The electrical properties of ion-implanted amorphous silicon programmable element in the unprogrammed state

An amorphous silicon layer, confined between metal and single-crystalline silicon, is created by the implantation of ions at high dose into silicon wafers followed by deposition of a metal film. The initial resistance of this structure is very high and drops several orders of magnitude after an external bias that is higher than a specific threshold voltage is applied. The current-voltage characteristics of the device at its initial off state are studied as a function of: (1) doping type and concentration; (2) amorphization ion energy, dose, and type; and (3) alloying conditions. Current measurements are reported as a function of temperature for fixed-bias conditions. The current-voltage characteristics of most of the data are functionally consistent with a Poole-Frenkel trap-to-trap field-induced charge-conduction model. However, there are some deviations from the Poole-Frenkel model that are probably due to the influence of the amorphous-layer boundaries with the metal and the substrate