A slow positron beam was used to investigate the depth dependence of the positron-electron pair momentum distribution in ZnSe layers which had been grown onto a GaAs substrate. It was deduced that the positrons annihilated in the lattice in undoped ZnSe, and at vacancies in heavily n-type ZnSe. It was also demonstrated that positrons, in semi-insulating ZnSe, drifted to GaAs under fields of 1 to 3kV/cm.

L.Liszkay, C.Corbel, P.Hautojärvi, R.Aulombard, T.Cloître, J.Griesche, F.Kiessling: Applied Physics Letters, 1997, 70[20], 2723-5