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Unformatted text preview: ELCT 363: Intro. to Microelectronics Lecture 13; Slide Mandal/Fall 2011 Fermi level in ntype semiconductor Ø In the ntype material most of the mobile charges are free electrons. Ø Therefore, the average energy of mobile charges is close to EC: Ø EF EC EFn Phosphorus (P) has 5 outer shell electrons. Extra free electron EC EV EFi 1 ELCT 363: Intro. to Microelectronics Lecture 13; Slide Mandal/Fall 2011 Position of Fermi level in nType Semiconductor n0 ni Nc e(EcE F )/kT = Nc e(EcEi)/kT = eE F /k T eE i /kT = e(E FE i ) /kT (EFE i ) = kT ln (n0/ni ) E c Ei E F EV EF  Ei ln (n0/ni ) = (EFE i )/kT ntype semiconductor: n0 = ND (EFE i ) = kT ln (ND/ni ) Position of Fermi level depends on doping concentration. 2 ELCT 363: Intro. to Microelectronics Lecture 13; Slide Mandal/Fall 2011 Fermi level in ptype semiconductor Ø In the ptype material most of the mobile charges are holes. Ø Therefore, the average energy of mobile charges is close to EV: Ø EF EV EFp EC EV Boron (B) has 3 outer shell electrons. Extra electron vacancy or hole EFi 3 ELCT 363: Intro. to Microelectronics Lecture 13; Slide Mandal/Fall 2011 Position of Fermi level in pType Semiconductor p0 pi N V e(EFEv)/kT = N V e(EiEv)/kT = eE F /kT e E i /kT = e(E iE F ) /kT (EiE F ) = kT ln (p0/pi ) Ec Ei E F EV Ei  EF Similarly, ( EiE F ) = kT ln (p0/ni ) Since ni = pi, ptype semiconductor: p0 = NA (EiE F ) = kT ln (NA/ni ) 4 ELCT 363: Intro. to MicroelectronicsELCT 363: Intro....
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 Spring '11
 Mandal
 Electron mobility, Ptype semiconductor, kT ln

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