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Introduction      Semiconductors      LED      Illustrations

Semiconductors That Emit Light

Figure 2: n-type and p-type semiconductors
Figure 2: n-type and p-type semiconductors

Semiconductors are materials that can conduct electricity fairly well − better than insulators but not as well as conductors [1]. This property makes them unique and extremely useful. Common semiconductor materials include silicon, germanium, gallium arsenide and silicon carbide. Semiconductors are the foundation of modern electronics and are widely used in everyday devices like phones and computers.

Semiconductors in their pure (normal) state are often not as useful as in their impure state. A semiconductor can be made impure by adding and/or removing electrons from some of its atoms [2]. As shown in Figure 2, an n-type semiconductor has an abundance of additional electrons. In a p-type semiconductor, some atoms have one or more electrons removed from them to create "holes". Due to the missing negatively-charged electrons, holes are said to be positively charged. Typically, when electrons and holes are brought together they will recombine. During recombination, the electrons will lose energy in the form of either heat or light, depending on the type of semiconductor used.

An LED uses n- and p-type semiconductors and the process of recombining electrons with holes to produce light [3]. Different semiconductor materials produce different colors (wavelengths) of light [4]. For example, aluminium gallium arsenide produces red light, indium gallium nitride produces green light and zinc selenide produces blue light.



[1] "Semiconductor." Wikipedia, The Free Encyclopedia. [Online]. Available: http://en.wikipedia.org/wiki/Semiconductor. [Accessed: Jun 4, 2012].
[2] "Doping_(semiconductor)." Wikipedia, The Free Encyclopedia. [Online]. Available: http://en.wikipedia.org/wiki/Doping_(semiconductor). [Accessed: Jun 4, 2012].
[3] "Light Emitting Diode," Oct 2, 2009. [Online]. Available: http://en.wikipedia.org/wiki/Light-emitting_diode. [Accessed: Jun 4, 2012].
[4] "Light Emitting Diode," Oct 2, 2009. [Online]. Available: http://en.wikipedia.org/wiki/Light-emitting_diode#Colors_and_materials. [Accessed: Jun 4, 2012].