Transient conduction of ZnO varistors under moderate time-varying voltages: Dynamics of interfacial charges of the double Schottky barrier

作者：Cheng, Zhuolin; Hou, Zongke; Wu, Tong; Wang, Yao; Li, Rou; Lin, Ying; Li, Jianying^*; Li, Shengtao; Wu, Kangning^*

来源：Journal of Applied Physics, 2023, 133(5): 054101.

DOI：10.1063/5.0127816

• GRAIN-BOUNDARIES
• ELECTRICAL-PROPERTIES
• MODEL
• STABILITY

ZnO varistors are widely employed for overvoltage protections and surge absorptions due to their excellent nonlinear current-voltage characteristics originating from double Schottky barriers (DSBs). In most cases, they are operating under moderate ac voltages, while calculating the transient current responses of DSBs remains a challenge, impeding the development of condition assessments. In this paper, a transient conducting model for the DSB is proposed by quantifying the charge trapping processes of the interface states. The DSB is found to quickly reach a quasi-steady state, where the interfacial charge stabilizes with only small modulations at a relatively high level above the dc equilibrium value, even though the applied ac voltage varies in time and polarity. This is the result of efficient charge trapping and slow de-trapping by grain boundary interface states. For charge compensation under the time-varying voltage, the width of the two depletion regions of the DSB shows periodic changes. The proposed model is validated by a satisfying agreement between experimentally measured current responses and simulation results of ZnO varistors. The findings of this study provide a perspective on investigating the time-varying conducting systems and open avenues for condition assessments of nonlinear conducting devices.

• 单位
  西安交通大学