Electro-Thermo-Mechanical Reliability of Recessed Barrier AlGaN/GaN Schottky Diodes Under Pulse Switching Conditions

Pulse reliability of AlGaN/GaN recessed Schottky diode is studied under transient overstress conditions, typically encountered in power converters. Degradation of the Schottky diode during both freewheeling operation (high forward current injection) and reverse blocking state (high-voltage stress) is studied. Defect generation and the associated degradation were found to be uncorrelated with the nature of interface formed due to various surface treatments (at metal/GaN Schottky interface). During forward conduction, trap-assisted Schottky interface degradation is studied using on-the-fly I-V and C-V characterization under high-current stress. Under high-voltage stress, in the reverse blocking mode, mechanical strain evolution and defects generation were found to be dominant degradation modes, which are studied in detail using on-the-fly micro-Raman spectroscopy. Post-failure analysis was performed using SEM, TEM, and EDX, which reveals distinct failure signatures at the safe operating area (SOA) boundary. TCAD simulations are used to gain deeper physical insights into the observed degradation mechanism. Finally, a qualitative failure model, explaining the distinct failure physics, is presented based on observations and findings, from various electrical, optical, Raman spectroscopy, and electron microscopy investigations.