Divacancy and resistivity profiles in n-type Si implanted with 1.15-MeV protons

Abstract

Defect profiles were determined in proton-implanted low-doped ([P]=1\ifmmode\times\else\texttimes\fi{}${10}^{14}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) n-type silicon layers by performing positron-electron pair momentum-distribution measurements with a slow-positron beam, conventional positron lifetime, and ${\mathrm{e}}^{+}$-${\mathrm{e}}^{\mathrm{\ensuremath{-}}}$ pair momentum-distribution measurements with a $^{22}\mathrm{source}$ and spreading resistance measurements. The dominant positron trap induced by 1.15 and 3.0 MeV proton implantations is the silicon divacancy ${\mathrm{V}}_{2}$. Compared to the values in bulk, the characteristic positron lifetime and the characteristic low- and high-momentum parameters of the ${\mathrm{e}}^{+}$-${\mathrm{e}}^{\mathrm{\ensuremath{-}}}$ pair momentum distribution at the divacancy are ${\mathrm{\ensuremath{\tau}}}_{\mathrm{d}}$=300 ps=1.35${\mathrm{\ensuremath{\tau}}}_{\mathrm{b}}$, ${\mathrm{S}}_{\mathrm{d}}$=1.${052\mathrm{S}}_{\mathrm{b}}$, and ${\mathrm{W}}_{\mathrm{d}}$=0.${78\mathrm{W}}_{\mathrm{b}}$, respectively. The divacancy is observed in the negative charge state ${\mathrm{V}}_{2}^{\mathrm{\ensuremath{-}}}$. The divacancy profile is determined in n-type Si implanted with 1.15-MeV (20 \ensuremath{\mu}m) protons to a dose 1\ifmmode\times\else\texttimes\fi{}${10}^{14}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ and the maximum concentration [${\mathrm{V}}_{2}^{\mathrm{\ensuremath{-}}}$]=4--8\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ is observed at depths 16--18 \ensuremath{\mu}m. The resistivity increases with increasing divacancy concentration. After annealing at 400 \ifmmode^\circ\else\textdegree\fi{}C the spreading resistance measurements reveal a region of shallow hydrogen-related donors at depths 15--21 \ensuremath{\mu}m. The positron annihilation results support the idea that the introduction of shallow donors is due to the formation of hydrogen-vacancy complexes during the annealing.