Surface passivation by atomic-layer-deposited Al2O3/TiO2 stacks

A detailed study of the passivation quality of Al₂O₃ and TiO₂ stacks on boron-doped emitters, where the stacks were deposited by thermal atomic layer deposition. The passivation quality was studied for different post-TiO₂ anneal temperature, as a function of Al₂O₃ and TiO₂ layer thickness. For annealed Al₂O₃ layers, as-deposited TiO₂ capping layer decreased emitter saturation current density considerably, which was more significant on Al₂O₃ with thickness below 10 nm. However, post-TiO₂ deposition anneal in O₂ environment degraded the passivation, which was attributed to the increasing interface trap density in spite of increasing effective fixed charge density.