Fundamental Study of Si/SiO2 Quantum Well Structure for Wide Bandgap Si Solar Cells

With a view to controlling the bandgap of Si by the quantum confinement effect, we have developed Si/SiO
₂
nano-wall arrays, and succeeded in fabricating Si walls with width of several nm embedded in SiO
₂
. Application of nanoimprint process and anisotropic wet etching process enabled us to fabricate the nano-wall arrays with height of 3 μm. It was confirmed that this process is applicable to large substrates such as 6-inch wafers in principle. To study the bandgap widening of fabricated nano-wall arrays, photoluminescence spectroscopy measurement was performed. The result indicated that the bandgap widens as the Si wall width decreases.