GeOI photonic crystal cavities probed by room-temperature photoluminescence

We have investigated pure germanium two-dimensional photonic crystals. The photonic crystals which exhibit resonances in the near infrared spectral range were fabricated on germanium-on-insulator substrates using standard silicon-based processing. The germanium-on-insulator substrate consists of a thin layer of pure germanium-on-oxide deposited on a silicon substrate. The optical properties are probed by the direct band gap optical recombination of pure germanium at room temperature. Resonant optical modes are evidenced between 1600 and 1400 nm in L3 type cavities. The spectral position of the modes is controlled by the lattice periodicity and air filling factor of the photonic crystals. Close to the Ge band edge, the quality factors are limited by the bulk material absorption.