A Semi-Floating Gate Transistor for Low-Voltage Ultrafast Memory and Sensing Operation

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Science  09 Aug 2013:
Vol. 341, Issue 6146, pp. 640-643
DOI: 10.1126/science.1240961

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Faster at the Gate

Advanced designs will be needed to continue to improve the performance of the main components of high-speed computing, metal-oxide semiconductor field-effect transistors (MOSFETs) and floating-gate (FG) MOSFETs. Wang et al. (p. 640) fabricated a semi-floating gate (SFG) transistor in which a tunneling field-effect transistor couples the positively doped floating gate to the negatively doped drain region. The charge stored on the SFG was used to shift the voltage threshold for switching the transistor, which in turn sped up its operation and lowered the power consumed. These devices were used for ultrahigh-speed memory and in light sensing and imaging.


As the semiconductor devices of integrated circuits approach the physical limitations of scaling, alternative transistor and memory designs are needed to achieve improvements in speed, density, and power consumption. We report on a transistor that uses an embedded tunneling field-effect transistor for charging and discharging the semi-floating gate. This transistor operates at low voltages (≤2.0 volts), with a large threshold voltage window of 3.1 volts, and can achieve ultra–high-speed writing operations (on time scales of ~1 nanosecond). A linear dependence of drain current on light intensity was observed when the transistor was exposed to light, so possible applications include image sensing with high density and performance.

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