Surface photovoltage analysis of phase transformation of copper in p-type silicon

Abstract

Surface photovoltage minority carrier lifetime/diffusion length analysis of copper contaminated p-type silicon was performed. It was observed that an optical or low-temperature thermal activation procedure on Cu-doped silicon significantly degrades the diffusion length. Unlike iron doped p-type silicon no recovery of diffusion length was observed following such an activation procedure. It is proposed that the activation procedure dissociates interstitial copper agglomerations and forms extended substitutional defects in silicon, which have much greater recombination efficiency. The change in phase of copper and the formation of associated defects is a function of activation light intensity, annealing time, and temperature. An activation energy of 0.419 eV is obtained for the process, which is in good agreement with copper diffusivity value in silicon. It is thus concluded that the change in phase of copper and the formation of extended defects with activation is a diffusion limited process. © 2000 American Institute of Physics.