The influence of target temperature and photon assistance on the radiation defect formation in low-fluence ion-implanted silicon

Abstract

The formation process of secondary radiation defects in silicon crystals subjected to low-dose photon-assisted ion implantation (PAI) was investigated by the deep-level transient spectroscopy (DLTS) method. Approximately equal amounts of primary radiation defects with similar spatial profiles were introduced in n- and p-Si samples by low ( ∼10 11 cm −2 ) dose implantation of oxygen, nitrogen or argon ions under varying temperature and photoexcitation conditions. The analysis of DLTS spectra of the samples produced has revealed significant differences in the process of defect formation as well as the nature of the defects generated in n- and p-Si. The position of the predominant peak on the n-Si DLTS spectra, attributed to the divacancy complexes, is shown to be independent of the implantation conditions. This is not the case for p-Si where the positions of dominant peaks are defined by the implantation temperature. This findings indicate the qualitative difference in the defects formed in n- and p-Si. The defects measured in n-Si are mainly divacancy complexes whereas two other kinds of competing defects are formed in p-Si, each having different optimum formation temperature. Both the low implantation temperature and low power density photoexcitation of the n-Si crystals were proved to stimulate the formation of divacancies. The same experimental conditions cause the suppression rather than stimulation of total defect formation in p-Si crystals. However, at high power density, the photoexcitation activated the formation of defects in either kind of Si samples. The efficiency of photoexcitation-prompt defect formation is temperature dependent both in n- and p-Si, the dependence being direct for the former and reverse for the latter Si types. In addition, the role of photon assistance in the process of defect formation in n-Si was shown to be influenced by the mass of implanted ions. The impact of photoexcitation is prominent for light ions and tends to decrease for the heavy ones.