Characterization of Diamond-Semiconductor Interfaces
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The extremely high thermal conductivity of diamond thin films makes them an ideal candidate for heat spreaders that can be integrated with electronic devices. By more effectively dissipating the heat generated during operation device dimensions can be shrunk increasing yield, performance losses due to self-heating can be mitigated, and the need for external cooling systems can be reduced or even eliminated. However, the extreme conditions required for diamond deposition can unintentionally impact the substrate the diamond is being deposited on.
This work focuses on characterizing the changes occurring near the diamond-substrate interface using transmission electron microscopy and chemical analysis by electron energy loss spectroscopy and energy dispersive X-ray spectroscopy. Variations in the changes occurring are studied both as a function of the method of diamond deposition (microwave plasma versus hot filament chemical vapor deposition) as well as substrate material (Si versus SiNx adhesion layers used to produce GaN-on-diamond structures). Finally, a detailed analysis of a GaN-diamond interface formed without the use of an adhesion layer created by a combination of selected area diamond seeding and epitaxial lateral overgrowth of the GaN is presented. An understanding of theses changes is necessary for process optimization to protect the substrate as well as to accurately model the thermal transport through the structure.