Semiconductor controlled rectifiers with a p-n junction having a shallow impurity concentration gradient

Claim 1

A SEMICONDUCTOR CONTROLLED RECTIFIER COMPRISING: FOUR SEMICONDUCTOR REGIONS OF ALTERNATE SEMICONDUCTIVITY TYPE WITH P-N JUNCTIONS THEREBETWEEN INCLUDING, IN SEQUENCE, A FIRST EMITTER REGION, A FIRST GASE REGION, A SECOND BASE REGION AND A SECOND EMITTER REGION; OHMIC CONTACTS ON SAID FIRST EMITTER, FIRST BASE AND SECOND EMITTER REGIONS; SAID FIRST BASE REGION HAVING A FIRST PORTION ADJACENT THE COLLECTOR JUNCTION FORMED WITH SAID SECOND BASE REGION AND A SECOND PORTION ADJACENT THE EMITTER JUNCTION FORMED WITH SAID FIRST EMITTER REGION, SAID FIRST PORTION HAVING A DOPING IMPURITY CONCENTRATION WHICH IS SUBSTANTIALLY DETERMINED BY A FIRST DOPING IMPURITY AND WHICH INCREASES AT A GRADUAL RATE AWAY FROM SAID COLLECTOR JUNCTION, SAID SECOND PORTION HAVING A DOPING IMPURITY CONCENTRATION WHICH IS SUBSTANTIALLY DETERMINED BY A SECOND DOPING IMPURITY AND WHICH INCREASES AWAY FROM SAID FIRST PORTION AT A GREATER RATE THAN THE IMPURITY CONCENTRATION OF SAID FIRST DOPING IMPURITY SO THAT A SHALLOW IMPURITY CONCENTRATION GRADIENT IS PROVIDED BY SAID FIRST DOPING IMPURITY AT SAID JUNCTION TO ACHIEVE A HIGH BREAKOVER VOLTAGE FOR THE DEVICE AND A DESIRED DOPING CONCENTRATION AT THE EMITTER JUNCTION IS PROVIDED BY SAID SECOND DOPING IMPURITY.