InAs Quantum Boxes: Active Probes For Air/GaAs Photonic Bandgap Microstructures

Abstract

Important technological efforts have been made in the last five years for implementing the concept of photonic bandgap (PBG) crystals [1] in the optical frequency range. Air/semiconductor crystals are very attractive in view of a monolithic integration in optoelectronic integrated circuits (OEICs), because their large modulation of the refractive index potentially allows to obtain large PBGs for each or eventually both polarizations of light. In order to display a PBG in the near-infrared, the period P of such crystals must however be scaled down to submicron sizes. Photonic properties are very sensitive to the porosity of the crystal as well as to some details of its pattern, which makes the demands in terms of regularity and uniformity difficult to satisfy even for state of the art microfabrication techniques. For instance, the dry etching in a single step of 3D [2] or 2D [3–5] PBG crystals illustrates the current limits of etching techniques: the deviations from a perfect anisotropy limit the depth of good quality crystals to typically 1 µm. Concerning alternative approaches now, the electrochemical etching of deep 2D crystals, which is very successful in the mid-infrared (P≈8 µm) [6], might prove difficult to implement in the near-infrared due to the thinness of the semiconductor sidewalls. Finally, imperfect mask alignment will also plague planar period by period fabrication of 3D PBG crystals [7]. Hopefully, thin 2D PBG crystals are in principle sufficient for most potential applications of PBG crystals in OEICs. Hybrid 3D microcavities formed by a 2D PBG crystal sandwiched by two bragg mirrors have also been proposed as a route toward full spontaneous emission control [3]. The structural quality of thin 2D PBG crystals fabricated by electron-beam lithography and reactive ion etching [3,5] is presumably already good enough to test these proposals.