Revealing Bulk Trap Distributions in GaN MESFETs Through Re-Defined AC-GmCharacterization Method under Irradiation and Stress
Bulk traps play a critical role in the reliability of GaN-based devices; however, existing characterization techniques are limited in their ability to simultaneously resolve trap energy, spatial location, and density. In this work, a redefined AC transconductance (AC-Gm) characterization method is proposed for GaN MESFETs, extending the conventional MOSFET-based AC-Gm framework to bulk trap analysis. A physical model based on Shockley-Read-Hall emission is developed to correlate frequency- and bias-dependent AC-Gm dispersion with the spatial and energetic distributions of bulk traps. The method is applied to GaN MESFETs subjected to heavy-ion irradiation and off-state electrical stress, enabling reconstruction of threedimensional bulk trap distribution maps under different degradation conditions. TCAD simulations using the Ginestra™ tool show strong agreement with the experimental analysis, verifying the accuracy and robustness of the proposed method. This work demonstrates that the redefined AC-Gm technique provides a reliable and complementary approach for depthresolved bulk trap characterization in GaN MESFETs.
