Ultra High Speed InP Heterojunction Bipolar Transistors Mattias Dahlström Troubl

Ultra High Speed InP Heterojunction Bipolar Transistors Mattias Dahlström Troubl www.phwiki.com

Ultra High Speed InP Heterojunction Bipolar Transistors Mattias Dahlström Troubl

Gonzalez, Hector, News Director has reference to this Academic Journal, PHwiki organized this Journal Ultra High Speed InP Heterojunction Bipolar Transistors Mattias Dahlström Trouble is my business, (Raymond Ch in addition to ler) Ultra High Speed InP Heterojunction Bipolar Transistors Introduction to HBT’s How to make a fast HBT Delay terms The graded base The base-collector grade Recent results Record fmax mesa DHBT Record f DHBT details regarding this to follow The transistor Schematic of an HBT Typical common-emitter characteristics Small change in base current large change in collector current

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InP lattice structure Nearest neighbor: 2.5 A Lattice constant: 5.86 A InP in addition to InGaAs have G-L separations of ~0.65 eV, vs ~0.4 eV as long as GaAs larger collector velocity InGaAs has a low electron effective mass lower base transit time InGaAs InP Objectives in addition to approach Objectives: fast HBTs mm-wave power, 160 Gb fiber optics desired: 440 GHz ft & fmax, 10 mA/mm2, Ccb/Ic<0.5 ps/V better manufacturability than transferred-substrate HBTs improved per as long as mance over transferred-substrate HBTs Approach: narrow base mesa moderately low Ccb very low base contact resistance required, in addition to good alignment carbon base doping, good base contact process high ft through high current density, thin layers b in addition to gap engineering: small device transit time with wide b in addition to gap emitter in addition to collector Potential uses of InP HBT Communication systems: wireless communication, fiber optics transceivers, digital processing in radar (ADCs, DACs) Types of circuits: broadb in addition to amplifiers, power amplifiers, laser/modulator drivers comparators, latches, fast logic Circuit characteristics 1-10 000 HBTs per IC Very high dem in addition to s as long as speed (40-200 GHz) Fast logic with moderate power consumption (~20 mW/gate) Moderate Output Power mmwave power amps, optical modulator drivers ~6 V at Jc=4 mA/m2 , ~2 V at Jc=8 mA/m2 DHBT b in addition to diagram: under bias base emitter collector High speed HBT: some st in addition to ard figures of merit Small signal current gain cut-off frequency (from H21) Maximum power gain ( from U) Collector capacitance charging time when switching : Scaling laws as long as fast HBTs as long as x 2 improvement of all parasitics: ft, fmax, logic speed base Ö2: 1 thinner collector 2:1 thinner emitter, collector junctions 4:1 narrower current density 4:1 higher emitter Ohmic 4:1 less resistive Challenges with Scaling: Collector mesa HBT: collector under base Ohmics. Base Ohmics must be one transfer length sets minimum size as long as collector Emitter Ohmic: hard to improve how Current Density: dissipation, reliability Loss of breakdown avalanche Vbr never less than collector Eg (1.12 V as long as Si, 1.4 V as long as InP) .sufficient as long as logic, insufficient as long as power narrow collector mesa transferred-substrate Contact resistance: tunneling through barrier High doping: 1-9 1019 cm-3 Small b in addition to gap: InAs

Base grading Graded b in addition to gap Graded doping Doping 8 5 1019 cm-3 Change in In:Ga ratio InAs: Eg=0.36 eV GaAs: Eg=1.43 eV Base grading: induced electric field Induced electric field accelerates electrons towards collector – decreases base transit time in addition to increases gain Limits: strain Limits: B in addition to gap narrowing, needs degenerate doping The effect of degenerate doping Evidence: Observed Vbe increase Von ~ bi , increases with Ev Nb=4 1019cm30.75 V Nb=8 1019cm30.83 V as long as graded base-emitter Strong variation in Fermi-level with doping at high doping levels

Base b in addition to gap narrowing Model after V. Pavlanovski B in addition to gap grade Doping grade BGN provides an electric field opposing the doping-induced field. ~1:5 in magnitude Base Transit time Ballistic effects may arise when Tb<180-200 @5 1019 cm-3 (Tessier, Ito) Results: B in addition to gap graded Doping graded DC gain 25 18 ft 250 GHz 282 GHz B in addition to gap grade in addition to doping grade give same b Collector design Transit time: Close inspection show velocity near base most important Use grade Use setback Ultra High Speed InP Heterojunction Bipolar Transistors Why this title Some recent conference results show transistor ft of 130 GHz InP is a brittle semiconductor with a metallic luster. We mix it with GaAs in addition to AlAs. Use Si in addition to C as dopants Heterojunction: contains junctions of different materials DHBT carrier profile quick comment that this is unbiased .under bias both DR will fill with E

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