Analytical model for dynamic avalanche onset of planar IGBTs

Abstract

Dynamic avalanche effect can occur due to the influence of free carrier on electric filed during inductive turn-off of IGBT, which is a critical factor influencing the device reliability. In this paper, a one-dimensional (1-D) analytical model for dynamic avalanche onset is at first derived based on the basic principles of semiconductor and it gives insight into the details of internal physical mechanisms of the device at the onset of dynamic avalanche. Then the critical structural parameters affecting the onset of dynamic avalanche are examined. By introducing a modification factor K into the 1-D model, a rough two-dimensional (2-D) analytical model that can reflect nonuniformity of the current distribution qualitatively during the turn-off of planar IGBTs is eventually obtained.