Development of Diamond Device-Level Heat Spreader for the Advancement of GaN HEMT Power and RF Electronics

Wide bandgap power electronics have been commercialized for many applications. Gallium nitride (GaN) high electron mobility transistor (HEMT) has superior performance in high power and high frequency applications. The thermal dissipation issues such as self-heating have been hurdles for power density and frequency increases. The efforts of thermal management for hot spots elimination have been ongoing to improve device reliability. GaN HEMT can be fabricated on different substrates. The power density has been shown to increase significantly by using substrate with high thermal conductivity. The proximity of diamond device-level heat spreader to active device areas not only improves thermal performance but also changes device characteristics. This overview emphasizes on the dependency of material and processing improvements on the advancement of the integration of GaN HEMT and diamond. This work first overviews the recent advancement of diamond growth processing technology, diamond properties improvement, and the reduction of thermal boundary resistance between GaN and diamond based on mechanisms. Then, the recent advancement of enabled and exploratory integration between GaN HEMT and diamond, device passivation, power density, and performance improvements are summarized. It is followed by a discussion of critical factors to be considered for GaN-on-diamond HEMT device design and optimization for high power and high frequency applications.