Photoluminescence signature of silicon interstitial cluster evolution from compact to extended structures in ion-implanted silicon

Abstract

Low temperature photoluminescence (PL) studies have been carried out on ion-implanted silicon in order to elucidate upon the structure evolution of the self-interstitial (I) clusters as a function of implantation dose, energy, species and post-implantation annealing conditions. PL measurements on as-implanted and low temperature annealed (up to 450 °C) Si show a sharp X band and a W band at 1200 nm and 1218 nm, respectively. The W band shows gradual quenching of PL above ∼60 K with a characteristic activation energy of 59 meV. We argue that the W band originates from a compact di-interstitial cluster in Si. Short duration annealing at 600 °C results in multiple sharp peaks in the range of 1228–1400 nm for the high energy (MeV) and high dose (⩾1 × 1012 cm−2) implantation, while low energy (keV) or low dose ions induce two broad peaks in the same wavelength range. Prolonged annealing at 600 °C induces primarily two broad peaks centred at 1322 nm and 1392 nm. These broad, but distinct, PL signatures are attributed to a chain of I-clusters, while the multiple sharp peaks possibly result from multiple configurations/excited states of the compact but bigger I-clusters. For annealing at and above 680 °C and dose of ⩾1 × 1013 cm−2, the sharp PL peak observed at 1376 is attributed to {3 1 1} rod-like defects. We argue that the changing line shape and energy of the PL spectra with processing temperature is a possible indicator of the shape evolution of the clusters from compact to extended structures as predicted recently from simulation.