Erbium-implanted silicon–germanium

Abstract

Rutherford backscattering/channeling technique complemented by transmission electron microscopy has been used to study the composition dependence and the effect of carbon codoping on thermal and structural properties of unstrained Si1−xGex (x=0.1–0.8) alloys implanted with Er+ at 70keV to a fluence of the order of ∼1015cm−2. It has been shown that implantation in the low-temperature regime (350°C) led to the formation of a ternary solid solution with a peak Er concentration of around 1at.%. Implanted Er atoms were found randomly distributed in the heavily damaged host matrix. Postimplantation annealing at different temperatures up to 600°C was observed to induce solid phase epitaxial regrowth leading to the recrystallization of the damaged matrix and the simultaneous removal of almost all the implanted Er. Both rate and activation temperature of the epitaxy in Si1−xGex were found to depend strongly on the stoichiometry of the alloy. Implantation of Er in the high-temperature regime (550°C) was found to lead to the spontaneous recovery of the host matrix crystallinity and the incorporation of Er atoms on regular lattice sites. Specific lattice positions Er can occupy were identified and they were found to have a strong dependence on both the alloy composition and foreign impurity (C codoping). Based on the channeling analysis, an interpretation of the diverse Er occupancy in Si1−xGex observed in our experiments is proposed.