Electro-Thermal Device-Package Co-Design for a High-Temperature Ultra-Wide-Bandgap Gallium-Oxide Power Module

Power electronic systems and components that can operate in environments with ambient temperatures exceeding 250 °C are needed for innovation in automotive, aerospace, and down-hole applications. With the imminent mass electrification of transportation and industry, the high-temperature electronics market value is anticipated to grow to $15 billion by the end of 2023. Conventionally, silicon (Si)-based converters are used in these applications; however, as operating temperatures continue to increase, the inherent limits of these systems are being met. The primary limitations for the high-temperature operation of semiconductor devices is the intrinsic carrier concentration, dictated primarily by the bandgap of the material, which increases with temperature. Wide-bandgap (WBG) power semiconductors, primarily silicon carbide (SiC) and gallium nitride (GaN), have been adopted for use in these applications, but exhibit a degradation in performance at elevated temperatures. As such, gallium oxide (Ga2O3), an ultrawide-bandgap (UWBG) material with controllable doping and the potential for inexpensive substrates, has presented itself as a potential contender for use in high-temperature power electronics applications.

The UWBG of Ga2O3, 4.8 eV compared to 1.1 eV for Si, 3.2 eV for SiC, and 3.4 eV for GaN, allows it to achieve nearly 1033 lower intrinsic carrier concentration than Si, permitting Ga2O3 power devices to theoretically operate at significantly higher temperatures. In addition, unipolar Ga2O3 devices have a better theoretical limit with respect to the relationship between on-resistance and breakdown voltage, which could enable higher power density and power conversion efficiency. While Ga2O3 exhibits potential in these regards, its low thermal conductivity (11–27.0 W/m·K compared to 148 W/m·K for Si, 350 W/m·K for SiC, and 130 W/m·K) means that standard packaging and cooling techniques are not suitable or effective. Furthermore, conventional polymeric and organic encapsulant materials are typically limited to operating temperatures of 200 °C and novel materials must be evaluated.

This work outlines and evaluates an electro-thermal device-package co-design modeling platform that can be utilized for the efficient and accurate modeling of Ga2O3 devices and their associated packaging, with the goal of overcoming the challenges of the low thermal conductivity of Ga2O3. This permits for the electrical and thermal performance of the devices and the package to be designed in tandem for an effective design. Next, six high-temperature encapsulation materials are evaluated and conclusions are drawn about each material's feasibility for use as a dielectric encapsulation material for a power module operating at temperatures exceeding 250 °C. This simulation platform and material analysis was then used to design and fabricate a 300 °C, 1.2 kV half-bridge power module utilizing Ga2O3 diodes to assess thermal and electrical performance.