MICROSTRUCTURE OF ERBIUM-IMPLANTED SI

A study is presented of the relation between microstructure and 1.54-mu-m photoluminescence (PL) in high-energy ion-implanted Er in Si as a function of implant dose, energy, and temperature and subsequent anneal. Transmission electron microscopy (TEM) of material implanted at 500 keV and > 100-degrees-C and annealed at 900-degrees-C to activate the Er PL suggests the solubility of Er in Si to be almost-equal-to 1.3 +/- 0.4 X 10(18) cm-3 at 900-degrees-C. Precipitates take the form of platelets (probably ErSi2) almost-equal-to 100-300 angstrom in diameter and almost-equal-to 10 angstrom thick. The 1.54-mu-m PL saturates at almost-equal-to 5 X 10(17) cm-3, before the apparent solubility limit. Layers in which the Si is fully amorphized and subsequently regrown by solid phase epitaxy during an anneal show increased Er incorporation in the crystalline Si but segregation at the amorphous-crystalline interface. In buried amorphous layers regrown from top and bottom, segregation leads to a line of high Er concentration near the center of the layer: Regrowth from a single interface leads to a segregation pileup of Er at the interface until the precipitation threshold is reached.