Effects of In Situ Boron Doping in Si Epitaxial Growth on a VIC Processed Poly-Si Seed Layer Using Hot-Wire CVD

Abstract

We investigated the epitaxial growth of large-grained poly-Si film on vapor induced crystallization (VIC) seed layer using hot-wire chemical vapor deposition(HWCVD) for hetero-junction Si solar cells. In this study, p-type poly-Si films were prepared by changing in-situ boron doping time. After epitaxial growth on VIC seed layer, average grain size of about 20μm, are obtained and the crystallographic defects in epitaxial poly-Si layer on VIC seed layer are mainly low angle grain boundaries (LAGB < 2°) and coincident site lattice boundaries (CSL), which are special boundaries of less electrical activity. Moreover, with decreasing in-situ boron doping time, mis-orientation angle and in-grain defects in epitaxial Si decrease. Using in-situ boron doping, highly doped p+ back surface field layer was fabricated, and it had high Hall mobility.