Investigation of nBTI degradation on GaN-on-Si E-mode MOSc-HEMT

In this paper, we investigate the influence of negative gate stress on threshold voltage V
_TH
instabilities in GaN-on-Si devices. This study has been carried out by using ultra-fast Measurement-Stress-Measurement (MSM) procedure on GaN-on-Si E-mode MOSc-HEMTs (Enhancement-mode MOS-channel HEMTs) for different gate lengths L
_G
. NBTI transients at different temperatures and complementary ToF-SIMS analysis reveal the influence of two trap populations involved on V
_TH
instabilities, both of them are related to the C
_N
acceptor traps. The first one is close to the interface between GaN and Al
₂
O
₃
gate oxide due to N-vacancies induced by the dry etching process, the second one is likely to be related to GaN:C layer. NBTI transients also exhibit a dependence with L
_G
, which is consistent with the E-field distribution of the gate region obtained by TCAD simulations at different gate stress voltages, and confirm the proximity of a C
_N
trap population to the gate oxide.