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

In this study, we investigate the difference between I-D (V-G) and C(V-G) pBTI shifts on GaN-on-Si E-mode MOS-channel HEMTs, under various gate voltage stresses (V-GStress) and temperatures (T). A new experimental setup using ultra-fast and simultaneous I-D(V-G) and C(V-G) measurements enables to monitor the threshold voltage V-TH drift through two metrics, Delta V-THI and Delta V-THC. Experimental pBTI results depict a difference between Delta V-THI and Delta V-THC, such as Delta V-THI < Delta V-THC. TCAD simulations support that I-D(V-G) shift (Delta V-THI) is related to charge trapping in Al2O3 gate oxide defects at the gate corners regions while C(V-G) shift (Delta V-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 Al2O3 defects density is more important at the gate corners than at the gate bottom.