PRECIPITATES AND INCLUSIONS IN BLOCK-CAST SILICON - ISOLATION AND ELECTRICAL CHARACTERIZATION

摘要

Silicon carbide and silicon-nitride precipitates appear often in the upper part of multicrystalline silicon blocks. It is well known that these precipitates may cause shunts in solar cells, but the electrical properties of the precipitates are unknown so far. To study their electrical properties, the precipitates were isolated from the Si bulk material. Silicon carbide filaments can cause severe ohmic shunts, so we concentrated on the investigations of the electrical properties of these filaments. It turns out that the filaments are highly conductive. Measurements of filaments, which are still embedded in the silicon bulk material, were also performed to study the heterojunction silicon carbide - silicon. The results show that there is only a low positive conduction band offset at the interface silicon - silicon carbide, hence it can be assumed that the shunt current flows inside of the filaments.