ABSTRACT
Previously reported optical inactivity of Yb in GaAs was attributed to very low fractions of Yb in substitutional position. In the present work it is demonstrated that Yb can be rendered optically active in GaAs if it is incorporated in three-component complexes (Yb+O+S/Se/Te). Oxygen seems to be a necessary component of Yb related centres in GaAs, its role in the optical activation on Yb is possibly due to its participation in the energy transfer process.
