Excited states of donor bound excitons in GaP

Abstract

We have investigated excited states of bound excitons in GaP:S and GaP:Se. The states were observed by using a near-band-gap tunable laser source to create a bound exciton in an excited state and by then monitoring the luminescence due to radiative recombination. The ${\mathrm{S}}_{O^{\prime }}$ line observed previously is identified to be an excitation of the hole to a higher-lying state about a core consisting of two electrons bound in a $D^{-}$ configuration. We find two other transitions which are relatively weak in the no-phonon transition while they are comparatively strong in the phonon-assisted transitions. We interpret these lines as being due to excitations of the core electrons in the bound exciton.