PROJECT TITLE :
Toward Understanding Positive Bias Temperature Instability in Fully Recessed-Gate GaN MISFETs
During this paper, totally recessed-gate GaN MISFETs with two different gate dielectrics, i.e., plasma-enhanced atomic layer deposition (PEALD) SiN and ALD Al2O3 gate dielectric, are used to review the origin of positive bias temperature instability (PBTI). By using a group of dedicated stress-recovery tests, we tend to study PBTI throughout the strain and relaxation. Hence, a defect band model with different distributions of defect levels inside the gate dielectric is proposed, which can excellently reproduce the experimental knowledge and offer insightful data regarding the origin of PBTI in GaN MISFETs. The results indicate that the intense PBTI within the device with PEALD SiN is mainly due to a wide distribution of defect levels ( eV), focused below the conduction band of GaN ( eV), and can be simply accessed by the channel carriers already at a coffee-gate voltage. On the other hand, ALD Al2O3 gate dielectric shows a narrower distribution of defects ( eV), that are far from the conduction band of GaN ( eV). This observations make a case for the improved PBTI reliability observed in devices with ALD Al2O3.
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