A career at the crossroads of research and defense
After completing a bachelor program in Physics and Technology in Nantes, France, Baptiste began his engineering studies at École Polytechnique (Palaiseau, France), where he followed a general engineering curriculum with a focus on Energy and Electronics. He then specialized in satellite design at ISAE-SUPAERO (Toulouse, France) and joined the French Ministry of Defence procurement agency (DGA).
It was during this time that he decided to pursue a PhD at the crossroads of physics and electronics, within CEA-Leti's cooled infrared imaging laboratory.
His research focuses on electron transport in the superlattices used in infrared detectors. These novel materials, made by repeatedly stacking nanometer-scale layers of two different semiconductors, InAs and InAsSb[1], enable infrared radiation to be absorbed.
Researchers suspect that these materials are highly anisotropic, meaning that their properties differ depending on the direction in which they are measured. The goal is therefore to understand how electrons actually move within these structures. Developing robust measurement methods is a key challenge in the development of future infrared sensors.
Studying electron behavior to improve detector performance
"To carry out this research, I built on work conducted by S. Bustillos, a former PhD student who worked on the Electron Beam Induced Current (EBIC) technique. This technique makes it possible to deposit charges very precisely within the detector, acting like an 'electron brush,' both spatially and temporally."
Baptiste adapted this method to etched samples in order to decouple the vertical and horizontal motion of electrons, and then analyzed the observations using 3D models. The distinctive feature of his approach is that observations are no longer limited to the surface but can also be performed in depth.
The results were published in the Journal of Electronic Materials and presented at the II-VI Workshop in Chicago. The paper describes a new method for measuring anisotropy using EBIC. It represents one of the first direct experiments reported in the literature to quantify this anisotropy.
Measurements of the lateral and vertical movement of charges revealed an anisotropy of approximately 2.7, significantly lower than expected. This result is particularly important because anisotropy is a key parameter determining infrared sensor performance.
Electrons must be collected at the right location to produce a sharp image. If they move too far laterally due to anisotropy, the resulting image becomes blurred.
For the PhD student, this international conference was a first. The infrared research community is relatively small, and researchers know one another well, making it important for young scientists to establish themselves.
"I was pleasantly surprised by the welcome I received and by the quality of the discussions. This experience made me realize just how relevant the research being conducted in our laboratory is," he explains—a perspective that becomes particularly clear when research is presented to and assessed by the scientific community.
Innovation in infrared imaging: promising materials
This research is being conducted in collaboration with Lynred, as an industrial partner of the laboratory. The aim is to gain a deeper understanding of the behavior of superlattices in order to develop new infrared sensors.
Historically, infrared detectors have relied on II-VI materials. Superlattices, on the other hand, belong to the III-V semiconductor family, a more recent technology platform that holds promise for more stable infrared sensors.
Infrared imaging has applications across defense, industry, and science, including surveillance and Earth observation.
This research directly contributes to the R&D activities of Lynred, a key French player in the field of infrared sensors.
[1] InAs (indium arsenide) and InAsSb (indium arsenide-antimonide) are semiconductor materials belonging to the III-V semiconductor family.