Integration of Microjet-Tesla Microchannels for Thermal Management of GaN-on-SiC HEMTs

Abstract

The self-heating effect in gallium nitride (GaN) high-electron-mobility-transistors (HEMTs) severely limits their output characteristics. In this work, a tesla-type microchannel (MC) heat sink integrated with microjet impingement is proposed to mitigate the self-heating effect in GaN HEMTs. The thermal performance of microjet-tesla MCs is evaluated through both experimental and numerical methods, and the electrical characteristics of the GaN HEMT are evaluated experimentally. The numerical results indicate that microjet-tesla MCs significantly improve convective heat transfer by enhancing the fluid mixing and periodic disruption of thermal and velocity boundary layers. This enables a remarkable performance evaluation criterion (PEC) of 1.371, demonstrating a substantial enhancement in heat transfer efficiency. Furthermore, the experimental results have verified the effectiveness of microjet-tesla MCs. Compared to remote cooling, a significant reduction in maximum junction temperature ( ${T}_{\text {j,max}}$ ) of $79.7~^{\circ }$ C was achieved, representing a 30.5% decrease. The total thermal resistance ( ${R}_{\text {th}}$ ) decreased from 12.96 to 7.96 K/W, corresponding to a 38.6% reduction. As a result, the saturation drain current increased from 3.47 to 4.22 A, indicating a significant improvement of 21.6%. In addition, microjet-tesla MCs yielded a further reduction in ${T}_{\text {j,max}}$ and ${R}_{\text {th}}$ by up to 8.8% and 9.5%, respectively, even compared with plain-wall MCs. Meanwhile, a pumping power of only 3.92 mW is sufficient to significantly improve output characteristics of GaN HEMTs. This dual-cooling design offers a promising approach for thermal management of wide-bandgap semiconductors like GaN.