In-Situ Extraction of Time-Resolved $e_{\text{oss}}$ on GaN Power Device Based on a Modified Hard Switching Platform

$C_{\text{OSS}}$ loss ( $E_{\text{OSS}}$ ) and Dynamic $R_{\text{ON}}$ , which combine switching loss and conduction loss in currently available GaN HEMTs, severely limit their performance in hard switching topologies. The effect of dynamic $R_{\text{ON}}$ under various stress conditions have been extensively explored. However, Coss discharge process remains elusive, as the current flowing through Coss cannot be detected directly. This work proposes an easy-to-implement method to extract the dynamic $E_{\text{OSS}}$ under long-term OFF-state drain stress and hard-switching stress. The dynamic FOM $R_{\text{ON}}\times E_{\text{OSS}}$ dependence on the continuous hard-switching stress is investigated, which is critical for the insights into the physical origin of $C_{\text{OSS}}$ loss and practical application.