Avalanche-Induced Negative Resistance in Thin Oxide Films

Abstract

A current-controlled negative resistance phenomenon, similar to that exhibited by a gas discharge tube, has been observed in suitably prepared thin oxide films of Nb, Ta, and Ti, sandwiched between thin-film metal electrodes, at frequencies up to 1 Mc/sec. The voltage required to sustain the negative resistance in both directions of current is independent of the electrode materials, apparent area and thickness (up to 500 Å) of the oxide film, and is about 0.4, 1.3, and 3.5 V for Ti, Nb, and Ta oxide films, respectively. The corresponding electric fields are approximately 0.8×106, 3×106, 9×106 V/cm. These values increase slightly with decrease of temperature. Experimental evidence supports the interpretation of the phenomenon in terms of avalanche multiplication of carriers in a thin region of the oxide film attended by space-charge-limited flow conditions.