Super-saturation of dopant atoms in silicon has been attracting interest because a high concentration of carriers in silicon is required in practical applications and is scientifically important. A high hole concentration of about 1 × 1021 cm-3 is obtained by implanting boron into silicon substrate with a dose of 1 × 1017 cm-2. In such super-saturated boron in silicon, it was found that the clustered boron atoms (B12) substitute silicon atoms. The results of a first-principles calculation indicated that the icosahedral boron cluster is energetically preferable to the cubo-octahedral cluster. As a practical application, low resistivity contact between aluminum and silicon of lower than 1 × 10-8 Ω cm2 was demonstrated by this high dose boron implantation technique with co-implantation of germanium.
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