sp05exam3_sol

# sp05exam3_sol - Problem 1 Find V T for a silicon FET with a...

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Unformatted text preview: Problem 1 Find V T for a silicon FET with a p +-polysilicon gate having the following parameters, N Agate =10 20 cm-3 N A =6 x 10 16 cm-3 in the channel t ox =4 nm Q f = q × 4 × 10 10 C/cm 2 Q it (2 φ s ) = q × 2 × 10 10 C/cm 2 Channel length 2 µ m Channel width 4 µ m Is this an enhancement or depletion device? 1. (cont.) Finding Φ MS E c E V =E f E g χ χ E g /2 E i-E f Φ MS = Φ M- Φ S = ( χ + E g ) - ( χ + E g /2+ φ f ) = E g /2 - φ f ( ) V 402 . 10 08 . 1 10 6 ln V 0259 . ln 10 16 = × × = = − = i A f i f N N q kT E E φ V 0.160 V 402 . 2 / 124 . 1 2 / = − = = − = Φ f g MS E φ Subtraction done before contact. Diagram after contact (cont.) 1. ( ) ( )( ) 2-9-19-2 10 i C/cm 10 6 . 9 C 10 1.6 cm 10 2 4 Q × = × × + = ( ) ( ) ( ) 2 7 7- 14 ox F/cm 10 63 . 8 cm 10 4 F/cm 10 85 . 8 9 . 3 C − − × = × × = = ox i t ε Finding capacitance across the insulator Finding fixed charge in the insulator (cont.) 1. Finding depletion charge ( ) ( ) ( )( ) ( ) ( ) 2 7 3- 16 19 14 C/cm 10 27 . 1 402 . cm 10 6 C 10 6 . 1 F/cm 10 85 . 8 8 . 11 2 2 ) 2 ( 2 2 1 2 1 2 1 − − −...
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sp05exam3_sol - Problem 1 Find V T for a silicon FET with a...

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