Passivating Properties of Hydrogenated Amorphous Silicon Carbide Deposited by PECVD Technique for Photovoltaic Applications
Résumé
Amorphous hydrogenated silicon carbide (a-SiC x :H) could be used as a passivating layer in solar cell configuration. We have deposited a-SiC x :H by plasma enhanced CVD on polished silicon wafers. Si-rich a-SiC x :H allows to reach a surface recombination velocity of 7.5 cm.s-1. The hydrogenation of silicon surface dangling bonds and the electrical field-effect near the interface are analyzed by minority carrier lifetime and C(V) measurements and additional FTIR and XPS spectroscopy. The fixed charges within the layers are found to be amphoteric. The interface trap density increases with carbon content in a-SiC x :H because of a lower hydrogen content at the a-SiC x :H/Si interface. The polarity of the fixed charge is depending on the presence of a metallic contact. As a-SiC x :H may be considered as a semiconductor, the a-SiC x :H/c-Si interface is in inversion regime at equilibrium inducing a band bending and accumulation when adding a metallic contact.
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