Oxidation precursor dependence of atomic layer deposited Al(2)O(3) films in a-Si:H(i)/Al(2)O(3) surface passivation stacks

In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al(2)O(3) stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al(2)O(3) film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al(2)O(3) stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al(2)O(3) stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(−2) eV(−1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(−2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al(2)O(3) deposition on Al(2)O(3) single layers and a-Si:H(i)/Al(2)O(3) stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.