Lecture12

Direct bandgap means k vectors match in conduclon and

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Unformatted text preview: ansistor controls the emijer ­collector current with a very small base ­ emijer current.   There is a very thin base layer between the emijer and collector. o  base ­emijer forward biased o  base ­collector reverse biased   Electrons from the emijer that flow into the base diffuse into the collector rather than go out though the base lead. 16 MOSFET A Field Effect Transistor controls the Source ­Drain voltage with a voltage on the Gate.   The tradiLonal MOSFET used a Metal Oxide on Silicon layer to insulate the Gate. (dielectric now)   Very high input impedance.   E ­field increases conducLvity in n ­channel between Source and Drain.   If VGB is high enough, a high concentraLon of negaLve charge carriers forms in an inversion layer located in a thin layer next to the interface between the semiconductor and the insulator.   17 Light EmiPng Diodes Electrons and holes combine (annihilate) giving off energy equal to the band ­gap.   Direct band ­gap means k ­ vectors match in conducLon and valence bands allowing photon emission.   Si and Ge k does not match and energy is transferred to the laPce; no photon....
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This note was uploaded on 02/24/2014 for the course PHYS 2D taught by Professor Hirsch during the Winter '08 term at UCSD.

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