An investigation of electronic passivation of silicon <100> surfaces in solutions of p-benzoquinone
Date
2013
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Silicon <100> surfaces under passivation by p-benzoquinone/methanol solu-
tions have shown significant increases in minority carrier lifetime relative to hydrogen
terminated surfaces. This appears to be a good candidate system for future improvements to existing Si solar technologies but little is known about the physical mechanism
of passivation. The following work focuses on three areas; the importance of solvent
choice in the observed passivation effect, passivation of surfaces with thin native oxides, and analysis of surface coverage and composition using X-ray Photoelectron Spectroscopy (XPS). Previous studies have largely ignored solvent choice, primarily using
methanol. It is shown that on Si <100> surfaces using methanol as a solvent provides
higher minority carrier lifetimes while also reaching plateau values more quickly than
solutions with diethyl ether as the solvent. Next oxidized wafers are investigated. A
wafer with native oxide of roughly 2 nm shows a significant increase in minority carrier
lifetime when immersed in solutions of p-benzoquinone/methanol. When the native
oxide layer is 22 nm thick however there is no observed passivation effect. Lastly a
surface analysis of Si <100> wafers out of the box (native oxide on the surface), after
etching with piranha and HF (hydrogen terminated surface), after 1 hour in methanol,
after 1 hour in p-benzoquinone/methanol, and after 1 hour in hydroquinone/methanol
was done by XPS. The p-benzoquinone and methanol treated surfaces show signs of
Si-O bonding however the peak heights after the 1 hour period are too small to be
conclusive. We conclude that there is insufficient surface coverage to provide sufficient
signal strength.