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Summary: A study into the applicability of pþ
nþ
(universal contact)
to power semiconductor diodes for faster reverse recovery
R.S. Anand, B. Mazhari *, J. Narain
Department of Electrical Engineering, Indian Institute of Technology, Kanpur 208016, India
Received 26 April 2002; received in revised form 20 June 2002; accepted 28 June 2002
Abstract
The use of pþ
nþ
universal contact for improving switching performance in diodes is studied in detail. A theoretical
framework is described which shows that the incorporation of universal contact either at the end of the lightly doped
region or in the injecting p or n regions of the diode can all be viewed as an attempt to reduce the effective minority
carrier lifetime in the diode by redistributing minority carrier current from the lightly doped region of the diode where
recombination lifetime is high to other regions of the diode where the presence of universal contact results in smaller
recombination lifetime. It is shown that the incorporation of universal contact allows a new tradeoff between the ef-
fective recombination lifetime and the reverse blocking voltage determined by the proximity of universal contact to the
lightly doped region of the diode. The impact of insertion of universal contact on reverse recovery is discussed as a
function of current density and reverse blocking voltage.
Ó 2002 Published by Elsevier Science Ltd.
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