title: Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon.
abstract: Solar cells based on epitaxial silicon layers as the absorber attract increasing attention because of the potential cost reduction. In this work, we studied the influence of the deposition rate on the structural properties of epitaxial silicon layers produced by plasma-enhanced chemical vapor deposition (epi-PECVD) using silane as a precursor and hydrogen as a carrier gas. We found that the crystalline quality of epi-PECVD layers depends on their thickness and deposition rate. Moreover, increasing the deposition rate may lead to epitaxy breakdown. In that case, we observe the formation of embedded amorphous silicon cones in the epi-PECVD layer. To explain this phenomenon, we develop a model based on the coupling of hydrogen and built-in strain. By optimizing the deposition conditions to avoid epitaxy breakdown, including substrate temperatures and plasma potential, we have been able to synthesize epi-PECVD layers up to a deposition rate of 8.3 Å/s. In such case, we found that the incorporation of hydrogen in the hydrogenated crystalline silicon can reach 4 at. % at a substrate temperature of 350 °C.
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.
authors.forename: Wanghua
authors.initials: W
authors.lastname: Chen
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Cariou
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.|Total SA, Tour Michelet, 24 Cours Michelet - La Défense 10, 92069 Paris La Défense Cedex, France.
authors.forename: Gwenaëlle
authors.initials: G
authors.lastname: Hamon
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.|Total SA, Tour Michelet, 24 Cours Michelet - La Défense 10, 92069 Paris La Défense Cedex, France.|IPVF (Institut Photovoltaïque d'Ile-de-France), 92160 Antony, France.
authors.forename: Ronan
authors.initials: R
authors.lastname: Léal
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Maurice
authors.affiliation: LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France.|IPVF (Institut Photovoltaïque d'Ile-de-France), 92160 Antony, France.
authors.forename: Pere Roca I
authors.initials: PR
authors.lastname: Cabarrocas