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 implanting ions at high dose into silicon wafers (thereby amorphizing the material) followed by deposition of a metal film. The initial resistance of that structure is very high and drops several orders of magnitude after an external bias, which is higher than a specific threshold voltage, is applied. The current-versus-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-in-duced 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.