Monitoring MBE substrate deoxidation via RHEED image-sequence analysis by deep learning

Reflection high-energy electron diffraction (RHEED) is a powerful tool in molecular beam epitaxy (MBE), but RHEED images are often difficult to interpret, requiring experienced operators. We present an approach for automated surveillance of GaAs substrate deoxidation in MBE using deep learning based RHEED image-sequence classification. Our approach consists of an non-supervised auto-encoder (AE) for feature extraction, combined with a supervised convolutional classifier network. We demonstrate that our lightweight network model can accurately identify the exact deoxidation moment. Furthermore we show that the approach is very robust and allows accurate deoxidation detection during months without requiring re-training. The main advantage of the approach is that it can be applied to raw RHEED images without requiring further information such as the rotation angle, temperature, etc.Comment: 6 pages, 6 figure

EPICENTRE : innovations technologiques en épitaxie par jets moléculaires

National audienc

Time lapse - MBE32 LAAS-CNRS - EpiCentre

2021 marks the departure of two Riber molecular beam epitaxy racks from the LAAS-CNRS laboratory to the CEA in Grenoble. The vacated clean room space will house new equipment developed in the framework of the LabCom EpiCentre.Thanks to CEA teams et BOVIS.LabCom EpiCentre vidéo : Q.GRAVELIER / A.ARNOULT music : KeysOfMoon - TheEpicHer

Time lapse - MBE32 LAAS-CNRS - EpiCentre

2021 marks the departure of two Riber molecular beam epitaxy racks from the LAAS-CNRS laboratory to the CEA in Grenoble. The vacated clean room space will house new equipment developed in the framework of the LabCom EpiCentre.Thanks to CEA teams et BOVIS.LabCom EpiCentre vidéo : Q.GRAVELIER / A.ARNOULT music : KeysOfMoon - TheEpicHer

Engineering the anisotropy of AlAs wet oxidation using silicon implantation

International audienceWe investigate the influence of silicon implantation on wet lateral oxidation of AlAs and show that the introduction of n-type doping silicon ions permits the adjustment of the oxidation kinetics and anisotropy. Using mesas with selectively patterned implantation regions, we demonstrate the fabrication of oxide apertures unachievable using the standard process such as oxide lateral gratings whose pitch can range down to 4 µm and crosses with 40°-angle tips. This approach thus constitutes an easy and flexible way to engineer the oxidation process and opens the path to new confinement geometries for lateral confinement patterns in photonics devices and in particular VCSELs

Links between bismuth incorporation and surface reconstruction for GaAsBi growth probed by in situ measurements

International audienceBismuth incorporation and surface reconstruction have been studied simultaneously during GaAsBi growth by molecular beam epitaxy by means of in-situ wafer curvature monitoring and reflection high energy electron diffraction, respectively. Growth temperature and flux ratio have been varied successively. As/Ga atomic ratio close to the unity has been applied for the study of growth temperature effect. During the growth regime under the (1x3) reconstruction, Bi incorporation is found to be independent of the growth temperature, for temperatures where Bi desorption is insignificant. On the contrary, Bi incorporation becomes highly dependent on growth temperature as soon as the (2x1) reconstruction regime is reached. Only for the lower temperatures, the Bi incorporation gets to the same level during the (2x1) reconstruction than for the (1x3) reconstruction. When the As/Ga fux ratio is increased, bismuth incorporation is observed to decrease for GaAsBi growth in the (2x1) reconstruction regime. Our results indicate that the (1x3) and (2x1) surface reconstructions are always successively observed, and that an energy barrier has to overcome to transit from the (1x3) to the (2x1) reconstruction, this mechanism being temperature dependent. Finally, a difference in surface stress with reconstruction has been identified

Notice Technique : Procédure de sortie de molybloc de la chambre d'introduction réacteurs MBE 32 et MBE 2300

Dans la notice qui suit, nous allons présenter de manière détaillé la procédure à suivre afin de sortir un molybloc de la chambre d’introduction des réacteurs MBE32 et MBE2300 du LAAS-CNRS. Ce document sert d’appuis au personnel formateur pour la formation à l’utilisation autonomes des réacteurs

Notice Technique : Procédure d'entrée de molybloc dans la chambre d'introduction réacteurs MBE 32 et MBE 2300

Dans la notice qui suit, nous allons présenter de manière détaillé la procédure à suivre afin de de d’introduire un molybloc, depuis l’extérieur, dans la chambre d’introduction des réacteurs MBE32 et MBE2300 au LAAS-CNRS. Ce document sert d’appuis au personnel formateur pour la formation à l’utilisation autonomes des réacteurs

Anisotropy in the wet thermal oxidation of AlGaAs: influence of process parameters

International audienceThe crystallographic anisotropy of the lateral selective thermal oxidation ofAlGaAs alloys is experimentally studied. The anisotropic behavior of this oxidation process,used primarily for building a lateral confinement in vertical surface emitting lasers (VCSEL),is quantified by varying different process parameters and the geometrical shapes of laterallyoxidized mesa structures. This experimental study aims to have a better control of the oxideaperture shape used in oxide-confined photonics devices

Bi-assisted nucleation of GaAs grown on 5°off (001) silicon substrates by molecular beam epitaxy

International audienc