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Offers : 101

Study of sidewall physical mechanisms involved in GaN µ-LEDs performance

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Start date : 01/10/2022

offer n° SL-DRT-23-0598

In the Optics and Photonics division of CEA-LETI, The Emissive Components Laboratory designs and fabricates micro-displays based on GaN micro-LEDs. One of the major issue of GaN µ-LEDs is the decrease of their efficiency with the size reduction. In literature, this degradation is attributed to SRH (Shockley-Read-Hall) non-radiative recombinations on pixel sidewalls, in defects induced during the pixel etching step. In the laboratory, we also observed that field effect on pixel sidewalls could have a major impact on µ-LEDs performance. Three phenomena may be in competition. Sidewalls defects can lead to SRH recombinations, but also to a presence of charge (field effect) depending on their ionization level (and so on their energy position in the semiconductor gap). Fixed or mobile charges may also exists on pixel sidewall or in the passivation dielectric. More over, a correlation between the carriers injection (P and N ohmic or Schottky contacts) and the impact of sidewalls on µ-LEDs performance was observed and could help to decorrelate the influence of the different factors. The goal of this thesis will be to study the impact of these different phenomena on µ-LEDs performance through TCAD simulations and electro-optical measurements on different test structures (different sizes LEDs, capacitances, TLM) and put in evidence the dominant phenomenon leading to the efficiency decrease of µ-LEDs.

  • Keywords : Engineering sciences, Technological challenges, Electronics and microelectronics - Optoelectronics, Photonics, Imaging and displays, DOPT, Leti
  • Laboratory : DOPT / Leti
  • CEA code : SL-DRT-23-0598
  • Contact : stephanie.jacob@cea.fr

Study of self-healing mechanisms for embedded systems

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Start date : 01/09/2023

offer n° SL-DRT-23-0475

While topics around protection mechanisms or threat detection are currently well covered, post-attack repair is still not very present in the scientific literature.

Objectives: The objective of this thesis is to identify solutions to restore critical functions or tasks of an embedded device after the detection of an unwanted event (due to a malicious attack or a software or hardware failure). For the last twenty years, many research works have focused on the definition of restoration solutions in the field of safety, the application of these techniques to the field of security is more recent, and still few works address the applicability of these methods to this field.

If the restoration principles can be identical in the safety and security domains, in the case of malicious action, it is necessary to make the restoration system robust against corruption attempts by the attacker. Indeed, the attacker can evolve his attack in order to lure the restoration system or even corrupt the restoration itself. One of the starting hypotheses taken in this thesis is that the system already has one or more modules for detecting abnormal events. From this abnormal state, the solution must allow the restoration of the software after having verified the integrity of the failed software block (rollback) thanks to a context backup (checkpoint) at regular intervals. Within the framework of this thesis, the study will only focus on embedded targets such as processors integrating an embedded Linux but should be portable to other environments

  • Keywords : Engineering sciences, Technological challenges, Computer science and software, Cyber security : hardware and sofware, DSYS, Leti
  • Laboratory : DSYS / Leti
  • CEA code : SL-DRT-23-0475
  • Contact : pierre-henri.thevenon@cea.fr

Study and fabrication of microoptics integrated to an infrared focal-plane array

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Start date : 01/09/2023

offer n° SL-DRT-23-0644

In recent years, the infrared imaging market has trended towards pixel size reduction. Interpixel crosstalk is a major limitation of small pitch devices, as it reduces the image resolution via the degradation of the modulation transfer function. The aim of this thesis is to study and fabricate pixel-level microoptics capable of reducing the crosstalk. The thesis will revolve around two main axes. Refractive microlenses will be studied both experimentally and by simulation to figure out their limitations when the pixel size approaches the detected wavelength, i.e. when diffraction effects Inside the pixel can no longer be neglected. Later on, other approaches such as metasurfaces or dedicated refractive designs will be intriduced to improve the performance. The thesis will provide a clearer picture of current limitations of pixel level micro optics for infrare Imaging at small pixel pitch.

  • Keywords : Condensed matter physics, chemistry & nanosciences, Technological challenges, Photonics, Imaging and displays, Solid state physics, surfaces and interfaces, DOPT, Leti
  • Laboratory : DOPT / Leti
  • CEA code : SL-DRT-23-0644
  • Contact : giacomo.badano@cea.fr

Advanced side channel applied on post-quantum cryptography

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Start date : 01/10/2023

offer n° SL-DRT-23-0648

The development of quantum computing threatens asymmetric cryptography. To address this threat, post-quantum cryptography (PQC) schemes, i.e. based on quantum computer resistant problems, have been proposed. The third round of the NIST PQC competition ended on July 5, 2022. The CRYSTALS-Kyber algorithm was selected for standardization. The history of cryptographic algorithms standardization shows that it should therefore be quickly adopted and soon embedded in secure products. Nevertheless, the road to fully secure implementations, in particular against physical attacks, remains long. The community is therefore actively studying the vulnerability of PQC schemes against physical attacks.

In parallel, the search for vulnerabilities remains a necessary step towards hardware-secure implementations, and advanced techniques of side-channel analysis have been developed. The LTSO laboratory contributes to the theoretical and material advances of the field, in particular via the contribution of artificial intelligence based methods.

The aim of this thesis is to characterize the vulnerability of PQC algorithms (in particular the CRYSTALS-Kyber scheme) against side-channel attacks in restrictive contexts (from the attacker perspective) such as implementations on high-end processors. The main research focus will be the exploration of new attacks that threaten the security of Kyber. This work will guide the development of countermeasures, as well as provide tools to characterize the security of our internal developments. Ultimately, the solutions of our partners will benefit from it.

The main topics that will be addressed in this thesis are:

– python programming,

– cryptography,

– statistics and artificial intelligence,

– embedded system (architecture, programming…),

– signal processing.

Skill in all these fields are not required. Nevertheless, a curiosity about these subjects will be appreciated. The candidate will be accompanied by the LTSO laboratory team, and will have access to its hardware resources, computing units and analysis tools.

  • Keywords : Engineering sciences, Technological challenges, Computer science and software, Cyber security : hardware and sofware, DSYS, Leti
  • Laboratory : DSYS / Leti
  • CEA code : SL-DRT-23-0648
  • Contact : maxime.lecomte@cea.fr

Development of Holographic Optical Elements Arrays with a micro-hologram printer

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Start date : 01/10/2023

offer n° SL-DRT-23-0609

CEA Leti has conceived a holographic printer as part of its development of optical components and systems for the field of Augmented Reality. This printer allows us to record micro-holograms that encode elementary angular functions. The current application of the printer concern the development of pixelated holograms recorded with phase and angular matching for the evaluation of an innovative near-to-eye display. To consolidate this research activity, our laboratory proposes a PhD that aims at enlarging the field of application of the tool to the manufacturing of Holographic Optical Elements arrays. These developments are done in the visible range and potentially in the Near Infra-Red. A typical application can address the field of the eye-tracker, used in Augmented and Mixed Reality, through the development of a catadioptric lens array based on a recent patent of the laboratory. The PhD student will take in the hand the holographic printer to record micro holograms. He will develop some simulation and conception tools to design and evaluate Holographic Optical Elements. He will test various holographic materials to cover a large domain of applications from visible to near Infra-Red spectra. Depending on the results of the research he will have in charge the development of a demonstrator of an optical system to validate the use of his optical component.

  • Keywords : Engineering sciences, Technological challenges, Optics - Laser optics - Applied optics, Photonics, Imaging and displays, DOPT, Leti
  • Laboratory : DOPT / Leti
  • CEA code : SL-DRT-23-0609
  • Contact : christophe.martinez@cea.fr
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