Electrical Behavior of Group III and V Implanted Dopants in Silicon

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Abstract
The anneal behavior of layers implanted with dopants from column III (B, Al, Ga, and Tl) and column V (As, Sb, and Bi) in silicon substrates has been investigated. The ranges of implant conditions were energy 20–50 keV, dose 1013–1015/cm2, and substrate temperature 23°–500°C. Hall‐effect and sheet resistivity measurements were used to determine the effective number of carriers/cm2 (Ns)eff and the effective mobility μeff. Analysis of nonuniform distributions of carrier densities and mobilities on these measurements shows that the values of (Ns)eff and μeff can be misleading unless the effect of the depth distributions is allowed for. These distributions have been determined in some cases by the use of layer removal techniques combined with Hall‐effect and sheet resistivity measurements. We find in well‐annealed implanted samples that the dependence of the mobility on carrier density follows that determined for bulk silicon. In many cases deviation from this relation can be accounted for on the basis of compensation. In the case of aluminum we suggest that this compensation may be accounted for by the presence of interstitial aluminum atoms acting as donors. We have found that interstitial thallium can behave as a donor. The anneal behavior of the implanted layer is influenced by ion species, dose, and substrate temperature. The carrier concentration measured in implantations of column III elements did not exceed the limits of thermal equilibrium solubility as is found for column V elements. In the former case, enhanced diffusion effects are observed. From the known substitutional behavior of column V elements, it is suggested that the anneal behavior in the 600°–800°C range is due to the dissociation of radiation damage complexes.