Electromagnetic Pulse Induced Failure Analysis of GaN HEMT Based Power Amplifier

In this article, we first reveal the performance degradation and physical failure mechanism of a lab-designed GaN power amplifier (PA) module based on a commercial GaN high-electron-mobility transistor (HEMT) with high-power electromagnetic pulse injected. We carried out a systematic step pulse injection experiment to hunt out the degradation and failure threshold of PA module by monitoring its S-parameter and the gate-source resister (RGS) of GaN HEMT. Moreover, the performance indexes of GaN PA, including gain, power-added efficiency, output power, and signal-to-noise ratio, have been measured before/after degradation for comparative analysis. The intact surface circuit microscope of PA module and the degradation electrical characteristics of GaN HEMT demonstrated that the GaN HEMT is the vulnerable component of GaN PA. Furthermore, the numerical simulations and decapsulation experiments are carried out for GaN HEMT to gain insight into the failure process and physical failure mechanism. The results reveal that the failure mode is thermal-induced gate metal melting of the GaN HEMT. The failure mechanism is mainly attributable to the impact ionization, which induced by the high pulse voltage under the gate near the source. This is followed by the thermal-electrical feedback state in the device internal until the temperature finally reaching the melting point of the gate metal.