Editing Photodiode (section)

==Related devices==
'''[[Avalanche photodiode]]s''' are photodiodes with structure optimized for operating with high reverse bias, approaching the reverse breakdown voltage. This allows each ''photo-generated'' carrier to be multiplied by [[avalanche breakdown]], resulting in internal gain within the photodiode, which increases the effective ''responsivity'' of the device.<ref name="pears2">{{cite book|last1=Pearsall|first1=Thomas|last2=Pollack|first2=Martin|title=Compound Semiconductor Photodiodes, Semiconductors and Semimetals, Vol 22D|publisher=Elsevier|date=1985|pages=173–245|url=https://www.sciencedirect.com/bookseries/semiconductors-and-semimetals/vol/22/part/PD|doi=10.1016/S0080-8784(08)62953-1}}</ref>[[File:IEEE 315-1975 (1993) 8.6.16.svg|100px|thumb|Electronic symbol for a phototransistor]]
[[File:PhotoTransistor.jpg|thumb|S604B PhotoTransistor]]
A '''phototransistor''' is a light-sensitive transistor. A common type of phototransistor, the ''bipolar phototransistor'', is in essence a [[bipolar transistor]] encased in a transparent case so that [[light]] can reach the ''base–collector [[p–n junction|junction]]''. It was invented by [[John N. Shive]] at Bell Labs in 1948<ref name="crystal-fire">{{cite book |year=1998
 | title = Crystal Fire: The Invention of the Transistor and the Birth of the Information Age
 | isbn = 9780393318517
 |author1=Riordan, Michael |author1-link=Michael Riordan (physicist) |author2=Hoddeson, Lillian | publisher = W. W. Norton & Company
 |author2-link=Lillian Hoddeson
}}</ref>{{rp|205}} but it was not announced until 1950.<ref>{{cite journal
 | url = http://www.smecc.org/phototransistor.htm
 | title = The phototransistor
 | date = May 1950
 | journal = Bell Laboratories Record
 | access-date = 2012-04-09
 | archive-date = 2015-07-04
 | archive-url = https://web.archive.org/web/20150704010847/http://www.smecc.org/phototransistor.htm
 | url-status = dead
 }}</ref> The electrons that are generated by photons in the base–collector junction are injected into the base, and this photodiode current is amplified by the transistor's current gain β (or h<sub>fe</sub>). If the base and collector leads are used and the emitter is left unconnected, the phototransistor becomes a photodiode. While phototransistors have a higher [[responsivity]] for light they are not able to detect low levels of light any better than photodiodes.{{Citation needed|date=May 2011}} Phototransistors also have significantly longer response times. Another type of phototransistor, the ''field-effect phototransistor'' (also known as photoFET), is a light-sensitive field-effect transistor. Unlike photobipolar transistors, photoFETs control drain-source current by creating a gate voltage.

A '''[[solaristor]]''' is a two-terminal gate-less phototransistor. A compact class of two-terminal phototransistors or solaristors have been demonstrated in 2018 by [[Catalan Institute of Nanoscience and Nanotechnology (ICN2)|ICN2]] researchers. The novel concept is a two-in-one power source plus transistor device that runs on solar energy by exploiting a memresistive effect in the flow of photogenerated carriers.<ref>{{Cite journal|last1=Pérez-Tomás|first1=Amador|last2=Lima|first2=Anderson|last3=Billon|first3=Quentin|last4=Shirley|first4=Ian|last5=Catalan|first5=Gustau|last6=Lira-Cantú|first6=Mónica|title=A Solar Transistor and Photoferroelectric Memory|journal=Advanced Functional Materials|volume=28|issue=17|pages=1707099|language=en|doi=10.1002/adfm.201707099|issn=1616-3028|year=2018|url=http://ddd.uab.cat/record/215011|hdl=10261/199048|s2cid=102819292 |hdl-access=free}}</ref>