Carbon-related pBTI degradation mechanisms in GaN-on-Si E-mode MOSc-HEMT

In this paper, threshold voltage VTH instabilities under positive gate voltage stress (VGStress) are thoroughly investigated on GaN-on-Si Enhancement-mode MOS-channel HEMTs. An analysis of pBTI transients performed at several VGStress and temperatures (T) reveals two trap populations close to the Al2O3/GaN interface namely (1) CN acceptors in the GaN substrate, and (2) defects in the Al2O3 gate oxide. Both trap populations lead to VTH instabilities via different underlying mechanisms as evidenced by TCAD simulations. At VGStress < 1.5 V, VTH drifts are ascribed to CN traps ionization localized at 0.8-0.9eV above the valence band (Ev). At higher VGstress, electron trapping also occurs in Al2O3 defects leading to stronger VTH degradation. DC AC pBTI transients have been modeled using Capture Emission Time (CET) map approach, which allowed the identification of both trap populations. Temperature-dependent CET maps extraction reveals a strong activation of CN traps with temperature, and confirms Arrhenius analysis consistency. This study provides a deep understanding of BTI reliability in GaN-HEMT technologies.