On the impact of interfacial SiOx-layer on the passivation properties of PECVD synthesized aluminum oxide

The interface passivation of a -AlOx/a -SiNx:H stacks deposited on p-type silicon by plasma enhanced chemical vapor deposition is investigated by means of charge carrier lifetime and surface photovoltage measurements. To control the quality of the interface, we performed different surface preparation steps prior to a -AlOx/a -SiNx:H stack deposition. Our investigation is focussing on the interface passivation upon post-deposition thermal treatments such as annealing at 425 °C and firing as applied in the silicon solar cell industry. We demonstrate that the interface recombination is mainly controlled by the interface state density as demonstrated by lifetime and SPV measurements. The increase of the negative charge density after thermal steps as revealed by FTIR spectroscopy evidences that the field effect has at least an enhancing effect in improving the passivation level (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)