Reliability Assessment of 650-V Schottky p-GaN HEMTs Under Reverse Conduction Stress

The GaN-based high-electron mobility transistors (HEMTs) can operate efficiently in reverse conduction mode without requiring an intrinsic antiparallel diode, reducing power losses and enabling higher switching frequencies. This study investigates degradation mechanisms in Schottky p-GaN gate HEMTs (SP-HEMTs) under reverse conduction mode on devices featuring different gate geometries. It assesses threshold voltage shift (Δ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>TH</roman></sub>), ON-resistance drift (Δ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>ON</roman></sub>), and device lifetime across a range of temperatures (10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C–175 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C) and negative drain-to-source voltages (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>DS</roman></sub>). Results reveal two distinct degradation mechanisms: the first occurring in the AlGaN barrier at the source-side gate edge, and a second, a long-term process at the metal/p-GaN Schottky junction, which leads to irreversible breakdown. Activation energy for both mechanisms has been determined using current deep-level transient spectroscopy (I-DLTS), providing insights into the temperature and voltage dependencies of mechanisms affecting SP-HEMTs reliability.