Comparison of thermal properties of packaged AlGaN/GaN HFETs on Si and n-SiC substrates

Purpose of the work High voltage power switching AlGaN/GaN HFETs are gaining considerable interest for future highly efficient power electronic applications. Due to its lower cost and production line compatibility, GaN-on-Silicon approaches are most attractive for industrial implementation. On the other hand, the Si substrate has a three times lower thermal conductivity as compared to the SiC substrate which is well established in RF technology. It is important to compare systematically power switching devices fabricated on Si substrates versus similar devices on SiC substrates in order to evaluate potential trade-offs. Here, we present a method of thermal characterization of AlGaN/GaN HFETs based on pulsed electrical measurements (dynamic IV analyses (DIVA)). First we compare small test transistors (two fingers, 0.25 mm gate width), on Si and SiC substrates and demonstrate the increased self-heating for the GaN-on-Si devices. Then we demonstrate pulsed characterizations of large periphery 60 m AlGaN/GaN HFETs with 214 mm gate width up to 120 A at base-plate temperatures up to 150 °C.