Shielded hydrogen passivation – a novel method for introducing hydrogen into silicon

This paper reports a new approach for exposing materials, including solar cell structures, to atomic hydrogen. This method is dubbed Shielded Hydrogen Passivation (SHP) and has a number of unique features offering high levels of atomic hydrogen at low temperature whilst inducing no damage. SHP uses a thin metallic layer, in this work palladium, between a hydrogen generating plasma and the sample, which shields the silicon sample from damaging UV and energetic ions while releasing low energy, neutral, atomic hydrogen onto the sample. In this paper, the importance of the preparation of the metallic shield, either to remove a native oxide or to contaminate intentionally the surface, are shown to be potential methods for increasing the amount of atomic hydrogen released. Excellent, damage free, surface passivation of thin oxides is observed by combining SHP and corona discharge, obtaining minority carrier lifetimes of 2.2 ms and J0 values below 5.47 fA/cm2. This opens up a number of exciting opportunities for the passivation of advanced cell architectures such as passivated contacts and heterojunctions.