High performance multicrystalline wafers with lifetime of 400µs at industrial scale

An improved nucleation method was used to fabricate high performance multicrystalline ingots with small grains. The objective of the technology is to reduce the generation of defects having high recombination activity. The crystal growth recipe, the hot zone design, and the nucleating method were improved. It is shown that wafers with uniformly small grains reach much higher effective carrier lifetimes than wafers with large grains but with non-uniform distribution. The crystal growth recipe was optimized to obtain such small grains. An average effective lifetime of 400 μs was achieved at an excess carrier density of 1×10
¹⁵
cm
^-3
. In the best optimized ingot, a best measured lifetime approaching 600 μs of these wafers was reached.