Lattice location of low-Z impurities in medium-Z targets using ion-induced x rays. II. Phosphorus and sulfur implants in germanium single crystals

Abstract

In the preceding paper, Paper I, we described an analytical technique, based on ion-induced x-ray yields, for detecting low-Z impurities in medium-Z targets. In this paper, Paper II, we report the application of this method to the lattice location of impurity atoms. Two systems have been examined to test the method, viz., P and S implants in Ge single crystals. The channeling effect was applied to the phosphorus and sulfur K x-ray yields excited by 0.5-MeV protons. Some 93% of implanted 31P (0.7 × 1015 atoms cm−2, room-temperature implant, 450°C anneal), were found to occupy substitutional sites; the fraction dropped to [inverted lazy s] 63% for an implant dose of 2.7 × 1015 atoms cm−2. Channeling effect results in 〈110〉, 〈111〉, and 〈100〉 directions for Ge(S), implanted at room temperature and annealed at 450°C, prescribe a preferred off-lattice (> 0.3 Å) site for the sulfur, necessarily different from the regular tetrahedral or hexagonal interstitial sites. For hot (220°C) implantation conditions, poorer crystal annealing and weaker channeling effects were observed.