Photonic Bandgap Engineering in Germanium Inverse Opals by Chemical Vapor Deposition

Germanium inverse opals with a full photonic bandgap in the NIR region are accessible by CVD. Deposition of digermane on sintered opals made of silica microspheres, followed by removal of the silica by etching, yields inverted Ge opals (see Figure for an SEM image of a cleaved edge, revealing the Ge layer) whose lattice parameters, network topology, and Ge coating thickness determine the optical properties of the inverse Ge opal.