Numerical analysis of an anomalous current assisted by locally generated deep traps in pn junctions

An anomalous current observed in reverse-biased pn junctions, highly-integrated with an extremely small cells, is analyzed with the help of device simulation. At the tail of the appearance probability, junction currents showed a steep increase and saturation as a function of applied bias. A model of localized deep-traps is proposed to explain the anomaly. The deep traps are formulated as a g/r center based on the Shockley-Read-Hall model. Simulation results clarify the mechanism of the current anomaly: when deep traps are included in the depletion layer, they act as a carrier generation center and the junction current steeply increases. The magnitude of the current after saturation is discussed, focusing on capture rate and trap density. Further, experimental features for the anomaly, e.g., the fluctuation in the critical voltage at which the current begins to increase and the structure dependence of the anomalous current, are also discussed using the present deep trap model.