Semiconductor device

Semiconductor device

Semiconductor device fundamentals
The main reason Semiconductor materials are so useful is that the behaviour of a Semiconductor can be easily manipulated by the addition of impurities, known as doping. Semiconductor conductivity can be controlled by introduction of an electric field, by exposure to light, and even pressure and heat; thus, semiconductors can make excellent sensors. Current conduction in a Semiconductor occurs via mobile or "free" electrons and holes (collectively known as charge carriers). Doping a Semiconductor such as silicon with a small amount of impurity atoms, 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 "p-type", and when it contains excess free electrons it is known as "n-type". The Semiconductor material used in devices is doped under highly controlled conditions in a fabrication facility, or fab, to precisely control the ******** and concentration of p- and n-type dopants. The junctions which form where n-type and p-type semiconductors join together are called p-n junctions.


Diode
The p-n junction diode is a device made from a p-n junction. At the junction of a p-type and an n-type Semiconductor there forms a region called the depletion zone which blocks current conduction from the n-type region to the p-type region, but allows current to conduct from the p-type region to the n-type region. Thus when the device is forward biased, with the p-side at higher electric potential, the diode conducts current easily; but the current is very small when the diode is reverse biased.

Exposing a Semiconductor to light can generate electron–hole pairs, which increases the number of free carriers and its 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.


Transistors

Two MOS transistors with common gate (****llic layers and dielectric removed for clarity).Bipolar junction transistors 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 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, or JFET; or by an electrode isolated from the bulk material by an oxide layer, forming a ****l-oxide-semiconductor field effect transistor, or MOSFET.



Cross-section through a MOS transistor (****llic layers and dielectric removed for clarity), foreground.The MOSFET is the most used Semiconductor device today. 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. Although the MOSFET is named in part for its "****l" gate, in modern devices polysilicon is typically used instead.
[IMG][/IMG]
device materials
Main article: Semiconductor materials
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 make it currently the best compromise among the various competing materials. Silicon used in Semiconductor device manufacturing is currently fabricated into boules that are large enough in diameter to allow the production of 300 mm (12 in.) wafers.

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.

Other less common materials are also in use or under investigation.

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. IMPATT diodes have also been fabricated from SiC.

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.


List of common Semiconductor devices
This list is incomplete; you can help by expanding it.
Two-terminal devices:

Avalanche diode (avalanche breakdown diode)
DIAC

Diode (rectifier diode)
Gunn diode
IMPATT diode
Laser diode
Light-emitting diode (LED)
Photocell
PIN diode
Schottky diode
Solar cell
Tunnel diode
VCSEL
VECSEL
Zener diode
Three-terminal devices:

Bipolar transistor
Darlington transistor
Field effect transistor
IGBT (Insulated Gate Bipolar Transistor)
SCR (Silicon Controlled Rectifier)
Thyristor
Triac
Unijunction transistor
Four-terminal devices:

Hall effect sensor (magnetic field sensor)
Multi-terminal devices:

Charge-coupled device (CCD)
Microprocessor
Random Access Memory (RAM)
Read-only memory (ROM)

الموضوع الأصلي: Semiconductor device || الكاتب: shady || المصدر: منتدى المهندس

www.oggosoft.com

كلمات البحث

هندسة,مهندس ,منتدى ,المهندس , الهندسة, أقسام ,هندسية, المهندسين,المهندسون العرب, برامج ,برنامج,برمجه,المبرومجون العرب, , معماري , مدني, كهربي, ميكانيكي, ميكاترونكس , ميكانيكا,السيارات,سيارات, طبية , كيمياء , طيران, بترول ,تعدين, اتصالات ,الكترونيات, ديكور ,برامج هندسية ,اعدادي , ملتقى ,الجامعات ,المعاهد ,العربية,التعليمي ,التكنولوجي, المعهد التكنولوجي العالي ,المعهد العالي للهندسة بالمنيا ,المعهد التكنولوجي العالي بالعاشر من رمضان, معهد العاشر,Scattered thoughts, magazine,Car,car 2010,استراحه,ترفيه , منتدى المهندس منتدى هندسى شامل يجمع الهندسة الميكانيكية والميكاترونكس والكهربائية والمدنى والعمارة وهندسة البترول والمعادن والاتصالات وتكنولوجيا المعلومات المهندس العربى الهندسة المهندسون المهندسين الميكانيكية والميكاترونكس المعمارية المعمارى الميكانيكى القوى المدنى مدنى ميكانيكا عمارة ميكاترونكس كهرباء الكهربية الكهربائية منتديات الكهرباء كيمياء فيزياء بترول المهندسين العرب لتبادل المعرفة والخبرة لغات البرمجة السى الفيجوال بيسك والماتلاب SIMULINK التبريد والتكييف MATLAB ,

المصدر: منتدى المهندس - من قسم: هندسة ميكاترونكس

---

Semiconductor device