Optical activation and excitation mechanisms of Er implanted in Si

Abstract

The several processes required to achieve Er luminescence in Si are investigated. In particular, the role of Er-O interactions to obtain the incorporation of high Er concentrations, electrically and optically active, in crystalline Si is addressed. Multiple Er and O implants were performed on n-type (100) Si crystals to obtain flat concentrations of \ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}${10}^{19}$ Er/${\mathrm{cm}}^{3}$ and \ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}${10}^{20}$ O/${\mathrm{cm}}^{3}$ over an \ensuremath{\sim}2-\ensuremath{\mu}m-thick layer. These implants produced also a 2.3-\ensuremath{\mu}m-thick amorphous Si (a-Si) layer. A subsequent thermal treatment at 620 \ifmmode^\circ\else\textdegree\fi{}C for 3 h induced the epitaxial regrowth of the whole layer and the incorporation of both Er and O in a good-quality single crystal. A further annealing at 900 \ifmmode^\circ\else\textdegree\fi{}C for 30 sec produced the electrical activation of the implanted Er in the presence of O, with an Er donor concentration of \ensuremath{\sim}8\ifmmode\times\else\texttimes\fi{}${10}^{18}$/${\mathrm{cm}}^{3}$ over an \ensuremath{\sim}1.8-\ensuremath{\mu}m-thick layer. This value is more than two orders of magnitude above the maximum Er donor concentration reported in the literature, demonstrating the crucial role of O in increasing the electrically active Er concentration in crystalline Si. The optical efficiency of this sample has been studied by photoluminescence. It is seen that an enhancement by a factor of \ensuremath{\sim}6 with respect to the literature data is obtained. Moreover, studies on the photoluminescence intensity as a function of the pump power give important information on the mechanisms underlying Er luminescence in Si and its competing phenomena. These data are presented and discussed. A plausible model based on the previous results is also presented.