Semiconductor conductivity can be controlled by the electric or magnetic field, by exposure to light or heat, or by the mechanical deformation of a doped mono crystalline grid; thus, semiconductors can make excellent sensors. Current conduction in a semiconductor occurs free of electrons and holes, collectively known as charge carriers. Doping of silicon is done by adding a small amount of impurity atoms and also for phosphorus or boron, significantly increases the number of electrons or holes within the semiconductor.
The junctions which formed where n-type and p-type semiconductors are joined together is called p—n junction. A semiconductor diode is a device typically made up of a single p-n junction. The junction of a p-type and n-type semiconductor forms a depletion region where current conduction is reserved by the lack of mobile charge carriers. When the device is forward biased, this depletion region is reduced, allowing for significant conduction, when the diode is reverse biased, the only less current can be achieved and the depletion region can be extended.
Exposing a semiconductor to light can produce electron hole pairs, which increases the number of free carriers and thereby the conductivity. Diodes optimized to take advantage of this phenomenon is known as photodiodes. Compound semiconductor diodes are also being used to generate light, light-emitting diodes and laser diodes.
Bipolar junction transistors are formed by two p-n junctions, in either p-n-p or n-p-n configuration. The middle or base, the region between the junctions is typically very narrow.
The other regions, and their related terminals, are known as the emitter and collector. A small current injected through the junction between the base and emitter change the properties of the base collector junction so it can be conduct current even though it is reverse biased. This creates a larger current between the collector and emitter, and controlled by the base-emitter current.
Another type of transistor named as field-effect transistor , it operates on the principle that semiconductor conductivity can increased or decreased by the presence of an electric field. An electric field can increase the number of electrons and holes in a semiconductor, thus changing its conductivity.
Depending upon the type of carrier in the channel, the device may be n-channel for electrons or p-channel for holes MOSFET. The silicon Si is most widely used material in semiconductor devices. Its useful temperature range makes it currently the best compromise among the various competing materials. Silicon used in semiconductor device manufacturing is presently fabricated into bowls that are large enough in diameter to allow the manufacture of mm 12 in.
Germanium Ge was a widely used in early semiconductor material, but its thermal sensitivity makes less useful than silicon. Nowadays, germanium is often alloyed with Si silicon for use in very-high-speed SiGe devices; IBM is a main producer of such devices. In the following year, , a group of scientists at Bell Laboratories created the first transistor. Transistors were much smaller, much lighter, more durable, and more efficient than vacuum tubes.
Their invention, followed by the development of the integrated circuit in the late s, paved the way for the revolution in personal computers and the rise of Silicon Valley. While the personal computer industry was still small in the s and s, large computers—even with sophisticated cooling techniques—started pushing past the power limits of early transistor technology. This paved the way for the integration of complementary metal-oxide semiconductor CMOS technology.
In comparison to earlier semiconductor technologies, CMOS technology came with the benefits of low power consumption and limited waste heat. CMOS technology facilitated the development of new logic and memory products in the personal and commercial branches of the computer industry by the mids.
Within a decade, however, power limits became an issue once again. This spurred the industry to adopt multicore processing to increase computational performance. Innovation has continued to drive new semiconductor technology in the present. In order to achieve performance comparable with previous decades, the industry has started to depart from past architectures and devise new solutions to meet present and future problems.
In an effort to maintain its steady rate of performance, the semiconductor industry has embraced two key types of techniques in an effort to overcome existing semiconductor limits: More Moore PDF, 2 MB and More than Moore. Demands for continued scaling and performance improvements have become especially important amid demand for new applications.
High-performance computing, mobile computing, and autonomous sensing and computing are driving More Moore technologies. These technologies target more performance at constant power and cost. But new demands and applications are likewise driving these solutions. The integration of new nondigital functions into personal electronics systems, for example, are spurring More than Moore solutions. We can see examples of these solutions in miniature camera modules, motion sensing, biometric identification, and health monitoring systems.
Future developments in nano- and biotechnology are also likely to continue spurring More than Moore technologies and products. With these developments on the horizon, the future of the semiconductor industry is headed Beyond CMOS.
More Moore techniques have already extended current CMOS scaling limits past an order of magnitude in feature size and two orders of magnitude in speed. A key goal of Beyond CMOS research and development is to replace commonly used static random-access memory and flash memory technologies with both new volatile and nonvolatile memory technologies.
Researchers hope to meet the demand for electronically accessible memories that are high speed, high density, low power, and embeddable. It will likely be a while before this technology is integrated in devices that are available to the general public. What is important, however, is that researchers are working toward new and exciting capabilities to meet market demands. The growth of fabless design houses and foundries has completely transformed the business of the semiconductor industry in the last fifteen years.
With fabless manufacturing, specialized manufacturers produce semiconductor devices while system integrators maintain control over the business model and design of semiconductor chips. This specialization allows system integrators to establish system requirements for new products at the start of a design cycle. Semiconductor manufacturers, in turn, meet demands that arise from these system requirements and make their way down the fabrication production chain. In the past, the creation of a newer, faster integrated circuit triggered the design of new personal computers.
But today the relationship between new devices and semiconductor tech is reversed: the design of new smartphones triggers the creation of new semiconductor devices. These recent transformations are part of a broader shift within the industry. The industry is moving away from being a monoculture and toward more diversity and innovation. This promises to eliminate some of the unfortunate consequences of previous industry development.
Namely, this shift reverses the architecture and industry consolidation that has limited industry participation and innovation and caused insecurity within the industry in the past. The rapid development of smartphones along with computers and other electronics has forced a significant downscaling in the physical size of devices. This, in turn, has necessitated constant improvement in the semiconductor industry. However, the industry also appears to be reaching the limits of miniaturization with existing technologies.
Graphene and related two-dimensional 2-D materials, for example, have great potential to overcome the limitations of silicon technology. As such, they offer hope for improvements in both device component function and performance in computational and noncomputational applications. In the realm of noncomputational applications, these materials can be integrated into future cameras, low-power optical data communications, and gas sensors and biosensors.
Compound semiconductors, which combine two or more chemical elements, are also at the forefront of developing semiconductor technologies. Companies are interested in compound semiconductors made of chemicals such as gallium nitride or gallium arsenide, for example, because of how they operate in comparison to silicon. Compound semiconductors can operate at higher frequencies and higher temperatures and also emit and detect light more efficiently.
As such, they have great potential value for applications involving power electronics, radio-frequency communications such as Wi-Fi, and photonics such as solar cells. As suggested above, recent advancements in semiconductor technologies have largely been demand driven. As the demand for new capabilities has grown, researchers and academics around the world have needed to turn to new Beyond CMOS technology. Recent Beyond CMOS advancements have also been made possible, however, due to the alignment of outside technological advancement and innovation as well as specialization within the industry.
Research on More Moore and More than Moore techniques has preceded much of the current need for newer, more advanced technology. Some companies have been key players in driving new semiconductor technology forward. Intel, for example, has created a magnetoelectric spin-orbit logic device. This device has the potential to reduce voltage by five times and energy between ten and thirty times current levels.
These are electronics necessary for operations at temperatures below four degrees Kelvin. Cryogenic technology can be applied to improve sensors, signal and media processing, and digital and quantum computing.
In the near future, semiconductors also have the potential to play a significant role in advances in electronics in the medical field. New sensors to monitor brain activity, new systems to deliver drugs and monitor exercise activities, and new communication networks to send data between patients and doctors will depend on semiconductors.
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