Positron lifetime and infra-red absorption spectroscopy were used to investigate the compensation defects which rendered undoped n-type liquid-encapsulated Czochralski-grown material semi-insulating under high-temperature annealing conditions. The positron measurements, carried out between 25 and 300K, revealed a positron lifetime of 282ps in as-grown material which was attributed to either an isolated In vacancy, VIn3-, or to related H complexes. The shallow donor complex, VInH4, which was responsible for much of the n-type conductivity and a strong infra-red absorption at 4320nm, was ruled out as being a significant trapping site because its neutral state was present in too low a concentration. Upon annealing at 950C, trapping at VIn-related centers was observed to increase slightly and an additional positron trapping defect with a lifetime of 330ps appeared in concentrations of some 1016/cm3; thus indicating divacancy trapping. Meanwhile, the VInH4 infra-red absorption signal disappeared. The results supported the suggestion that the VInH4 complex in as-grown material dissociated during annealing so as to form VInHn(3-n)- complexes, where n was between 0 and 3, and that recombination of VIn with a P atom resulted in the formation of EL2-like deep-donor PIn antisite defects which compensated the material. It was suggested that the divacancy which formed during annealing was VInVP, and that this defect was probably a by-product of PIn antisite formation.

Positron-lifetime study of compensation defects in undoped semi-insulating InP C.D.Beling, A.H.Deng, Y.Y.Shan, Y.W.Zhao, S.Fung, N.F.Sun, T.N.Sun, X.D.Chen: Physical Review B, 1998, 58[20], 13648-53