Optical properties of Cd-O and Zn-O complexes in GaP

Abstract

We report sharp line spectra, due to Cd and O impurities in GaP, which show that the red luminescence previously attributed to recombination between distant donor-acceptor pairs arises instead from nearest-neighbor Cd-O complexes. The binding energy of isolated O donors is thus shown to be ∼1 eV. The energy levels and the optical selection rules for the complexes are found to be consistent with the C3v symmetry of these centers. The spectra reveal three local phonon modes which we identify with the symmetric modes of vibration of the O atom and its four nearest neighbors. We show that the broad red emission band from Zn- and O-doped GaP is attributable to similar complexes having a strongly damped local vibrational mode. © 1968 The American Physical Society.