Photoluminescence of CdTe thin films doped with Yb

In this paper, for the first time, we investigated the influence of ytterbium doping on the radiative recombination processes in CdTe thin films deposited on a glass substrate by means of the close-spaced vacuum sublimation technique. This allowed to determine the nature and energy structure of the intrinsic defects, residual impurities and complex acceptor centers in the films. It was found that the optical spectra of such films reflect the processes of formation of free excitons and radiative recombination with the participation of bound excitons as well as donor-acceptor pairs. For the first time, emission associated with intracenter optical transitions of Yb3+ ions in CdTe was detected and its nature was established. CdTe: Yb thin films have been shown to have very high crystalline and optical quality. It is established to be a result of a strong decrease in the concentration of shallow acceptor centers associated with residual atoms and cadmium vacancies. This is due to the formation of complex centers with the participation of Yb3+ ions and the mentioned acceptors, i.e by gettering of residual atoms in CdTe:Yb thin films. In addition, in this case we can expect the conversion of their conductivity from p-to n-type. These results open a unique opportunity to control the crystalline and optical quality, as well as the conductivity type of semiconductor crystals II-VI by doping them with rare earth elements.