Positron annihilation methods were used to investigate compensating defects in Si δ-doped superlattices in (001)GaAs. The results revealed the presence of vacancies, and ion-type defects, which were located between the δ planes in undoped GaAs. The vacancy defect was identified as being the Ga vacancy, and the negative ion was suggested to be the Ga antisite. The concentrations of these defects increased strongly when the areal concentrations of free carriers were reduced at the δ planes.

T.Laine, K.Saarinen, J.Mäkinen, P.Hautojärvi, C.Corbel, M.J.Ashwin, R.C.Newman: Applied Physics Letters, 1997, 71[13], 1843-5