Bulk "On", "Off", and negative resistance modes in neutron-irradiated silicon

Extremely sharp Zener-like bulk characteristics, symmetrical and asymmetrical, have been obtained in fast-neutron-irradiated silicon. The volt-ampere characteristic consists of a high-resistivity ("off") Ohm\´s law region, breaking sharply into an essentially vertical ("on") region. The "on" region extends several orders of magnitude in current at constant voltage. The mechanism is not related to Zener breakdown (except in appearance); it is rather a trap-filling process, agreeing completely with a theoretical model proposed by M. A. Lampert (1956) for single injection in the presence of a discrete trap. These results were obtained at 77°K due to the necessity of biasing the thermodynamic Fermi level to the vicinity of the desired trap. Other traps are present, and efforts are presently under way to extend the mechanism to the range of room temperature. Limited success has been achieved.