Carrier transport at grain boundaries in semiconductors

Abstract

This review describes the characteristics of dislocations in dislocation arrays and grain boundaries as they appear in imperfect and polycrystalline semiconductors. To further the understanding of the electronic features of these structures, metallurgical and crystallographic aspects of grain boundaries are reviewed. Grain-boundary diffusion is discussed as part of the metallurgy of bicrystal interfaces. Carrier transport at grain boundaries is described as it has been developed from the studies on germanium and III-V-compound bicrystals. Important features are lateral blocking layers, longitudinal or sheet conduction, space-charge extension with lateral bias, recombination and photovoltaic effects. Attention is focused on the activity to understand grain-boundary effects in silicon and their influence on electronic materials properties, a research area of particular importance during recent years. The application of silicon polycrystals in solar cells and in microcircuitry in the form of polycrystalline thin films has enhanced the understanding of dislocations and grain boundaries as they are considered here. Propositions for future research conclude this review.