Abstract
In the past decades, Si has been the most important material for electronics. By exploiting this mature semiconductor
fabrication technique, it is also highly desired to use Si for applications in other areas. Here we report the use of Si
micro-structures for optical-communications and Si nano-structures for energy applications. Sub-micron Si waveguides
is fabricated on Si substrates rather than SOI (silicon on insulator) substrate using laser reformation technique. This
method helps solve the incompatible problem for the integration of optics and electronics on a single Si chip. The typical
thickness of the oxide layer on the CMOS transistor layer is below 100nm which, however, creates excessive optical loss
due to the light coupling into Si substrate. Besides, fabricating Si photonics on Si wafer is much cheaper than that on SOI
wafer. The method is using high-power pulse laser to melt high-aspect ratio Si ridges. This creates a structure with wider
upper portion and narrower lower portion, which can be further oxidized and forming waveguides. For energy
applications, Si nanostructures are fabricated using the metal-assisted chemical etching (MacEtch) technique. Si
nanostructures could greatly reduce the surface reflection to enhance light harvest. In addition, Si nanowires are further
combined with organic materials to form hetero-junction solar cells using low-cost solution process. Furthermore, the Si
nanostructures and MacEtch process are refined to form completely single-crystal Si thin film. Thus the material cost of
Si solar cells can be potentially reduced to only 1/10 of current ones.
