Photonic band engineering in opals by growth of Si/Ge multilayer shells

The optimization of the procedure to grow accurate amounts of amorphous silicon and germanium by chemical vapor deposition (CVD) free of contamination in opals has been performed. The samples have been optically characterized and results agree with theoretical calculations of band structures. Multilayer systems of both semiconductors have been fabricated. Samples have been optically characterized and observed with a scanning electron microscope. Selective removal of germanium with aqua regia has proven to be possible. Theoretical calculations show that subtle variations of the topography may give rise to important effects (flat bands, pseudogap openings, etc). As an example, a photonic band structure with a complete photonic band gap between the 5 and 6 band has been provided along with a method to obtain it. It would be impossible to discuss all the possible structures that could be obtained from samples with different number of layers and materials forming them. However, there are many interesting topographies that could be fabricated in a relatively straightforward manner following the techniques described here.