Abstract
Approximate ground state wavefunctions and potentials for iron group transition metal impurity centres in semiconductors, for instance Cr, Fe, Cu, Ni, Co, Mn in GaAs are calculated using a model in which both the screened long range Coulomb potential and the short range core potential are taken into consideration. The magnitude and the wavelength dependence of the photoionization cross section are obtained via the wavefunction, in favourable agreement with experiment.