Dynamic Temperature Measurements of a GaN DC–DC Boost Converter at MHz Frequencies

For reliability predictions, gallium nitride transistors require accurate estimations of the peak operating temperatures within the device. This article presents a new application of thermoreflectance-based temperature measurements performed on a gallium nitride high electron mobility transistor. The submicron spatial and nanosecond temporal resolutions of the measurement system enables for the first time, the dynamic temperature measurement of a transistor operating up to 5 MHz. The gallium nitride transistor is first biased in class-A and excited with a 1 MHz ac signal to demonstrate the dynamic temperature measurement. The transistor is, then, incorporated in a 20-40 V dc-dc boost converter to measure the dynamic temperature distributions across the semiconductor die operating under real loading conditions at 1 and 5 MHz switching frequencies. This technique captures the temperature variations that occur during the switching of the transistor and the recorded peak temperatures are 7.4 °C higher compared with conventional measurement and simulation approaches.