Impact of a-Si:H hydrogen depth profiles on passivation properties in a-Si:H/c-Si heterojunctions

We explore the (near-)interface structure of amorphous/crystalline silicon (a-Si:H/c-Si) heterojunctions as employed in high-efficiency heterojunction solar cells. We make use of secondary-ion-mass-spectroscopy profiles and minority carrier lifetime measurements taken on undoped deuterated amorphous silicon [(i)a-Si:D] layers deposited on c-Si from deuterated silane at identical conditions as the hydrogenated layers we have analyzed previously [T. F. Schulze et al., Appl. Phys. Lett. 96 (2010) 252102]. We briefly discuss the implications of the local interface structure for the c-Si surface passivation as well as for the heterojunction band offsets, and identify a route towards optimization of (i)a-Si:H layers as passivating buffers in a-Si:H/c-Si high-efficiency heterojunction solar cells.

► We analyze the (near-)interface structure of a-Si:H/c-Si heterojunctions.
► Inhomogeneity in a-Si:H hydrogen profile appears depending on growth conditions.
► Poor growth conditions (e.g. low temperature) lead to H pileup at heterointerface.
► The a-Si:H layers with highest bulk quality are prone to epitaxial growth.
► The a-Si:H/c-Si interface passivation is directly linked to local structure.