Influence of copper on the carrier lifetime of n-type and p-type silicon

Abstract

Controlled contamination by ion implantation and careful surface passivation has been used to study the effect of copper on the recombination rate of charge carriers in silicon wafers. Our results confirm that copper strongly reduces the lifetime of n-type silicon, which approximately follows an Ncu .0.55 dependence on the copper dose. The effect of copper on p-type silicon, commonly used for solar cells, has been found to be as severe as on n-type silicon, when wafers having a similar dopant concentration are compared. The lifetime of copper contaminated silicon, both n-type and p-type is correlated to the phosphorus or boron concentration, respectively, with decreasing lifetimes corresponding to increasing doping levels. The fact that both the copper dose and the dopant concentration have a strong effect on the lifetime is an essential consideration for future studies of copper in silicon.