Transfer of knowledge to industry
Département des Plateformes Technologiques (LETI)
Laboratoire des Matériaux pour la photonique
01-03-2021
PsD-DRT-21-0035
As part of the Carnot PIRLE project starting in early 2021, we are looking for a candidate for a post-doctoral position of 24 months (12 months renewable) with a specialty in material science. The project consists in developing a relaxed pseudo-substrate based on III-N materials for µLEDs applications, especially for emission in red wavelength. The work will focus on developing an InGaN-based epitaxy MOCVD growth process, on an innovative substrate based on electrochemically anodized and relaxed materials. He (She) will have characterize both the level of relaxation of the re-epitaxied layer and its crystalline quality. These two points will promote the epitaxial regrowth of an effective red LED. The candidate will be part of the team, working on the PIRLE project, will be associated to the work on red LED growth and its optical and electro-optical characterizations.
Département des Plateformes Technologiques (LETI)
Laboratoire des Matériaux pour la photonique
01-03-2021
PsD-DRT-21-0043
Imaging in the infrared wavelength is today a crucial enabler of new industries such as autonomous mobility, augmented reality and biometrics? Extensive deployment of infrared cameras is however prevented by high manufacturing cost. The ideal, simple solution is to monolithically integrate an absorber layer directly on top of the silicon-based readout integrated circuit. Proof-of-concept image sensors with thin film photodetector active layer have already been demonstrated with different materials (organic absorber, solution processed thin film with polymer and Quantum Dots (QD)?). We propose in this post-doctoral position to develop the building blocks for realization of a monolithic image sensor targeted for the infrared range up to the wavelengths close to 2 µm based on a solution processed QD absorbing layer. The chemical synthesis development of QD material with tunable absorption from 1-2.5 µm will be made by CEA-IRIG. In our side we will take a stepwise approach to develop a photodiode stack. We will use, at first step, glass substrates with indium tin oxide contacts with all additional layers such as electron transport layer and hole transport layer. The QDs will be deposited by spin coating or dip coating from a colloidal solution to form the absorbing stack layer. The stacks thus prepared will be characterized electrically and under illumination. Current-voltage curves will be acquired systematically under dark and multiple light levels. External quantum efficiency spectra will be acquired over a wide range of wavelengths. Modifications will have to be implemented on the optical bench to carry out more advanced characterizations (capacitance-voltage and capacitance-frequency measurements). The post-doctoral project will be dedicated to the technological fabrication as well as the opto-electronic characterizations and optimizations of the IR-photodiodes in close collaboration with IRIG colleagues.
Département des Plateformes Technologiques (LETI)
Laboratoire
01-01-2021
PsD-DRT-20-0113
UV-C LEDS are to replace Hg based UV-lamps for applications related to air and water sterilization and decontamination , a subject of importance in the present day health context. However, UV-C LEDs, which rely on the use of AlGaN nitride alloy epitaxial layers, are still not efficient enough to be considered as a possible alternative on a large industrial scale. This is so for different reasons, related to the quality of the nitride material and/or to the technology employed for fabricating the diodes. We have created an academic consortium which, around LETI, can address the different issues at stake, in order to develop a true technology stream in this field. One of the issue concerns the structural quality of the epitaxial layers, dislocations being non-radiative defects that kill the internal efficiency of the LED. Within the consortium, we are in charge of developping new and optimized template layers, i.e. the epitaxial layer nucleated on the surface of the sapphire substrate, since an important part of the defects in the LEDs arise from this nucleation layer. To address this point, we will develop new and original methods for the deposition of AlN and AlGaN templates: reactive sputtering, co-sputtering (for alloy templates) and Pulsed laser Deposition (PLD). The layers will be characterized on the Nano-Characterization Platfom of LETI and will be evaluated according to the electro-optical properties of the LEDs structures that will be grown by epitaxy on top of these templates.
