Grainger CEME

M.S. student Ross Liederbach with advisors P. T. Krein, K. Kim, and E. Rosenbaum
Wide-bandgap device materials offer promising characteristics for power conversion at high temperatures. Several applications already benefit from high temperature (~200 °C) power conversion electronics, but pushing to more extreme temperatures, 250 ° up to 400° C, could prove even more advantageous. By increasing the power circuitry operating temperature capability, power conversion may be implemented closer to high-temperature sensors, reducing power connection length. Additional benefits include a reduction in cooling requirements and unit size. Of particular interest are gallium nitride (GaN) transistors, which should be able to withstand these extreme temperatures. Currently, GaN devices have not been pushed past 250° C, as this requires an entire circuit capable of the same temperatures, and all of the circuit elements undergo their own changes across such a temperature sweep. This research aims to compile a combination of circuit elements that will operate in conjunction with GaN devices to provide efficient power conversion up to the extreme temperatures mentioned (250° to 400°C) and to characterize device operation at these temperatures.
In addition to characterizing commercially available devices, GaN devices are being produced
(Figure 27) which could better meet the needs of a 400° C power converter. Room temperature operation of these devices has been demonstrated and their operating curves are shown in Figure 28. By extending the known operating characteristics of the GaN devices and other circuit elements to higher temperatures, increased reliability and efficiency at this extreme operating point may be reached.
This research is supported by a National Science Foundation Graduate Research Fellowship and the Strategic Research Initiative.

Figure 27: In-house produced GaN HEMTs

Figure 28: Room temperature I-V curves Vg = 0 to -8 V