S. Pocas’s research while affiliated with Atomic Energy and Alternative Energies Commission and other places

In microelectronics, photonics, opto-electronics, high frequency or high power device applications, the needs for specific substrate solutions are more and more required. Smart Cut™ technology appears as the technological answer that enables the industrial to provide engineered substrate solutions tailored to the applications. For instance a large spectrum of SOI type structures are today in volume manufacturing. At present the industrial is focused on composite substrates. This paper focuses on the realization of advanced SOI, strained SOI, SOQ substrates and many other examples of engineered substrates. Highlights are given on the most recent developments.

We show that it is possible to combine both silicon on insulator and strained silicon structures, which are usually considered as independent solutions to improve the performance of silicon-based CMOS transistors. Using Raman spectrometry and electron microscopy, we studied one kind of virtual Si1−xGex substrate produced by reduced pressure-chemical vapor deposition, and the strained silicon thin film grown on top of this substrate. These structures are transferred on a silicon substrate using the SMART CUTTM process to form strained silicon on insulator wafers (SSOI). The main result is that the overlayers in the silicon on insulator structures keep the same stress than they had before transfer. The stress, measured in SSOI wafers with Si layers as thin as 10 nm, is not affected by high temperature annealing up to 1000 °C.

Strained Silicon On Insulator wafers are today envisioned as a natural and powerfulenhancement to standard SOI and/or bulk-like strained Si layers. For MOSFETs applications, thisnew technology potentially combines enhanced devices scalability allowed by thin films andenhanced electron and hole mobility in strained silicon. This paper is intended to demonstrate byexperimental results how a layer transfer technique such as the Smart Cut™ technology can be usedto obtain good quality tensile Strained Silicon On insulator wafers. Detailed experiments andcharacterizations will be used to characterize these engineered substrates and show that they arecompatible with the applications.

The general objective of this presentation is to demonstrate the great potential of two dimensional (2D) Photonic Crystals (PC) based on InP-membranes bonded onto silica on silicon substrates, with a special emphasis on the development of various classes of 2D PC microlasers. The basic building block consists in an InP (and related material) membrane including a 2D PC formed by a lattice of holes : the membrane is bonded onto low index material,e.g. silica on silicon substrate, in the prospect of heterogeneous integration with silicon based microelectronics. Examples of devices will be presented, specifically micro-lasers based on 2D PC micro-cavities as well as on 2D in plane and surface emitting Bloch modes (2D Distributed-Feed-Back micro-laser).

The SmartCut process was first developed to obtain silicon-on-insulator (SOI) materials. Now an industrial process, the main Unibond SOI-structure trends are reported in this paper. Many material combinations can be achieved by this process, because it appears to enable the generic development of new structures. Several of the new structures combining different materials and different bonding layers are described. These include SiGe and strained-Si films onto an oxidized Si wafer, silicon-on-insulating multilayer (SOIM) structures, and InP or 4H-SiC film transfers onto low-cost substrates via metallic or even refractory conductive-film bonding layers. More recently, an original bonding process based on mark patterning, wafer bonding, and layer transfer has been proposed to obtain structures in which the relative crystalline-axis orientations of both the film and the substrate can be controlled accurately. In this case, a SmartCut process that includes a mark-patterning step appears well suited for precise control of axis orientations. A procedure is described to obtain an ultra-thin Si film bonded onto a Si wafer. An example of a pure screw-dislocation network achieved by the mark patterning, bonding, and layer-transfer process is reported in this paper. The results have important implications for nanostructure development.

We report on 2D photonic crystal InP membrane micro-lasers transferred onto a silicon wafer. Two types of lasers are investigated: microcavities and defect-free structures, exploiting either conventional defect modes, or DFB-like modes. Room temperature low threshold laser operation has been performed for low sized devices.

We report results on hexagonal-shaped microlasers formed from two-dimensional photonic crystals (PCs) using InP-based materials transferred and bonded onto SiO₂/ Si wafers. Two types of hexagonal cavities are investigated : single defect (one hole missing) cavities, so-called H1 cavities (1 μm in diameter) and two holes missing per side H2 cavities (2 μm in diameter). Their optical properties are analyzed using photoluminescence experiments, and plane wave method simulations have been performed for comparison. High Q modes (∼600/700) have been measured and they have been shown to enable laser effect at room temperature, under pulsed optical pumping (15% duty cycle and 25-ns pulsewidth). The study of these efficient mode characteristics gives guidance for further improvement of the operation conditions of PC lasers, such as the reduction of the threshold pumping power.

We present simulation and experimental results on hexagonal-shaped microcavities formed in two-dimensional (2D) photonic crystals (PC’s). The PC structures, realized with InP-based materials, are studied in two configurations : Air-suspended membranes (A type) and membranes supported by silica (S type). The optical properties of these microcavities are analyzed through photoluminescence experiments. Plane-wave expansion method calculations provide simulation results that are consistent with experimental data. The influence on spectral properties of various parameters, such as cavity size or air filling factor (f), is thoroughly analyzed, and their effect on resonator loss mechanisms is extracted, to give guidance for further PC laser improvement, e.g., threshold reduction. © 2003 American Institute of Physics.

Defectless two-dimensional photonic crystal structures have been fabricated by drilling holes in a thin multi-quantum-well InP-based heterostructure transferred onto a silicon host wafer. Extremely low group velocity modes, which correspond to the predicted photonic valence band edge, have been observed for different filling factors. Under pulsed optical pumping, room temperature laser operation around 1.5 mum has been achieved on these structures with a threshold in the milliwatt range. (C) 2002 American Institute of Physics. [DOI: 10.1063/1.1532554].