Editing Photodiode (section)

=={{anchor|LEAD}}Unwanted and wanted photodiode effects==
Any p–n junction, if illuminated, is potentially a photodiode. Semiconductor devices such as diodes, transistors and ICs contain p–n junctions, and will not function correctly if they are illuminated by unwanted light.<ref>Shanfield, Z. et al (1988) [http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA210165 Investigation of radiation effects on semiconductor devices and integrated circuits]{{dead link|date=June 2022|bot=medic}}{{cbignore|bot=medic}}, DNA-TR-88-221</ref><ref>Iniewski, Krzysztof (ed.) (2010), ''Radiation Effects in Semiconductors'', CRC Press, {{ISBN|978-1-4398-2694-2}}</ref> This is avoided by encapsulating devices in opaque housings. If these housings are not completely opaque to high-energy radiation (ultraviolet, X-rays, gamma rays), diodes, transistors and ICs can malfunction<ref>{{cite journal | last1 = Zeller | first1 = H.R. | year = 1995 | title = Cosmic ray induced failures in high power semiconductor devices | journal = Solid-State Electronics| volume =  38| issue = 12| pages = 2041–2046| doi=10.1016/0038-1101(95)00082-5| bibcode = 1995SSEle..38.2041Z }}</ref> due to induced photo-currents. Background radiation from the packaging is also significant.<ref>{{cite journal|title=Alpha-particle-induced soft errors in dynamic memories|journal=IEEE Transactions on Electron Devices|volume=26|issue=1|pages=2–9|doi=10.1109/T-ED.1979.19370|year=1979|last1=May|first1=T.C.|last2=Woods|first2=M.H.|bibcode=1979ITED...26....2M|s2cid=43748644}} Cited in {{cite journal|author=Baumann, R. C. |title=Soft errors in commercial integrated circuits|journal=[[International Journal of High Speed Electronics and Systems]]|volume=14|issue=2|pages=299–309|doi=10.1142/S0129156404002363|quote=alpha particles emitted from the natural radioactive decay of uranium, thorium, and daughter isotopes present as impurities in packaging materials were found to be the dominant cause of [soft error rate] in [dynamic random-access memories].|year=2004}}</ref> [[Radiation hardening]] mitigates these effects.

In some cases, the effect is actually wanted, for example to use [[LED]]s as light-sensitive devices (see [[LED circuit#LED as a light sensor|LED as light sensor]]) or even for [[energy harvesting]], then sometimes called ''light-emitting and light-absorbing diodes'' (LEADs).<ref>{{cite journal |title=Halbleitertechnik Der LED fehlt der Doppelpfeil |author-first=Arno |author-last=Erzberger |journal=Elektronik |language=de |date=2016-06-21 |url=http://www.elektroniknet.de/elektronik/power/der-led-fehlt-der-doppelpfeil-131470.html |access-date=2017-02-14 |url-status=live |archive-url=https://web.archive.org/web/20170214181713/http://www.elektroniknet.de/elektronik/power/der-led-fehlt-der-doppelpfeil-131470.html |archive-date=2017-02-14}}</ref>