Study of passivation mechanisms induced by negative charge Al2O3 films

In the recent years, it was reported that surface passivation of crystalline solar cell with aluminum oxide (Al2O3) deposited by atomic layer deposition (ALD) seems to be a good candidate for surface passivation of c-Si Solar cells for both n-type and p-type Si due to its very high negative fixed charge density (Qf ~1012-1013 cm -2) in combination with a low level of interface state density (Dit). This paper assesses the study of passivation quality of Al2O3 deposited by Atomic Layer Deposition with two different technics: plasma-enhanced-atomic layer deposition (PE-ALD) and Thermal-atomic layer deposition (T-ALD). MOS-capacitors has been fabricated and characterized to extract the interface trap charge densities (Dit) at the silicon/Al2O3 interface and effective charge (Qf) in the dielectric. Lifetime measurements were performed with quasi-steady-state photo-conductance decay and transient methods to extract surface recombination velocity (SRV)