Symmetrical switching diode

Claim 1

A SYMMETRICAL THREE-LAYER AVALANCHE DIODE COMPRISING A THIN WAFER OF MONOCRYSTALLINE SILICON HAVING A P-TYPE CENTRAL REGION BETWEEN TWO DIFFUSED N-TYPE OUTER REGIONS, THE N-TYPE REGIONS BEING UNIFORMLY SPACED FROM ONE ANOTHER THROUGH THE P-TYPE REGION BY ABOUT 0.6 TO 1.0 MIL SO THAT THE APPARENT GAIN OF THE TRANSISTOR-LIKE DEVICE INHERENT IN THE GEOMETRY OF THE THREE LAYER STRUCTURE WILL BE RELATIVELY LOW, THE N-TYPE REGIONS BEING SUBSTANTIALLY EQUIVALENT TO ONE ANOTHER IN PHYSICAL DIMENSIONS AND IMPURITY CONCENTRATIONS, THE P-TYPE REGION HAVING AN IMPURITY CONCENTRATION WHICH IS UNIFORM IN A DIRECTION PERPENDICULAR TO THE PLANE OF THE WAFER, SAID IMPURITY CONCENTRATION OF THE P-TYPE REGION HAVING LESS THAN THAT OF SAID N-TYPE REGIONS, THE IMPURITY CONCENTRATION OF THE P-TYPE REGION RELATIVE TO THE IMPURITY CONCENTRATIONS OF THE N-TYPE REGIONS AND THE THICKNESS OF THE P-TYPE REGION PREVENTING PUNCH-THROUGH FROM OCCURRING AT A BIAS VOLTAGE LOWER THAN AVALANCHE BREAKDOWN, AND A PAIR OF METALLIC CONTACTS ADHERENT TO THE N-TYPE REGIONS FOR PROVIDING OHMIC CONNECTIONS THERETO.