physics and technology of semiconductor devices pdf

Physics And Technology Of Semiconductor Devices Pdf

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Physics of Semiconductor Devices

A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material primarily silicon , germanium , and gallium arsenide , as well as organic semiconductors for its function. Semiconductor devices have replaced vacuum tubes in most applications.

They use electrical conduction in the solid state rather than the gaseous state or thermionic emission in a vacuum. Semiconductor devices are manufactured both as single discrete devices and as integrated circuit IC chips, which consist of two or more devices—which can number from the hundreds to the billions—manufactured and interconnected on a single semiconductor wafer also called a substrate. Semiconductor materials are useful because their behavior can be easily manipulated by the deliberate addition of impurities, known as doping.

Semiconductor conductivity can be controlled by the introduction of an electric or magnetic field, by exposure to light or heat, or by the mechanical deformation of a doped monocrystalline silicon grid; thus, semiconductors can make excellent sensors. Current conduction in a semiconductor occurs due to mobile or "free" electrons and electron holes , collectively known as charge carriers. Doping a semiconductor with a small proportion of an atomic impurity, such as phosphorus or boron , greatly increases the number of free electrons or holes within the semiconductor.

When a doped semiconductor contains excess holes, it is called a p-type semiconductor p for positive electric charge ; when it contains excess free electrons, it is called an n-type semiconductor n for negative electric charge. A majority of mobile charge carriers have negative charge. The manufacture of semiconductors controls precisely the location and concentration of p- and n-type dopants.

The connection of n-type and p-type semiconductors form p—n junctions. As of , billions of MOS transistors are manufactured every day. A semiconductor diode is a device typically made from a single p—n junction. At the junction of a p-type and an n-type semiconductor there forms a depletion region where current conduction is inhibited by the lack of mobile charge carriers.

When the device is forward biased connected with the p-side at higher electric potential than the n-side , this depletion region is diminished, allowing for significant conduction, while only very small current can be achieved when the diode is reverse biased and thus the depletion region expanded.

Exposing a semiconductor to light can generate electron—hole pairs , which increases the number of free carriers and thereby the conductivity. Diodes optimized to take advantage of this phenomenon are known as photodiodes. Compound semiconductor diodes can also be used to generate light, as in light-emitting diodes and laser diodes.

Bipolar junction transistors BJTs are formed from two p—n junctions, in either n—p—n or p—n—p configuration. The middle, or base , region between the junctions is typically very narrow. The other regions, and their associated terminals, are known as the emitter and the collector. A small current injected through the junction between the base and the emitter changes the properties of the base-collector junction so that it can conduct current even though it is reverse biased.

This creates a much larger current between the collector and emitter, controlled by the base-emitter current. Another type of transistor, the field-effect transistor FET , operates on the principle that semiconductor conductivity can be increased or decreased by the presence of an electric field.

An electric field can increase the number of free electrons and holes in a semiconductor, thereby changing its conductivity. The field may be applied by a reverse-biased p—n junction, forming a junction field-effect transistor JFET or by an electrode insulated from the bulk material by an oxide layer, forming a metal—oxide—semiconductor field-effect transistor MOSFET.

It accounts for at least The gate electrode is charged to produce an electric field that controls the conductivity of a "channel" between two terminals, called the source and drain. Depending on the type of carrier in the channel, the device may be an n-channel for electrons or a p-channel for holes MOSFET. By far, silicon Si is the most widely used material in semiconductor devices. Its combination of low raw material cost, relatively simple processing, and a useful temperature range makes it currently the best compromise among the various competing materials.

Germanium Ge was a widely used early semiconductor material but its thermal sensitivity makes it less useful than silicon. Today, germanium is often alloyed with silicon for use in very-high-speed SiGe devices; IBM is a major producer of such devices. Gallium arsenide GaAs is also widely used in high-speed devices but so far, it has been difficult to form large-diameter boules of this material, limiting the wafer diameter to sizes significantly smaller than silicon wafers thus making mass production of GaAs devices significantly more expensive than silicon.

Silicon carbide SiC has found some application as the raw material for blue light-emitting diodes LEDs and is being investigated for use in semiconductor devices that could withstand very high operating temperatures and environments with the presence of significant levels of ionizing radiation.

Various indium compounds indium arsenide, indium antimonide , and indium phosphide are also being used in LEDs and solid state laser diodes. Selenium sulfide is being studied in the manufacture of photovoltaic solar cells. The most common use for organic semiconductors is organic light-emitting diodes.

All transistor types can be used as the building blocks of logic gates , which are fundamental in the design of digital circuits.

In digital circuits like microprocessors , transistors act as on-off switches; in the MOSFET , for instance, the voltage applied to the gate determines whether the switch is on or off. Transistors used for analog circuits do not act as on-off switches; rather, they respond to a continuous range of inputs with a continuous range of outputs.

Common analog circuits include amplifiers and oscillators. Circuits that interface or translate between digital circuits and analog circuits are known as mixed-signal circuits. Power semiconductor devices are discrete devices or integrated circuits intended for high current or high voltage applications. Power integrated circuits combine IC technology with power semiconductor technology, these are sometimes referred to as "smart" power devices.

Several companies specialize in manufacturing power semiconductors. The type designators of semiconductor devices are often manufacturer specific. Nevertheless, there have been attempts at creating standards for type codes, and a subset of devices follow those. Semiconductors had been used in the electronics field for some time before the invention of the transistor.

Around the turn of the 20th century they were quite common as detectors in radios , used in a device called a "cat's whisker" developed by Jagadish Chandra Bose and others.

These detectors were somewhat troublesome, however, requiring the operator to move a small tungsten filament the whisker around the surface of a galena lead sulfide or carborundum silicon carbide crystal until it suddenly started working. At the time their operation was completely mysterious. After the introduction of the more reliable and amplified vacuum tube based radios, the cat's whisker systems quickly disappeared. The "cat's whisker" is a primitive example of a special type of diode still popular today, called a Schottky diode.

Another early type of semiconductor device is the metal rectifier in which the semiconductor is copper oxide or selenium. Westinghouse Electric was a major manufacturer of these rectifiers.

During World War II, radar research quickly pushed radar receivers to operate at ever higher frequencies and the traditional tube based radio receivers no longer worked well. The introduction of the cavity magnetron from Britain to the United States in during the Tizard Mission resulted in a pressing need for a practical high-frequency amplifier. On a whim, Russell Ohl of Bell Laboratories decided to try a cat's whisker. By this point they had not been in use for a number of years, and no one at the labs had one.

After hunting one down at a used radio store in Manhattan , he found that it worked much better than tube-based systems. Ohl investigated why the cat's whisker functioned so well.

He spent most of trying to grow more pure versions of the crystals. He soon found that with higher quality crystals their finicky behaviour went away, but so did their ability to operate as a radio detector. One day he found one of his purest crystals nevertheless worked well, and it had a clearly visible crack near the middle.

However as he moved about the room trying to test it, the detector would mysteriously work, and then stop again. After some study he found that the behaviour was controlled by the light in the room — more light caused more conductance in the crystal. He invited several other people to see this crystal, and Walter Brattain immediately realized there was some sort of junction at the crack.

Further research cleared up the remaining mystery. The crystal had cracked because either side contained very slightly different amounts of the impurities Ohl could not remove — about 0. One side of the crystal had impurities that added extra electrons the carriers of electric current and made it a "conductor". The other had impurities that wanted to bind to these electrons, making it what he called an "insulator". Because the two parts of the crystal were in contact with each other, the electrons could be pushed out of the conductive side which had extra electrons soon to be known as the emitter and replaced by new ones being provided from a battery, for instance where they would flow into the insulating portion and be collected by the whisker filament named the collector.

However, when the voltage was reversed the electrons being pushed into the collector would quickly fill up the "holes" the electron-needy impurities , and conduction would stop almost instantly. This junction of the two crystals or parts of one crystal created a solid-state diode, and the concept soon became known as semiconduction. The mechanism of action when the diode is off has to do with the separation of charge carriers around the junction.

This is called a " depletion region ". Armed with the knowledge of how these new diodes worked, a vigorous effort began to learn how to build them on demand. Within a year germanium production had been perfected to the point where military-grade diodes were being used in most radar sets.

After the war, William Shockley decided to attempt the building of a triode -like semiconductor device. He secured funding and lab space, and went to work on the problem with Brattain and John Bardeen.

The key to the development of the transistor was the further understanding of the process of the electron mobility in a semiconductor. It was realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built. For instance, if contacts are placed on both sides of a single type of crystal, current will not flow between them through the crystal.

However if a third contact could then "inject" electrons or holes into the material, current would flow. Actually doing this appeared to be very difficult. If the crystal were of any reasonable size, the number of electrons or holes required to be injected would have to be very large, making it less than useful as an amplifier because it would require a large injection current to start with.

That said, the whole idea of the crystal diode was that the crystal itself could provide the electrons over a very small distance, the depletion region. The key appeared to be to place the input and output contacts very close together on the surface of the crystal on either side of this region.

Brattain started working on building such a device, and tantalizing hints of amplification continued to appear as the team worked on the problem. Sometimes the system would work but then stop working unexpectedly. In one instance a non-working system started working when placed in water. Ohl and Brattain eventually developed a new branch of quantum mechanics , which became known as surface physics , to account for the behaviour.

The electrons in any one piece of the crystal would migrate about due to nearby charges. Electrons in the emitters, or the "holes" in the collectors, would cluster at the surface of the crystal where they could find their opposite charge "floating around" in the air or water. Yet they could be pushed away from the surface with the application of a small amount of charge from any other location on the crystal. Instead of needing a large supply of injected electrons, a very small number in the right place on the crystal would accomplish the same thing.

Their understanding solved the problem of needing a very small control area to some degree.

The Physics of Semiconductor Devices

Download PDF Flyer. DOI: Recommend this Book to your Library. This well organized reference book covers the newest and most important practically applicable results in thin film-based semiconductor A2B6-A4B6 and chalcogenide sensors, heterojunction-based active elements and other devices. This book is written for researchers, material scientists and advanced students who wish to increase their familiarity with different topics of novel semiconductor material science related to production of thin film-based sensors and active elements for micro- and nanoelectronics.

Semiconductor Devices: Physics and Technology

Physics of Semiconductor Devices -. A scanning electron micrograph of an array of the floating-gate nonvolatile semiconductor memory. NVSM magnified , times. For a discussion of this device, see Chapter 6.

Physics and Technology of Semiconductor Thin Film-Based Active Elements and Devices

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Sze, Kwok K. This is the third edition of the book and it has been completely revised and updated to meet the requirements of students. It covers all the topics comprehensively and explains in details the features of all major bipolar, field—effect, microwave, photonic and sensor devices.

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[PDF] Physics Of Semiconductor Devices By Simon M. Sze, Kwok K. Ng Book Free Download

A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material primarily silicon , germanium , and gallium arsenide , as well as organic semiconductors for its function. Semiconductor devices have replaced vacuum tubes in most applications.

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