Fabrication of silicon nano-wall for bandgap control by quantum size effect

We have developed very thin silicon nano-walls with a view to applying them to wide bandgap silicon solar cells. Employing nanoimprint lithography, anisotropic wet etching, and oxidation techniques, we formed a nano-wall array on silicon wafers. The width and height of the walls fabricated were several nm and about 1 μm, respectively. The pitch of the array was 150 nm. Photoluminescence and cathodoluminescence measurements were carried out for these samples to evaluate the bandgap broadening by the quantum size effect. As a result, we obtained a characteristic signal relating to the silicon nano-wall structure. The origin of the signal was discussed on the basis of a model, and the bandgap broadening of the nano-wall was indirectly suggested.