Morley 1
J. David Morley
Computer Arch. and Org.
Dr. Jon Beck
30 April 2001
Nanocomputing: Resonance Tunneling Transistors
In current computers, one barrier to smaller processors is the size of transistors.
As processors increase in speed, more and more transistors are required. The most
common type of transistor currently used is the metal-oxide-semiconductor field effect
transistor (MOSFET). This transistor consists of two contacts separated by a section of
semi conducting material over which is a metal gate. When no charge is applied to the
gate, the semiconductor remains in its natural state, not allowing electrons to flow from
contact to contact. However, when a charge is applied to the gate, it becomes positively
charged, creating a negatively charged path in the semiconductor between the contacts,
allowing electrons to flow.
These transistors have many advantages. They are easy to manufacture, cheap,
and relatively small. They are also popular because they are very predictable down to
sizes as small as 100 nanometers across. However, at sizes smaller than this, their actions
become unpredictable. As the semiconductor becomes smaller and smaller, the
likelihood of electrons randomly jumping across the barrier is increased. This jumping is
known as “tunneling.” Tunneling prevents the manufacture of useful MOSFETs smaller
than 100 nanometers across.
Oddly enough, the very concept that made MOSFETs ineffective at smaller sizes
is precisely the design principle that allowed for a new type of transistor: the resonance
tunneling transistor.