The different behaviour of C iO i and C iC s defects in SiGe

Abstract

The behaviour of C iO i and C iC s defects in Si x Ge 1− x with the change of alloy composition were investigated. In photoluminescence (PL) spectra, the photon energy for C iO i is very sensitive to Ge content, shifting to higher energy with the increase of Ge content. In contrast, the C iC s is almost not affected with the Ge content in the studied composition range. The broadening of the zero-phonon lines for these carbon-related defects in dilute Si x Ge 1− x is induced primarily by the atomic mismatch of Ge atoms in Si environment. By comparing the numerically calculated results with the measured data, it is shown that the C iO i have site preference for Ge atoms, but C iC s do not display such a trend. With the effective-mass model for the defects in excited states, and reference to the deep-level transient spectroscopy (DLTS) data, the different PL characteristics between C iO i and C iC s can be explained.