Question

what are the quantum phenomena to improve the speed of FET transistors

Answer 1

Solution-There are following quantum phenomena to improve the speed of FET transistors-

(1) Probing quantum phenomen - The effectiveness of the material falls under its structure, which is a one-dimensional nanowire consisting of a core of silicon atoms by a shell of germenium atoms. The germanium shell is where the action takes place: close-packed alignment of pz-orbitals between germanium atoms enables electrons to jump from one atom to another in an atomic game of hopscotch called quantum tunneling.This creates a much higher electrical current when the materials is switched on. In the case of homogeneous silicon nanowires, there is no close-packed alignment of the pz-orbitals, which explains why they are less effective FETs.

Ranjit Pati, a professor of physics at Michigan Tech, led the work along with his graduate students Kamal Dhungana and Meghnath Jaishi. He explains how quantum tunneling -- a kind of atomic game of hopscotch -- works in the nanowires. "Imagine a fish being trapped inside a fish tank; if the fish has enough energy, it could jump up over the wall," Pati says. "Now imagine an electron in the tank: if it has enough energy, the electron could jump out -- but even if it doesn't have enough energy, the electron can tunnel through the side walls, so there is a finite probability that we would find an electron outside the tank.

  For Pati, catching the electron in action inside the nanowire transistors is the key to understanding their superior performance. He and his team used what is called a first-principles quantum transport approach to know what causes the electrons to tunnel efficiently in the core-shell nanowires. There are many potential uses for nanowire FETs. Pati and his team write in their Nano Letters paper that they "expect that the electronic orbital level understanding gained in this study would prove useful for designing a new generation of core−shell nanowire FETs."

Specifically, having a heterogeneous structure offers additional mobility control and superior performance over the current generation of transistors, in addition to compatibility with the existing silicon technology. The core-shell nanowire FETs could transform our future by making computers more powerful, phones and wearables smarter, cars more interconnected and electrical grids more efficient. The next step is simply taking a small quantum leap.

(2) Quantum dot field effect transistors - The use of colloidal quantum dots (QDs) in films for electronic and optoelectronic applications was suggested soon after the discovery of a quantum size effect in these semiconductor nanostructures. Since then the advantages of inexpensive solution processed colloidal QDs such as size tunable band gap, a small exciton binding energy and high photoluminescence (PL) quantum yields have been successfully demonstrated in thin film optoelectronic devices, for example, in solar cells and light-emitting diodes. Yet, charge transport measurements on QD films in field-effect transistors (FETs) have shown rather limited promise, lagging well behind commercial silicon and even organic active channel FETs until recently, largely as a result of poor carrier mobilities due to the choice of interparticle ligand materials. In the following sections we describe the synthesis of colloidal QDs with traditional long chain organic ligands, the device physics of QD based FETs, and go on to discuss the development of chemical treatments that are now being applied to vastly improve QD active channel FET performance.

(3) Quantum field-effect transistor (QFET) or Quantum-well field-effect transistor (QWFET) -   This is a type of MOSFET that takes advantage of quantum Tunneling to greatly increase the speed of transistor operation by eliminating the conventional transistor field of electron conduction which usually slows the carrier by a factor of 3000. The result is an increase in logic speed by a factor of 10 with a simultaneous decrease in the component. Power requirement and size also by a factor of 10.It achieves these things through the manufacturing process known as rapid thermal processing (RTP) which uses ultrafine layers of building materials.