30-band k.p method for quantum semiconductor heterostructures

International audienceWe illustrate how the linear combination of zone center bulk bands combined with the full-zone k*p method can be used to accurately compute the electronic states in semiconductor nanostructures. To this end we consider a recently developed 30-band model which carefully reproduces atomistic calculations and experimental results of bulk semiconductors. The present approach is particularly suited both for short-period superlattices and large nanostructures where a three-dimensional electronic structure is required. This is illustrated by investigating ultrathin GaAs/ AlAs superlattices

Theoretical study of highly strained InAs material from first-principles modelling: application to an ideal QD

International audienceWe study the properties of highly strained InAs material calculated from first principles modeling using ABINIT packages. We first simulate the characteristic of bulk InAs crystal and compare them with both experimental and density functional theory (DFT) results. Secondly, we focus our attention on the strain effects on InAs crystal with a gradual strain reaching progressively the lattice matched parameters of InP, GaAs and GaP substrates. The final part is dedicated to the study of a hypothetic spherical InAs/GaP quantum dot. The effect of hydrostatic deformations for both InAs Zinc-Blende phase and InAs RockSalt phase is discussed

Predicting progression of mild cognitive impairment to dementia using neuropsychological data: a supervised learning approach using time windows

Background: Predicting progression from a stage of Mild Cognitive Impairment to dementia is a major pursuit in current research. It is broadly accepted that cognition declines with a continuum between MCI and dementia. As such, cohorts of MCI patients are usually heterogeneous, containing patients at different stages of the neurodegenerative process. This hampers the prognostic task. Nevertheless, when learning prognostic models, most studies use the entire cohort of MCI patients regardless of their disease stages. In this paper, we propose a Time Windows approach to predict conversion to dementia, learning with patients stratified using time windows, thus fine-tuning the prognosis regarding the time to conversion. Methods: In the proposed Time Windows approach, we grouped patients based on the clinical information of whether they converted (converter MCI) or remained MCI (stable MCI) within a specific time window. We tested time windows of 2, 3, 4 and 5 years. We developed a prognostic model for each time window using clinical and neuropsychological data and compared this approach with the commonly used in the literature, where all patients are used to learn the models, named as First Last approach. This enables to move from the traditional question "Will a MCI patient convert to dementia somewhere in the future" to the question "Will a MCI patient convert to dementia in a specific time window". Results: The proposed Time Windows approach outperformed the First Last approach. The results showed that we can predict conversion to dementia as early as 5 years before the event with an AUC of 0.88 in the cross-validation set and 0.76 in an independent validation set. Conclusions: Prognostic models using time windows have higher performance when predicting progression from MCI to dementia, when compared to the prognostic approach commonly used in the literature. Furthermore, the proposed Time Windows approach is more relevant from a clinical point of view, predicting conversion within a temporal interval rather than sometime in the future and allowing clinicians to timely adjust treatments and clinical appointments.FCT under the Neuroclinomics2 project [PTDC/EEI-SII/1937/2014, SFRH/BD/95846/2013]; INESC-ID plurianual [UID/CEC/50021/2013]; LASIGE Research Unit [UID/CEC/00408/2013

Diode GaAsP/GaP :Vers la photonique sur Silicium

National audienc

Développement de nanostructures sur silicium pour l'émission laser à grande longueur d'onde

National audienc

Super lattice band diagram calculation using 30 band k.p method

International audienceWe illustrate how the linear combination of bulk bands combined with a 30-band full-zone k.p method can be used to accurately compute the electronic states in semiconductor nanostructures. First applications for ultrathin GaAs/AlAs superlattices are presented and discussed

Growth and characterization of single phase GaP on Si(001)

PosterNational audienc

X-ray study of antiphase domains and their stability in MBE grown GaP on Si.

International audience90 and 20 nm thick GaP layers on Si substrate grown by various MBE growth modes are studied. A complete analysis is performed using AFM, TEM imaging and X-ray diffraction giving crucial information on structural defects properties and here particularly on antiphase domains. Thermodynamic evolution of antiphase boundaries is then discussed

Croissance par MBE de Boites quantiques InP sur GaP/Si

National audienc

Toward a light-emitter on Si: Growth of InAs and InP nanostructure on GaP substrate

International audienc