Grain Boundaries in Multicrystalline Silicon. Characterization by Admittance and EBIC Measurements

Abstract

A model is introduced which describes the electrical properties of a grain boundary under electron irradiation. The barrier height lowering under e‐beam irradiation of selected grain boundaries is determined by admittance measurements and can be described in the framework of the model presented. Admittance and EBIC measurements at differently processed grain boundaries (annealed, solar processed) are not uniformly correlated. Calculations based on our GB model indicate that the observed, partially diverging, trends of barrier heights and EBIC contrasts may be caused by the different levels of e‐beam irradiation at which admittance and EBIC are operated. A discrete trap level at Ev + 504 meV is generated at the grain boundary interface by intentional iron contamination. In this specific case, the electrical properties of the considered grain boundary are consistently described in the framework of our model by admittance and EBIC measurements.

Improved modeling of grain boundary recombination in bulk and p-n junction regions of polycrystalline silicon solar cells

“…Hassler et al 25 modeled barrier height measurements on a silicon bicrystal with a midgap grain boundary trap with a trap state density of 7.3ϫ10 11 cm Ϫ2 , an electron capture cross section, n , of 10 Ϫ17 cm 2 , and a hole capture cross section, p , of 6.7ϫ10 Ϫ14 cm 2 . Murti and Reddy 26 examined the temperature dependence of photovoltage across a single grain boundary in Wacker multicrystalline silicon to obtain a n of 1.16ϫ10 Ϫ16 cm Ϫ2 .…”

Impurity Precipitation, Dissolution, Gettering and Passivation in PV Silicon: Final Technical Report, 30 January 1998--29 August 2001

“…A significant increase in the recombination activity of iron-contaminated dislocations, silicon-oxide precipitates, and misfit dislocations in Si/SiGe epitaxial structures has been reported in Refs. [133][134][135][136][137][138][139]. However, the formation of distinctive large iron-silicide precipitates at extended defects is very uncommon.…”