Marie Lesecq

All-optical tunability of InGaAsP/InP microdisk resonator by infrared light irradiation

We report the optical characterization of an InP structure constituted by waveguides coupled to microcavity disk resonators. The lateral waveguide confinement is obtained by deep reactive ion etching through the guiding layer. We demonstrate the possibility of tuning optically the resonance wavelength into the illuminating disk resonator. We obtained a blueshift of 3 nm by laser irradiation at 980 nm corresponding to a photoinduced change in the effective refractive index of 6 x 10(-3). The InP structure behaves as a tunable optical demultiplexer.

Power Performance at 40 GHz of AlGaN/GaN High-Electron Mobility Transistors Grown by Molecular Beam Epitaxy on Si(111) Substrate

This letter reports on the demonstration of microwave power performance at 40 GHz on AlGaN/GaN high-electron mobility transistor grown on silicon (111) substrate by molecular beam epitaxy. A maximum dc current density of 1.1 A· mm-1 and a peak extrinsic transconductance of 374 mS · mm-1 are obtained for 75-nm gate length device. At VDS = 25 V, continuous-wave output power density of 2.7 W · mm-1 is achieved at 40 GHz associated with 12.5% power-added efficiency and a linear power gain (G p) of 6.5 dB. The device exhibits an intrinsic current gain cutoff frequency FT of 116 GHz and a maximum oscillation frequency FMAX of 150 GHz. This performance demonstrates the capability of low cost microwave power devices up to Ka-band.

Optimization of

In this paper, we propose to optimize Al0.29Ga0.71N/GaN heterostructures on silicon substrate to obtain high electron mobility transistors featuring high-power/frequency performances. The polarization electric fields are engineered by varying the layer thicknesses of the cap and the barrier, and by changing the type of buffer (GaN or AlGaN). The aim of this paper is to find the best tradeoff between the active layer thickness reduction and the achievement of a reasonable drain current to satisfy the requirements for high performances. The optimum heterostructure device presents an output power density of 1.5 W/mm at 40 GHz, among the best reported on silicon substrate.

{\rm Al}_{0.29}{\rm Ga}_{0.71}{\rm N}/{\rm GaN}

This letter provides an experimental demonstration of high-performance industrial MOSFETs thinned down to 5.7 μm and transferred onto a 125-μm-thick polyethylene naphthalate foil. The die stack transferred onto the organic substrate comprises the 200-nm-thick active layer and the 5.5-μm-thick interconnection multilayer stack resulting in a light, compact, and bendable thin film. We unveil that dc and RF performances are invariant even for ultimate thinning down to the buried oxide layer. Furthermore, n-MOSFET performance is improved by 1.5× compared with previous work, and the first demonstration of 100-GHz p-MOSFETs on an organic substrate is presented. Unity-current-gain cutoff and maximum oscillation frequencies as high as 150/160 GHz for n-MOSFETs and 100/130 GHz for p-MOSFETs on a plastic substrate have been measured, respectively.

High Electron Mobility Heterostructures for High-Power/Frequency Performances

The ability to realize flexible circuits integrating sensing, signal processing, and communicating capabilities is of central importance for the development of numerous nomadic applications requiring foldable, stretchable, and large area electronics. A key challenge is, however, to combine high electrical performance (i.e., millimeter wave, low noise electronics) with mechanical flexibility required for chip form adaptivity in addition to highly stable electrical performance upon deformation. Here, we describe a solution based on ultimate thinning and transfer onto a plastic foil of high frequency CMOS devices initially processed on conventional silicon-on-insulator wafers. We demonstrate a methodology relying on neutral plane engineering to provide high performance stability upon bending, by locating the active layer, i.e., the transistor channel, at the neutral fiber of the flexible system. Following this strategy, record frequency performance of flexible n-MOSFETs, featuring fT/fMAX of 120/145 GHz, is ...

150-GHz RF SOI-CMOS Technology in Ultrathin Regime on Organic Substrate

We report on the characterization of an InP/InGaAsP-material-based microdisk resonator optical filter. The originality here is constituted by the use of a localized control electrode that is used for the tuning of the resonance wavelength of the filter via the injection of a driving current. Tuning of the resonance wavelength close to 8 nm has been experimentally achieved for a drive current of 80 mA.

A converging route towards very high frequency, mechanically flexible, and performance stable integrated electronics

We report on a new type of optical switch based on submicron structures and present the results obtained on the first nanophotonics based optical switch. First, we present results obtained on passive components that are required in an optical switch or switching matrix: straight waveguides, bend waveguides and Y junctions. Measured propagation loss are lower than 1dB/mm for waveguides wider than 1&mgr;m. Excess bending loss is 1dB for curvature radius as small as 30&mgr;m. Loss due to branching angle in a Y junction is 2dB for angle as wide as 20°. Optical switch design is based on two dissymmetric DOS like active junctions; theoretical crosstalk is 28dB, 14dB for each junction. We present the technological process to realize this active component. Finally, we report on the first characterization of a single Y junction a crosstalk of 11dB.

Wide electrical tunability of a GaInAsP/InP microdisk resonator

In this paper, we propose to take advantage of specific properties of nanophotonics to achieve microwave functions which are difficult to get with more conventional ways. With this goal, we developed new technologies to fabricate III-V nanowaveguides. Two ways were explored: the first one by deep etching of conventional epitaxies and the second one by embedding nanowires in polymer. We show in this paper some results on first devices mainly based on nanowires embedded in polymer.

Optical switch using InP optical wire technology

This letter reports on a new method for the characterization of transistors transient self-heating based on gate end-to-end resistance measurement. An alternative power signal is injected to the device output (between drain and source) at constant gate-to-source voltage. The dependence of gate resistance with temperature is used to extract the thermal impedance of the device in frequency domain via electrical measurement. This new method is validated on common-gate AlGaN/GaN high-electron-mobility transistors on Si substrate under different experimental conditions, which demonstrates its potential to provide complete dynamic self-heating models for power transistors.

Optical Nanowires for Microwave Applications

The role that the mother substrate plays to influence the performance of InGaN/GaN-based light-emitting diodes (LEDs) onto the adhesive flexible tapes is addressed in this letter. For this purpose, the electroluminescent (EL) spectra and current density-voltage (J-V) characteristics of flexi-LEDs are studied under different convex bending configurations (from a curvature radius of infinity to 1.4 cm), showing only one peak around 442 nm in all the cases. Both the EL spectra and J-V characteristics are affected by the applied tensile stress when the flexi-LED is bent. In fact, an increase of the applied tensile strain from 0.02% to 0.09% results in a red-shift of the EL peak energy by 3 meV at 0.7 mA, and a drop of the current at high forward bias. In addition, such flexi-LEDs exhibit a reversible response when a significant mechanical deformation is applied.