Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

International audienceThe growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20-200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results

Thermoelectric properties of InAs/InP nanostructures

International audienc

Local reactivity of metal-insulator-semiconductor photoanodes imaged by photoinduced electrochemiluminescence microscopy

International audienceLocalized photoinduced electrochemiluminescence (PECL) is studied on photoanodes composed of Ir microbands deposited on n-Si/SiO(x). We demonstrate that PECL microscopy precisely imaged the hole-driven heterogeneous photoelectrochemical reactivity. The method is promising for elucidating the local activity of photoelectrodes that are employed in solar energy conversion

Investigation des propriétés optiques des microdisques de phosphure de gallium

National audienc

High stability of a MBE grown GaAs/Si photocathode for solar H2 production.

International audienc

Performance of epitaxial GaAs/Si vs GaAs photocathodes for solar hydrogen production.

International audienc

Impact of Antiphase Boundaries on Non-linear Frequency Conversion in GaP/Si Microdisks

International audienc

Excitons bounded around In-rich antiphase boundaries

International audienceWith the combination of the mature silicon-microelectronic technology and the advantages of optical data processing, silicon photonics becomes more and more essential for future low-cost, high-speed technology[1]. The antiphase boundaries (APBs), which are believed to be detrimental defects for optical devices, have always been seen as one of the tough hurdles for the development of silicon photonics[2]. However, in this work we provided a new insight into the APBs which are involved in an efficient luminescence process. Temperature-and power-dependent photoluminescence (PL), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) elemental mapping techniques have been employed for a thorough analysis of APBs' contribution to optical and structural properties of an InGaP/SiGe/Si sample. The main PL peak is attributed to the recombination of excitons bounded around the neutralized In-rich APBs[3], which behave as vertical nanostructures. This scenario is in good correlation with previous theoretical works[4]

Photoelectrode/Electrolyte interfacial band lineup engineering with alloyed III-V thin films grown on Si substrate.

International audienceIn this work, we demonstrate how the classical concept of band gap engineering usually used in III–V semiconductor devices can be extended to the engineering of the band lineup between semiconducting photoelectrodes and electrolytes. The performances of photoelectrodes made of GaP1−xAsx epilayers in the full compositional range and grown on low-cost Si substrates were studied and compared with those of photoelectrodes grown on GaAs and GaP substrates. We first show that the changes of incident photon to current conversion efficiency (IPCE) with the As content in GaP1−xAsx alloys are related to the band gap nature (direct or indirect) and band gap energy variations. Then, from flat band potential measurements during Mott–Schottky experiments, valence and conduction band energies of GaP1−xAsx alloys are positioned versus the reversible hydrogen potential. A weak change of conduction band energies and a large evolution of valence band energies are obtained, in good agreement with expected theoretical trends. Such results show that both band gaps and semiconductor/electrolyte band lineups can be engineered through alloying of III–V semiconductors deposited on silicon substrates. This band lineup engineering strategy is expected to be of great interest to address specific redox reactions in the electrolyte, provided that suitable protecting or passivating layers can be used to limit surface/interface recombinations

Carbon nanotubes incorporated-hybrid waveguides for photonics applications

International audienceSemiconducting carbon nanotubes (CNT) exhibit large nonlinear- and strong quasi-one dimensional excitonic optical properties. Their integration in integrated waveguides could lead to very efficient light-emitting devices or optical signal processing functions. We described the fabrication and optical characterization of hybrid planar waveguides incorporating CNT. Ways of further enhancing light interaction with the CNT namely ridge waveguides processing and CNT alignment are also presented