Ion mass effect on vacancy-related deep levels in Si induced by ion implantation

Abstract

The ion mass effect on the dominating vacancy related deep levels in Cz-Si implanted with 4-MeV C ions and 6-MeV Si ions has been investigated by deep level transient spectroscopy (DLTS). It is found that the intensity of the DLTS signal for the doubly negative charge state of the divacancy $[{V}_{2}(=/\ensuremath{-})]$ deviates from a one-to-one correlation with that of the singly negative charge state of the divacancy $[{V}_{2}(\ensuremath{-}/0)]$ and decreases, compared to ${V}_{2}(\ensuremath{-}/0),$ with increasing ion mass. Capture kinetics studies reveal that the electron-capture rate for ${V}_{2}(=/\ensuremath{-})$ decreases with increasing ion mass, while that for ${V}_{2}(\ensuremath{-}/0)$ has a weaker dependence on ion mass. In this work, we suggest a model to explain most of the known experimental observations of the ion mass effect for ${V}_{2}(=/\ensuremath{-}).$ The model assumes a local compensation of the carrier concentration in highly disordered regions located within the collision cascades. In addition, it has been observed that the DLTS signal of the vacancy-oxygen pair exhibits a trend similar to that for ${V}_{2}(=/\ensuremath{-})$ regarding the ion mass effect.