Experimental Study and Characterization on the Thermo-Electro Multiphysics Coupling Failure of GaN HEMTs Under High-Power Microwave Pulse

The harsh electromagnetic environment poses a threat to the reliability and safe operation of Gallium nitride (GaN) radio frequency and microwave high-electron-mobility transistors (HEMTs). In this work, we experimentally investigate the thermo-electro multiphysics coupling failure of GaN HEMTs under high-power microwave (HPM) pulse stress. A transient thermal response test and surface electric field distribution measurement methods of GaN HEMTs under HPM stress were proposed. This study demonstrates that at low power HPM injection, the peak temperature of 51 °C is located at the gate–drain access region near the gate side. As the HPM injection power approaches the destruction threshold level, an obvious hot spot of 64 °C is found however strangely in the gate–source access region at the gate edge, in the vicinity of the gate bond pad, or in other words, the input end of the microwave signals. The damage spot is exactly sitting on the hot spot, and also overlapping with the electric field concentration observed by the electric field scanning. This means it is the thermo-electro multiphysics coupling but not solely the thermal burnout that causes the device failure under HPM pulse stress. These findings are of great significance for predicting damage location and improving the reliability design against the complex electromagnetic environments.