Lifetime Prediction of GaN PN Power Diodes Using Step-Stress Accelerated Life Testing

Abstract

Gallium nitride (GaN) power devices have emerged as a key technology for next-generation power electronics due to their high breakdown voltage, high efficiency, and capability to operate under high power densities. However, accurate lifetime prediction remains a critical challenge for their practical deployment. In this study, the reliability and lifetime of vertical GaN PN diodes fabricated on bulk GaN substrates are investigated using step-stress accelerated life testing (SSALT) combined with Weibull statistical modeling. All devices were electrically characterized through capacitance–voltage (C–V) and current–voltage (I–V) measurements to evaluate doping profiles, breakdown voltage, and overall device performance. Accelerated lifetime testing was conducted by applying incrementally increasing reverse voltage stress until a defined failure criterion was reached. Failure time data were analyzed using a Weibull-based model with cumulative exposure theory, and model parameters were extracted using maximum likelihood estimation. The results demonstrate that the Weibull step-stress model accurately captures the failure behavior of GaN PN diodes. Lifetime projections indicate that the devices can achieve a 10-year operational lifetime at an applied voltage of approximately 956 V. Furthermore, the devices remained electrically functional after testing, suggesting that the method captures the onset of degradation rather than catastrophic failure. This work provides an effective framework for evaluating the reliability and lifetime of GaN power devices while minimizing destructive testing.