imported>Chunbum Park |
imported>John Stephenson |
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| {{Image|Two diode structures.PNG|right|200px|Mesa diode structure (top) and planar diode structure with guard-ring (bottom).}} | | {{:{{FeaturedArticleTitle}}}} |
| | | <small> |
| A '''[[semiconductor diode]]''' is a two-terminal device that conducts current in only one direction, made of two or more layers of which at least one is a semiconductor. An example is the ''pn''-diode, made by joining a ''p''-type semiconducting layer to an ''n''-type semiconducting layer. For a discussion of dopant impurities and the terminology ''p-'' and ''n-''type. see [[Semiconductor#Dopant_impurities|dopant impurities]].
| | ==Footnotes== |
| | | {{reflist|2}} |
| The figure shows two of the many possible structures used for ''pn-''semiconductor diodes, both adapted to increase the voltage the devices can withstand in reverse bias. The top structure uses a mesa to avoid a sharp curvature of the ''p<sup>+</sup>-''region next to the adjoining ''n-''layer. The bottom structure uses a lightly doped ''p-''guard-ring at the edge of the sharp corner of the ''p<sup>+</sup>-''layer to spread the voltage out over a larger distance and reduce the electric field. (Superscripts like ''n<sup>+</sup>'' or ''n<sup>−</sup>'' refer to heavier or lighter impurity doping levels.)
| | </small> |
| ==Types== | |
| Semiconductor diodes come in a large variety of types:
| |
| *''pn''-diode: The ''pn'' junction diode consists of an ''n''-type semiconductor joined to a ''p''-type semiconductor.
| |
| *Zener diode: The Zener diode is a special type of ''pn''-diode made to operate in the reverse breakdown region, and used often as a voltage regulator. The breakdown voltage in these diodes is sometimes called the ''Zener voltage''. Depending upon the voltage range designed for, the diode may break down by either Zener breakdown, an electron tunneling behavior, or by avalanche breakdown.
| |
| *Schottky diode: The Schottky diode is made using a metal such as aluminum or platinum, on a lightly doped semiconductor substrate.
| |
| *Tunnel diode: Like the Zener diode, the tunnel diode (or Esaki diode) is made up of heavily doped ''n-'' and ''p''-type layers with a very abrupt transition between the two types. Conduction takes place by electron tunneling.
| |
| *Light-emitting diode: The light-emitting diode is designed to convert electrical current into light.
| |
| *Photodiode: The photodiode is the inverse of the light-emitting diode, acting as a photodetector, converting incident light to a detectable electric current.
| |
| *''pin''-diode: The ''pin''-diode is made of three layers: an intrinsic (undoped) layer between the ''p''- and ''n''-type layers. Because of its rapid switching characteristics it is used in microwave and radio-frequency applications.
| |
| *Gunn diode: The Gunn diode is a ''transferred electron device'' based upon the Gunn effect in III-V semiconductors, and is used to generate microwave oscillations.
| |
| *Varactor: a ''pn''-junction used in reverse bias as a voltage-variable capacitor for tuning radio receivers. The term ''varactor'' also is used for devices that behave like back-to-back Zener diodes.
| |
| | |
| [[semiconductor diode|...]]
| |
Latest revision as of 10:19, 11 September 2020
The Irvin pin. The eyes have always been red, but there are
urban legends about the meanings of other colors.
A pin from another company, possibly Switlik or Standard Parachute. This style is common in catalogs and auctions of military memorabilia.
The Caterpillar Club is an informal association of people who have successfully used a parachute to bail out of a disabled aircraft. After authentication by the parachute maker, applicants receive a membership certificate and a distinctive lapel pin.
History
Before April 28, 1919 there was no way for a pilot to jump out of a plane and then to deploy a parachute. Parachutes were stored in a canister attached to the aircraft, and if the plane was spinning, the parachute could not deploy. Film industry stuntman Leslie Irvin developed a parachute that the pilot could deploy at will from a back pack using a ripcord. He joined the Army Air Corps parachute research team, and in April 1919 he successfully tested his design, though he broke his ankle during the test. Irvin was the first person to make a premeditated free fall jump from an airplane. He went on to form the Irving Airchute Company, which became a large supplier of parachutes. (A clerical error resulted in the addition of the "g" to Irvin and this was left in place until 1970, when the company was unified under the title Irvin Industries Incorporated.) The Irvin brand is now a part of Airborne Systems, a company with operations in Canada, the U.S. and the U.K.[1].
An early brochure [2] of the Irvin Parachute Company credits William O'Connor 24 August 1920 at McCook Field near Dayton, Ohio as the first person to be saved by an Irvin parachute, but this feat was unrecognised. On 20 October 1922 Lieutenant Harold R. Harris, chief of the McCook Field Flying Station, jumped from a disabled Loening W-2A monoplane fighter. Shortly after, two reporters from the Dayton Herald, realising that there would be more jumps in future, suggested that a club should be formed. 'Caterpillar Club' was suggested because the parachute canopy was made of silk, and because caterpillars have to climb out of their cocoons and fly away. Harris became the first member, and from that time forward any person who jumped from a disabled aircraft with a parachute became a member of the Caterpillar Club. Other famous members include General James Doolittle, Charles Lindbergh and (retired) astronaut John Glenn.
In 1922 Leslie Irvin agreed to give a gold pin to every person whose life was saved by one of his parachutes. By 1945 the number of members with the Irvin pins had grown to over 34,000. In addition to the Irvin Air Chute Company and its successors, other parachute manufacturers have also issued caterpillar pins for successful jumps. Irvin/Irving's successor, Airborne Systems Canada, still provides pins to people who made their jump long ago and are just now applying for membership. Another of these is Switlik Parachute Company, which though it no longer makes parachutes, still issues pins.
