Injection level dependence of the defect-related carrier lifetime in light-degraded boron-doped Czochralski silicon

Abstract

The carrier recombination lifetime in light-degraded boron-doped 1 Ω cm Czochralski-grown silicon wafers is measured as a function of the bulk excess carrier concentration $\mathrm{\Delta n.}$ The measurements are performed with the quasi-steady state photoconductance method and cover a large injection level range between ${10}^{13}$ and ${\text{1.5×10}}^{17}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}.$ We observe a very strong increase of the carrier lifetime in the $\mathrm{\Delta n}$ range between ${10}^{14}$ and ${\text{2×10}}^{16}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}},$ which is attributed to boron–oxygen $({\mathrm{B}}_i{\mathrm{O}}_i)$ defect pairs. The observed strong increase of the defect-related carrier lifetime allows us to determine the previously unknown hole capture cross section ${\sigma }_p$ of the ${\mathrm{B}}_i{\mathrm{O}}_i$ pair. Our analysis gives a ${\sigma }_p$ value of ${\text{(0.45–1.2)×10}}^{\text{−15}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}},$ which is 2–3 orders of magnitude smaller than the corresponding electron capture cross section.