Optical properties of transition metal impurities in CdSe II. Photoionization spectra

The photoionization absorption spectra of Cr and Fe impurities in CdSe are presented. They are very well described in terms of photo‐transitions from the localized 3d shell to the conduction band. The ionization energies and the matrix elements of electric dipole transitions are determined. It is found that deep donor levels of Cr2+ and Fe2+ arc 0.62 and 0.63 eV above the top of the valence band, respectively and are temperature‐indepenent. Observed spectra of CdSe:Fe2+ are succesfully correlated with previously published results of photosensitive EPR of CdSe:Fe3+. The photoionization processes for other transition metal impurities are discussed. The ionization energies for some of them are estimated.