Boron reactivation kinetics in hydrogenated silicon after annealing in the dark or under illumination

Abstract

The reactivation kinetics of passivated boron in hydrogenated silicon are studied systematically with respect to temperature, acceptor concentration, and illumination. The change of the net inactive boron concentration R versus annealing time t satisfies the equation dR/dt=-${\mathit{rR}}^{2}$/(${\mathit{N}}_{\mathit{A}}$-R${)}^{2}$, where ${\mathit{N}}_{\mathit{A}}$ is the total boron concentration. The annealing parameter r does not depend on ${\mathit{N}}_{\mathit{A}}$, but shows a linear dependence on the optically generated electron concentration, provided the light intensity exceeds a threshold value. The annealing process is rate limited by the formation of a stable electrically inactive complex H${\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}_{2}$, which involves two H atoms. The formation of H${\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}_{2}$ strongly depends on the charge state of H, which is controlled by a H donor level located in the upper half of the band gap.