594A_set_1

594A_set_1 - ECE145C /218C notes, M. Rodwell, copyrighted...

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ECE145C /218C notes, M. Rodwell, copyrighted ECE145C / 218C Notes set 1: device models & device characteristics: Mark Rodwell University of California, Santa Barbara rodwell@ece.ucsb.edu 805-893-3244, 805-893-3262 fax
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ECE145C /218C notes, M. Rodwell, copyrighted Objectives: train graduate students in: --high frequency transistor modeling --high frequency circuit design fast analog and digital microwave ICs* The microwave IC design material will be covered in 145ab --but I cannot provide a coherent course without coverage of substantial amount of review material.
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Active Devices: Bipolar Transistors Field-Effect Transistors
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ECE145C /218C notes, M. Rodwell, copyrighted Physical structure, symbolic base BC grade collector N+ sub collector semi-insulating InP substrate emitter emitter contact base contact c T b,cont W e W eb W under W N- drift collector base contact collector contact b T c W EB grade
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ECE145C /218C notes, M. Rodwell, copyrighted Physical structure- Real Urteaga et al Teledyne 500 nm process 2006 emitter base contact base via
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ECE145C /218C notes, M. Rodwell, copyrighted Typical Physical structure, III-V HBT scale: 1x1 um deposit interconnect metal
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ECE145C /218C notes, M. Rodwell, copyrighted Transistor Physical Structure, Si/SiGe HBT Emitter Width: 0.1 um Emitter Current Density 20 mA/um 2 Polysilicon Emitter Contact metal-semiconductor contact area >> emitter junction area --> low Rex Polysilicon base contact low sheet resistance in extrinsic base small extrinsic collector-base junction area ft~200 GHz, fmax~200 GHz
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ECE145C /218C notes, M. Rodwell, copyrighted Band structure, III-V HBT -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 0 50 100 150 200 250 Energy, eV position, nm setback grade drift collector base emitter cap emitter V q base V q collector V q
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ECE145C /218C notes, M. Rodwell, copyrighted Bipolar Transistor DC-IV Characteristics
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ECE145C /218C notes, M. Rodwell, copyrighted Bipolar Transistor: Carrier Transit Times
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ECE145C /218C notes, M. Rodwell, copyrighted Base resistance & collector-base capacitance base contact emitter W C W E L base contact R bb = 1 2 L ρ contact , horizontal + ρ sheet 12 L W E C cb = ε L T c W c collector contact SI substrate base sub collector Scaling emitter width does reduce base spreading resistance. – but – Minimum base resistance set by base contact resistance. Minimum collector capacitance set by minimum base contact size
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ECE145C /218C notes, M. Rodwell, copyrighted HBT hybrid-Pi equivalent-circuit model ) exp( c mo m j g g ωτ = c b f τ + τ = τ The delay associated with the gm element is essential if common-base input impedance is to be modeled correctly at high frequencies. C cbi C cbx R be R bb BC E R ex R c V be C je C be,diff =g m τ f g m V be e -j ωτ c m be g R / β =
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ECE145C /218C notes, M. Rodwell, copyrighted Bipolar Transistor T-model V be E B C R ex R bb C cbx C cbi R ce R cb C be,depl α(ω)∗ I’ e r e =1/g m I’ e () τ + τ ω + α ωτ + ωτ + α ωτ ωτ + α ω α ) ( 1 1 1 1 1 1 exp 1 1 ) ( 0 0 0 b b c b c b j j j j j
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This note was uploaded on 08/06/2008 for the course ECE 145 taught by Professor Rodwell during the Fall '07 term at UCSB.

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594A_set_1 - ECE145C /218C notes, M. Rodwell, copyrighted...

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