Heteroepitaxial bonding of Si for hybrid photonic devices
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Heteroepitaxial bonding of Si for hybrid photonic devices Eric Le Bourhis1, Anne Talneau2, Isabelle Sagnes2, Gilles Patriarche2, Ludovic Largeau2 and David Troadec3 1 Institut P’, CNRS - Université de Poitiers – ENSMA - UPR 3346, SP2MI-Téléport 2-Bd Marie et Pierre Curie, B.P. 30179, 86962 Futuroscope-Chasseneuil Cedex, France. 2 Laboratoire de Photonique et de Nanostructures, UPR 20 CNRS, Route de Nozay, 91460 Marcoussis, France. 3 Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), Avenue Poincaré, 59652 Villeneuve d'Ascq cedex, France ABSTRACT New fabrication routes for hybrid photonic devices are explored. We report on silicon bonding to III-V semi-conducteurs e.g. Si/InP for emission/amplification function. The materials have been bonded to silicon since it can be nanostructured to obtain optical guides. The bonded surfaces are of the order of ~ 1 cm2. Special attention has been paid to the surface preparation. The obtained structure has been characterized employing XRD while the mechanical response and interface strength have been investigated employing instrumented nanoindentation. INTRODUCTION The future of integrated optics will be on silicon, not only as a motherboard where all the individual devices are stick on, but to take advantage of the excellent performances of silicon on insulator -SOI- optical waveguides at the telecom wavelengths. Hybrid integration of III-Vbased materials, especially InP-based materials, on Silicon is the best choice for emission/amplification at 1.55 µm. InP dies are bonded on a SOI wafer, and then processed to fabricate devices lithographically aligned to the underneath silicon waveguide. Bonding of III-V materials on Si is always performed including an intermediate amorphous layer. CEA-Leti has developed a molecular bonding including a SiO2 intermediate layer [1]. A thin native oxide layer is used in the realization of Bowers’ group in Santa Barbara, leading to interesting results for integrated lasers and amplifiers [2]. The approach including a BCB intermediate layer has been developed in the University of Ghent, with successful results [3]. Including an intermediate bonding layer composed of a dielectric material, thus amorphous, with a poor thermal conductivity could not be favorable for devices performances. Although, this layer will degrade any nano-structuration which could be realized on the Si substrate and such a nano-structuration could be beneficial for the behavior and performances of the integrated devices. On producing bonding without any intermediate layer, it is mandatory that all bonds at the interface be reconstructed in order to preserve the crystalline properties and nanostructuration of each material. In order to characterize the membrane and interface strengths, the nanoindentation technique has proved to be of great help. This technique allows testing structured materials as well as interfaces since the probe size can be scaled to the studied object adjusting the load applied to the indenter [4]. We report on heteroepitaxial bon
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