High-resolution spectroscopy of silver-doped silicon

Silver-doped silicon was investigated by using transmission and photothermal ionization spectroscopy (PTIS). A spectrum of sharp lines was detected between 6200 and 6700 ${\mathrm{cm}}^{\mathrm{-}1}$. In PTIS, strong phonon-assisted Fano resonances were observed which involved f TO and g LO intervalley phonons. It was therefore possible to identify the silver-related center as a donor. The Ag spectrum differs from previously reported donor spectra in silicon in the sense that excitations to excited p states do not dominate. 2$p_0$ and 3$p_0$ lines were weakly observed, and none of the usually strong $p_{\pm }$ lines were detected. By comparing spectra of P and neutral Te with the spectrum obtained for Ag, it is shown that the Ag spectrum is dominated by excitations to s states.