Temperature vs temperature carrier concentration ee

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Unformatted text preview: Temperature Carrier Concentration EE 332 Spring 2013 Operating Temperature of Semiconductor Operating Temperature of Semiconductor EE 332 Spring 2013 Dependence of EF oon Temperature and Doping Dependence of E n Temperature and Doping F EE 332 Spring 2013 A Real Example An Example – MOS Transistor EE 332 Spring 2013 Compensation Compensation Process Process • Semiconductors can be doped with both donors and acceptors simultaneously. • Assume a material doped with Nd>Na predominantly n-type so EF lies above acceptor level Ea completely full, however, with EF above Ei, the hole concentration cannot be equal to Na. • Mechanism: – Electrons are donated to the conduction band from the donor level. – An acceptor state gets filled by a valence band electron, thus creating a hole in the valence band. – An electron from the conduction band recombines with this hole. – Extending this logic, it is expected that the resultant concentration of electrons in the conduction band would be Nd-NA instead of Nd. – This process is called compensation. • By compensation, an n-type material can be made intrinsic (by making Nd=NA ) or even p-type (for NA>...
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