New recombination centres in InP:Fe doped by neutron transmutation

Neutron transmutation doping (NTD) has been used to introduce several amounts of tin atoms into semi-insulating InP:Fe samples. Defects related to the doping method which includes the transmutation process and the subsequent annealing procedure necessary to activate the donors have been studied by photoluminiscence (PL) and positron annihilation spectroscopy (PAS). In PL spectra two new donor–acceptor emissions arise. The nearest band-edge emission line has an energy of 1.39 eV, and does not depend on the annealing temperature. However, all the parameters of the second emission band, centred at 1.35 eV, change with temperature, annealing and optical laser power. The results indicate that this band is related to a transition between a donor with a complex structure and residual acceptors. The change in the PAS parameters are related to defects produced during the doping process. The dependence of the PAS parameters on the annealing temperature indicates that the positron trap induced by the NTD process in InP:Fe is formed by an association between iron atoms and indium vacancies.