Measurement of collector-base junction avalanche multiplication effects in advanced UHV/CVD SiGe HBT's

This paper presents measurements of the avalanche multiplication factor (M-1) in SiGe HBTs using a new technique capable of separating the avalanche multiplication and Early effect contributions to the increase of collector current with collector-base bias, as well as allowing safe measurements at p...

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Bibliographic Details
Published in:IEEE transactions on electron devices 1999-05, Vol.46 (5), p.1007-1015
Main Authors: Niu, G., Cressler, J.D., Zhang, S., Gogineni, U., Ahlgren, D.C.
Format: Article
Language:English
Subjects:
Accumulators
Avalanches
Chemical vapor deposition
Collectors
Current density
Current measurement
Density measurement
Doping profiles
Germanium silicon alloys
Impact ionization
Ionization
Multiplication
Production
Silicon
Silicon germanides
Silicon germanium
Temperature
Time measurement
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Summary:This paper presents measurements of the avalanche multiplication factor (M-1) in SiGe HBTs using a new technique capable of separating the avalanche multiplication and Early effect contributions to the increase of collector current with collector-base bias, as well as allowing safe measurements at practical current densities. The impact of collector doping, current density, Ge profile, and operation temperature are reported for the first time using measured and simulated results from a production quality UHV/CVD SiGe HBT technology. Limitations of the technique in the presence of significant self-heating are discussed. By turning on the secondary hole impact ionization, we revealed the difference in impact ionization between strained SiGe and Si in the presence of the "dead space" effect. Despite its smaller bandgap, the compressively strained SiGe layer shows an apparent decrease in the secondary hole impact ionization rate compared to Si.
ISSN:0018-9383
1557-9646
DOI:10.1109/16.760410