ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Anomalous currents (I) in worst-bit cells in high-density dynamic random-access memories are theoretically analyzed with temperature (T) as a parameter. And activation energy (Ea) is evaluated from the slopes of (log I) versus (1/T) plots. It is found that the anomaly in Ea as a function of applied bias (V), i.e., a steep decrease and saturation in Ea–V curves, can be clearly explained by introducing spatial locality in the deep-trap distribution. Moreover, it is shown that the anomaly in Ea–V curves occurs synchronously with an anomaly of current; i.e., a steep increase and saturation in I–V curves. Simulated electron-hole distributions clarify the physical mechanism of these anomalies; that is, when applied reverse bias is low and the spatially localized deep traps are outside of the depletion layer, Ea is near Eg because of electrical nonactivity of deep traps. And when applied reverse bias is high and the deep traps are spatially included in the depletion layer, carriers generated from deep-trap centers dominate the carrier transport and Ea is around the energy level (Et) of deep traps located near the midgap. The steep decrease in Ea is thus a result from mixing of the two energy levels (Eg and midgap). Further, it is found that deep-trap-assisted tunneling under a high-field condition reduces Ea. The activation energy defined by the slope in the (log I) versus (1/T) plots is therefore not considered a direct indicator of real Et. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.373498
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