The HPSI SiC composite substrate is P-Grade/D-Grade SiC composite substrate material achieved through advanced wafer bonding and layer transfer technologies. Serving as a base substrate, it enables the production of SiC-based GaN epitaxial wafers via epitaxial processes, which are ultimately used to fabricate microwave/RF devices such as high-electron-mobility transistors (HEMTs). These devices find critical applications in information and communication systems, radio detection, and related fields.