Hydrogen Passivation of B-O Defects in Czochralski Silicon

Abstract

We report on hydrogen passivation of boron-oxygen defects through manipulation of the hydrogen charge states within the silicon. Standard hydrogenation processes which do not control hydrogen charge states do not appear to passivate a significant quantity of boron-oxygen defects and may result in a reduction in lifetime for wafers with high boron doping concentrations. An improved hydrogenation process through charge state manipulation is observed to lead to substantial improvements in the lifetimes of standard 2Ωcm commercial grade boron-doped Czochralski wafers and experimental compensated 2Ωm Czochralski grown wafers. The passivation of boron-oxygen defects using hydrogen is a fully reversible process, and hence subsequent processes can lead to a net reactivation of boron- oxygen defects if there are insufficient quantities of atomic hydrogen in the correct charge state. Through improved hydrogenation, independently confirmed open circuit voltages in excess of 680mV are demonstrated on solar cells fabricated using standard commercial grade boron-doped Czochralski grown wafers on an industrial production line.