Diamond-SiC composite substrates: A novel strategy as efficient heat sinks for GaN-based devices

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Combining the structural advantages of SiC with super thermal conductivity of diamond to construct an efficient heat dissipation substrate for GaN-based transistors is a promising strategy to solve the self-heating problem. Herein, a scheme for direct growth of polycrystalline diamond on 4H–SiC substrate, followed by thinning of the 4H–SiC substrate to an optimum thickness, is designed and implemented. Diamond-SiC composite substrates consisting of 200 μm 4H–SiC and 200 μm diamond are fabricated. The simulation of GaN devices is carried out to provide theoretical support for device fabrication. Then, compatible with established epitaxial and device manufacturing technology on SiC substrate, GaN devices are fabricated on diamond-SiC composite substrates. A 52.5 °C reduction in surface temperature and about 41 % reduction in thermal resistance of the improved heat dissipation structures are exhibited, by contrast with GaN-on-SiC technology at base temperature of Tb = 25 °C and dissipation power of Pdiss = 7.2 W mm−1. The stable output characteristics and reliability of GaN-on-diamond/SiC structures are confirmed at high temperatures. This work is anticipated to afford a promising heat dissipation strategy for devices with high power density and illuminate a new perspective on exploring and constructing novel composite substrates with diamond.