Study of passivation mechanisms induced by negative charge Al2O3 films

Kotipalli, Raja Venkata Ratan [UCL] Delamare, Romain [UCL] Francis, Laurent [UCL] Flandre, Denis [UCL]

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).