The main project final achievements are the following:
* Isotopic separation has been studied and suitable 28Si separation cost effective technique was determined at lab scale,
* Excellent SiC epitaxial layers were obtained on off-axis SiC substrates with high electrical resistivity,
* Development of high quality SiC epitaxy on to on-axis substrates without 3C inclusion for GaN epitaxial growth was achieved,
* High electrical resistivity of on-axis SiC epilayers and tailored resistivity for PiN and Schottky diodes with or without isotopic SiC have been obtained,
* Isotopic thermal conductivity: Following initial value obtained by Linköping University, isotopic SiC thermal characterisation showed an improvement of 23.6 % in a-direction and 16.7 % in c-direction instead of the initially foreseen 30%, It was determined that the isotopic heavy Si atom purity has the highest impact on thermal conductivity while lighter C atoms have a lower impact,
* The full chain of metrology was used and very good coherence was obtained between thermal conductivity assessment, device thermal characterisation by Raman as well as Infrared microscopy by simulations,
* OSIRIS project has allowed to improve the material and device characterization by different means especially for Intraspec Technologies, CIMAP, Linköping University and STUBA,
* Device processing shows that new epitaxial SiC material is compatible with SiC diodes and GaN HEMT. Manufacturing yield has not been impacted strongly by using isotopic material, especially in case of SiC diodes. Additional work would have to be carried out on a much larger set of samples to go to obtain statistical figures,
* GaN thermal resistance of 0.15µm gate length HEMT devices grown on semi-insulating 70 µm thick isotopic SiC for 30GHz telecom application has improved by 10%, which is in line with thermal modelling. The GaN buffer acts as a thermal barrier which screened the 23.6% isotopic SiC thermal improvement,
* Devices grown on isotopic SiC emitting CW 2.8W/mm at 30GHz with 32% power added efficiencies were obtained. The maximum output power reached 10W/mm which are record values. The power performance improvement is finally marginal in agreement with limited 10% thermal resistance improvement,
* GaN/isotopic HEMT reliability data is more favorable as 10% thermal improvement could give rise to 7 times longer lifetime,
* 2.5A 10kV pin diodes have been obtained with both natural and isotopic SiC material. No advantage but thermal one (16% for the vertical thermal conductivity and 33% for the lateral conductivity) was observed. Packaging itself is a limiting factor to get all benefits of the isotopic approach,
For the dissemination activity, STUBA has designed and implemented an e-learning site supporting OSIRIS project and CIMAP has developed a Website for OSIRIS project (
http://osiris-ecselju.eu(s’ouvre dans une nouvelle fenêtre)). 11 articles have been published. OSIRIS project dissemination get a steep increase to 2290 views at project completion at the end of 2018, which shows the great interest for this research,
* Main Osiris objectives have been fulfilled. Additional work would have to be undertaken for industrialization, especially by producing at competitive cost 28Si isotopes.
