Anomalous Reverse Recovery of Body Diode in 4H-SiC Superjunction DMOSFET

Abstract:

We report an anomalous reverse-recovery (RR) of the body diode in a 3.3 kV 4H-SiC superjunction (SJ) DMOSFET: at 77 K, Q_RR,sp increases by 1.4×–3.5× versus room temperature and 5× versus 195 K, and J_PR increases by >2×, while t_RR changes by only <30ns. A clear dependence of Q_RR,sp on the ramp rate at 77K indicates the Q_RR,sp is not due to additional depletion charge. Current-controlled negative resistance (CCNR) is also observed solely for the SJ body diode at 77K. The voltage waveforms strongly suggest the additional Q_RR,sp is due to dynamic breakdown of the SJ due to transient charge imbalance of the pillars caused by delayed hole emissions of the deep acceptors. The anomalous behavior is qualitatively reproduced in simulation. We also benchmark a 3.3kV Charge Balance (CB) 4H-SiC DMOSFET along with the SJ device from 77–423 K using an inductive double-pulse test. For T > 77 K the switching for both devices is dominated by the depletion capacitance (weak Q_RR,sp dependence on the ramp rate): the SJ device turns off faster (t_RR = 0.3–0.8× CB), is snappier (t_B/t_A = 0.23–0.56× CB), and shows larger J_PR (1.8–2.8× CB) while recovering less charge (Q_RR,sp = 0.4–0.8× CB). The CB device shows the expected increase of Q_RR,sp with temperature and only modest t_RR temperature variation. Overall, the CB device provides softer, predictable RR without a cryogenic anomaly, whereas SJ delivers the shortest t_RR above 77 K but exhibits the 77 K anomalous increase and is consistently snappier.

• Periodical: Key Engineering Materials (Volume 1057)
• Pages: 111-118
• DOI: https://doi.org/10.4028/p-Xxkc5I
• Online since: May 2026
• Authors: Giorgian Borca-Tasciuc*, Reza Ghandi, Collin W. Hitchcock, Tat Sing Paul Chow
• Keywords: Charge-Balance, Dynamic Breakdown, Reverse Recovery, Superjunction (SJ)

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