ASGEIR

Gallium Nitride (GaN) and its related compounds (III-Nitrides) have become the second most used technology in the semiconductor market, but still far behind Silicon (Si). Their outstanding properties in terms of large bandgap, critical electric field and carrier velocity have allowed the development of critical devices such as visible light emitting diodes (LEDs), power switching devices and RF amplifiers based on High Electron Mobility Transistors (HEMTs). However, the low availability of GaN substrates makes the hetero-epitaxial growth on foreign substrates necessary. Among these substrates, Silicon is highly preferred to access to infrastructures already available for large diameter substrates. Nonetheless, the hetero-epitaxy of III-Nitrides on large diameter low cost Si substrates is still facing difficulties related to the large mismatch of crystal lattice parameters and thermal expansion coefficients. ASGEIR project aims at tackling these issues by providing one original Silicon based compliant substrate able to accommodate the huge stress induced by the hetero-epitaxial growth. The project intends to produce III-Nitrides epitaxial structures with noticeably reduced bow of the substrate and much less risks of layer cracking and substrate breaking as well as more freedom to design high thickness epilayers with better quality and uniformity. To validate the proof of concept, compliant substrates based on graphene/mesoporous Si nanocomposite will be jointly developed by GREMAN, LN2 and CRHEA. IIINitride epilayers will be grown at CRHEA. All the partners will bring their expertise to characterize the new substrate and the III-Nitride epi-layers. Transistors and LEDs will be fabricated at LN2 and CRHEA respectively. Both partners and GREYC will perform the device characterizations. Thermal aspects will be studied by GREYC. The first success criteria of the ASGEIR project will be the achievement of a process scalable to substrate with diameter up to minimum 8 in. with better uniformities and reduced residual strain for devices with performances better than their counterparts on standard Silicon substrates. Last, the project aims to use the advantages provided by this new substrate to go further in the optimization of epitaxy for enhancing the device performances.

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