LATTICE SITE LOCATION OF THULIUM AND ERBIUM IMPLANTED GAAS

The lattice site location of Tm and Er implanted in GaAs were studied using the RBS/channeling technique. For implanted doses up to 10(14) c m(-2) both elements show nearly 100% substitutionality in the GaAs lat tice. Further increasing the Er concentration causes a fraction to occ upy an interstitial regular site. Axial channeling measurements along planar directions show that Er forms ErAs precipitates. The angular sc ans are compared with Monte Carlo simulations and the Er fractions in the different lattice sites are calculated. With the incorporation of oxygen in the GaAs matrix the fraction of Er in substitutional sites i ncreases. Taking into account these results the photoluminescence (PL) behavior of Er in these samples is discussed and results obtained wit h Er doped GaAs grown by Molecular Beam Epitaxy are understood. (C) 19 98 Elsevier Science B.V.