A team of scientists at Penn State, University Park, PA, say that a new type of transistor could make fast, low-power computing devices possible for energy-constrained applications such as implantable medical electronics, smart sensor networks, and ultra-mobile computing. Called a near broken-gap tunnel field effect transistor (TFET), the new device uses the quantum mechanical tunneling of electrons through an ultrathin energy barrier to provide high current at low voltage.

A scanning electron micro- scope top view of the TFET.

TFETs are considered to be a potential replacement for current CMOS transistors, as device makers work to shrink the size of transistors and pack more transistors into a given area. The main challenge facing current chip technology is that as size decreases, the power needed to operate transistors does not decrease, resulting in batteries that drain faster and increasing heat dissipation that can damage delicate electronic circuits. Various new types of transistor architecture using materials other than the standard silicon are being studied to overcome the power consumption challenge.

For implanted devices, generating too much power and heat can damage the surrounding tissue that is being monitored, while draining the battery requires frequent replacement surgery. The researchers tuned the material composition of the indium gallium arsenide/gallium arsenide antimony so that the energy barrier was close to zero, or near broken gap, which allowed electrons to tunnel through the barrier when desired. To improve amplification, the researchers moved all the contacts to the same plane at the top surface of the vertical transistor.

This device was developed as part of a larger program sponsored by the National Science Foundation through the Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (NERC-ASSIST). The broader goal of the ASSIST program is to develop battery-free, body-powered wearable health monitoring systems with Penn State, North Carolina State University, University of Virginia, and Florida International University as participating institutions.