Surface Passivation of Boron-Diffused p-Type Silicon Surfaces With (1 0 0) and (1 1 1) Orientations by ALD Al$_{2}$O$_{3}$ Layers

Boron-diffused p+/n/p+ and undiffused silicon samples with (1 0 0) and (1 1 1) orientations passivated by aluminum oxide (Al2O3) that is synthesized by atomic layer deposition (ALD) have been investigated. Emitter saturation current densities of ~24, 29, and 33 fA/cm2 were obtained for (1 0 0) samples with symmetrical 85Ω/□ B diffusions that were passivated by plasma-assisted, H2O-based, and O3-based ALD Al2O3, respectively. Compared with undiffused samples, it was found that the additional surface doping from the diffusion reduces recombination at the Al2O3/Si interface in the case of relatively low surface boron concentrations (