Exponential Band Tails at Silicon Grain Boundaries

Abstract

The energy-distribution of interface states at grain boundaries in fine-grained silicon films is measured by two independent methods. The analysis reveals deep exponential band tails in the two-dimensional density of states within the band gap. It is proposed that these tails originate from Anderson localization of free carriers within potential fluctuations along the grain boundary plane. The measurements are in good agreement with this model.