Power electronics

In our daily lives, the need to convert electrical energy into usable voltage and current to power and recharge a wide variety of devices (cell phones, computers, electric cars, etc.) has continued to grow. This conversion is most often achieved using a transformer, which, unfortunately, is the source of losses of varying degrees. It is therefore essential to develop transformers that can significantly reduce these losses while also reducing their size and cost. With this in mind, many academic groups as well as industrial firms are currently developing components based on so-called “wide-bandgap” materials such as silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

The development of III-N material epitaxy for power electronics began at CRHEA in the late 2000s. Building on its expertise in epitaxy and through the development of new structures, CRHEA has become a key national player in this field. Numerous projects at the national level (ANR, GaNeXT LabEx, IPCEI, PEPR Electronics) and at the European level (ECSEL JU GaN4AP) have been initiated with academic partners (IEMN, LAAS, AMPERE, GREMAN, LN2, CNR-IMM...) as well as industrial partners (STMicroelectronics, NOVASIC/SOITEC,…) and institutions such as CEA-LETI.

Currently, this research aligns with the global trend toward increasing breakdown voltages in the III-N material family on silicon substrates. The goal is to exceed 650 V for HEMT (High Electron Mobility Transistor) devices. At CRHEA, this objective is currently being addressed by increasing the aluminum content in the structure [1,2]. Furthermore, the reduction of access resistances is being addressed through the development of ScAlN as a new barrier material [3], while localized epitaxy is used to increase the thickness of buffer layers [4] as well as to develop “normally-off” devices [5]. Furthermore, as part of the IPCEI initiatives (Nano 2022, Nano 2025) led by STMicroelectronics, the validation of a hybrid epitaxy process (AlN/Si template via MBE followed by growth continuation via MOCVD) is underway with the startup EasyGaN, which originated from CRHEA.

Another area of research is the development of vertical power devices based on III-N materials. Schottky diodes and p-n junctions are fabricated on GaN substrates to validate the quality of both the material and the manufacturing processes used (ECSEL JU GaN4AP project, GaNeXT VERTIGaN LabEx, ANR C-Pi-GaN). These devices serve as a reference [6] for studying structures developed via heteroepitaxy on sapphire and silicon substrates (VERTIGO targeted project under the PEPR Electronics program, ANR ELEGANT project, IPCEI Nano 2025). Vertical FINFET and MOSFET transistors are also being developed, and localized GaN epitaxy is being studied to facilitate heteroepitaxy on silicon substrates [7].

  • [1] - High Al-content AlGaN channel high electron mobility transistors on silicon substrate – e-Prime - Advances in Electrical Engineering, Electronics and Energy 3, 100114 (2023) - https://doi.org/10.1016/j.prime.2023.100114
  • [2] - Effects of GaN channel downscaling in AlGaN-GaN high electron mobility transistor structures grown on AlN bulk substrate – J. Appl. Phys., 133, 145705, (2023) – https://doi.org/10.1063/5.0147048
  • [3] - Influence of the temperature on growth by ammonia source molecular beam epitaxy of wurtzite phase ScAlN alloy on GaN – APL Materials, 11, 031105, (2023) – https://doi.org/10.1063/5.0139588
  • [4] - Epitaxial growth of AlGaN/GaN HEMTs on patterned Si substrate for high voltage power switching applications – Microelectron Eng, 277, 112017, (2023) – https://doi.org/10.1016/j.mee.2023.112017
  • [5] - Selective sublimation of GaN and regrowth of AlGaN to co-integrate enhancement mode and depletion mode high electron mobility transistors – J. Cryst. Growth, 593, 126779, (2022) – https://doi.org/10.1016/j.jcrysgro.2022.126779
  • [6] - Comprehensive characterization of vertical GaN-on-GaN Schottky barrier diodes – Microelectronics J, 128, 105575, (2022) – https://doi.org/10.1016/j.mejo.2022.105575
  • [7] - Characterization of unintentional doping in localized epitaxial GaN layers on Si wafers by scanning spreading resistance microscopy – Microelectron Eng, 273, 111964, (2023) – https://doi.org/10.1016/j.mee.2023.111964

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