Until now, the continuous development of electronics has been characterized by Moore’s
law. The scale down resulted in the nanosized CMOS integrated circuits, pushing the
“red brick wall” towards the lower dimensions.
Although the current CMOS integrated circuit development is driven by a lot of innovations,
there are still some limits determined by unavoidable physical effects such as tunneling
of charge carriers through thin insulating regions and statistical irregularities
in the number of dopant atoms.
On the other hand, there are many new ideas for building atomic or molecular scale
devices for the information technology. However, there is still a gap between the
up-to-date “top-down” CMOS technology and the “bottom-up” devices, i.e. molecular
electronics, nanotubes, single electron transistors. A new functional thermal-electronic
device (phonsistor) and the CMOS compatible thermal-electronic logic circuit (TELC)
[1,2] may help to fill this gap. The operation of these functional devices is based
on the semiconductor-metal transition (SMT) effect shown by certain materials, for
example VO2. This effect allows an electric resistance change in three to four orders
of magnitude induced by thermal or electrical excitation. [3]
The recently proposed novel active device (phonon transistor = phonsistor) is made
up of only bulk type semiconductor domains, consisting of significantly less regions,
interfaces, and providing advanced functionality compared to a monolithic MOSFET (there
are no differently doped regions, p-n junctions at all). This way the single switches
can be processed in steps that are technologically less demanding and fewer in number.
The switches in the thermal-electronic logic circuit (TELC) can be excited by electronic
and thermal signals as well, thus two different physical parameters are available
for representing the different logic states. This is similar to neurons in the nervous
system, where information is transmitted by different mechanisms for short and long
distances and allows the realization of more complex logical connections as well as
modeling of data processing in nervous systems.
Due to its simple structure and process technology the TELC can be built as real 3D
structure and can be made compatible with current CMOS technology enabling a smooth
transition between the two integrated circuit concepts. With its extended logical
functionality, TELC represent a higher level of integration that can be achieved with
currently available technology.
If scaled down to nanosize, the heat is distributed not only by diffusion, as it is
characteristic for macroscopic structures. Quantum and hot electron effects enable
the device to operate faster than current CMOS switches. SMT properties of VO2 have
been demonstrated down to 10 nm crystal size [4], thus scale down will be possible
at least to this device size.
The presentation will introduce the application of the SMT properties of vanadium
dioxide in a novel thermal-electronic switching device called phonsistor, the operational
principles of the phonsistor and the integration possibilities into logic circuits.
A proof of concept for the device operation will be demonstrated. Further development,
device scaling and integration issues will be discussed.
References
[1]J. Mizsei, J. Lappalainen, and M.C. Bein, “Thermal-electronic integrated logic,”
in Thermal Investigations of ICs and Systems (THERMINIC), 2013 19th International
Workshop on, pp. 128–134, Sept. 2011.
[2]J. Mizsei and J. Lappalainen, “Logic arrangement,” WIPO/ PCT Patent WO2013/160709
A2, Oct. 31, 2013.
[3]A. Zylbersztejn and N.F. Mott, “Metal-insulator transition in vanadium dioxide,”
Phys. Rev. B, vol. 11, no. 11, pp. 4383–4395, Jun. 1975.
[4]J. Nag and R.F. Haglund, “Synthesis of vanadium dioxide thin films and nanoparticles,”
J. Phys.: Condens. Matter, vol. 20, no. 26, p. 264016, Jun. 2008.
