Unformatted text preview: n band is a range of energy Between levels where there are no allowed states for an electron levels This is the band gap E G In silicon at room temperature [in electron volts]: E G = 1.1 eV Electron volt is an atomic measurement unit, 1 eV energy is Electron necessary to decrease of the potential of the electron with 1 V. necessary
1eV = 1.602 × 10 −19 joule Impurities Impurities
s s s Silicon crystal in pure form is Silicon good insulator - all electrons are bonded to silicon atom bonded Replacement of Si atoms can alter Replacement electrical properties of semiconductor semiconductor Group number - indicates number Group of electrons in valence level (Si Group IV) Group Impurities Impurities
s s Replace Si atom in crystal with Group V atom – substitution of 5 electrons for 4 electrons in outer shell – extra electron not needed for crystal bonding structure » can move to other areas of semiconductor » current flows more easily - resistivity decreases » many extra electrons > “donor” or n-type material Replace Si atom with Group III atom – substitution of 3 electrons for 4 electrons substitution – extra electron now needed for crystal bonding structure » “hole” created (missing electron) » hole can move to other areas of semiconductor if electrons continually fill holes » again, current flows more easily - resistivity decreases » electrons needed > “acceptor” or p-type material COUNTER DOPING COUNTER Insert more than one type of...
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- Winter '08
- Electron, Electrons, P-n junction