Study on the difference between ID(VG) and C(VG) pBTI shifts in GaN-on-Si E-mode MOSc-HEMT

摘要

In this study, we investigate the difference between ID(VG) and C(VG) pBTI shifts on GaN-on-Si E-mode MOS-channel HEMTs, under various gate voltage stresses (VGStress) and temperatures (T). A new experimental setup using ultra-fast and simultaneous ID(VG) and C(VG) measurements enables to monitor the threshold voltage VTHdrift through two metrics, $mathrm{Delta}mathrm{V}_{ext{THI}}$ and $mathrm{Delta}mathrm{V}_{ext{THC}}$. Experimental pBTI results depict a difference between $mathrm{Delta}mathrm{V}_{ext{THI}}$ and $mathrm{Delta}mathrm{V}_{ext{THC}}$, such as $mathrm{Delta}mathrm{V}_{ext{THI}} < mathrm{Delta}mathrm{V}_{ext{THC}}$. TCAD simulations support that ID(VG) shift ($mathrm{Delta}mathrm{V}_{ext{THI}}$) is related to charge trapping in Al2O3gate oxide defects at the gate corners regions while C(VG) shift ($mathrm{Delta}mathrm{V}_{ext{THC}}$) is mainly ascribed to the gate bottom, due to the presence of a back-barrier layer in the epitaxy. These previous results enable to deduce that the Al2O3defects density is more important at the gate corners than at the gate bottom.