Lattice Location of Rare Earth Ions in Semiconductors and Their Optical Activity

Lattice location experiments performed on Yb- and Er-doped III-V semiconducting compounds using Rutherford backscattering and channeling have been reviewed. It has been shown that Yb atoms locate substitutionally in InP and InP-based ternary alloys, while in gallium compounds no substitutional fraction of Yb could be detected. An intense intra-4f-shell luminescence of Yb$\text{}^{3+}$ has been observed in In compounds. The photoluminescence spectra of Yb$\text{}^{3+}$ reflect local alloy disorder in InPAs and GaInP, suggesting that the Yb atoms are tetrahedrally coordinated. No Yb-related emission could be observed in gallium compounds, except a weak Yb$\text{}^{3+}$ photoluminescence in GaP. An evidence has been presented that Er atoms introduced into III-V compounds locate predominantly at interstitial positions. In GaAs they move into tetrahedral lattice sites as a result of thermal annealing at temperatures higher than 600°C. The location of Er atoms at substitutional positions is accompanied with the disappearance of the intra-4f-shell luminescence of Er$\text{}^{3+}$. The reasons of the observed correlation of luminescence properties and positions of Er and Yb atoms in zincblende lattices are discussed.