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A beneficial effect of argon (Ar) ion bombardment for crystalline silicon (c-Si) surface passivation has been studied. Experiments of an Ar plasma treatment over an hydrogenated amorphous silicon (a-Si:H) layer grown on c-Si are performed, where an a-Si:H layer is prepared at different levels of defect density. Interestingly, the c-Si surface passivation is improved by an Ar plasma treatment for a defect-rich, i.e. low-quality, a-Si:H layer, while it is deteriorated by the treatment for a low-defect, i.e. high-quality, a-Si:H layer. The improvement of passivation is discussed in terms of microstructural changes of a-Si:H, associated with redistribution of hydrogen, where mobile hydrogens play an important role.

Interface defects in state-of-the-art semiconductors have a strong impact on device performance. These defects are often generated during device fabrication, in which a variety of plasma processing is used for deposition, etching and implantation. Here, we present the ion-induced defects in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) heterojunction. The experiments of argon ion (Ar+) irradiation over an a-Si:H/c-Si stack are systematically performed. The results suggest that the defects are generated not only by the impact of Ar+ (i.e. well-known effects), but also by another unique effect associated with “hot” mobile hydrogens (H). The mobile H atoms generated near the a-Si:H surface by the impact of Ar+ diffuse deeper, and they generate the a-Si:H/c-Si interface defects such as dangling bonds. The diffusion length of mobile H is determined to be 2.7 ± 0.3 nm, which indicates efficient reactions of mobile H with weak bonds in an a-Si:H network structure.

Passivating antireflection coating of crystalline silicon has been experimentally studied using a three-layered stack, consisting of an i/n a-Si:H/SiN trilayer. The passivation property is characterized by the minority carrier lifetime, which shows ≳ 1 ms for the i/n a-Si:H/SiN trilayer prepared at a temperature as low as 250 ∘C. The antireflection property is confirmed by a reflection of light of ≲ 2.0% at 550 nm and a low reflection in a wide range of visible and near-infrared regions, which is adequate for solar cell application, particularly in back-contact structure. The roles of each layer are discussed in terms of the chemical and field-effect passivation as well as the antireflection property. The optoelectronic properties of a neat SiN layer are also discussed to achieve a stable and reliable antireflection performance under the low-temperature growth conditions.