New Options for GaN RF

Smart Cut™ enables innovative substrate solutions


GaN HEMT technology holds enormous promise for increasing the power of commercial RF applications. However, challenges both technological and economic remain to be resolved before GaN can realize its full potential beyond the very high-end niche.

Device manufacturers are currently investigating solutions such as GaN grown on silicon and silicon carbide, which shows great promise for RF and microwave components aimed respectively at the wireless industry and defence. GaN increases the output power of such devices compared to GaAs, while silicon offers lower procurement costs and larger diameter wafers than traditional SiC substrates. This makes it an excellent option for commercial RF applications such as mobile base station power amplifiers, in which production costs have to be competitive.

However, at a certain point – somewhere in the 10GHz range, silicon can no longer adequately evacuate the heat generated by the HEMT. Traditionally, SiC has been the substrate of choice in the higher ranges. However, it is too expensive to enter the wider commercial markets.

The novel combination of techniques such as MBE-based epitaxial growth and the Smart Cut™ layer splitting/transfer/bonding technology should enable material solutions that are both cost competitive and high- performance. Thanks to the multi-layer structure, this technology allows independent optimization of the seed material on the front side and the carrier material on the backside of the substrate.

Engineered substrate manufacturing using Smart Cut™ technology offers the possibility of innovative layering of silicon, and polycrystalline silicon carbide for GaN microelectronic applications. The suitability of engineered substrates solutions such as SopSic for high thermal dissipation and good quality epitaxial re-growth have been studied by simulation and demonstrated experimentally. Device data is the next step.

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