Research

Epitaxial growth of III–V and group IV compounds, followed by the fabrication of optoelectronic devices based on these materials, lies at the core of our research activities. Using advanced deposition techniques, we engineer high-quality crystalline layers with precise control over composition, thickness, and interface properties.

Author : Alex Brice Poungoué Mbeunmi

New architecture of solar cells called duplicated junction cells. The concept constitutes an innovative alternative to conventional III-V multi-junction cells and consists in duplicating each sub-cell in several p-n junctions of the same material. The architecture makes it possible to considerably reduce resistive losses and therefore to operate efficiently at very high concentration factors (> 1000 suns).

Author : Mohamed El-Gahouchi

This research project explores several key topics, including the growth of monolayer graphene on semiconductor substrates (Ge, GaAs, etc.), wafer-scale single-crystalline 2D graphene (100–300 mm), detachable III–V/IV/graphene heterostructures for optoelectronic and photovoltaic applications.

Author : Thierno Mamoudou Diallo

Silicon and germanium are semiconductors of interest for energy applications. Electrochemical etching allows to nanostructurated semiconductors with nanoscale size and tunable morphology. Chemical vapor infiltration with acetylene and controled steps as well as temperature control conduct to graphene deposition into the mesoporous structure (all the surface is covered). Then advanced material characterizations using Raman, SEM, TEM, XPS for understanding the structure and nature of the deposition are performed. Finally, thermoelectric properties are studied on this new kind of nanomaterial.

Author : Stephanie Sauze

A perfectly compliant substrate would allow the monolithic integration of high-quality semiconductor materials such as Ge and III-V on Silicon (Si) substrate, enabling novel functionalities on the well-established low-cost Si technology platform. Here, we demonstrate a compliant Si substrate allowing defect-free epitaxial growth of lattice mismatched materials. The method is based on the deep patterning of the Si substrate to form micrometer-scale pillars and subsequent electrochemical porosification. The investigation of the epitaxial Ge crystalline quality by X-ray diffraction, transmission electron microscopy and etch-pits counting demonstrates the full elastic relaxation of defect-free microcrystals. The achievement of dislocation free heteroepitaxy relies on the interplay between elastic deformation of the porous micropillars, set under stress by the lattice mismatch between Ge and Si, and on the diffusion of Ge into the mesoporous patterned substrate attenuating the mismatch strain at the Ge/Si interface.

Author : Alexandre Heintz

We use electrochemical etching of Ge/Si substrates to create voids along dislocations, followed by thermal annealing to promote their coalescence. These voids deflect or annihilate dislocations, lowering threading dislocation density to ~10⁴/cm². This method is a promising route for integrating III–V materials on silicon for high-efficiency solar cells.

Author : Jonathan Henriques

High-performance anode materials like silicon and germanium face challenges such as volumetric expansion and solid electrolyte interface (SEI) formation. Nanostructuring improves their lifetime and mechanical stability, while carbon functionalization reduces SEI and irreversible capacity. Building on this, we developed mesoporous germanium–graphene nanocomposites using scalable electrochemical etching and chemical vapor deposition, achieving superior electrochemical performance in both high-energy and high-power applications.

Author : Arthur Dupuy