Nucleation of Multicrystalline Silicon during Directional Solidification

Abstract

In this work, directional solidification was performed for multicrystalline silicon (mc-Si) ingot casting. The initial nucleation at the bottom of the silicon melt could be controlled by changing the cooling rate from 9 to 20μm/s. Metallographic microscope, X-Ray Diffraction (XRD), Microwave photoconductivity decay meter (μ-PCD) and four-point probe resistivity tester were used to investigate the microstructure, crystal orientation and electrical properties of the mc-Si ingots. The obtained results showed that cooling rate at 17μm/s is the optimum condition for the mc-Si ingots casting, under which the prepared ingot has lower dislocation density of 6×10-3 cm-2, better electrical properties, more uniformer resistivity distribution with an average value of 0.68 Ω×cm and higher minority carrier lifetime with a maximum value of 1.8 μs than that of in the other cooling rate conditions.