First Demonstration of GaN RF HEMTs on Engineered Substrate.

GaN transistors have continued to push the limits of high power density, high frequency semiconductor devices. Novel GaN devices have been developed with engineered linearity [1], novel heterogeneous integration with state-of-the-art Silicon (Si) control circuits [2], complementary n- and p-channels [3], and advanced physics-based modeling [4]. Such devices will contribute to the foundation of the next generation of RF and mixed-signal circuits for a diverse set of applications ranging from 6G to hypersonic vehicles [5]–[7]. For these RF applications, Silicon Carbide has long been the substrate of choice for GaN HEMTs due to its low lattice mismatch with GaN, high thermal conductivity, and extremely high substrate resistivity; however, it remains as one of the most expensive growth substrates and scalability to large wafer diameters is a major concern. On the other hand, Silicon is also a common substrate for GaN HEMTs as it is cost effective and scalable, but suffers from a high lattice mismatch [8]–[9]. The engineered substrate (Qromis QST®) offers a cost effective, scalable solution similar to silicon but with thermal lattice matching and lower dislocation density [10]. Early device experiments on GaN -on-engineered substrates have focused on power transistors [11]–[12], but RF applications remain yet to be explored.