Near-junction thermal management is critical to achieving the promise of electronic and photonic devices using wide bandgap materials. In such devices, including GaN HEMTs in PAs, the thermal resistance associated with the "nearjunction" region dominates the heat removal path and is often as large as the thermal resistance of all the other elements in the resistance chain. As part of DARPA's portfolio in Thermal Management Technologies (TMT), efforts are underway to develop transformative, paradigm-changing cooling techniques. This paper will briefly review the thermal management needs of WBG devices and DARPA's Thermal Management Technologies portfolio, with emphasis on the goals and status of these efforts relative to the current State-of-the-Art. Attention will then turn to promising options in near-junction cooling and the challenges inherent in realizing their potential for WBG device thermal management.
Successful utilization of the inherent capability of wide bandgap materials and architectures for radio frequency (RF) power amplifiers (PAs) necessitates the creation of an alternative thermal management paradigm. Recent “embedded cooling” efforts in the aerospace industry have focused on overcoming the near-junction thermal limitations of conventional electronic materials and enhancing removal of the dissipated power with on-chip cooling. These efforts, focusing on the use of diamond substrates and microfluidic jet impingement, are ushering in a new generation (Gen3) of thermal packaging technology. Following the introduction of a modified Johnson's figure-of-merit (JFOM-k), which includes thermal conductivity to reflect the near-junction thermal limitation, attention is turned to the options, challenges, and techniques associated with the development of embedded thermal management technology (TMT). Record GaN-on-Diamond transistor linear power of 11 W/mm, transistor power fluxes in excess of 50 kW/cm2, and heat fluxes, above 40 kW/cm2, achieved in Defense Advanced Research Projects Agency (DARPA)'s near-junction thermal transport (NJTT) program, are described. Raytheon's ICECool demonstration monolithic microwave integrated circuits (MMICs), which achieved 3.1× the CW RF power output and 4.8× the CW RF power density relative to a baseline design, are used to illustrate the efficacy of Gen3 embedded cooling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.