Surface passivation by atomic-layer-deposited Al 2 O 3 /TiO 2 stacks

A detailed study of the passivation quality of Al 2 O 3 and TiO 2 stacks on boron-doped emitters, where the stacks were deposited by thermal atomic layer deposition. The passivation quality was studied for different post-TiO 2 anneal temperature, as a function of Al 2 O 3 and TiO 2 layer thickness. For annealed Al 2 O 3 layers, as-deposited TiO 2 capping layer decreased emitter saturation current density considerably, which was more significant on Al 2 O 3 with thickness below 10 nm. However, post-TiO 2 deposition anneal in O 2 environment degraded the passivation, which was attributed to the increasing interface trap density in spite of increasing effective fixed charge density.