Low-Cost Gallium Nitride (GaN) on Diamond Semiconductors for Microwave Power Amplifiers

A process is proposed for manufacturing low-cost, high-quality, GaN-on-Diamond wafers, so as to enable production of high-power RFICs at costs that substantially outperform their equivalent circuits manufactured on GaN-on-SiC. The process utilizes an epitaxial transfer approach in which gallium nitride is grown epitaxially on silicon carbide handle wafers, removed from the handles, and bonded to diamond wafers. The approach relies on Modern Microsystems’ proprietary plasma polishing and diamond bonding technologies to ensure that the GaN-Diamond bond interface is smooth, uniform, and strong, with minimal thermal boundary resistance.An epitaxial transfer approach to GaN-on-Diamond allows selection of the best GaN and diamond materials taking into account both cost and performance considerations, resulting in much lower cost per chip. GaN grown on SiC exhibits better electrical performance than GaN grown on Si due to the lower lattice mismatch with the growth substrate. Similarly, epitaxial transfer permits use of the growth face of the diamond substrate at the interface with the GaN. The growth face of diamond has larger grains and fewer defects than the seed face, resulting in higher thermal conductivity in the most-critical near-interface region. The approach results in higher-quality GaN-on-Diamond at much lower cost.