GaN-on-QST

GaN epitaxial growth is a key step of the GaN power technology. Currently, GaN-on-Si and GaN-on-sapphire are the most common platforms in the industry, both presenting advantages and drawbacks. GaN-on-sapphire comes from long-term experience in LED and offers a cost-effective solution with a relatively simple buffer structure. However, scalability above 6 inches is still challenging due to uniformity issues, increasing manufacturing cost/die, and the substrate thermal conductivity is low, increasing the device junction-to-case resistance. GaN-on-Si is very attractive from the cost point of view since 8-inch substrates are readily available and wafers can be processed in conventional Si fabs, reducing the cost. Nevertheless, a sophisticated GaN buffer is required, whose thickness is limited to about 5 um by the large lattice mismatch between GaN and Si. This can result in dynamic Ron degradation and limit the maximum voltage rating of the GaN device due to vertical buffer breakdown.

GaN-on-QST successfully addresses these challenges. Being the QST engineered to have the same thermal expansion coefficient as GaN, it enables thick epitaxial layers, improving reliability and addressing voltage ratings above 650 V. In addition, the QST substrate exhibits larger thermal conductance, improving the device’s thermal dissipation and enabling more power at a lower temperature rise. Finally, GaN-on-QST is readily available in an 8-inch substrate, enabling a reduction of the manufacturing cost per die.

Here at NovaWave, we provide cutting-edge GaN-on-QST devices specifically designed to take full advantage of the QST substrate to deliver optimal performance.