Radiation Effects on Silicon Schottky Barriers

Because of a variety of important new applications, it is desirable to determine the effects of radiation on silicon Schottky barrier diodes. In the present study, both neutron and low-energy electron irradiation were employed and a variety of Schottky diode structures were investigated. These included the p-n junction guard ring structure and a gate-controlled structure which was used to separate surface from bulk effects. The two main effects of low-energy electron irradiation are: increase of surface recombination velocity and buildup of a positive space charge in the oxide. These results are consistent with previous studies of p-n junction diodes. For Schottky diodes without gate electrodes, the breakdown voltage is decreased and some excess current is present at low forward bias after irradiation. The effects of nuclear irradiation are (in addition to the surface effects mentioned above): decrease of bulk lifetime and carrier removal, again consistent with previous studies on p-n junction devices. Recombination-generation current increases manyfold due to the decrease in lifetime after irradiation. This component of current is important for Pt Schottky diodes which have a high barrier (0.85 eV). However, for Al diodes, since the barrier is relatively low (0.69 eV) and the thermionic emission current relatively high, recombination-generation current is not important until very high neutron dosage.