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

The formation process of secondary radiation defects in silicon crystals su bjected to low-dose photon-assisted ion implantation (PAI) was investigated by the deep-level transient spectroscopy (DLTS) method. Approximately equa l amounts of primary radiation defects with similar spatial profiles were i ntroduced in n- and p-Si samples by low (similar to 10(11) cm(-2)) dose imp lantation of oxygen, nitrogen or argon ions under varying temperature and p hotoexcitation conditions. The analysis of DLTS spectra of the samples prod uced has revealed significant differences in the process of defect formatio n as well as the nature of the defects generated in n- and p-Si. The positi on of the predominant peak on the n-Si DLTS spectra, attributed to the diva cancy 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 de fined by the implantation temperature. This findings indicate the qualitati ve 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 d efects are formed in p-Si, each having different optimum formation temperat ure. Both the low implantation temperature and low power density photoexcit ation of the n-Si crystals were proved to stimulate the formation of divaca ncies. The same experimental conditions cause the suppression rather than s timulation of total defect formation in p-Si crystals. However, at high pow er density, the photoexcitation activated the formation of defects in eithe r kind of Si samples. The efficiency of photoexcitation-prompt defect forma tion is temperature dependent both in n- and p-Si, the dependence being dir ect for the former and reverse for the latter Si types. In addition, the ro le of photon assistance in the process of defect formation in n-Si was show n to be influenced by the mass of implanted ions. The impact of photoexcita tion is prominent for light ions and tends to decrease for the heavy ones. (C) 2001 Elsevier Science B.V. All rights reserved.