Control of lifetime-sensitive device characteristics by electron bombardment

It is known that bombardment of silicon with highly energetic radiation deteriorates the lifetime of minority carriers. In some semiconductor devices, e.g., the p-n-p-n transistors, a particular value of the lifetime at a prescribed current density may be required in order to obtain a suitable device characteristic. It is shown that electron bombardment of silicon p-n-p-n transistors is a process which is capable of controlling the turn-on current of the device satisfactorily over wide ranges provided the starting lifetime of the material is high enough. Bombardment with electrons from a Van de Graaff accelerator and with β rays of Sr^∞has been performed. The increase of the turn-on current with bombardment is almost linear over about two orders of magnitude. The rate of increase varies almost linearly with the prebombardment turn-on current. These results are in agreement with the Shockley-Read recombination theory.