New recombination centres in InP : Fe doped by neutron transmutation

Neutron transmutation doping (NTD) has been used to introduce several amoun ts 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 p hotoluminiscence (PL) and positron annihilation spectroscopy (PAS). In PL s pectra two new donor-acceptor emissions arise. The nearest band-edge emissi on line has an energy of 1.39 eV, and does not depend on the annealing temp erature. However, all the parameters of the second emission band, centred a t 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 accepters. The change in the PAS para meters are related to defects produced during the doping process. The depen dence 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 associa tion between iron atoms and indium vacancies. (C) 2000 Published by Elsevie r Science S,A. All rights reserved.