Pictured: SEM micrograph of a fabricated transistor with a 20 nm spacing between the source and the drain metals. The mark at the bottom is 100 nm.

A research team with department staff members has fabricated transistors with 20nm channel lengths.

The team, comprised of researchers from the University of Maryland, the Naval Research Laboratory and the Laboratory for Physical Sciences, has been working on a field-effect transistor based on quantum tunneling. According to this operating principle, the gate field strongly modulates the tunneling probability of electrons in between the source and the drain, and the new transistor is inherently free of the conventional short-channel effects.

Scaling of conventional MOSFET’s has been successful in the past in increasing the density and functionality of integrated circuits. However, the scaling approach is expected to meet its limit when the effective channel length reaches 0.07 micrometers due to the short-channel effects.

A recent experimental realization has demonstrated the proposed operating principle of these quantum transistors using a vertically-stacked InAs/AlSb heterostructures grown by molecular beam epitaxy. Strikingly, the desirable three-terminal characteristics persist even when the metallurgical channel length is as short as 20 nanometers. In comparison, such short channels would have caused negligible gating effects in any conventional FET.

The finding was recently published in Applied Physics Letters. In principle, the channel length can be reduced even further to nanometers. Since the channel length is the smallest, most critical feature size in MOSFET fabrication, the realization of a 20 nm channel length implies that a transistor of lateral area of 20 nm by 60 nm is readily available. Further downscaling to nanometers would bring 100 folds increase in VLSI circuit complexity over that of today’s 0.1 micron MOSFET technology.

Asssociate Professor Chia-Hung Yang, head of the Maryland research group, has been with the department for 8 years. He received his Ph.D. degree from Princeton University.

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