Scanning transmission electron microscope analysis of amorphous-Si insertion layers prepared by catalytic chemical vapor deposition, causing low surface recombination velocities on crystalline silicon wafers

Abstract

Microstructures of stacked silicon-nitride/amorphous-silicon/crystalline-silicon (SiNx/a-Si/c-Si) layers prepared by catalytic chemical vapor deposition were investigated with scanning transmission electron microscopy to clarify the origin of the sensitive dependence of surface recombination velocities (SRVs) of the stacked structure on the thickness of the a-Si layer. Stacked structures with a-Si layers with thicknesses greater than 10 nm exhibit long effective carrier lifetimes, while those with thin a-Si layers have very short effective carrier lifetimes. A remarkably close correlation was found between the dependence of interface structures on the thicknesses of a-Si layers and the SRVs. In samples with a-Si layers less than 10 nm thick, significant damage occurred in c-Si wafers close to the interfaces, while those near a-Si layers larger than 10 nm remained nearly defect-free during observations over long periods. The observation of stacked structures without an SiNx layer, along with energy dispersive spectroscopy and secondary ion mass spectroscopy analyses of nitrogen atom distributions, suggest that the preferential damage in c-Si wafers with thin a-Si layers is caused by nitrogen atoms in the interface regions of c-Si wafers that diffuse during the growth of SiNx layers.

Minority Carrier Recombination Properties of Crystalline Defect on Silicon Surface Induced by Plasma Enhanced Chemical Vapor Deposition

“…The dark contrast in this study is similar to the results found in damage formation promoted by nitrogen atoms during electron beam irradiation. 26,27 Nitrogen atoms were introduced into the silicon substrates during PECVD process and the crystalline defect might be formed by electron irradiation. On the other hand, hydrogen atoms could be introduced into the near-surface region of silicon substrates during the plasma process.…”

Toward Efficiency Limits of Crystalline Silicon Solar Cells: Recent Progress in High‐Efficiency Silicon Heterojunction Solar Cells

“…[23] Another technique that has been used for SHJ production is catalytic chemical vapor deposition (cat-CVD). [24] TCO layers on the front and rear sides are deposited by a physical vapor deposition process (PVD), either magnetron sputtering or reactive plasma deposition. Finally, the electrodes are made by methods such as screen printing, where a low-temperature curing silver paste is usually printed.…”

“…The plasma-free CVD deposition such as cat-CVD has been used to deposit high-quality passivation layers. [24,127] The thickness and sharpness of the epitaxial layer on the surface of c-Si can be determined by using conventional high-resolution TEM (HRTEM). [117,124,128] According to an investigation by Matsumura et al, the cat-CVD can realize very sharp a-Si:H/c-Si interfaces and thin transition-layers from c-Si to a-Si:H (<0.6 nm), which is 1.8 nm for PECVD.…”

Cat-doping: Novel method for phosphorus and boron shallow doping in crystalline silicon at 80 °C

“…14 All these experiments including the present Cat-doping demonstrates that foreign atoms can be incorporated into c-Si at low temperatures when it is exposed to species generated by catalytic cracking reactions with heated W catalyzer. Although the mechanism is not clearly explained, it is clear that the phenomena concerned with low-temperature doping surely exist.…”