Identification of boron clusters and boron-interstitial clusters in silicon

Abstract

The identity of boron clusters and boron interstitial clusters in Si, produced by radiation or implantation, has been studied theoretically. Local vibration modes of the single-boron interstitial and the diboron split interstitial $({\mathrm{B}}_{2}\mathrm{I})$ and its metastable isomer as well as substitutional dimers are found to be in good agreement with observations. The modes of a diboron defect that has trapped three interstitials ${\mathrm{B}}_{2}{\mathrm{I}}_{3}$ are close to those observed for the boron-related $I2$ luminescent center. The annealing of these centers around $400\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ coincides with the main recovery of the electrical activity of boron, but the formation of defects which are metastable casts doubt on previous modeling strategies.