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Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

Patients with Alzheimer’s disease after an initial response to cholinesterase inhibitors may complain a later lack of efficacy. This, in association with incident neuropsychiatric symptoms, may worsen patient quality of life. Thus, the switch to another cholinesterase inhibitor could represent a valid therapeutic strategy. The aim of this study was to investigate the effectiveness of the switch from one to another cholinesterase inhibitor on cognitive and affective symptoms in mild to moderate Alzheimer disease patients. Four hundred twenty-three subjects were included from the EVOLUTION study, an observational, longitudinal, multicentre study conducted on Alzheimer disease patients who switched to different cholinesterase inhibitor due either to lack/loss of efficacy or response, reduced tolerability or poor compliance. All patients underwent cognitive and neuropsychiatric assessments, carried out before the switch (baseline), and at 3 and 6-month follow-up. A significant effect of the different switch types was found on Mini-Mental State Examination score during time, with best effectiveness on mild Alzheimer’s disease patients switching from oral cholinesterase inhibitors to rivastigmine patch. Depressive symptoms, when measured using continuous Neuropsychiatric Inventory values, decreased significantly, while apathy symptoms remained stable over the 6 months after the switch. However, frequency of both depression and apathy, when measured categorically using Neuropsychiatric Inventory cut-off scores, did not change significantly during time. In mild to moderate Alzheimer disease patients with loss of efficacy and tolerability during cholinesterase inhibitor treatment, the switch to another cholinesterase inhibitor may represent an important option for slowing cognitive deterioration. The evidence of apathy stabilization and the positive tendency of depressive symptom improvement should definitively be confirmed in double-blind controlled studies.

International audience; Direct metal bonding represents an advanced joining technology that allows vertical stacking with electrical conduction and even heat dissipation. For most metals used as bonding layers, direct bonding when operating under ambient conditions involves metal oxides. The bonding interface saddles with a trapped oxide layer that might affect electrical conduction and even complete sealing of bonding interface. Titanium especially because of its high affinity with oxygen makes oxide free direct bonding very difficult. In the mean time, the remarkable getter effect of Ti matrix allows the dissolution of oxygen during post bonding annealing. In this paper, the bonding limits with regards to the titanium thickness have been investigated. The key role of layer roughness on the bonding quality and energy has been pointed out. A titanium thickness below 10 nm appears as a limit for an oxide free bonding in our conditions. (C) 2013 The Electrochemical Society.

International audience

We developed an InP-based photodetector which was bonded on a CMOS wafer containing a Si3N4-wiring photonic circuit. The detector fabrication is compatible with wafer scale processing steps, guaranteeing compatibility towards future generation electronic IC processing. Integration technology and experimental results are presented in this paper. © 2009 IEEE.

We present the design, fabrication and characterization of a compact photodetector suitable for photonic interconnections on electronic ICs. In our approach, the InP-based optical sources and detectors are linked via Si photonic waveguides in an interconnection layer on top of the CMOS circuitry. The photonic device processing is compatible with Si wafer scale fabrication steps, which guarantees compatibility with future ICs manufacture. The detector maskes use of an InP membrane waveguide to couple the light out of the interconnection layer and carry it towards the absorption region. A responsivity of 0.45 A/W and a rather flat frequency response in the 0-20 GHz range were measured.

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We demonstrate a compact photodetector suitable for photonic interconnections on electronic ICs. In such applications, the InP-based optical sources and detectors are linked via Si photonic waveguides in an interconnection layer on top of the CMOS circuitry. The photonic device processing is compatible with Si wafer scale fabrication steps, which guarantees compatibility with future IC manufacturing. In our approach, an InP membrane waveguide is used to couple the light out of the interconnection layer and carry it towards the detector absorption region. A responsivity of 0.45 A/W and an electrical frequency response 3-dB cut-off point at 15 GHz were measured.

We demonstrate an optical interconnection link on silicon. Compact InP-based micro-disk lasers and photodetectors (PDs) are connected via Si photonic waveguides on top of a Si wafer. The photonic devices are fabricated in a way compatible with wafer scale processing steps, guaranteeing compatibility towards future generation electronic IC processing. Device design, fabrication, integration scheme and preliminary measurements of the full optical link are described in this paper.

A new process was recently developed to manufacture silicon carbide on insulator structures (SiCOI). The process consists of several steps: (i) hydrogen implantation into an oxidised SiC wafer, (ii) bonding the oxidised surface of this wafer to an oxidised silicon substrate and (iii) high temperature splitting of a thin SiC film from the SiC wafer at the depth of the maximum hydrogen concentration and further annealing of the splitted film. The defect generation occurring during this process was investigated by synchrotron radiation X-ray diffraction topography, with special emphasis on to the last two steps. Various X-ray topographic techniques were used to characterise the lattice defects inside the SiC wafer, to quantify the strong lattice distortion near the edges of the splitted SiC film and to reveal SiC film regions lost during the splitting process. Moreover, we show that the strain fields of dislocations, observed in the silicon substrate after high temperature splitting and annealing of the splitted structure, induce a corresponding deformation in the thin SiC overlayer, despite the presence of the sandwiched oxide film. The defect density is much lower in the central region of the SiCOI structure.