Investigation of the long-term dynamic RDS(on) variation and dynamic high temperature operating life test robustness of Schottky gate and ohmic gate GaN HEMT with comparable stress conditions

Abstract

The Dynamic High Temperature Operating Life (DHTOL) test, outlined in JEDEC standard JEP180.01, validates the long-term switching reliability of Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) for power management applications. Despite the standardized testing framework, variability in switching test conditions across manufacturers necessitates a thorough investigation of GaN HEMT's long-term switching reliability within specific applications. This study adopts a holistic approach encompassing technological considerations and application demands to assess the long-term switching reliability of p-GaN HEMTs. The analysis emphasizes monitoring the degradation of the dynamic on-state resistance (dR_DS(on)). A structured methodology is employed to precisely model and validate current and voltage peaks via parasitic extraction, defining switching stress conditions. Junction temperature is estimated through FEM simulation of the package model, followed by long-term testing to evaluate degradation. In addition to the hard-switching stress tests with variable voltages, peak current, slew rates, and duty cycles, stress tests with switching loss-free conditions at different temperatures are also performed to assess the primary degradation mechanism. The comparison of long-term hard-switching stress tests and tests conducted under switching loss-free conditions highlights the hot electron effect as the primary contributor to long-term degradation during the hard-switching operation. The substantial influence of voltage and current overlap on degradation is validated by testing Schottky gate p-GaN HEMT with different slew rates. Furthermore, ohmic gate p-GaN HEMT is found to be relatively robust compared to Schottky gate-p-GaN HEMT under similar long-term hard-switching stress conditions.