14.HBTs_basic

14.HBTs_basic - Schematic of InGaP/GaAs HBT Schematic...

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1 Schematic of Schematic of InGaP/GaAs InGaP/GaAs HBT HBT • Epitaxial structure • Dissimilar emitter and base materials • Highly doped base • Dual B and C contacts • Identify W B and R B
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2 HETEROJUNCTION BIPOLAR TRANSISTORS • The major development in bipolar transistors (since 1990) • HBTs break the link between N B and β • Do this by making different barrier heights for electrons and holes •N B can reach 1E20cm -3 e - h + • Key feature is the wide-bandgap emitter - this improves f T and f max - this allows reduction of both W B and R B SHBT An example of Bandgap Engineering
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3 Selecting an emitter for a Selecting an emitter for a GaAs GaAs base base AlGaAs / GaAs 2.5 2 1.5 1 0.5 0 5.4 5.5 5.6 5.7 5.8 5.9 6 6.1 Lattice Constant, A Ba nd ga p, eV Si Ge GaAs GaP AlP AlAs InAs InP 90 80 70 60 50 40 30 20 10 a = 5.6533 A matched to GaAs ° ° a = 5.8688 A matched to InP ° InGaP / GaAs
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4 Preparing to compute I Preparing to compute I C • 1-D representation of HBT • Biased in active mode • Why do we show asymmetrical hemi-Maxwellians?
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This note was uploaded on 11/10/2010 for the course EECE 480 taught by Professor David during the Fall '09 term at UBC.

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14.HBTs_basic - Schematic of InGaP/GaAs HBT Schematic...

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