The Theory of Rare-Earth Impurities in Semiconductors

Abstract

ABSTRACTThe chemical trends of rare-earth impurities in semiconductors are analyzed on the basis of a selfconsistent tight-binding Green's function technique. The 4f states are treated as a frozen core and we get essentially no 5d derived states in the gap. We calculate the 4f ionization levels in the solid and conclude that the stable state is mostly 3+. We then describe the results of a LDA calculation for Er in silicon which we find to be stable in the interstitial position. Finally we consider in some detail the case of Yb in InP where we discusss the possible origin of the shallow gap levels and the mechanisms for luminescence excitation and quenching.