Current gain rolloff in graded-base SiGe heterojunction bipolar transistors
- 1 April 1993
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Electron Device Letters
- Vol. 14 (4) , 193-195
- https://doi.org/10.1109/55.215153
Abstract
The authors report the experimental observation of a novel effect in SiGe heterojunction bipolar transistors (HBTs) with graded bases which results in a significant emitter-base bias dependence of the current gain. The nonideal collector current is caused by the interaction of the bias dependence of the emitter-base space-charge region width and the exponential dependence of the collector current on the germanium concentration at the edge of the space-charge region. The resulting current gain rolloff must be taken into account for accurate modeling of bipolar transistors with bandgap grading in the base.Keywords
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