A Comprehensive Analytical Study on Dielectric Modulated Drift Regions—Part II: Switching Performances

A comprehensive study on the dielectric modulated (DM) drift region for power devices is presented in this paper. The performance of this drift region structure is theoretically analyzed and compared with other two structures: conventional and superjunction. In this paper, a study is focused on switching performance. The $C$ – $V$ relationships during switching are analytically derived, and the depletion widths predicted by the proposed analytical model agree well with simulation in a wide reverse bias region. The switching energy loss is evaluated based on the analytical model and its accuracy is verified by 2-D simulations. An effective depletion charge $Q_{D}$ is defined as $E_{\mathrm {loss}}$ / breakdown voltage (BV), from which a figure of merit (FOM) of $R_{\mathrm{\scriptscriptstyle ON},\mathrm {sp}}{}^\ast Q_{D}$ is proposed to compare the performances of these different drift region structures, considering both the conduction and switching losses. The discussions in part I on Si and silicon carbide device structures are extended in part II to include FOMs. It is found that the DM drift region structures show better $R_{\mathrm{\scriptscriptstyle ON},\mathrm {sp}}$ -BV tradeoffs compared with the conventional structures, but slighter inferior FOMs. However, DM structures are still attractive for applications, where switching loss is less critical than the conduction loss, such as low frequency or soft switching.