Carrier recombination activity and structural properties of small-angle grain boundaries in multicrystalline silicon

The carrier recombination activity and structural properties of small-angle (SA) grain boundaries (GBs) in multicrystalline Si (mc-Si) were systematically investigated by electron-beam-induced current (EBIC) and by transmission electron microscopy (TEM). At 300 K, SA-GBs with a tilt angle from 0 to 10 degrees generally showed weak EBIC contrast (0 -10%) with a maximum contrast appearing at 2 degrees, while some special SA-GBs with a tilt angle of 2-3 degrees showed particularly strong contrast (-30%). At a low temperature (100 K), all the SA-GBs showed strong EBIC contrast despite the tilt angle. Possible explanations for the variation of the EBIC contrast are discussed in terms of the interaction and reconstruction of the boundary dislocations. When decorated with a metal impurity such as Fe, the SA-GBs showed much stronger EBIC contrast than the large-angle GBs, indicating that SA-GBs are effective gettering sites for impurities due to their particular boundary dislocation structures.