General Scope: Semiconductor p-n junctions serve as fundamental building blocks in devices like solar cells, avalanche photodetectors or light emitting diodes. Nonetheless, the visualization of electrically active doping levels in semiconducting materials with nanometer precision remains a formidable challenge, particularly in wide bandgap materials characterized by high dopant activation energies.
Internship Objective: This internship aims to make a significant contribution to the investigation of p-n junction semiconducting materials, focusing specifically on their electrical properties at the nanometer scale. The selected student will become an integral part of a multi-institutional, interdisciplinary research team. Their primary responsibility will involve the fabrication of electrical contacts for p-n junction nanowires and thin films composed of various materials, including GaN and AlN. These p-n junctions will be electrically connected to membrane chips that are compatible with transmission electron microscopy (TEM) measurements. Additionally, the student will be responsible for conducting initial electrical characterization. By combining in situ biasing techniques with 4D scanning TEM (4D-STEM) methods sensitive to electric fields, our goal is to achieve a precise quantitative description of the electrical properties of these objects at the nanometer scale.

Master+PhD Position: OPEN
Nitride/Oxide Heterostructures for Power Electronics

Context: The increasing demand of growth of electricity consumption, linked to the challenges of digital and ecological transition, is boosting the market for power electronics. With their high breakdown electric field, ultra-wide-bandgap semiconductors (UWBG) like gallium oxide (Ga₂O₃) and aluminum nitride (AlN) are promising competitors for the next generation of power electronics, surpassing not only traditional silicon- based materials but also GaN and SiC. UWBG materials can handle higher voltages, temperatures, and power densities. Nitride/oxide heterostructures hold great promise for power electronics by offering a compelling combination of UWBG properties, high breakdown voltage and fast switching capabilities.
Targets and strategy: The fabrication of an AlN/oxide device requires to address a number of material challenges, particularly the nucleation of epitaxial AlN on Ga₂O₃ managing the polarity of the AlN layer and the eventual activation of thermal interdiffusion. These phenomena can determine the electronic properties of the heterojunction. During this internship, we will optimize the AlN/Ga₂O₃ interface in terms of structural quality and electrical performance. Our ultimate goal is the fabrication of a chemically-sharp AlN/Ga₂O₃ heterostructructure hosting a polarization-induced two-dimensional electron gas at the interface. The student will be trained in epitaxial growth of III-nitride semiconductors on gallium oxide. He/she will perform structural characterization of the samples using atomic force microscopy, scanning electron microscopy and x-ray diffraction. Transmission electron microscopy will also be accessible through in-place collaborations. Additionally, the student will be trained in cleanroom processing to perform basic electrical characterization of the material.