34