Manhong Zhang, Yi Zhai
Recovering the carrier number conservation in SPICE simulation of PIN diodes and IGBT devices
Solid-State Electronics
Available online 7 February 2022, 108239
DOI: 10.1016/j.sse.2022.108239
North China Electric Power University, Beijing 102206, China
Abstract: In SPICE simulations of PIN diodes and IGBT devices using finite difference method, one discretizes an undepleted N- region into several equally spaced nodes with a time-dependent distance of Δx(t). Then transforms the ambipolar diffusion equation, a time-space partial differential equation, into a set of time-dependent ordinary differential equations. However, the time-dependent property of Δx(t) destroys the carrier number conservation. In this paper, we propose an approach to account for the effect of the Δx(t) by introducing an auxiliary system. It has the same total current and the total carrier number in the undepleted N- region as the real system, but has different electron and hole current components. The difference is caused by adding compensation current terms with the equal amplitude and opposite sign to the electron and hole current terms in the auxiliary system. These compensation current terms are proportional to the boundary speed of the undepleted N- region and do not change the total current. The auxiliary system can be easily solved using SPICE behavior models and its carrier density is a good approximation to the real one. Our simulations show that the compensation current correction is important for fast switching PIN diodes, but may not be very important in IGBT devices due to their large gate-related capacitance.
FIG: SPICE simulation model of PIN diodes and IGBT devices
