The self-heating and high-power microwave (HPM) effects that can cause device heating are serious reliability issues for gallium nitride (GaN) high-electron-mobility transistors (HEMT), but the specific mechanisms are disparate. The different impacts of the two effects on enhancement-mode p-gate AlGaN/GaN HEMT are first investigated in this paper by simulation and experimental verification. The simulation models are calibrated with previously reported work in electrical characteristics. By simulation, the distributions of lattice temperature, energy band, current density, electric field strength, and carrier mobility within the device are plotted to facilitate understanding of the two distinguishing mechanisms. The results show that the upward trend in temperature, the distribution of hot spots, and the thermal mechanism are the main distinctions. The effect of HPM leads to breakdown and unrecoverable thermal damage in the source and drain areas below the gate, while self-heating can only cause heat accumulation in the drain area. This is an important reference for future research on HEMT damage location prediction technology and reliability enhancement.

Currently, severe electromagnetic circumstances pose a serious threat to electronic systems. In this paper, the damage effects of a high-power electromagnetic pulse (EMP) on the GaN high-electron-mobility transistor (HEMT) were investigated in detail. The mechanism is presented by analyzing the variation in the internal distribution of multiple physical quantities in the device. The results reveal that the device damage was dominated by different thermal accumulation effects such as self-heating, avalanche breakdown and hot carrier emission during the action of the high-power EMP. Furthermore, a multi-scale protection design for the GaN HEMT against high-power electromagnetic interference (EMI) is presented and verified by a simulation study. The device structure optimization results demonstrate that the symmetrical structure, with the same distance from the gate to drain (Lgd) and gate to source (Lgs), possesses a higher damage threshold compared to the asymmetrical structure, and that a proper passivation layer, which enhances the breakdown characteristics, can improve the anti-EMI capability. The circuit optimization results present the influences of external components on the damage progress. The findings show that the resistive components which are in series at the source and gate will strengthen the capability of the device to withstand high-power EMP damage. All of the above conclusions are important for device reliability design using gallium nitride materials, especially when the device operates under severe electromagnetic circumstances.