Bonding GaN on high thermal conductivity graphite composite with adequate interfacial thermal conductance for high power electronics applications

We demonstrate an efficient heat transport hybrid structure by means of bonding GaN on a high thermal conductivity graphite composite (GC). The heterogeneous GaN/GC of the fine bonding interface, without air voids and cracks, is confirmed. More interestingly, GaN bonded on GC is stress-free and quite beneficial for device performance, the degradation of which is partially subject to the stress induced by the fabrication and packaging processes. Moreover, the thermal boundary conductance (TBC) across the GaN/GC interface is accurately estimated to be approximately 67 MW/m2K, based on the measured TBC between Ti and GC, in excellent agreement with the prediction using the corrected diffuse mismatch model. According to the finite element modeling results, the GaN-on-GC power transistor shows superiority and possesses greatly improved thermal performance due to the high thermal conductivity of GC and adequate TBC across the GaN/GC interface, compared to the commercially available GaN-on-SiC and GaN-on-Si transistors. Our findings highlight the potential of GC as a promising alternative heat spreading substrate candidate for thermal management applications in GaN-based next-generation high power electronics, including radio frequency amplifiers, high voltage power switches, and high breakdown voltage diodes.