Overcoming transistor miniaturization limits due to ‘quantum tunneling’

Breakthrough could jumpstart further miniaturization of transistors, possibly extending Moore's law
June 7, 2018

An illustration of a single-molecule device that blocks leakage current in a transistor (yellow: gold transistor electrodes) (credit: Haixing Li/Columbia Engineering)

A team of researchers at Columbia Engineering and associates* have synthesized a molecule that could overcome a major physical limit to miniaturizing computer transistors at the nanometer scale (under about 3 nanometers) — caused by “leakage current.”

Leakage current between two metal transistor electrodes results when the gap between the electrodes narrows to the point that electrons are no longer contained by their barriers — a phenomenon known as quantum tunneling.

The researchers synthesized the first molecule** capable of insulating (preventing electron flow) at the nanometer scale more effectively than a vacuum barrier (the traditional approach). The molecule bridges the nanometer gap between two metal electrodes.

Constructive interference (left) between two waves increases the resulting wave; destructive interference (right) decreases the resulting wave. (credit: Wikipedia)

The silicon-based molecule design uses “destructive quantum interference,” which occurs when the peaks and valleys of two waves are placed exactly out of phase, annulling oscillation.

“We’ve reached the point where it’s critical for researchers to develop creative solutions for redesigning insulators. Our molecular strategy represents a new design principle for classic devices, with the potential to support continued miniaturization in the near term,” said Columbia Engineering physicist Latha Venkataraman, Ph.D.

The research bucks the trend of most research in transistor miniaturization, which aims to create highly conducting contact electrodes, typically using carbon nanotubes (see “Method to replace silicon with carbon nanotubes developed by IBM Research”).

* Other researchers on the team were from Columbia University Department of Chemistry, Shanghai Normal University, and the University of Copenhagen.

** The molecule is bicyclo[2.2.2]octasilane.