Vanadium in silicon: Lattice positions and electronic properties

Abstract

The electronic properties of vanadium in silicon have been studied using deep level transient spectroscopy (DLTS), high resolution Laplace DLTS, capacitance voltage measurements and secondary ion mass spectroscopy (SIMS). Vanadium was implanted into float zone (FZ) grown n-type and FZ and Czochralski (Cz) grown p-type Si and implantation damage was removed through annealing between 700 and 900 °C. DLTS measurements were carried out to determine the electronic characteristics of vanadium-related defects in silicon. It is argued that the dominant electrically active defect is related to interstitial vanadium (Vi) atoms. The distribution of implanted vanadium is seen to differ between Czochralski and FZ silicon, with redistribution of vanadium atoms occurring significantly faster in Cz-Si. We suggest that in FZ-Si the Vi atoms interact with implantation induced vacancies and move to the substitutional site where they are much less mobile. At the peak concentration of vanadium, determined by SIMS to be ∼1015cm−3 in FZ-Si, the electrically active fraction is significantly lower (∼1013cm-3). As we see no evidence of precipitation occurring in the region close to the implant peak, it is concluded that a large portion of V atoms should be located at the substitutional site. Despite the ab-initio modeling predictions of substitutional vanadium, Vs, introducing a shallow acceptor level in the silicon band gap, no electrical activity associated with the Vs fraction has been observed in this work in spite of its concentration being at a measurable level. As such, our results indicate that substitutional vanadium is electrically inactive in silicon.