Impact of Carbon Diffusion Induced Stress on the Properties of Diamond/GaN Heterojunctions.

Integrating diamond with GaN provides an effective pathway to mitigate self-heating. However, the thermal boundary resistance (TBR) remains a persistent bottleneck for further heat dissipation. While carbon (C) diffusion into the SiNx interlayer is known to reduce TBR, the associated stress evolution and its impact on device performance remain underexplored. In this work, the synergistic regulation of heat transport and electrical performance induced by C diffusion was systematically investigated. Transmission electron microscopy (TEM) was employed to characterize the interfacial microstructure and the influence of C diffusion on the interface. To further assess the resulting impact on heat dissipation, transient thermoreflectance was utilized to precisely quantify the thermal transport within the heterostructures. Classical molecular dynamics (MD) simulations were then performed to analyze the underlying physical mechanisms, revealing that intensifying C diffusion increases the phonon density of states overlap and effectively reduces the TBR. Furthermore, the intrinsic stress was quantified through geometric phase analysis (GPA) based on TEM images, demonstrating that the stress induced during the diffusion process propagates to the AlGaN/GaN heterostructure. Crucially, this stress modulation enhances the piezoelectric polarization by approximately 32%, resulting in a 5% increase in the two-dimensional electron gas (2DEG) sheet density. These findings provide a comprehensive strategy for optimizing the thermal management and mechanical reliability of high-power GaN devices.