Enhanced Transient Behavior in MIS(p) Tunnel Diodes by Trench Forming at the Gate Edge

Abstract

In this article, a new type of metal-insulator-semiconductor (MIS) tunnel diode (TD), trench MIS TD, was investigated. From the current-voltage characteristics, memory retention, and memory endurance measurements, we found that the trench MIS TDs not only have lower reverse bias current, but also show stronger transient current compared to traditional planar structure MIS TDs. For example, in the 1000-cycle memory endurance test, we observed a 25 times larger current window (CW) in trench devices than the CW of planar devices. We attribute the lower reverse bias current to the fewer minority carriers (electrons) in trench MIS TDs, which is supported by the high-frequency capacitance-voltage (C-V) measurement. As for the enhanced transient behavior of trench MIS TDs, we proposed a mechanism based on the understanding of fewer minority carriers in trench devices to explain our observation. Eventually, we examined the effect of different equivalent oxide thicknesses (EOTs) on the CW and found that the trench devices have better CW in a wide EOT range. Because of the enhanced transient behavior leading to better memory CW, trench MIS TDs have the potential to serve as memory devices.