March 27, 2012

More Energy Efficient Transistors through Quantum Tunneling

Researchers at the University of Notre Dame and Pennsylvania State University have announced breakthroughs in the development of tunneling field effect transistors (TFETs), a semiconductor technology that takes advantage of the quirky behavior of electrons at the quantum level.

TFETs are on track to solve power leakage and heat problems of regular transistors and delivering comparable performance to today’s transistors, but with much greater energy efficiency.

They do this by taking advantage of the ability of electrons to “tunnel” through solids, an effect that would seem like magic at the human scale but is normal behavior at the quantum level.

“A transistor today acts much like a dam with a moveable gate” says Alan Seabaugh, professor of electrical engineering at Notre Dame and the Frank M. Freimann Director of MIND. “The rate at which water flows, the current, depends on the height of the gate.”

“With tunnel transistors, we have a new kind of gate, a gate that the current can flow through instead of over. We adjust the thickness of the gate electrically to turn the current on and off.”

“Electron tunneling devices have a long history of commercialization,” adds Seabaugh, “You very likely have held more than a billion of these devices in a USB flash drive. The principle of quantum mechanical tunneling is already used for data storage devices.”

While TFETs don’t yet have the energy efficiency of current transistors, papers released in December 2011 by Penn State and March 2012 by Notre Dame demonstrate record improvements in tunnel transistor drive current, and more advances are expected in the coming year.

Electron Device Letters - AlGaSb/InAs Tunnel Field-Effect Transistor With On-Current of 78 μA/ μm at 0.5 V

March, 2012, Record high on-current of 78 μA/ μm in a tunnel field-effect transistor (TFET) is achieved at 0.5 V at room temperature. The TFET employs a staggered AlGaSb/InAs heterojunction with the tunneling direction oriented in-line with the gate field. The measured results are consistent with numerical simulation of the device structure. Simulations of optimized structures suggest that switching speed comparable to that of the MOSFET should be achievable with improvements in the source and drain resistances.

Semiconductor Today - IQE and Penn State present arsenide/antimonide vertical hetero tunnel FETs

Dec, 2011 - The paper ‘Demonstration of MOSFET-Like On-Current Performance in Arsenide/Antimonide Tunnel FETs with Staggered Heterojunctions for 300mV Logic Applications’ describes the demonstration experimentally of a vertical hetero tunnel field-effect transistor (HTFET) with a record high drive current (ION) of 190µA/µm and 100µA/µm at VDS=0.75V and 0.3V, respectively.

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