A Numerical Study of the Impact Ionization Coefficient Approximation Model of 2-D Lateral Power Devices

Due to the complexity of the impact ionization process in power devices, the classic 1-D Fulop and Chynoweth approximation is no longer appliable to the 2-D lateral power devices. In this paper, a numerical study is conducted to explore the sensitivity of the impact ionization coefficient on the structure parameters of 2-D lateral power devices in both full- and partial-depletion cases. As a result of the 2-D RESURF effect, the structure parameters are imposing a more complicated influence on the impact ionization coefficient and therefore can not be simply considered as a function of electric field profile. Therefore, based on the 2-D Poisson’s equation and avalanche breakdown criteria, a new impact ionization coefficient approximation model for a 2-D lateral power device is presented. Based on the proposed model and 2-D Poisson’s equation, the avalanche breakdown voltage (BV) can be obtained with high veracity and effectiveness. The modeling results are compared with simulations obtained by commercial TCAD numerical simulations, which are found to be in good agreement and provide guidance for the design and optimization of 2D lateral power devices.