Waveguide Photonic Microstructures in III-V Semiconductors

Photonic microstructures are a class of periodic dielectric structures which could lead to a significant evolution in optoelectronic devices. There are, however, several problems with photonic crystals, not least of which is the fabrication of these artificial structures. The fabrication of these artificial crystals in III-V semiconductor materials, specifically optical waveguide heterostructures, have been investigated. Improvements in the fabrication of GaAs/AlGaAs photonic bandgap structures have been made and the development of an AlAs epitaxial layer as a pattern transfer mask has been demonstrated. Two-dimensional photonic bandgap structures have been characterised and good agreement has been obtained between theory and experimental measurements. Subsequently, semiconductor microcavities incorporating photonic bandgap mirrors have been fabricated with mirror reflectivities higher than 90% and high mode Q factors, Q≈500. The results indicate that photonic bandgap technology has the potential to provide the desired engineering of the environment of a light emitter which will allow control of the emission process. The microstructuring of the material, however, creates significant obstacles to electroluminescence and much research in this area is required if any benefit of photonic microstructures are to be seen