Nucleation of p-Type Microcrystalline Silicon on Amorphous Silicon for n-i-p Solar Cells Using B(CH3)3 And BF3 Dopant Source Gases

Abstract

ABSTRACTReal time spectroscopic ellipsometry (RTSE) has been applied to identify optimal conditions for the nucleation and growth of 120 Å microcrystalline silicon (μc-Si:H) p-layers by rf plasma-enhanced chemical vapor deposition (PECVD) at 200°C on amorphous silicon (a-Si:H) i-layers in the n-i-p solar cell configuration. Analysis of the RTSE data provide the bulk p-layer dielectric function (2.5-4.3 eV), whose amplitude and shape yield insights into the structural quality and crystallinity of the p-layer. Among the deposition parameters varied include the underlying i-layer surface treatment, the p-layer plasma power flux, and the p-layer dopant source gas and flow ratio. Here we focus on the differences between p-layer deposition using trimethyl boron, B(CH3)3, and boron trifluoride, BF3, source gases. We find significant differences attributed to the differing effects of F and CH3radicals in the plasma on silicon crystallite growth.