Transistor with an elevated switching speed and a reduced sensitivity to secondary opening

摘要

A power transistor having improved turn-off characteristics and enhanced reversed second breakdown capabilities is described wherein the emitter of the transistor includes first and second regions, the first region 46 being laterally surrounded by the second region 42, 44 and having lower gain than the second region. Turn off is enhanced as essentially no current flows under the lower gain first region during turn off thereby facilitating the removal of excess charge carriers when the device is in the turn-off stage. The lower gain for the first region is obtained typically by reducing its thickness which in one embodiment is zero. The lower gain may also be obtained by isolating the emitter electrode from the central portion of an emitter region of uniform thickness. Preferably, the emitter region is comb-shaped. IMAGE