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The first technology enabling large-scale gallium nitride industrialisation for mainstream power electronics and RF applications

Periodic Reporting for period 2 - eleGaNt (The first technology enabling large-scale gallium nitride industrialisation for mainstream power electronics and RF applications)

Reporting period: 2020-10-01 to 2021-11-30

eleGaNt aims at developing a high quality planar GaN material for the power electronics markets through advanced nanowire technology addressing the shortcomings of conventional GaN platforms. The technology drastically lowers dislocation densities that typically prevents high voltage operation and causes high leakage currents which limits energy efficiency. Further, the technology enables thick crack-free layers and thereby enables vertical architectures and thus addresses high power segments where to date only the cost inefficient SiC is used.
By increasing material quality, more energy efficient devices can be manufactured at improved cost structure and energy savings in multiple areas such as consumer electronics, home appliances, data centers, EV/EHV markets, photovoltaic energy conversion, and many industrial applications. This will help boost the transition to a more sustainable society at large.
The project objectives are reduction in defect densities, demonstrating layers above 10µm in thickness, scaling technology to a commercially relevant wafer size (6") and engage with industrial partners in order to secure a joint development program.
To conclude, the project has experienced delays but has in the end successfully demonstrated GaN-on-Si wafers with defect densities at par with state-of-the-art and ready to demonstrate 6” wafers.
The project has focussed initially on solving issues relating to wafer pre-processing in terms of lithography and dry etching before GaN epitaxial growth. Further, GaN nanowire growth was developed to support the key eleGaNt coalescence technology, in the beginning on wafer pieces and at the end on full 50mm wafers. The main focus has been on the coalescence step to reshape the GaN nanowires into planar GaN layers that are fully compatible with conventional planar epitaxy and subsequent device processing. In the first part of the project coalescence was mainly done on sapphire but in the final part focus was on GaN on Si. The project resulted in 2µm GaN films on 50mm Si wafers that were almost crack free with dislocation densities in the mid 108 cm-2. Modelling was used to guide the stress compensation work and Hexagem will continue the development to remove cracks and increase film thickness further.
The project outcomes has resulted in outreach and initial discussions with industrial partners on joint development projects to scale the technology to 150mm wafer sizes and to demonstrate electrical devices.
In terms of dissemination, project results have been published in peer-reviewed papers, presented at several highly attended conferences, and published in media both online and in print, in Sweden and in Europe.
The progress has demonstrated dislocation densities at par with or slightly better than state-of-the-art commercial GaN-on-Si and through modelling verified that the eleGaNt technology will enable thick layers (up to 10-15µm) on silicon wafers. Further Hexagem is entering several discussions on joint development projects with power electronics players with aim to develop 900-1200V GaN technology on 150mm wafer size.
Through high quality material, compatible with low cost Si platforms eleGaNt technology enables improved energy efficiency and cost and will impact society positively in terms energy savings and thereby reduction in CO2 emission by an increased incorporation of efficent GaN technology in home appliances, EV/EHV, PV, data centers, and consumer electronics. A reduction in cost for several key high power markets will enable a faster adoption of more efficient technologies and thereby faster job creation in particular in sustainable energy sectors such as PV, EV/EHV, and wind.
10µm thick crack-free GaN on sapphire