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 VTH 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 LG. NBTI transients at different temperatures and complementary ToF-SIMS analysis reveal the influence of two trap populations involved on VTH instabilities, both of them are related to the CN acceptor traps. The first one is close to the interface between GaN and Al2O3 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 LG, 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 CN trap population to the gate oxide.