On the profile design and optimization of epitaxial Si- and SiGe-base bipolar technology for 77 K applications. I. Transistor DC design considerations

The DC design considerations associated with optimizing epitaxial Si- and SiGe-base bipolar transistors for the 77-K environment are examined in detail. Transistors and circuits were fabricated using four different vertical profiles, three with a graded-bandgap SiGe base, and one with a Si base for...

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Bibliographic Details
Published inIEEE transactions on electron devices Vol. 40; no. 3; pp. 525 - 541
Main Authors Cressler, J.D., Comfort, J.H., Crabbe, E.F., Patton, G.L., Stork, J.M.C., Sun, J.Y.-C., Meyerson, B.S.
Format Journal Article
LanguageEnglish
Published New York, NY IEEE 01.03.1993
Institute of Electrical and Electronics Engineers
Subjects
Applied sciences
Bipolar transistors
Circuits
Degradation
Design optimization
Electronics
Exact sciences and technology
Germanium silicon alloys
Heterojunctions
Logic
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Silicon germanium
Temperature
Transconductance
Transistors
Transistor base
Static characteristic
Thermal characteristic
Transistor parameter
Epitaxy
Doping profile
Germanium Silicides
Optimization
Bipolar transistor
Semiconductor device
Liquid nitrogen
Silicon
Current gain
Low temperature
Electrical characteristic
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Summary:The DC design considerations associated with optimizing epitaxial Si- and SiGe-base bipolar transistors for the 77-K environment are examined in detail. Transistors and circuits were fabricated using four different vertical profiles, three with a graded-bandgap SiGe base, and one with a Si base for comparison. All four epitaxial-base profiles yield transistors with DC properties suitable for high-speed logic applications in the 77-K environment. The differences between the low-temperature DC characteristics of Si and SiGe transistors are highlighted both theoretically and experimentally. A performance tradeoff associated with the use of an intrinsic spacer layer to reduce parasitic leakage at low temperatures and the consequent base resistance degradation due to enhanced carrier freeze-out is identified. Evidence that a collector-base heterojunction barrier effect severely degrades the current drive and transconductance of SiGe-base transistors operating at low temperatures is provided.< >
ISSN:0018-9383
1557-9646
DOI:10.1109/16.199358