Quantum Nanoelectronics

An Introduction to Electronic Nanotechnology and Quantum Computing

Edward L. Wolf

• Publisher: Wiley-VCH
• Year: 2015
• ISBN:
  9783527665389
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

A tutorial coverage of electronic technology, starting from the basics of condensed matter and quantum physics. Experienced author Ed Wolf presents established and novel devices like Field Effect and Single Electron Transistors, and leads the reader up to applications in data storage, quantum computing, and energy harvesting.
Intended to be self-contained for students with two years of calculus-based college physics, with corresponding fundamental knowledge in mathematics, computing and chemistry.

1
Introduction and Review of Electronic Technology

Electronic devices are central to modern technology. Silicon chips are everywhere, including cars and appliances, and have transformed computation, information processing, and communications, culminating in the modern Internet. The silicon revolution started with the transistor, leading to the integrated circuit, and to the Pentium chip. A related semiconductor device, the solid-state junction laser, in conjunction with the optical fiber, has led to cheap, reliable virtually instantaneous worldwide communication. Outsourcing, globalization, and the “flat world” have been enabled by these technical advances.

The assumption of this book is that this revolution is not over, but rather is entering a new phase. The era of microelectronics is opening to a future of nanoelectronic technology.

The central feature of the silicon revolution has been the miniaturization of transistors and their grouping into integrated circuits, which now contain billions of identical transistor elements. In very large scale integration (VLSI), a whole computer can exist on a square centimeter of silicon. Smaller transistors are cheaper, more are available on a single chip, and operate more quickly, now as fast as 3 billion steps per second. Gordon Moore, a founder of the Intel Corporation, noted long ago that the number of transistors per chip, roughly one square centimeter, tended to double every 18 months or so as the technology improved and larger markets appeared. “Moore’s law” has seen the transistor count increase from hundreds to hundreds of millions! Chips containing 0.8 billion transistors on roughly one square centimeter are being produced as described in Chapter 7 [1].

The key to this advance has been the “scaling” to smaller size of the active cells, containing field effect transistors (FETs) and other devices. Scaling has taken silicon electronics into the nanometer domain, where it now is approaching its limit, set by the size of atoms. The smallest dimension in the FET has been the thickness of the thermally grown silicon dioxide insulator for the gate electrode. It has long been recognized that scaling will work only down to thicknesses large compared to the silicon and oxygen atomic radii in the SiO₂, needed to preserve the desired insulating property. Intel Corporation [1] has abandoned the scaled silicon dioxide to insulate the gate electrode, in favor of deposited “high dielectric constant” oxides based on the heavy metals hafnium and zirconium. Literally, the thermally grown silica, forced thinner and thinner by the scaling formula, contained only a handful of silicon atoms across its thickness, allowing electrons to “leak” through by the quantum mechanical tunneling effect.

A second imperative for a new era in nanoelectronics comes from the limit of patterning resolution, limited by wavelength of the light used to imprint patterned features onto the chip. The smallest feature size in the newest generation of silicon devices is 45 nm, achieved by artful use of light of 193 nm wavelength.

The equipment for producing and applying the patterning light is a leading cost in a fabrication facility, and reducing the wavelength of patterning light has become increasingly difficult and costly. Energy conservation is also a driving force for technology change. Large computing installations consume megawatts of power. Laptop computers run hot and their batteries frequently need recharging.

A third indicator, an opportunity for change, comes from new computing technologies. One of these, the Josephson junction-based “rapid single flux quantum” technology, has logic circuits that are wholly superconducting and thus use less energy. An entirely new concept is “quantum computing,” in which the binary bit is replaced by a “qubit” that can take on more than two values, which is inherently faster in solving certain types of computations, including factoring of large numbers, of great interest in cryptography. The first realization of this new class of “quantum computers” has also been based on Josephson junctions, using superconducting niobium at very low temperature. A large installation of this type would use much less power than today’s supercomputer.

The traditional scaling to smaller sizes in the silicon technology has come to an end. As noted, the Intel Corporation has abandoned the thermal silicon gate oxide, and the photolithography cannot proceed further without abandoning lenses of any sort. Size reduction will continue for several more generations, but increasingly requires further essential innovation. Nonetheless, it is entirely clear that the present silicon computer technology has essentially reached its final form.

The several aspects of this new situation are the topics of this book. A new era in electronics is opening, with opportunities for new ideas, new companies, and new jobs for technologists.

Of course, the present state of computing technology is highly advanced, delivering huge performance at still decreasing cost. This technology will not disappear. The new evolution may resemble that of automobiles. One can argue that automobiles have only incrementally changed since the introduction of the automatic transmission and air conditioning, and a similar outcome is not unreasonable for electronics. It is unlikely that there will be a change away from silicon electronics as dramatic and complete as the recent tipping point in which digital photography replaced silver halide photography. It does seem likely, though, that in some application areas there will be reason enough to have major innovation.

The important point is that still there is room for much improvement. As we will see, the laws of physics still allow huge advances, perhaps a factor of 10000, in device density and computer performance beyond the present levels in the semiconductor technology. For example, the area of the repeating unit cell in the most recent [1] 45 nm Intel CMOS (complementary metal oxide silicon) technology is 0.346 μm², corresponding to device density of 2.89 × 10¹² m⁻¹ or 2.89 × 10⁸ cm⁻². (“45 nm” refers to the smallest feature size F, but the si...

Table of contents

• Cover
• Table of Contents
• Series
• Title
• The Author
• Copyright
• Dedication
• Preface
• 1 Introduction and Review of Electronic Technology
• 2 From Electronics to Nanoelectronics: Particles, Waves, and Schrödingerߣs Equation
• 3 Quantum Description of Atoms and Molecules
• 4 Metals, Semiconductors, and Junction Devices
• 5 Some Newer Building Blocks for Nanoelectronic Devices
• 6 Fabrication and Characterization Methods
• 7 The Field Effect Transistor: Size Limits
• 8 Devices Based upon Electron Tunneling: Resonant Tunnel Diodes
• 9 Single-Electron Transistors, Molecular and Hybrid Electronics
• 10 Devices Based on Electron Spin and Ferromagnetism for Storage and Logic
• 11 Qubits Versus Binary Bits in a Quantum Computer
• 12 Applications of Nanoelectronic Technology to Energy Issues
• 13 Future of Nanoelectronic Technology
• Exercises
• Abbreviations
• Some Useful Constants
• Index
• Wiley End User License Agreement