Influence of Carbon on pBTI Degradation in GaN-on-Si E-Mode MOSc-HEMT

In this article, threshold-voltage VTH instabilities under positive gate voltage stress VGStress in GaN-on-Si devices are thoroughly investigated. Measurement-stress-measurement pBTI technique using ultrafast VG ramp was applied in this study. PBTI transients performed at different VGStress and several temperatures highlight the influence of two trap populations, one being related to Al2O3 gate oxide defects and the other one to CN acceptors in GaN lattice. Both trap populations are located close to the Al2O3/GaN interface and lead to VTH instabilities via two different underlying mechanisms simulated by TCAD. PBTI transients obtained under several dc and ac stress conditions have also been modeled using capture emission time (CET) maps and allowed the identification of the two trap populations. Analysis of the temperature-dependent CET maps gives an activation energy of 0.8–0.9 eV related to CN traps and an energy range between 0.7 and 1.5 eV ascribed to Al2O3 defects above the GaN conduction band energy. This study provides a better understanding of the underlying physical mechanisms, leading to BTI degradation in GaN-HEMT technologies.