Epitaxial growth of silicon in a high purity A1-22 wt% Si alloy

Abstract

By inserting single crystal silicon seeds with (111)Si or (100)Si faces into the melt of high purity A1-22 wt% Si alloy, epitaxial growth of silicon from the seeds and the effect of modification with sodium were studied. Results show that primary silicon grows platelike epitaxially from certain sites of the surfaces of the seeds, with lateral faces of {111}Si and preferred directions of <112>Si. It appeared that an addition of 0.6 wt% Na into the melt decreases markedly the number of epitaxial primary silicon plates from the seeds and causes primary silicon to grow more packed and thicker in lateral size, while the lateral faces and preferred directions of epitaxial primary silicon plates remain the same as in the pure alloy. After a discussion on the experimental phenomena, it is suggested that modification with sodium affects both nucleation and growth of silicon phase, whereas the TRPE mechanism still plays an important role in the growth of silicon phase when Na is present.