GOALI: An Experimental Study of Electric Field Driven Non-Fourier Thermal Transport in High Power Electronic Devices

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Featuring broadband operation and high efficiency, gallium nitride-based radio frequency power amplifiers are key components to realize reliable, energy efficient, and ubiquitous wireless 5G networks that billions of devices use for data collection and computation. However, full implementation of gallium nitride microelectronics for 5G wireless networks requires overcoming concerns about overheating. This project will investigate and identify the thermal transport mechanisms leading to the discrepancies between theoretical predictions and experimental observations, to allow design of effective thermal management for reliable performance. Moreover, this project will encompass educational tasks designed to bridge the gap between thermal sciences and electronic device physics and to lower the entry barrier for undergraduate students to study nanoscale heat transfer principles. The educational activities will also expose underrepresented students to industry-driven academic research and inspire K-12 students to pursue STEM-related fields.The research goal of this project is to experimentally identify and probe nanoscopic, non-Fourier thermal transport mechanisms that are responsible for the amplified heating within gallium nitride transistors simultaneously subjected to extreme electric field and heat flux conditions. It is hypothesized that the observed amplified heating is a combined result of nanoscale heat source size effects, electric field induced deformation of the gallium nitride crystal, and thermal non-equilibrium among energy carriers, all of which are caused by a nanoscale electric field spike. A deep ultraviolet thermal imaging capability which offers the highest spatial resolution among commercial thermal imaging systems will be developed in order to test this hypothesis and to study the fundamental physics in gallium nitride transistors. The developed deep ultraviolet thermal imaging technique will be used together with Raman spectroscopy, photoluminescence, and a novel multi-scale electro-thermal modeling scheme to study the physical origins of the amplified heating in high voltage-biased gallium nitride transistors. Research outcomes will facilitate electro-thermal co-design and improve industry standard methods for lifetime assessment of gallium nitride power amplifiers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.