Atomic layer deposited dielectric and/or semiconducting oxide bilayers for crystalline silicon surface passivation

This study deals with the silicon surface passivation by thermal ALD deposited oxides bilayer of HfO2/Al2O3 as well as single layer of Al rich ZnO (AZO) in the form of ZnO and Al2O3 multilayers. A significant improvement in the effective minority carrier lifetime (τeff ~ 1.3ms) of n-type Si is observed after deposition of HfO2(5nm)/Al2O3(5nm)/Si compared to that of the single layer Al2O3(10nm)/Si (~0.6ms). Better surface passivation is due to a significant increase in the effective charge density in the bilayer system. Also, the sequence of the dielectric layers is found to play an important role in the quality and effectiveness of the passivation. Further, high τeff (~1.5ms) is also realized for p-type Si passivated by ALD deposited AZO films as compared to single layer of pure ZnO (~35μs) when annealed in hydrogen ambient at 450℃ for 30mins.