Wide bandgap power semiconductor devices, especially Gallium Nitride (GaN) high electron mobility transistors (HEMTs), have gained a lot of attention for high power applications due to their low on-resistance and high switching speed compared to their silicon counterparts. However, the reliability and failure issues related to dynamic performance, gate reliability, and electrostatic discharge have limited the wide applications of GaN power devices. This dissertation presents a systematic study of reliability and failure analysis of GaN-on-Si power devices. Firstly, the correlation between the physical trap mechanisms and the dynamic on-resistance (Ron) degradation has been investigated using a multi-frequency C-V measurement during pulse-mode stress. The experimental results indicate that the deep-level traps originated from the buffer layer play a dominant role in the dynamic Ron degradation. Secondly, the Si substrate in GaN-on-Si lateral power devices can be used as an independent contact termination rather than a thermal cooling pad. Therefore, the substrate bias effect in dynamic Ron and Gate Charge (Qg) is necessary to explore both conduction and switching loss in GaN-based converter. A reverse dual polarity (RDP) substrate pulse technique has been developed to mitigate the dynamic Ron degradation. Thirdly, the gate reliability issues, including Time-dependent dielectric breakdown (TDDB), and Bias Temperature Instability (BTI) have been explored to improve the current capability. The physical model of TDDB in GaN power devices has been established by applying the substrate biases. And three phases of threshold voltage degradation have been presented under Negative Bias Temperature Instability stress. Lastly, the ESD characteristics of GaN power devices are considered for the development of a monolithic GaN-on-Si platform. The breakdown mechanisms under ESD stress have been comprehensively studied using Transmission Line Pulse (TLP) and Very-fast Transmission Line Pulse (VFTLP) measurements.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Yang, Wen, "Reliability and Failure Analysis of GaN-on-Si Power Devices" (2021). Electronic Theses and Dissertations, 2020-. 787.