This Small Business Innovation Research (SBIR) Phase 1 project will demonstrate a novel micro-scale thermal management concept for removing waste heat generated in the active regions of a pulsed semiconductor device. In these devices, each duty cycle consists of a period of heat generating pulse on the order of a few microseconds followed by an inactive period of about 100 microseconds. The continuous thermal cycling and high junction temperature cause thermal stresses leading to device fatigue and ultimately, reduction in life. An innovative micro-scale thermal management design is proposed in the project that can achieve 20% reduction in peak junction temperature, 50% improvement in power dissipation, and reduced temperature spike. The Phase 1 effort will involve fabrication and integration of the proposed cooling concept in GaN devices followed by testing the thermal and electrical performance. This design is scalable and can be applied to different semiconductor material based devices. The overall cost of the device will decrease due to the improved performance, reliability and life span with minimal changes in the device design.
The broader impact/commercial potential of this project is geared towards addressing the increasing demands of the electronics industry for higher performance in smaller packages. For example, the state-of-the-art pulsed GaN-based devices typically operate at one-tenth of their electrically achievable power densities in order to stay within the maximum allowable junction temperature. In other words, thermal management is the bottleneck to achieving the devices? full performance potential. The proposed technology will tackle three scientific areas: thermal, electrical and mechanical, to increase the reliability and performance of state-of-the-art high power density RF devices used in applications that drive wireless and broadband communications. This technology has the potential to be a driving force for pulsed power devices and high voltage switches to reach new performance heights, consequently leading to new lucrative markets for these devices. In large datacenter computer server equipment, the technology has the potential to significantly reduce the energy consumption required for cooling and therefore minimize the adverse impact on the environment.
This Small Business Innovation Research Phase II project proposes a novel micro-scale thermal management design to remove the heat generated in the active regions of a pulsed mode Gallium nitride (GaN) semiconductor RF device. RF and microwave applications are becoming increasingly important with the huge demand for wireless telecommunications which is commensurate with the need for high power, high frequency transistors. The next generation GaN-based RF power transistor technology offers the unique combination of higher power, higher efficiency and wider bandwidth than competing GaAs and Si based technologies. The extremely high power densities available in GaN devices create new challenges for heat dissipation. Therefore, regardless of the unprecedented power densities demonstrated in these devices, commercial GaN devices typically operate at much lower power densities (4-6 W/mm) to stay within a maximum allowable junction temperature. Advanced Cooling Technologies, Inc. (ACT) and Massachusetts Institute of Technology (MIT) were successful in demonstrating the first integration of GaN power transistors with a phase change material (PCM) based cooling solution. Appropriate devices were designed and fabricated during the Phase I program. Experimental characterization of the new PCM-enabled devices under pulsed modes agreed well with simulations and has showed up to 10% improvement in the electrical device performance (due to enhanced thermal management) than in the baseline (current state of the art without PCM) GaN transistors used as a reference. Work performed during Phase II involves optimization of the PCM material and the quantity/location that is expected to improve this performance even further. This cooling technology now opens up new doors for GaN device applications as they can be operated at higher power densities than the current norms.
