INTERFACE ISSUES OF ALL-PECVD SYNTHESIZED ALOX/SINX PASSIVATION STACKS FOR SILICON SOLAR CELLS

摘要

The interface passivation of a-AlOx/a-SiNx:H stacks deposited on p-type silicon by in-line plasmaenhanced chemical vapor deposition is investigated by means of charge carrier lifetime, field dependent surfacephotovoltage and capacitance voltage measurements as well as Fourier transform infrared spectroscopy. To controlthe quality of the interface, we performed different wet chemical surface preparation steps prior to a-AlO_x/a-SiN_x:Hstack deposition. Our investigation is focusing on the interface passivation upon post-deposition thermal treatmentssuch as annealing at 425 °C and firing at 860 °C as applied in the silicon solar cell industry. We demonstrate that theinterface recombination is mainly controlled by the interface state density as demonstrated by the correlation betweenthe surface recombination velocity and interface state density inferred from lifetime and SPV measurements. Theincrease of the negative charge density after thermal steps as revealed by capacitance-voltage measurementscorrelates with the increase of the density of negatively charged AlO_4 tetrahedra as revealed by infrared spectroscopysuggesting that the tetrahedrally coordinated Al contribute to the formation of the negative charge.