GaAs Photonic Crystals on SiO₂ Fabricated by Very-High-Frequency Anode-Coupled Reactive Ion Etching and Wafer Bonding

High-aspect-ratio, two-dimensional (2D) air-column GaAs photonic crystals (PhCs) on SiO₂ layers with a lattice constant ranging from 240 nm to 1.0 µm have been fabricated using a novel method combining wafer bonding and low-temperature very-high-frequency (VHF) reactive ion etching (RIE). The obtained PhCs exhibit near-field patterns of sixfold symmetry or fourfold symmetry due to lateral interference, depending on the lattice structure. We have obtained photoluminescence (PL) spectra of PhCs which reveal the low damage feature of the combined process of low-temperature RIE and wafer bonding. Reflectance spectra exhibit fine structures which originate from the resonance coupling of the external light to the zone-folded bands of the photonic structure. This vertical confinement structure, obtained by forming GaAs PhCs on SiO₂, is useful for taking advantage of 2D photonic crystals since it prevents photon dissipation from the lattice plane. The fabrication method combining low-temperature RIE with wafer bonding is a promising process for developing 2D photonic crystals on SiO₂ layers.