Submicrometer scale growth morphology control for the making of photonic crystal structures
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Submicrometer scale growth morphology control for the making of photonic crystal structures E. Gil-Lafon 1, A. Trassoudaine 1, D. Castelluci 1, A. Pimpinelli 1, R. Saoudi 2, O. Parriaux 2, A. Muravaud 2, C. Darraud 3 1 LASMEA UMR CNRS 6602, Université Blaise Pascal, Campus Universitaire des Cézeaux, 63177 Aubière Cedex, France 2 LTSI UMR CNRS 5516, 23 rue du Docteur Paul Michelon, 42023 Saint-Etienne Cedex 02, France 3 IRCOM UMR CNRS 6615, Université de Limoges, 123 avenue A. Thomas, 87060 Limoges Cedex, France
ABSTRACT The feasibility of micrometer scale dielectric periodic structures by using a single selective hydride vapour phase epitaxy (HVPE) step was assessed. HVPE is a near-equilibrium growth process which offers perfect selectivity whatever the pattern design, thus giving rise to a great flexibility. The HVPE growth is also mainly governed by the intrinsic anisotropy of the surface kinetics of the crystal. We demonstrate here that micrometer scale dielectric periodic structures, constituted of perfectly defined 1µm wide GaAs beams alternately stacked with air, can be grown by selective HVPE by controlling the hierarchy of the growth rates of the low index faces of the III-V crystal via the growth temperature and the composition of the vapour phase. Potential of the HVPE growth technic for the making of submicrometer scale structures is finally discussed.
INTRODUCTION Since Yablonovitch’s original idea consisting in building periodic material arrangements in which propagation of photons within particular energy ranges could be forbidden, the study of photonic band gap (PBG) or photonic crystals (PC) have moved from curiosity to theoretical and application maturity [1]. The making of artificial optical structures reveals itself an exciting technical challenge : one must generate one-dimensional (1D), and preferentially twodimensional (2D) and three-dimensional (3D) ordered structures presenting periodically modulated refractive index with low absorption and controlled inclusion of defect states for confinement. The key problem relies on the technical feasibility of these PC micro- and nanostructures with a view to reliable industrialized process routes. Today microstructuring techniques permit the making of high quality optical materials with a significant flexibility. The most common approach for generating 1D (multilayer stack alternating high and low refractive indices) or 2D (periodic patterns of air-holes embedded in a matrix) PC semiconductor structures involves optical UV beam contact and projection lithography, electron and ion beam lithography, X-ray lithography and advanced etching techniques on a deep submicron scale. Electron-beam (e-beam) and X-ray lithographies are used to define masks with submicrometer and nanometer scale periodic features on a substrate such as silicon or III-V semiconductors such as GaAs or InP that present high-dielectric constants (3.5(110) so that a beam-like shape morphology shoud be developed for [1-10] oriented stripes [6]. SEM pictures of sample 2 are displa
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