A hybrid fast power diode with strongly improved reverse recovery

It is shown that the reverse recovery behaviour of a (bipolar) power diode can be strongly improved by splitting the diode area into two domains, D1, D2, which have different base widths. The domain D1 of this 'hybrid diode' has a small base width, w/sub 1/, just sufficient for the desired blocking voltage, the domain D2 a much larger base width, w/sub 2/, needed for soft recovery. The two domains are designed by area and carrier lifetime in a manner, that the main portion of the forward current flows through the thin-base domain D1, the current through D2 being approximately by a factor (w/sub 1//w/sub 2/)/sup 2/ smaller. Compared with recent fast diode concepts, a reduction of the recovery charge by a factor of about 3 can be obtained in this way without loss in softness. Adding a small-area thick-base diode, a main thin-base diode which itself is very fast but snappy, can be made soft without noticeable increase of the maximum reverse current. Analytical estimates, numerical simulations and experimental results are presented.<>