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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum
1960. That sustained rate of progress has resulted in low-cost volume manufacturing of high-density memories with 64 million bits of memory on a chip and complex, high-performance logic chips with ~10 million transistors on a chip. This trend is projected to continue for the next several years.
If the silicon integrated circuit is the engine that powers the computing and communications revolution, optical fibers are the highways for the Information Age. Although fiber optics is a relatively recent entrant in the high technology arena, the impact of this technology is enormous and growing. It is now the preferred technology for transmission of information over long distances. There are already approximately 30 million km of fiber installed in the United States and an estimated 100 million km installed worldwide. Due in part to the faster than exponential growth of connections to the Internet, the installation of optical fiber worldwide is occurring at an accelerated rate of over 20 million km per year—more than 2,000 km/h, or around Mach 2. In addition, the rate of information transmission down a single fiber is increasing exponentially at a rate of a factor of 100 every decade. Transmission in excess of 1 terabit per second has been demonstrated in the research laboratory, and the time lag between laboratory demonstration and commercial system deployment is about 5 years.
Compound semiconductor diode lasers provide the laser photons that are the vehicles that transport information along the optical information highways. Semiconductor diode lasers are also at the heart of optical storage and compact disk technology. In addition to their use in very-high-performance microelectronics applications, compound semiconductors have proven to be an extremely fertile field for advancing our understanding of fundamental physical phenomena. Exploiting decades of basic research, we are now beginning to be able to understand and control all aspects of compound semiconductor structures, from mechanical through electronic to optical, and to grow devices and structures with atomic layer control, in a few specific materials systems. This capability allows the manufacture of high-performance, high-reliability, compound semiconductor diode lasers that can be modulated at gigahertz frequencies to send information over the fiber-optical networks. High-speed semiconductor-based detectors receive and decode this information. These same materials provide the billions of light-emitting diodes sold annually for displays, free-space or short-range high-speed communication, and other applications. In addition, very-high-speed, low-power compound semiconductor electronics play a major role in wireless communication, especially for portable units and satellite systems.
Another key enabler of the information revolution is low-cost, low-power, high-density information storage that keeps pace with the exponential growth of computing and communication capability. Both magnetic and optical storage are in wide use. Very recently, the highest-performance magnetic storage/readout devices have begun to rely on giant magnetoresistance (GMR), a phenomenon that was discovered by building on more than a century of research in magnetic materials. Although Lord Kelvin discovered magnetoresistance in 1856, it was not until the early 1990s that commercial products using this technology were introduced. In the last decade, the condensed-matter and materials understanding converged with advances in our ability to deposit materials with atomic-level control to produce the GMR heads that were introduced in workstations in late 1997. It is hoped that, with additional research and development, spin valve and colossal magnetoresistance technology may be understood and applied to workstations of the future. This increased understanding, provided in part by our increased computational ability arising from the increasing power of silicon ICs, coupled with atomic-level control of materials, led to exponential growth in the storage density of magnetic materials analogous to Moore' s law for transistor density in silicon ICs.
Future Directions and Research Priorities
Numerous outstanding scientific and technological research needs have been identified in electronic, photonic, and magnetic materials and phenomena. If those needs are met, it is anticipated that these technology areas will continue to follow their historical exponential growth in capability per unit cost for the next few years. Silicon integrated circuits are expected to follow Moore's law at least until the limits of optical lithography are reached, transmission bandwidth of optical fibers is expected to grow exponentially with advances in optical technology and the development of soliton propagation, and storage density in magnetic media is expected to grow exponentially with the maturation of GMR and development of colossal magnetoresistance in the not too distant future. Although these changes will have a major impact on computing and communications over the next few years, it is clear that extensive research will be required to produce new concepts and that new approaches must be developed