Self-heating of high-voltage (6 kV class) 4H-SiC rectifier p(+)-n-n(+) diodes under the action of a single 20 mu s forward current surge pulse has been studied experimentally up to current densities j approximate to 100 kA/cm(2). The diode parameters are stable after a single surge pulse with current density j approximate to 60 kA/cm(2), although the estimated temperature of the diode at the end of this pulse similar to 1650 K. After several pulses of this amplitude or after subjecting the diode to pulses with higher current density, the diode degrades. The degradation is manifested in an irreversible decrease of the differential resistance of the diode under a high forward bias. Even a single 20 Its pulse with peak current density j approximate to 100 kA/cm(2) leads to total destruction of the device. (C) 2008 Elsevier Ltd. All rights reserved.