2003 · 15 citations · 8 references
EngineeringElectrical EngineeringMaterials ScienceMicroelectronicsSemiconductor DevicesSemiconductor MaterialsBipolar Junction TransistorsDopingHigh-frequency Semiconductor DevicesSemiconductor Device MaterialsSemiconductor HeterostructuresSemiconductor PhysicsCutoff FrequencyHeterojunction Bipolar TransistorsHeterostructure TransistorsHigh-frequency ElectronicsHigh-frequency PerformanceMicrowave DevicesRadio-frequency DevicesSubstitutional Doping
The authors report high-performance InAlAs/InGaAs heterojunction bipolar transistors with base doping graded exponentially from 5*10/sup 18/ cm/sup -3/ at the collector junction to 5*10/sup 19/ cm/sup -3/ at the emitter junction. The built-in field reduces the base transit time and results in 20% and 30% improvement in cutoff frequency f/sub t/ and maximum oscillation frequency f/sub max/, respectively, compared to devices with uniformly doped base. For 1- mu m emitter devices, f/sub t/ of 65 GHz and f/sub max/ of 120 GHz were obtained. A graded InGaAlAs emitter-base junction is also incorporated which results in lower V/sub be/ and higher beta compared to abrupt junction devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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