Charge‐Trapping Multilayer Electrets for Partial Discharge Mitigated AlN Substrates

High electric fields within power devices can trigger partial discharge (PD), which can gradually degrade insulation materials, such as ceramic substrates and encapsulation compounds. This work counters and reduces electric fields using multilayer thin‐film electret structures incorporating , , , and AlN to mitigate PD in WBG power electronic packages. The proposed thin film structures can be conductively charged, allowing charges to be injected and trapped within the thin film stack. The stored charges generate electric fields and reduce intensified local fields that cause PD. The proposed electret design allows in‐situ conductive charging, unlike previous electrets that required pre‐charging through an external charging system. To evaluate the electric field suppression capabilities, PD measurements were performed under steep (high‐dV/dt), high‐voltage pulse excitations. The results show a decrease in PD activity, indicating a successful electric field reduction. Finite‐element simulation of the measured structure shows that the retained charge reduces the field at the triple point by about 32, and the measured apparent charge decreases in almost all conditions above the inception voltage. Overall, the proposed approach provides a promising way to improve insulation performance in high‐voltage WBG power modules.