Asymmetrical thyristor and method for producing same

摘要

An asymmetrical thyristor having an n+pn-np- zone sequence whose functionability is not impaired and, in particular, whose reverse blocking characteristic is not degraded, if it fires after a forward current load and subsequent commutation before its turn-off time has expired due to the positive voltage increasing again. This insensitivity to refiring after commutation when falling below the turn-off time is realized by a flat rise of the doping concentration from the n--type zone to the n-type zone, with the doping concentration in the n-type layer increasing approximately exponentially over a path of at least 50 mu . In order to keep the forward off-state current low with a flat nn- junction, the thickness and doping of the n--type layer are dimensioned such that at the highest intended forward off-state voltage the electric field intensity at the pn- junction is about 1.5x105 V/cm, drops approximately linearly in the n--type layer and, at the nn- junction, has approximately 1/4 of the value it has at the pn- junction. Methods for producing such a thyristor are also disclosed.